TeleMetrum

Owner's Manual for the TeleMetrum System

Bdale Garbee

Keith Packard

+ This document is released under the terms of the + + Creative Commons ShareAlike 3.0 + + license. +

Revision History
Revision 0.3	12 November 2010
+ Add instructions for re-flashing devices using AltosUI +
Revision 0.2	18 July 2010
Significant update
Revision 0.1	30 March 2010
Initial content

Chapter 1. Introduction and Overview

+ Welcome to the Altus Metrum community! Our circuits and software reflect + our passion for both hobby rocketry and Free Software. We hope their + capabilities and performance will delight you in every way, but by + releasing all of our hardware and software designs under open licenses, + we also hope to empower you to take as active a role in our collective + future as you wish! +

+ The focal point of our community is TeleMetrum, a dual deploy altimeter + with fully integrated GPS and radio telemetry as standard features, and + a "companion interface" that will support optional capabilities in the + future. +

+ Complementing TeleMetrum is TeleDongle, a USB to RF interface for + communicating with TeleMetrum. Combined with your choice of antenna and + notebook computer, TeleDongle and our associated user interface software + form a complete ground station capable of logging and displaying in-flight + telemetry, aiding rocket recovery, then processing and archiving flight + data for analysis and review. +

+ More products will be added to the Altus Metrum family over time, and + we currently envision that this will be a single, comprehensive manual + for the entire product family. +

Chapter 2. Getting Started

Table of Contents

FAQ

+ This chapter began as "The Mere-Mortals Quick Start/Usage Guide to + the Altus Metrum Starter Kit" by Bob Finch, W9YA, NAR 12965, TRA 12350, + w9ya@amsat.org. Bob was one of our first customers for a production + TeleMetrum, and the enthusiasm that led to his contribution of this + section is immensely gratifying and highy appreciated! +

+ The first thing to do after you check the inventory of parts in your + "starter kit" is to charge the battery by plugging it into the + corresponding socket of the TeleMetrum and then using the USB A to B + cable to plug the Telemetrum into your computer's USB socket. The + TeleMetrum circuitry will charge the battery whenever it is plugged + into the usb socket. The TeleMetrum's on-off switch does NOT control + the charging circuitry. When the GPS chip is initially searching for + satellites, the unit will pull more current than it can pull from the + usb port, so the battery must be plugged in order to get a good + satellite lock. Once GPS is locked the current consumption goes back + down enough to enable charging while + running. So it's a good idea to fully charge the battery as your + first item of business so there is no issue getting and maintaining + satellite lock. The yellow charge indicator led will go out when the + battery is nearly full and the charger goes to trickle charge. +

+ The other active device in the starter kit is the half-duplex TeleDongle + rf link. If you plug it in to your computer it should "just work", + showing up as a serial port device. If you are using Linux and are + having problems, try moving to a fresher kernel (2.6.33 or newer), as + there were some ugly USB serial driver bugs in earlier versions. +

+ Next you should obtain and install the AltOS utilities. The first + generation sofware was written for Linux only. New software is coming + soon that will also run on Windows and Mac. For now, we'll concentrate + on Linux. If you are using Debian, an 'altos' package already exists, + see http://altusmetrum.org/AltOS for details on how to install it. + User-contributed directions for building packages on ArchLinux may be + found in the contrib/arch-linux directory as PKGBUILD files. + Between the debian/rules file and the PKGBUILD files in + contrib, you should find enough information to learn how to build the + software for any other version of Linux. +

+ When you have successfully installed the software suite (either from + compiled source code or as the pre-built Debian package) you will + have 10 or so executable programs all of which have names beginning + with 'ao-'. + ('ao-view' is the lone GUI-based program, the rest are command-line + oriented.) You will also have man pages, that give you basic info + on each program. + You will also get this documentation in two file types in the doc/ + directory, telemetrum-doc.pdf and telemetrum-doc.html. + Finally you will have a couple control files that allow the ao-view + GUI-based program to appear in your menu of programs (under + the 'Internet' category). +

+ Both Telemetrum and TeleDongle can be directly communicated + with using USB ports. The first thing you should try after getting + both units plugged into to your computer's usb port(s) is to run + 'ao-list' from a terminal-window to see what port-device-name each + device has been assigned by the operating system. + You will need this information to access the devices via their + respective on-board firmware and data using other command line + programs in the AltOS software suite. +

+ To access the device's firmware for configuration you need a terminal + program such as you would use to talk to a modem. The software + authors prefer using the program 'cu' which comes from the UUCP package + on most Unix-like systems such as Linux. An example command line for + cu might be 'cu -l /dev/ttyACM0', substituting the correct number + indicated from running the + ao-list program. Another reasonable terminal program for Linux is + 'cutecom'. The default 'escape' + character used by CU (i.e. the character you use to + issue commands to cu itself instead of sending the command as input + to the connected device) is a '~'. You will need this for use in + only two different ways during normal operations. First is to exit + the program by sending a '~.' which is called a 'escape-disconnect' + and allows you to close-out from 'cu'. The + second use will be outlined later. +

+ Both TeleMetrum and TeleDongle share the concept of a two level + command set in their firmware. + The first layer has several single letter commands. Once + you are using 'cu' (or 'cutecom') sending (typing) a '?' + returns a full list of these + commands. The second level are configuration sub-commands accessed + using the 'c' command, for + instance typing 'c?' will give you this second level of commands + (all of which require the + letter 'c' to access). Please note that most configuration options + are stored only in DataFlash memory, and only TeleMetrum has this + memory to save the various values entered like the channel number + and your callsign when powered off. TeleDongle requires that you + set these each time you plug it in, which ao-view can help with. +

+ Try setting these config ('c' or second level menu) values. A good + place to start is by setting your call sign. By default, the boards + use 'N0CALL' which is cute, but not exactly legal! + Spend a few minutes getting comfortable with the units, their + firmware, and 'cu' (or possibly 'cutecom'). + For instance, try to send + (type) a 'c r 2' and verify the channel change by sending a 'c s'. + Verify you can connect and disconnect from the units while in your + terminal program by sending the escape-disconnect mentioned above. +

+ Note that the 'reboot' command, which is very useful on TeleMetrum, + will likely just cause problems with the dongle. The *correct* way + to reset the dongle is just to unplug and re-plug it. +

+ A fun thing to do at the launch site and something you can do while + learning how to use these units is to play with the rf-link access + of the TeleMetrum from the TeleDongle. Be aware that you *must* create + some physical separation between the devices, otherwise the link will + not function due to signal overload in the receivers in each device. +

+ Now might be a good time to take a break and read the rest of this + manual, particularly about the two "modes" that the TeleMetrum + can be placed in and how the position of the TeleMetrum when booting + up will determine whether the unit is in "pad" or "idle" mode. +

+ You can access a TeleMetrum in idle mode from the Teledongle's USB + connection using the rf link + by issuing a 'p' command to the TeleDongle. Practice connecting and + disconnecting ('~~' while using 'cu') from the TeleMetrum. If + you cannot escape out of the "p" command, (by using a '~~' when in + CU) then it is likely that your kernel has issues. Try a newer version. +

+ Using this rf link allows you to configure the TeleMetrum, test + fire e-matches and igniters from the flight line, check pyro-match + continuity and so forth. You can leave the unit turned on while it + is in 'idle mode' and then place the + rocket vertically on the launch pad, walk away and then issue a + reboot command. The TeleMetrum will reboot and start sending data + having changed to the "pad" mode. If the TeleDongle is not receiving + this data, you can disconnect 'cu' from the Teledongle using the + procedures mentioned above and THEN connect to the TeleDongle from + inside 'ao-view'. If this doesn't work, disconnect from the + TeleDongle, unplug it, and try again after plugging it back in. +

+ Eventually the GPS will find enough satellites, lock in on them, + and 'ao-view' will both auditorially announce and visually indicate + that GPS is ready. + Now you can launch knowing that you have a good data path and + good satellite lock for flight data and recovery. Remember + you MUST tell ao-view to connect to the TeleDongle explicitly in + order for ao-view to be able to receive data. +

+ Both RDF (radio direction finding) tones from the TeleMetrum and + GPS trekking data are available and together are very useful in + locating the rocket once it has landed. (The last good GPS data + received before touch-down will be on the data screen of 'ao-view'.) +

+ Once you have recovered the rocket you can download the eeprom + contents using either 'ao-dumplog' (or possibly 'ao-eeprom'), over + either a USB cable or over the radio link using TeleDongle. + And by following the man page for 'ao-postflight' you can create + various data output reports, graphs, and even kml data to see the + flight trajectory in google-earth. (Moving the viewing angle making + sure to connect the yellow lines while in google-earth is the proper + technique.) +

+ As for ao-view.... some things are in the menu but don't do anything + very useful. The developers have stopped working on ao-view to focus + on a new, cross-platform ground station program. So ao-view may or + may not be updated in the future. Mostly you just use + the Log and Device menus. It has a wonderful display of the incoming + flight data and I am sure you will enjoy what it has to say to you + once you enable the voice output! +

FAQ

+ The altimeter (TeleMetrum) seems to shut off when disconnected from the + computer. Make sure the battery is adequately charged. Remember the + unit will pull more power than the USB port can deliver before the + GPS enters "locked" mode. The battery charges best when TeleMetrum + is turned off. +

+ It's impossible to stop the TeleDongle when it's in "p" mode, I have + to unplug the USB cable? Make sure you have tried to "escape out" of + this mode. If this doesn't work the reboot procedure for the + TeleDongle *is* to simply unplug it. 'cu' however will retain it's + outgoing buffer IF your "escape out" ('~~') does not work. + At this point using either 'ao-view' (or possibly + 'cutemon') instead of 'cu' will 'clear' the issue and allow renewed + communication. +

+ The amber LED (on the TeleMetrum/altimeter) lights up when both + battery and USB are connected. Does this mean it's charging? + Yes, the yellow LED indicates the charging at the 'regular' rate. + If the led is out but the unit is still plugged into a USB port, + then the battery is being charged at a 'trickle' rate. +

+ There are no "dit-dah-dah-dit" sound like the manual mentions? + That's the "pad" mode. Weak batteries might be the problem. + It is also possible that the unit is horizontal and the output + is instead a "dit-dit" meaning 'idle'. +

+ It's unclear how to use 'ao-view' and other programs when 'cu' + is running. You cannot have more than one program connected to + the TeleDongle at one time without apparent data loss as the + incoming data will not make it to both programs intact. + Disconnect whatever programs aren't currently being used. +

+ How do I save flight data? + Live telemetry is written to file(s) whenever 'ao-view' is connected + to the TeleDongle. The file area defaults to ~/altos + but is easily changed using the menus in 'ao-view'. The files that + are written end in '.telem'. The after-flight + data-dumped files will end in .eeprom and represent continuous data + unlike the rf-linked .telem files that are subject to the + turnarounds/data-packaging time slots in the half-duplex rf data path. + See the above instructions on what and how to save the eeprom stored + data after physically retrieving your TeleMetrum. Make sure to save + the on-board data after each flight, as the current firmware will + over-write any previous flight data during a new flight. +

Chapter 3. Specifications

+ Recording altimeter for model rocketry. +
+ Supports dual deployment (can fire 2 ejection charges). +
+ 70cm ham-band transceiver for telemetry downlink. +
+ Barometric pressure sensor good to 45k feet MSL. +
+ 1-axis high-g accelerometer for motor characterization, capable of + +/- 50g using default part. +
+ On-board, integrated GPS receiver with 5hz update rate capability. +
+ On-board 1 megabyte non-volatile memory for flight data storage. +
+ USB interface for battery charging, configuration, and data recovery. +
+ Fully integrated support for LiPo rechargeable batteries. +
+ Uses LiPo to fire e-matches, support for optional separate pyro + battery if needed. +
+ 2.75 x 1 inch board designed to fit inside 29mm airframe coupler tube. +

Chapter 4. Handling Precautions

+ TeleMetrum is a sophisticated electronic device. When handled gently and + properly installed in an airframe, it will deliver impressive results. + However, like all electronic devices, there are some precautions you + must take. +

+ The Lithium Polymer rechargeable batteries used with TeleMetrum have an + extraordinary power density. This is great because we can fly with + much less battery mass than if we used alkaline batteries or previous + generation rechargeable batteries... but if they are punctured + or their leads are allowed to short, they can and will release their + energy very rapidly! + Thus we recommend that you take some care when handling our batteries + and consider giving them some extra protection in your airframe. We + often wrap them in suitable scraps of closed-cell packing foam before + strapping them down, for example. +

+ The TeleMetrum barometric sensor is sensitive to sunlight. In normal + mounting situations, it and all of the other surface mount components + are "down" towards whatever the underlying mounting surface is, so + this is not normally a problem. Please consider this, though, when + designing an installation, for example, in a 29mm airframe with a + see-through plastic payload bay. +

+ The TeleMetrum barometric sensor sampling port must be able to + "breathe", + both by not being covered by foam or tape or other materials that might + directly block the hole on the top of the sensor, but also by having a + suitable static vent to outside air. +

+ As with all other rocketry electronics, TeleMetrum must be protected + from exposure to corrosive motor exhaust and ejection charge gasses. +

Chapter 5. Hardware Overview

+ TeleMetrum is a 1 inch by 2.75 inch circuit board. It was designed to + fit inside coupler for 29mm airframe tubing, but using it in a tube that + small in diameter may require some creativity in mounting and wiring + to succeed! The default 1/4 + wave UHF wire antenna attached to the center of the nose-cone end of + the board is about 7 inches long, and wiring for a power switch and + the e-matches for apogee and main ejection charges depart from the + fin can end of the board. Given all this, an ideal "simple" avionics + bay for TeleMetrum should have at least 10 inches of interior length. +

+ A typical TeleMetrum installation using the on-board GPS antenna and + default wire UHF antenna involves attaching only a suitable + Lithium Polymer battery, a single pole switch for power on/off, and + two pairs of wires connecting e-matches for the apogee and main ejection + charges. +

+ By default, we use the unregulated output of the LiPo battery directly + to fire ejection charges. This works marvelously with standard + low-current e-matches like the J-Tek from MJG Technologies, and with + Quest Q2G2 igniters. However, if you + want or need to use a separate pyro battery, you can do so by adding + a second 2mm connector to position B2 on the board and cutting the + thick pcb trace connecting the LiPo battery to the pyro circuit between + the two silk screen marks on the surface mount side of the board shown + here [insert photo] +

+ We offer two choices of pyro and power switch connector, or you can + choose neither and solder wires directly to the board. All three choices + are reasonable depending on the constraints of your airframe. Our + favorite option when there is sufficient room above the board is to use + the Tyco pin header with polarization and locking. If you choose this + option, you crimp individual wires for the power switch and e-matches + into a mating connector, and installing and removing the TeleMetrum + board from an airframe is as easy as plugging or unplugging two + connectors. If the airframe will not support this much height or if + you want to be able to directly attach e-match leads to the board, we + offer a screw terminal block. This is very similar to what most other + altimeter vendors provide and so may be the most familiar option. + You'll need a very small straight blade screwdriver to connect + and disconnect the board in this case, such as you might find in a + jeweler's screwdriver set. Finally, you can forego both options and + solder wires directly to the board, which may be the best choice for + minimum diameter and/or minimum mass designs. +

+ For most airframes, the integrated GPS antenna and wire UHF antenna are + a great combination. However, if you are installing in a carbon-fiber + electronics bay which is opaque to RF signals, you may need to use + off-board external antennas instead. In this case, you can order + TeleMetrum with an SMA connector for the UHF antenna connection, and + you can unplug the integrated GPS antenna and select an appropriate + off-board GPS antenna with cable terminating in a U.FL connector. +

Chapter 6. Operation

Table of Contents

Configurable Parameters

Radio Channel
Apogee Delay
Main Deployment Altitude

Calibration

Radio Frequency
Accelerometer

Firmware Modes

+ The AltOS firmware build for TeleMetrum has two fundamental modes, + "idle" and "flight". Which of these modes the firmware operates in + is determined by the orientation of the rocket (well, actually the + board, of course...) at the time power is switched on. If the rocket + is "nose up", then TeleMetrum assumes it's on a rail or rod being + prepared for launch, so the firmware chooses flight mode. However, + if the rocket is more or less horizontal, the firmware instead enters + idle mode. +

+ At power on, you will hear three beeps + ("S" in Morse code for startup) and then a pause while + TeleMetrum completes initialization and self tests, and decides which + mode to enter next. +

+ In flight or "pad" mode, TeleMetrum turns on the GPS system, + engages the flight + state machine, goes into transmit-only mode on the RF link sending + telemetry, and waits for launch to be detected. Flight mode is + indicated by an audible "di-dah-dah-dit" ("P" for pad) on the + beeper, followed by + beeps indicating the state of the pyrotechnic igniter continuity. + One beep indicates apogee continuity, two beeps indicate + main continuity, three beeps indicate both apogee and main continuity, + and one longer "brap" sound indicates no continuity. For a dual + deploy flight, make sure you're getting three beeps before launching! + For apogee-only or motor eject flights, do what makes sense. +

+ In idle mode, you will hear an audible "di-dit" ("I" for idle), and + the normal flight state machine is disengaged, thus + no ejection charges will fire. TeleMetrum also listens on the RF + link when in idle mode for packet mode requests sent from TeleDongle. + Commands can be issued to a TeleMetrum in idle mode over either + USB or the RF link equivalently. + Idle mode is useful for configuring TeleMetrum, for extracting data + from the on-board storage chip after flight, and for ground testing + pyro charges. +

+ One "neat trick" of particular value when TeleMetrum is used with very + large airframes, is that you can power the board up while the rocket + is horizontal, such that it comes up in idle mode. Then you can + raise the airframe to launch position, use a TeleDongle to open + a packet connection, and issue a 'reset' command which will cause + TeleMetrum to reboot, realize it's now nose-up, and thus choose + flight mode. This is much safer than standing on the top step of a + rickety step-ladder or hanging off the side of a launch tower with + a screw-driver trying to turn on your avionics before installing + igniters! +

GPS

+ TeleMetrum includes a complete GPS receiver. See a later section for + a brief explanation of how GPS works that will help you understand + the information in the telemetry stream. The bottom line is that + the TeleMetrum GPS receiver needs to lock onto at least four + satellites to obtain a solid 3 dimensional position fix and know + what time it is! +

+ TeleMetrum provides backup power to the GPS chip any time a LiPo + battery is connected. This allows the receiver to "warm start" on + the launch rail much faster than if every power-on were a "cold start" + for the GPS receiver. In typical operations, powering up TeleMetrum + on the flight line in idle mode while performing final airframe + preparation will be sufficient to allow the GPS receiver to cold + start and acquire lock. Then the board can be powered down during + RSO review and installation on a launch rod or rail. When the board + is turned back on, the GPS system should lock very quickly, typically + long before igniter installation and return to the flight line are + complete. +

Ground Testing

+ An important aspect of preparing a rocket using electronic deployment + for flight is ground testing the recovery system. Thanks + to the bi-directional RF link central to the Altus Metrum system, + this can be accomplished in a TeleMetrum-equipped rocket without as + much work as you may be accustomed to with other systems. It can + even be fun! +

+ Just prep the rocket for flight, then power up TeleMetrum while the + airframe is horizontal. This will cause the firmware to go into + "idle" mode, in which the normal flight state machine is disabled and + charges will not fire without manual command. Then, establish an + RF packet connection from a TeleDongle-equipped computer using the + P command from a safe distance. You can now command TeleMetrum to + fire the apogee or main charges to complete your testing. +

+ In order to reduce the chance of accidental firing of pyrotechnic + charges, the command to fire a charge is intentionally somewhat + difficult to type, and the built-in help is slightly cryptic to + prevent accidental echoing of characters from the help text back at + the board from firing a charge. The command to fire the apogee + drogue charge is 'i DoIt drogue' and the command to fire the main + charge is 'i DoIt main'. +

Radio Link

+ The chip our boards are based on incorporates an RF transceiver, but + it's not a full duplex system... each end can only be transmitting or + receiving at any given moment. So we had to decide how to manage the + link. +

+ By design, TeleMetrum firmware listens for an RF connection when + it's in "idle mode" (turned on while the rocket is horizontal), which + allows us to use the RF link to configure the rocket, do things like + ejection tests, and extract data after a flight without having to + crack open the airframe. However, when the board is in "flight + mode" (turned on when the rocket is vertical) the TeleMetrum only + transmits and doesn't listen at all. That's because we want to put + ultimate priority on event detection and getting telemetry out of + the rocket and out over + the RF link in case the rocket crashes and we aren't able to extract + data later... +

+ We don't use a 'normal packet radio' mode because they're just too + inefficient. The GFSK modulation we use is just FSK with the + baseband pulses passed through a + Gaussian filter before they go into the modulator to limit the + transmitted bandwidth. When combined with the hardware forward error + correction support in the cc1111 chip, this allows us to have a very + robust 38.4 kilobit data link with only 10 milliwatts of transmit power, + a whip antenna in the rocket, and a hand-held Yagi on the ground. We've + had flights to above 21k feet AGL with good reception, and calculations + suggest we should be good to well over 40k feet AGL with a 5-element yagi on + the ground. We hope to fly boards to higher altitudes soon, and would + of course appreciate customer feedback on performance in higher + altitude flights! +

Configurable Parameters

+ Configuring a TeleMetrum board for flight is very simple. Because we + have both acceleration and pressure sensors, there is no need to set + a "mach delay", for example. The few configurable parameters can all + be set using a simple terminal program over the USB port or RF link + via TeleDongle. +

Radio Channel

+ Our firmware supports 10 channels. The default channel 0 corresponds + to a center frequency of 434.550 Mhz, and channels are spaced every + 100 khz. Thus, channel 1 is 434.650 Mhz, and channel 9 is 435.550 Mhz. + At any given launch, we highly recommend coordinating who will use + each channel and when to avoid interference. And of course, both + TeleMetrum and TeleDongle must be configured to the same channel to + successfully communicate with each other. +

+ To set the radio channel, use the 'c r' command, like 'c r 3' to set + channel 3. + As with all 'c' sub-commands, follow this with a 'c w' to write the + change to the parameter block in the on-board DataFlash chip on + your TeleMetrum board if you want the change to stay in place across reboots. +

Apogee Delay

+ Apogee delay is the number of seconds after TeleMetrum detects flight + apogee that the drogue charge should be fired. In most cases, this + should be left at the default of 0. However, if you are flying + redundant electronics such as for an L3 certification, you may wish + to set one of your altimeters to a positive delay so that both + primary and backup pyrotechnic charges do not fire simultaneously. +

+ To set the apogee delay, use the [FIXME] command. + As with all 'c' sub-commands, follow this with a 'c w' to write the + change to the parameter block in the on-board DataFlash chip. +

+ Please note that the TeleMetrum apogee detection algorithm always + fires a fraction of a second *after* apogee. If you are also flying + an altimeter like the PerfectFlite MAWD, which only supports selecting + 0 or 1 seconds of apogee delay, you may wish to set the MAWD to 0 + seconds delay and set the TeleMetrum to fire your backup 2 or 3 + seconds later to avoid any chance of both charges firing + simultaneously. We've flown several airframes this way quite happily, + including Keith's successful L3 cert. +

Main Deployment Altitude

+ By default, TeleMetrum will fire the main deployment charge at an + elevation of 250 meters (about 820 feet) above ground. We think this + is a good elevation for most airframes, but feel free to change this + to suit. In particular, if you are flying two altimeters, you may + wish to set the + deployment elevation for the backup altimeter to be something lower + than the primary so that both pyrotechnic charges don't fire + simultaneously. +

+ To set the main deployment altitude, use the [FIXME] command. + As with all 'c' sub-commands, follow this with a 'c w' to write the + change to the parameter block in the on-board DataFlash chip. +

Calibration

+ There are only two calibrations required for a TeleMetrum board, and + only one for TeleDongle. +

Radio Frequency

+ The radio frequency is synthesized from a clock based on the 48 Mhz + crystal on the board. The actual frequency of this oscillator must be + measured to generate a calibration constant. While our GFSK modulation + bandwidth is wide enough to allow boards to communicate even when + their oscillators are not on exactly the same frequency, performance + is best when they are closely matched. + Radio frequency calibration requires a calibrated frequency counter. + Fortunately, once set, the variation in frequency due to aging and + temperature changes is small enough that re-calibration by customers + should generally not be required. +

+ To calibrate the radio frequency, connect the UHF antenna port to a + frequency counter, set the board to channel 0, and use the 'C' + command to generate a CW carrier. Wait for the transmitter temperature + to stabilize and the frequency to settle down. + Then, divide 434.550 Mhz by the + measured frequency and multiply by the current radio cal value show + in the 'c s' command. For an unprogrammed board, the default value + is 1186611. Take the resulting integer and program it using the 'c f' + command. Testing with the 'C' command again should show a carrier + within a few tens of Hertz of the intended frequency. + As with all 'c' sub-commands, follow this with a 'c w' to write the + change to the parameter block in the on-board DataFlash chip. +

Accelerometer

+ The accelerometer we use has its own 5 volt power supply and + the output must be passed through a resistive voltage divider to match + the input of our 3.3 volt ADC. This means that unlike the barometric + sensor, the output of the acceleration sensor is not ratiometric to + the ADC converter, and calibration is required. We also support the + use of any of several accelerometers from a Freescale family that + includes at least +/- 40g, 50g, 100g, and 200g parts. Using gravity, + a simple 2-point calibration yields acceptable results capturing both + the different sensitivities and ranges of the different accelerometer + parts and any variation in power supply voltages or resistor values + in the divider network. +

+ To calibrate the acceleration sensor, use the 'c a 0' command. You + will be prompted to orient the board vertically with the UHF antenna + up and press a key, then to orient the board vertically with the + UHF antenna down and press a key. + As with all 'c' sub-commands, follow this with a 'c w' to write the + change to the parameter block in the on-board DataFlash chip. +

+ The +1g and -1g calibration points are included in each telemetry + frame and are part of the header extracted by ao-dumplog after flight. + Note that we always store and return raw ADC samples for each + sensor... nothing is permanently "lost" or "damaged" if the + calibration is poor. +

Chapter 7. Updating Device Firmware

Table of Contents

Updating TeleMetrum Firmware
Updating TeleDongle Firmware

+ The big conceptual thing to realize is that you have to use a + TeleDongle as a programmer to update a TeleMetrum, and vice versa. + Due to limited memory resources in the cc1111, we don't support + programming either unit directly over USB. +

+ You may wish to begin by ensuring you have current firmware images. + These are distributed as part of the AltOS software bundle that + also includes the AltosUI ground station program. Newer ground + station versions typically work fine with older firmware versions, + so you don't need to update your devices just to try out new + software features. You can always download the most recent + version from http://www.altusmetrum.org/AltOS/. +

+ We recommend updating TeleMetrum first, before updating TeleDongle. +

Updating TeleMetrum Firmware

+ Find the 'programming cable' that you got as part of the starter + kit, that has a red 8-pin MicroMaTch connector on one end and a + red 4-pin MicroMaTch connector on the other end. +
+ Take the 2 screws out of the TeleDongle case to get access + to the circuit board. +
+ Plug the 8-pin end of the programming cable to the + matching connector on the TeleDongle, and the 4-pin end to the + matching connector on the TeleMetrum. +
+ Attach a battery to the TeleMetrum board. +
+ Plug the TeleDongle into your computer's USB port, and power + up the TeleMetrum. +
+ Run AltosUI, and select 'Flash Image' from the File menu. +
+ Pick the TeleDongle device from the list, identifying it as the + programming device. +
+ Select the image you want put on the TeleMetrum, which should have a + name in the form telemetrum-v1.0-0.7.1.ihx. It should be visible + in the default directory, if not you may have to poke around + your system to find it. +
+ Make sure the configuration parameters are reasonable + looking. If the serial number and/or RF configuration + values aren't right, you'll need to change them. +
+ Hit the 'OK' button and the software should proceed to flash + the TeleMetrum with new firmware, showing a progress bar. +
+ Confirm that the TeleMetrum board seems to have updated ok, which you + can do by plugging in to it over USB and using a terminal program + to connect to the board and issue the 'v' command to check + the version, etc. +
+ If something goes wrong, give it another try. +

Updating TeleDongle Firmware

+ Updating TeleDongle's firmware is just like updating TeleMetrum + firmware, but you switch which board is the programmer and which + is the programming target. +

+ Find the 'programming cable' that you got as part of the starter + kit, that has a red 8-pin MicroMaTch connector on one end and a + red 4-pin MicroMaTch connector on the other end. +
+ Find the USB cable that you got as part of the starter kit, and + plug the "mini" end in to the mating connector on TeleMetrum. +
+ Take the 2 screws out of the TeleDongle case to get access + to the circuit board. +
+ Plug the 8-pin end of the programming cable to the (latching) + matching connector on the TeleMetrum, and the 4-pin end to the + matching connector on the TeleDongle. +
+ Attach a battery to the TeleMetrum board. +
+ Plug both TeleMetrum and TeleDongle into your computer's USB + ports, and power up the TeleMetrum. +
+ Run AltosUI, and select 'Flash Image' from the File menu. +
+ Pick the TeleMongle device from the list, identifying it as the + programming device. +
+ Select the image you want put on the TeleDongle, which should have a + name in the form teledongle-v0.2-0.7.1.ihx. It should be visible + in the default directory, if not you may have to poke around + your system to find it. +
+ Make sure the configuration parameters are reasonable + looking. If the serial number and/or RF configuration + values aren't right, you'll need to change them. The TeleDongle + serial number is on the "bottom" of the circuit board, and can + usually be read through the translucent blue plastic case without + needing to remove the board from the case. +
+ Hit the 'OK' button and the software should proceed to flash + the TeleDongle with new firmware, showing a progress bar. +
+ Confirm that the TeleDongle board seems to have updated ok, which you + can do by plugging in to it over USB and using a terminal program + to connect to the board and issue the 'v' command to check + the version, etc. Once you're happy, remove the programming cable + and put the cover back on the TeleDongle. +
+ If something goes wrong, give it another try. +

+ Be careful removing the programming cable from the locking 8-pin + connector on TeleMetrum. You'll need a fingernail or perhaps a thin + screwdriver or knife blade to gently pry the locking ears out + slightly to extract the connector. We used a locking connector on + TeleMetrum to help ensure that the cabling to companion boards + used in a rocket don't ever come loose accidentally in flight. +

Chapter 8. Using Altus Metrum Products

Table of Contents

Being Legal

In the Rocket
On the Ground
Data Analysis
Future Plans

+ How GPS Works +

Being Legal

+ First off, in the US, you need an [amateur radio license](../Radio) or + other authorization to legally operate the radio transmitters that are part + of our products. +

In the Rocket

+ In the rocket itself, you just need a [TeleMetrum](../TeleMetrum) board and + a LiPo rechargeable battery. An 860mAh battery weighs less than a 9V + alkaline battery, and will run a [TeleMetrum](../TeleMetrum) for hours. +

+ By default, we ship TeleMetrum with a simple wire antenna. If your + electronics bay or the airframe it resides within is made of carbon fiber, + which is opaque to RF signals, you may choose to have an SMA connector + installed so that you can run a coaxial cable to an antenna mounted + elsewhere in the rocket. +

On the Ground

+ To receive the data stream from the rocket, you need an antenna and short + feedline connected to one of our [TeleDongle](../TeleDongle) units. The + TeleDongle in turn plugs directly into the USB port on a notebook + computer. Because TeleDongle looks like a simple serial port, your computer + does not require special device drivers... just plug it in. +

+ Right now, all of our application software is written for Linux. However, + because we understand that many people run Windows or MacOS, we are working + on a new ground station program written in Java that should work on all + operating systems. +

+ After the flight, you can use the RF link to extract the more detailed data + logged in the rocket, or you can use a mini USB cable to plug into the + TeleMetrum board directly. Pulling out the data without having to open up + the rocket is pretty cool! A USB cable is also how you charge the LiPo + battery, so you'll want one of those anyway... the same cable used by lots + of digital cameras and other modern electronic stuff will work fine. +

+ If your rocket lands out of sight, you may enjoy having a hand-held GPS + receiver, so that you can put in a waypoint for the last reported rocket + position before touch-down. This makes looking for your rocket a lot like + Geo-Cacheing... just go to the waypoint and look around starting from there. +

+ You may also enjoy having a ham radio "HT" that covers the 70cm band... you + can use that with your antenna to direction-find the rocket on the ground + the same way you can use a Walston or Beeline tracker. This can be handy + if the rocket is hiding in sage brush or a tree, or if the last GPS position + doesn't get you close enough because the rocket dropped into a canyon, or + the wind is blowing it across a dry lake bed, or something like that... Keith + and Bdale both currently own and use the Yaesu VX-7R at launches. +

+ So, to recap, on the ground the hardware you'll need includes: +

+ an antenna and feedline +
+ a TeleDongle +
+ a notebook computer +
+ optionally, a handheld GPS receiver +
+ optionally, an HT or receiver covering 435 Mhz +

+ The best hand-held commercial directional antennas we've found for radio + direction finding rockets are from + + Arrow Antennas. + + The 440-3 and 440-5 are both good choices for finding a + TeleMetrum-equipped rocket when used with a suitable 70cm HT. +

Data Analysis

+ Our software makes it easy to log the data from each flight, both the + telemetry received over the RF link during the flight itself, and the more + complete data log recorded in the DataFlash memory on the TeleMetrum + board. Once this data is on your computer, our postflight tools make it + easy to quickly get to the numbers everyone wants, like apogee altitude, + max acceleration, and max velocity. You can also generate and view a + standard set of plots showing the altitude, acceleration, and + velocity of the rocket during flight. And you can even export a data file + useable with Google Maps and Google Earth for visualizing the flight path + in two or three dimensions! +

+ Our ultimate goal is to emit a set of files for each flight that can be + published as a web page per flight, or just viewed on your local disk with + a web browser. +

Future Plans

+ In the future, we intend to offer "companion boards" for the rocket that will + plug in to TeleMetrum to collect additional data, provide more pyro channels, + and so forth. A reference design for a companion board will be documented + soon, and will be compatible with open source Arduino programming tools. +

+ We are also working on the design of a hand-held ground terminal that will + allow monitoring the rocket's status, collecting data during flight, and + logging data after flight without the need for a notebook computer on the + flight line. Particularly since it is so difficult to read most notebook + screens in direct sunlight, we think this will be a great thing to have. +

+ Because all of our work is open, both the hardware designs and the software, + if you have some great idea for an addition to the current Altus Metrum family, + feel free to dive in and help! Or let us know what you'd like to see that + we aren't already working on, and maybe we'll get excited about it too... +

+ How GPS Works +

+ Placeholder. +

TeleMetrum

Owner's Manual for the TeleMetrum System

Bdale Garbee

Keith Packard

- This document is released under the terms of the - - Creative Commons ShareAlike 3.0 - - license. -

Revision History
Revision 0.3	12 November 2010
- Add instructions for re-flashing devices using AltosUI -
Revision 0.2	18 July 2010
Significant update
Revision 0.1	30 March 2010
Initial content

Chapter 1. Introduction and Overview

- Welcome to the Altus Metrum community! Our circuits and software reflect - our passion for both hobby rocketry and Free Software. We hope their - capabilities and performance will delight you in every way, but by - releasing all of our hardware and software designs under open licenses, - we also hope to empower you to take as active a role in our collective - future as you wish! -

- The focal point of our community is TeleMetrum, a dual deploy altimeter - with fully integrated GPS and radio telemetry as standard features, and - a "companion interface" that will support optional capabilities in the - future. -

- Complementing TeleMetrum is TeleDongle, a USB to RF interface for - communicating with TeleMetrum. Combined with your choice of antenna and - notebook computer, TeleDongle and our associated user interface software - form a complete ground station capable of logging and displaying in-flight - telemetry, aiding rocket recovery, then processing and archiving flight - data for analysis and review. -

- More products will be added to the Altus Metrum family over time, and - we currently envision that this will be a single, comprehensive manual - for the entire product family. -

Chapter 2. Getting Started

Table of Contents

FAQ

- This chapter began as "The Mere-Mortals Quick Start/Usage Guide to - the Altus Metrum Starter Kit" by Bob Finch, W9YA, NAR 12965, TRA 12350, - w9ya@amsat.org. Bob was one of our first customers for a production - TeleMetrum, and the enthusiasm that led to his contribution of this - section is immensely gratifying and highy appreciated! -

- The first thing to do after you check the inventory of parts in your - "starter kit" is to charge the battery by plugging it into the - corresponding socket of the TeleMetrum and then using the USB A to B - cable to plug the Telemetrum into your computer's USB socket. The - TeleMetrum circuitry will charge the battery whenever it is plugged - into the usb socket. The TeleMetrum's on-off switch does NOT control - the charging circuitry. When the GPS chip is initially searching for - satellites, the unit will pull more current than it can pull from the - usb port, so the battery must be plugged in order to get a good - satellite lock. Once GPS is locked the current consumption goes back - down enough to enable charging while - running. So it's a good idea to fully charge the battery as your - first item of business so there is no issue getting and maintaining - satellite lock. The yellow charge indicator led will go out when the - battery is nearly full and the charger goes to trickle charge. -

- The other active device in the starter kit is the half-duplex TeleDongle - rf link. If you plug it in to your computer it should "just work", - showing up as a serial port device. If you are using Linux and are - having problems, try moving to a fresher kernel (2.6.33 or newer), as - there were some ugly USB serial driver bugs in earlier versions. -

- Next you should obtain and install the AltOS utilities. The first - generation sofware was written for Linux only. New software is coming - soon that will also run on Windows and Mac. For now, we'll concentrate - on Linux. If you are using Debian, an 'altos' package already exists, - see http://altusmetrum.org/AltOS for details on how to install it. - User-contributed directions for building packages on ArchLinux may be - found in the contrib/arch-linux directory as PKGBUILD files. - Between the debian/rules file and the PKGBUILD files in - contrib, you should find enough information to learn how to build the - software for any other version of Linux. -

- When you have successfully installed the software suite (either from - compiled source code or as the pre-built Debian package) you will - have 10 or so executable programs all of which have names beginning - with 'ao-'. - ('ao-view' is the lone GUI-based program, the rest are command-line - oriented.) You will also have man pages, that give you basic info - on each program. - You will also get this documentation in two file types in the doc/ - directory, telemetrum-doc.pdf and telemetrum-doc.html. - Finally you will have a couple control files that allow the ao-view - GUI-based program to appear in your menu of programs (under - the 'Internet' category). -

- Both Telemetrum and TeleDongle can be directly communicated - with using USB ports. The first thing you should try after getting - both units plugged into to your computer's usb port(s) is to run - 'ao-list' from a terminal-window to see what port-device-name each - device has been assigned by the operating system. - You will need this information to access the devices via their - respective on-board firmware and data using other command line - programs in the AltOS software suite. -

- To access the device's firmware for configuration you need a terminal - program such as you would use to talk to a modem. The software - authors prefer using the program 'cu' which comes from the UUCP package - on most Unix-like systems such as Linux. An example command line for - cu might be 'cu -l /dev/ttyACM0', substituting the correct number - indicated from running the - ao-list program. Another reasonable terminal program for Linux is - 'cutecom'. The default 'escape' - character used by CU (i.e. the character you use to - issue commands to cu itself instead of sending the command as input - to the connected device) is a '~'. You will need this for use in - only two different ways during normal operations. First is to exit - the program by sending a '~.' which is called a 'escape-disconnect' - and allows you to close-out from 'cu'. The - second use will be outlined later. -

- Both TeleMetrum and TeleDongle share the concept of a two level - command set in their firmware. - The first layer has several single letter commands. Once - you are using 'cu' (or 'cutecom') sending (typing) a '?' - returns a full list of these - commands. The second level are configuration sub-commands accessed - using the 'c' command, for - instance typing 'c?' will give you this second level of commands - (all of which require the - letter 'c' to access). Please note that most configuration options - are stored only in DataFlash memory, and only TeleMetrum has this - memory to save the various values entered like the channel number - and your callsign when powered off. TeleDongle requires that you - set these each time you plug it in, which ao-view can help with. -

- Try setting these config ('c' or second level menu) values. A good - place to start is by setting your call sign. By default, the boards - use 'N0CALL' which is cute, but not exactly legal! - Spend a few minutes getting comfortable with the units, their - firmware, and 'cu' (or possibly 'cutecom'). - For instance, try to send - (type) a 'c r 2' and verify the channel change by sending a 'c s'. - Verify you can connect and disconnect from the units while in your - terminal program by sending the escape-disconnect mentioned above. -

- Note that the 'reboot' command, which is very useful on TeleMetrum, - will likely just cause problems with the dongle. The *correct* way - to reset the dongle is just to unplug and re-plug it. -

- A fun thing to do at the launch site and something you can do while - learning how to use these units is to play with the rf-link access - of the TeleMetrum from the TeleDongle. Be aware that you *must* create - some physical separation between the devices, otherwise the link will - not function due to signal overload in the receivers in each device. -

- Now might be a good time to take a break and read the rest of this - manual, particularly about the two "modes" that the TeleMetrum - can be placed in and how the position of the TeleMetrum when booting - up will determine whether the unit is in "pad" or "idle" mode. -

- You can access a TeleMetrum in idle mode from the Teledongle's USB - connection using the rf link - by issuing a 'p' command to the TeleDongle. Practice connecting and - disconnecting ('~~' while using 'cu') from the TeleMetrum. If - you cannot escape out of the "p" command, (by using a '~~' when in - CU) then it is likely that your kernel has issues. Try a newer version. -

- Using this rf link allows you to configure the TeleMetrum, test - fire e-matches and igniters from the flight line, check pyro-match - continuity and so forth. You can leave the unit turned on while it - is in 'idle mode' and then place the - rocket vertically on the launch pad, walk away and then issue a - reboot command. The TeleMetrum will reboot and start sending data - having changed to the "pad" mode. If the TeleDongle is not receiving - this data, you can disconnect 'cu' from the Teledongle using the - procedures mentioned above and THEN connect to the TeleDongle from - inside 'ao-view'. If this doesn't work, disconnect from the - TeleDongle, unplug it, and try again after plugging it back in. -

- Eventually the GPS will find enough satellites, lock in on them, - and 'ao-view' will both auditorially announce and visually indicate - that GPS is ready. - Now you can launch knowing that you have a good data path and - good satellite lock for flight data and recovery. Remember - you MUST tell ao-view to connect to the TeleDongle explicitly in - order for ao-view to be able to receive data. -

- Both RDF (radio direction finding) tones from the TeleMetrum and - GPS trekking data are available and together are very useful in - locating the rocket once it has landed. (The last good GPS data - received before touch-down will be on the data screen of 'ao-view'.) -

- Once you have recovered the rocket you can download the eeprom - contents using either 'ao-dumplog' (or possibly 'ao-eeprom'), over - either a USB cable or over the radio link using TeleDongle. - And by following the man page for 'ao-postflight' you can create - various data output reports, graphs, and even kml data to see the - flight trajectory in google-earth. (Moving the viewing angle making - sure to connect the yellow lines while in google-earth is the proper - technique.) -

- As for ao-view.... some things are in the menu but don't do anything - very useful. The developers have stopped working on ao-view to focus - on a new, cross-platform ground station program. So ao-view may or - may not be updated in the future. Mostly you just use - the Log and Device menus. It has a wonderful display of the incoming - flight data and I am sure you will enjoy what it has to say to you - once you enable the voice output! -

FAQ

- The altimeter (TeleMetrum) seems to shut off when disconnected from the - computer. Make sure the battery is adequately charged. Remember the - unit will pull more power than the USB port can deliver before the - GPS enters "locked" mode. The battery charges best when TeleMetrum - is turned off. -

- It's impossible to stop the TeleDongle when it's in "p" mode, I have - to unplug the USB cable? Make sure you have tried to "escape out" of - this mode. If this doesn't work the reboot procedure for the - TeleDongle *is* to simply unplug it. 'cu' however will retain it's - outgoing buffer IF your "escape out" ('~~') does not work. - At this point using either 'ao-view' (or possibly - 'cutemon') instead of 'cu' will 'clear' the issue and allow renewed - communication. -

- The amber LED (on the TeleMetrum/altimeter) lights up when both - battery and USB are connected. Does this mean it's charging? - Yes, the yellow LED indicates the charging at the 'regular' rate. - If the led is out but the unit is still plugged into a USB port, - then the battery is being charged at a 'trickle' rate. -

- There are no "dit-dah-dah-dit" sound like the manual mentions? - That's the "pad" mode. Weak batteries might be the problem. - It is also possible that the unit is horizontal and the output - is instead a "dit-dit" meaning 'idle'. -

- It's unclear how to use 'ao-view' and other programs when 'cu' - is running. You cannot have more than one program connected to - the TeleDongle at one time without apparent data loss as the - incoming data will not make it to both programs intact. - Disconnect whatever programs aren't currently being used. -

- How do I save flight data? - Live telemetry is written to file(s) whenever 'ao-view' is connected - to the TeleDongle. The file area defaults to ~/altos - but is easily changed using the menus in 'ao-view'. The files that - are written end in '.telem'. The after-flight - data-dumped files will end in .eeprom and represent continuous data - unlike the rf-linked .telem files that are subject to the - turnarounds/data-packaging time slots in the half-duplex rf data path. - See the above instructions on what and how to save the eeprom stored - data after physically retrieving your TeleMetrum. Make sure to save - the on-board data after each flight, as the current firmware will - over-write any previous flight data during a new flight. -

Chapter 3. Specifications

- Recording altimeter for model rocketry. -
- Supports dual deployment (can fire 2 ejection charges). -
- 70cm ham-band transceiver for telemetry downlink. -
- Barometric pressure sensor good to 45k feet MSL. -
- 1-axis high-g accelerometer for motor characterization, capable of - +/- 50g using default part. -
- On-board, integrated GPS receiver with 5hz update rate capability. -
- On-board 1 megabyte non-volatile memory for flight data storage. -
- USB interface for battery charging, configuration, and data recovery. -
- Fully integrated support for LiPo rechargeable batteries. -
- Uses LiPo to fire e-matches, support for optional separate pyro - battery if needed. -
- 2.75 x 1 inch board designed to fit inside 29mm airframe coupler tube. -

Chapter 4. Handling Precautions

- TeleMetrum is a sophisticated electronic device. When handled gently and - properly installed in an airframe, it will deliver impressive results. - However, like all electronic devices, there are some precautions you - must take. -

- The Lithium Polymer rechargeable batteries used with TeleMetrum have an - extraordinary power density. This is great because we can fly with - much less battery mass than if we used alkaline batteries or previous - generation rechargeable batteries... but if they are punctured - or their leads are allowed to short, they can and will release their - energy very rapidly! - Thus we recommend that you take some care when handling our batteries - and consider giving them some extra protection in your airframe. We - often wrap them in suitable scraps of closed-cell packing foam before - strapping them down, for example. -

- The TeleMetrum barometric sensor is sensitive to sunlight. In normal - mounting situations, it and all of the other surface mount components - are "down" towards whatever the underlying mounting surface is, so - this is not normally a problem. Please consider this, though, when - designing an installation, for example, in a 29mm airframe with a - see-through plastic payload bay. -

- The TeleMetrum barometric sensor sampling port must be able to - "breathe", - both by not being covered by foam or tape or other materials that might - directly block the hole on the top of the sensor, but also by having a - suitable static vent to outside air. -

- As with all other rocketry electronics, TeleMetrum must be protected - from exposure to corrosive motor exhaust and ejection charge gasses. -

Chapter 5. Hardware Overview

- TeleMetrum is a 1 inch by 2.75 inch circuit board. It was designed to - fit inside coupler for 29mm airframe tubing, but using it in a tube that - small in diameter may require some creativity in mounting and wiring - to succeed! The default 1/4 - wave UHF wire antenna attached to the center of the nose-cone end of - the board is about 7 inches long, and wiring for a power switch and - the e-matches for apogee and main ejection charges depart from the - fin can end of the board. Given all this, an ideal "simple" avionics - bay for TeleMetrum should have at least 10 inches of interior length. -

- A typical TeleMetrum installation using the on-board GPS antenna and - default wire UHF antenna involves attaching only a suitable - Lithium Polymer battery, a single pole switch for power on/off, and - two pairs of wires connecting e-matches for the apogee and main ejection - charges. -

- By default, we use the unregulated output of the LiPo battery directly - to fire ejection charges. This works marvelously with standard - low-current e-matches like the J-Tek from MJG Technologies, and with - Quest Q2G2 igniters. However, if you - want or need to use a separate pyro battery, you can do so by adding - a second 2mm connector to position B2 on the board and cutting the - thick pcb trace connecting the LiPo battery to the pyro circuit between - the two silk screen marks on the surface mount side of the board shown - here [insert photo] -

- We offer two choices of pyro and power switch connector, or you can - choose neither and solder wires directly to the board. All three choices - are reasonable depending on the constraints of your airframe. Our - favorite option when there is sufficient room above the board is to use - the Tyco pin header with polarization and locking. If you choose this - option, you crimp individual wires for the power switch and e-matches - into a mating connector, and installing and removing the TeleMetrum - board from an airframe is as easy as plugging or unplugging two - connectors. If the airframe will not support this much height or if - you want to be able to directly attach e-match leads to the board, we - offer a screw terminal block. This is very similar to what most other - altimeter vendors provide and so may be the most familiar option. - You'll need a very small straight blade screwdriver to connect - and disconnect the board in this case, such as you might find in a - jeweler's screwdriver set. Finally, you can forego both options and - solder wires directly to the board, which may be the best choice for - minimum diameter and/or minimum mass designs. -

- For most airframes, the integrated GPS antenna and wire UHF antenna are - a great combination. However, if you are installing in a carbon-fiber - electronics bay which is opaque to RF signals, you may need to use - off-board external antennas instead. In this case, you can order - TeleMetrum with an SMA connector for the UHF antenna connection, and - you can unplug the integrated GPS antenna and select an appropriate - off-board GPS antenna with cable terminating in a U.FL connector. -

Chapter 6. Operation

Table of Contents

Configurable Parameters

Radio Channel
Apogee Delay
Main Deployment Altitude

Calibration

Radio Frequency
Accelerometer

Firmware Modes

- The AltOS firmware build for TeleMetrum has two fundamental modes, - "idle" and "flight". Which of these modes the firmware operates in - is determined by the orientation of the rocket (well, actually the - board, of course...) at the time power is switched on. If the rocket - is "nose up", then TeleMetrum assumes it's on a rail or rod being - prepared for launch, so the firmware chooses flight mode. However, - if the rocket is more or less horizontal, the firmware instead enters - idle mode. -

- At power on, you will hear three beeps - ("S" in Morse code for startup) and then a pause while - TeleMetrum completes initialization and self tests, and decides which - mode to enter next. -

- In flight or "pad" mode, TeleMetrum turns on the GPS system, - engages the flight - state machine, goes into transmit-only mode on the RF link sending - telemetry, and waits for launch to be detected. Flight mode is - indicated by an audible "di-dah-dah-dit" ("P" for pad) on the - beeper, followed by - beeps indicating the state of the pyrotechnic igniter continuity. - One beep indicates apogee continuity, two beeps indicate - main continuity, three beeps indicate both apogee and main continuity, - and one longer "brap" sound indicates no continuity. For a dual - deploy flight, make sure you're getting three beeps before launching! - For apogee-only or motor eject flights, do what makes sense. -

- In idle mode, you will hear an audible "di-dit" ("I" for idle), and - the normal flight state machine is disengaged, thus - no ejection charges will fire. TeleMetrum also listens on the RF - link when in idle mode for packet mode requests sent from TeleDongle. - Commands can be issued to a TeleMetrum in idle mode over either - USB or the RF link equivalently. - Idle mode is useful for configuring TeleMetrum, for extracting data - from the on-board storage chip after flight, and for ground testing - pyro charges. -

- One "neat trick" of particular value when TeleMetrum is used with very - large airframes, is that you can power the board up while the rocket - is horizontal, such that it comes up in idle mode. Then you can - raise the airframe to launch position, use a TeleDongle to open - a packet connection, and issue a 'reset' command which will cause - TeleMetrum to reboot, realize it's now nose-up, and thus choose - flight mode. This is much safer than standing on the top step of a - rickety step-ladder or hanging off the side of a launch tower with - a screw-driver trying to turn on your avionics before installing - igniters! -

GPS

- TeleMetrum includes a complete GPS receiver. See a later section for - a brief explanation of how GPS works that will help you understand - the information in the telemetry stream. The bottom line is that - the TeleMetrum GPS receiver needs to lock onto at least four - satellites to obtain a solid 3 dimensional position fix and know - what time it is! -

- TeleMetrum provides backup power to the GPS chip any time a LiPo - battery is connected. This allows the receiver to "warm start" on - the launch rail much faster than if every power-on were a "cold start" - for the GPS receiver. In typical operations, powering up TeleMetrum - on the flight line in idle mode while performing final airframe - preparation will be sufficient to allow the GPS receiver to cold - start and acquire lock. Then the board can be powered down during - RSO review and installation on a launch rod or rail. When the board - is turned back on, the GPS system should lock very quickly, typically - long before igniter installation and return to the flight line are - complete. -

Ground Testing

- An important aspect of preparing a rocket using electronic deployment - for flight is ground testing the recovery system. Thanks - to the bi-directional RF link central to the Altus Metrum system, - this can be accomplished in a TeleMetrum-equipped rocket without as - much work as you may be accustomed to with other systems. It can - even be fun! -

- Just prep the rocket for flight, then power up TeleMetrum while the - airframe is horizontal. This will cause the firmware to go into - "idle" mode, in which the normal flight state machine is disabled and - charges will not fire without manual command. Then, establish an - RF packet connection from a TeleDongle-equipped computer using the - P command from a safe distance. You can now command TeleMetrum to - fire the apogee or main charges to complete your testing. -

- In order to reduce the chance of accidental firing of pyrotechnic - charges, the command to fire a charge is intentionally somewhat - difficult to type, and the built-in help is slightly cryptic to - prevent accidental echoing of characters from the help text back at - the board from firing a charge. The command to fire the apogee - drogue charge is 'i DoIt drogue' and the command to fire the main - charge is 'i DoIt main'. -

Radio Link

- The chip our boards are based on incorporates an RF transceiver, but - it's not a full duplex system... each end can only be transmitting or - receiving at any given moment. So we had to decide how to manage the - link. -

- By design, TeleMetrum firmware listens for an RF connection when - it's in "idle mode" (turned on while the rocket is horizontal), which - allows us to use the RF link to configure the rocket, do things like - ejection tests, and extract data after a flight without having to - crack open the airframe. However, when the board is in "flight - mode" (turned on when the rocket is vertical) the TeleMetrum only - transmits and doesn't listen at all. That's because we want to put - ultimate priority on event detection and getting telemetry out of - the rocket and out over - the RF link in case the rocket crashes and we aren't able to extract - data later... -

- We don't use a 'normal packet radio' mode because they're just too - inefficient. The GFSK modulation we use is just FSK with the - baseband pulses passed through a - Gaussian filter before they go into the modulator to limit the - transmitted bandwidth. When combined with the hardware forward error - correction support in the cc1111 chip, this allows us to have a very - robust 38.4 kilobit data link with only 10 milliwatts of transmit power, - a whip antenna in the rocket, and a hand-held Yagi on the ground. We've - had flights to above 21k feet AGL with good reception, and calculations - suggest we should be good to well over 40k feet AGL with a 5-element yagi on - the ground. We hope to fly boards to higher altitudes soon, and would - of course appreciate customer feedback on performance in higher - altitude flights! -

Configurable Parameters

- Configuring a TeleMetrum board for flight is very simple. Because we - have both acceleration and pressure sensors, there is no need to set - a "mach delay", for example. The few configurable parameters can all - be set using a simple terminal program over the USB port or RF link - via TeleDongle. -

Radio Channel

- Our firmware supports 10 channels. The default channel 0 corresponds - to a center frequency of 434.550 Mhz, and channels are spaced every - 100 khz. Thus, channel 1 is 434.650 Mhz, and channel 9 is 435.550 Mhz. - At any given launch, we highly recommend coordinating who will use - each channel and when to avoid interference. And of course, both - TeleMetrum and TeleDongle must be configured to the same channel to - successfully communicate with each other. -

- To set the radio channel, use the 'c r' command, like 'c r 3' to set - channel 3. - As with all 'c' sub-commands, follow this with a 'c w' to write the - change to the parameter block in the on-board DataFlash chip on - your TeleMetrum board if you want the change to stay in place across reboots. -

Apogee Delay

- Apogee delay is the number of seconds after TeleMetrum detects flight - apogee that the drogue charge should be fired. In most cases, this - should be left at the default of 0. However, if you are flying - redundant electronics such as for an L3 certification, you may wish - to set one of your altimeters to a positive delay so that both - primary and backup pyrotechnic charges do not fire simultaneously. -

- To set the apogee delay, use the [FIXME] command. - As with all 'c' sub-commands, follow this with a 'c w' to write the - change to the parameter block in the on-board DataFlash chip. -

- Please note that the TeleMetrum apogee detection algorithm always - fires a fraction of a second *after* apogee. If you are also flying - an altimeter like the PerfectFlite MAWD, which only supports selecting - 0 or 1 seconds of apogee delay, you may wish to set the MAWD to 0 - seconds delay and set the TeleMetrum to fire your backup 2 or 3 - seconds later to avoid any chance of both charges firing - simultaneously. We've flown several airframes this way quite happily, - including Keith's successful L3 cert. -

Main Deployment Altitude

- By default, TeleMetrum will fire the main deployment charge at an - elevation of 250 meters (about 820 feet) above ground. We think this - is a good elevation for most airframes, but feel free to change this - to suit. In particular, if you are flying two altimeters, you may - wish to set the - deployment elevation for the backup altimeter to be something lower - than the primary so that both pyrotechnic charges don't fire - simultaneously. -

- To set the main deployment altitude, use the [FIXME] command. - As with all 'c' sub-commands, follow this with a 'c w' to write the - change to the parameter block in the on-board DataFlash chip. -

Calibration

- There are only two calibrations required for a TeleMetrum board, and - only one for TeleDongle. -

Radio Frequency

- The radio frequency is synthesized from a clock based on the 48 Mhz - crystal on the board. The actual frequency of this oscillator must be - measured to generate a calibration constant. While our GFSK modulation - bandwidth is wide enough to allow boards to communicate even when - their oscillators are not on exactly the same frequency, performance - is best when they are closely matched. - Radio frequency calibration requires a calibrated frequency counter. - Fortunately, once set, the variation in frequency due to aging and - temperature changes is small enough that re-calibration by customers - should generally not be required. -

- To calibrate the radio frequency, connect the UHF antenna port to a - frequency counter, set the board to channel 0, and use the 'C' - command to generate a CW carrier. Wait for the transmitter temperature - to stabilize and the frequency to settle down. - Then, divide 434.550 Mhz by the - measured frequency and multiply by the current radio cal value show - in the 'c s' command. For an unprogrammed board, the default value - is 1186611. Take the resulting integer and program it using the 'c f' - command. Testing with the 'C' command again should show a carrier - within a few tens of Hertz of the intended frequency. - As with all 'c' sub-commands, follow this with a 'c w' to write the - change to the parameter block in the on-board DataFlash chip. -

Accelerometer

- The accelerometer we use has its own 5 volt power supply and - the output must be passed through a resistive voltage divider to match - the input of our 3.3 volt ADC. This means that unlike the barometric - sensor, the output of the acceleration sensor is not ratiometric to - the ADC converter, and calibration is required. We also support the - use of any of several accelerometers from a Freescale family that - includes at least +/- 40g, 50g, 100g, and 200g parts. Using gravity, - a simple 2-point calibration yields acceptable results capturing both - the different sensitivities and ranges of the different accelerometer - parts and any variation in power supply voltages or resistor values - in the divider network. -

- To calibrate the acceleration sensor, use the 'c a 0' command. You - will be prompted to orient the board vertically with the UHF antenna - up and press a key, then to orient the board vertically with the - UHF antenna down and press a key. - As with all 'c' sub-commands, follow this with a 'c w' to write the - change to the parameter block in the on-board DataFlash chip. -

- The +1g and -1g calibration points are included in each telemetry - frame and are part of the header extracted by ao-dumplog after flight. - Note that we always store and return raw ADC samples for each - sensor... nothing is permanently "lost" or "damaged" if the - calibration is poor. -

Chapter 7. Updating Device Firmware

Table of Contents

Updating TeleMetrum Firmware
Updating TeleDongle Firmware

- The big conceptual thing to realize is that you have to use a - TeleDongle as a programmer to update a TeleMetrum, and vice versa. - Due to limited memory resources in the cc1111, we don't support - programming either unit directly over USB. -

- You may wish to begin by ensuring you have current firmware images. - These are distributed as part of the AltOS software bundle that - also includes the AltosUI ground station program. Newer ground - station versions typically work fine with older firmware versions, - so you don't need to update your devices just to try out new - software features. You can always download the most recent - version from http://www.altusmetrum.org/AltOS/. -

- We recommend updating TeleMetrum first, before updating TeleDongle. -

Updating TeleMetrum Firmware

- Find the 'programming cable' that you got as part of the starter - kit, that has a red 8-pin MicroMaTch connector on one end and a - red 4-pin MicroMaTch connector on the other end. -
- Take the 2 screws out of the TeleDongle case to get access - to the circuit board. -
- Plug the 8-pin end of the programming cable to the - matching connector on the TeleDongle, and the 4-pin end to the - matching connector on the TeleMetrum. -
- Attach a battery to the TeleMetrum board. -
- Plug the TeleDongle into your computer's USB port, and power - up the TeleMetrum. -
- Run AltosUI, and select 'Flash Image' from the File menu. -
- Pick the TeleDongle device from the list, identifying it as the - programming device. -
- Select the image you want put on the TeleMetrum, which should have a - name in the form telemetrum-v1.0-0.7.1.ihx. It should be visible - in the default directory, if not you may have to poke around - your system to find it. -
- Make sure the configuration parameters are reasonable - looking. If the serial number and/or RF configuration - values aren't right, you'll need to change them. -
- Hit the 'OK' button and the software should proceed to flash - the TeleMetrum with new firmware, showing a progress bar. -
- Confirm that the TeleMetrum board seems to have updated ok, which you - can do by plugging in to it over USB and using a terminal program - to connect to the board and issue the 'v' command to check - the version, etc. -
- If something goes wrong, give it another try. -

Updating TeleDongle Firmware

- Updating TeleDongle's firmware is just like updating TeleMetrum - firmware, but you switch which board is the programmer and which - is the programming target. -

- Find the 'programming cable' that you got as part of the starter - kit, that has a red 8-pin MicroMaTch connector on one end and a - red 4-pin MicroMaTch connector on the other end. -
- Find the USB cable that you got as part of the starter kit, and - plug the "mini" end in to the mating connector on TeleMetrum. -
- Take the 2 screws out of the TeleDongle case to get access - to the circuit board. -
- Plug the 8-pin end of the programming cable to the (latching) - matching connector on the TeleMetrum, and the 4-pin end to the - matching connector on the TeleDongle. -
- Attach a battery to the TeleMetrum board. -
- Plug both TeleMetrum and TeleDongle into your computer's USB - ports, and power up the TeleMetrum. -
- Run AltosUI, and select 'Flash Image' from the File menu. -
- Pick the TeleMongle device from the list, identifying it as the - programming device. -
- Select the image you want put on the TeleDongle, which should have a - name in the form teledongle-v0.2-0.7.1.ihx. It should be visible - in the default directory, if not you may have to poke around - your system to find it. -
- Make sure the configuration parameters are reasonable - looking. If the serial number and/or RF configuration - values aren't right, you'll need to change them. The TeleDongle - serial number is on the "bottom" of the circuit board, and can - usually be read through the translucent blue plastic case without - needing to remove the board from the case. -
- Hit the 'OK' button and the software should proceed to flash - the TeleDongle with new firmware, showing a progress bar. -
- Confirm that the TeleDongle board seems to have updated ok, which you - can do by plugging in to it over USB and using a terminal program - to connect to the board and issue the 'v' command to check - the version, etc. Once you're happy, remove the programming cable - and put the cover back on the TeleDongle. -
- If something goes wrong, give it another try. -

- Be careful removing the programming cable from the locking 8-pin - connector on TeleMetrum. You'll need a fingernail or perhaps a thin - screwdriver or knife blade to gently pry the locking ears out - slightly to extract the connector. We used a locking connector on - TeleMetrum to help ensure that the cabling to companion boards - used in a rocket don't ever come loose accidentally in flight. -

Chapter 8. Using Altus Metrum Products

Table of Contents

Being Legal

In the Rocket
On the Ground
Data Analysis
Future Plans

- How GPS Works -

Being Legal

- First off, in the US, you need an [amateur radio license](../Radio) or - other authorization to legally operate the radio transmitters that are part - of our products. -

In the Rocket

- In the rocket itself, you just need a [TeleMetrum](../TeleMetrum) board and - a LiPo rechargeable battery. An 860mAh battery weighs less than a 9V - alkaline battery, and will run a [TeleMetrum](../TeleMetrum) for hours. -

- By default, we ship TeleMetrum with a simple wire antenna. If your - electronics bay or the airframe it resides within is made of carbon fiber, - which is opaque to RF signals, you may choose to have an SMA connector - installed so that you can run a coaxial cable to an antenna mounted - elsewhere in the rocket. -

On the Ground

- To receive the data stream from the rocket, you need an antenna and short - feedline connected to one of our [TeleDongle](../TeleDongle) units. The - TeleDongle in turn plugs directly into the USB port on a notebook - computer. Because TeleDongle looks like a simple serial port, your computer - does not require special device drivers... just plug it in. -

- Right now, all of our application software is written for Linux. However, - because we understand that many people run Windows or MacOS, we are working - on a new ground station program written in Java that should work on all - operating systems. -

- After the flight, you can use the RF link to extract the more detailed data - logged in the rocket, or you can use a mini USB cable to plug into the - TeleMetrum board directly. Pulling out the data without having to open up - the rocket is pretty cool! A USB cable is also how you charge the LiPo - battery, so you'll want one of those anyway... the same cable used by lots - of digital cameras and other modern electronic stuff will work fine. -

- If your rocket lands out of sight, you may enjoy having a hand-held GPS - receiver, so that you can put in a waypoint for the last reported rocket - position before touch-down. This makes looking for your rocket a lot like - Geo-Cacheing... just go to the waypoint and look around starting from there. -

- You may also enjoy having a ham radio "HT" that covers the 70cm band... you - can use that with your antenna to direction-find the rocket on the ground - the same way you can use a Walston or Beeline tracker. This can be handy - if the rocket is hiding in sage brush or a tree, or if the last GPS position - doesn't get you close enough because the rocket dropped into a canyon, or - the wind is blowing it across a dry lake bed, or something like that... Keith - and Bdale both currently own and use the Yaesu VX-7R at launches. -

- So, to recap, on the ground the hardware you'll need includes: -

- an antenna and feedline -
- a TeleDongle -
- a notebook computer -
- optionally, a handheld GPS receiver -
- optionally, an HT or receiver covering 435 Mhz -

- The best hand-held commercial directional antennas we've found for radio - direction finding rockets are from - - Arrow Antennas. - - The 440-3 and 440-5 are both good choices for finding a - TeleMetrum-equipped rocket when used with a suitable 70cm HT. -

Data Analysis

- Our software makes it easy to log the data from each flight, both the - telemetry received over the RF link during the flight itself, and the more - complete data log recorded in the DataFlash memory on the TeleMetrum - board. Once this data is on your computer, our postflight tools make it - easy to quickly get to the numbers everyone wants, like apogee altitude, - max acceleration, and max velocity. You can also generate and view a - standard set of plots showing the altitude, acceleration, and - velocity of the rocket during flight. And you can even export a data file - useable with Google Maps and Google Earth for visualizing the flight path - in two or three dimensions! -

- Our ultimate goal is to emit a set of files for each flight that can be - published as a web page per flight, or just viewed on your local disk with - a web browser. -

Future Plans

- In the future, we intend to offer "companion boards" for the rocket that will - plug in to TeleMetrum to collect additional data, provide more pyro channels, - and so forth. A reference design for a companion board will be documented - soon, and will be compatible with open source Arduino programming tools. -

- We are also working on the design of a hand-held ground terminal that will - allow monitoring the rocket's status, collecting data during flight, and - logging data after flight without the need for a notebook computer on the - flight line. Particularly since it is so difficult to read most notebook - screens in direct sunlight, we think this will be a great thing to have. -

- Because all of our work is open, both the hardware designs and the software, - if you have some great idea for an addition to the current Altus Metrum family, - feel free to dive in and help! Or let us know what you'd like to see that - we aren't already working on, and maybe we'll get excited about it too... -

- How GPS Works -

- Placeholder. -