TeleMetrum

Owner's Manual for the TeleMetrum System

Bdale Garbee

Keith Packard

+TeleMetrum

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 0.1	30 March 2010
Initial content

Revision History
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 @@ -25,7 +25,11 @@ 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. -

Chapter 2. Getting Started

Table of Contents

FAQ

+ 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 @@ -67,21 +71,22 @@

When you have successfully installed the software suite (either from compiled source code or as the pre-built Debian package) you will - have 10 executable programs all of which have names beginning with 'ao-'. - ('ao-view' is the lone GUI-based program. - The rest are command-line based.) You will also - have 10 man pages, that give you basic info on each program. - And you will also get this documentation in two file types, - telemetrum.pdf and telemetrum.html. - Finally you will have a couple of control files that allow the ao-view + 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 (I use konsole for this,) to see what - port-device-name each device has been assigned by the operating system. + '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. @@ -103,8 +108,8 @@ 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 + 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 @@ -121,10 +126,11 @@ 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, 'cu' (and possibly 'cutecom') For instance, try to send - (type) a 'cr2' and verify the channel change by sending a 'cs'. - Verify you can connect and disconnect from the units while in 'cu' - by sending the escape-disconnect mentioned above. + 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 @@ -184,11 +190,12 @@

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. Mostly you just use + 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 @@ -230,8 +237,10 @@ 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. -

Chapter 3. Specifications

+ 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). @@ -255,7 +264,7 @@ 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 @@ -276,17 +285,18 @@ 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's see-through - plastic payload bay. + 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", + 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 @@ -324,8 +334,8 @@ 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 + 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 @@ -338,7 +348,7 @@ 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

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 @@ -348,12 +358,13 @@ 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 + 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 mode, TeleMetrum turns on the GPS system, engages the flight + 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 @@ -385,7 +396,7 @@ 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 @@ -404,7 +415,7 @@ 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, @@ -427,7 +438,7 @@ 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 @@ -453,18 +464,18 @@ 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 a test flight above 12k AGL with good reception, and calculations - suggest we should be good to 40k AGL or more with a 5-element yagi on + 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. @@ -476,8 +487,9 @@ 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. -

Apogee Delay

+ 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 @@ -488,7 +500,16 @@ 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. -

Main Deployment Altitude

+ 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 @@ -501,10 +522,10 @@ 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 @@ -528,7 +549,7 @@ 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 @@ -553,13 +574,13 @@ 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. Using Altus Metrum Products

Table of Contents

Being Legal

In the Rocket
On the Ground
Data Analysis
Future Plans

+

Chapter 7. 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. @@ -569,7 +590,7 @@ 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 @@ -621,7 +642,7 @@ 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 @@ -636,7 +657,7 @@ 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 @@ -652,7 +673,7 @@ 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

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