Copyright © 2015 Bdale Garbee and Keith Packard
This document is released under the terms of the Creative Commons ShareAlike 3.0 license.
Thanks to Anthony (AJ) Towns for major contributions including the TeleGPS graphing and site map code and associated documentation. Free software means that our customers and friends can become our collaborators, and we certainly appreciate this level of contribution!
Have fun using these products, and we hope to meet all of you out on the rocket flight line somewhere.
Bdale Garbee, KB0G
NAR #87103, TRA #12201
Keith Packard, KD7SQG
NAR #88757, TRA #12200
Table of Contents
List of Figures
List of Tables
TeleGPS is designed to be easy to use. Requiring no external components, flying takes just a few steps.
TeleGPS has a two pin JST PH series connector to connect up a single-cell Lithium Polymer cell (3.7V nominal). You can purchase matching batteries from the Altus Metrum store, or other vendors, or you can make your own. Pin 1 of the connector is positive, pin 2 is negative. Spark Fun sells a cable with the connector attached, which they call a JST Jumper 2 Wire Assembly
Many RC vendors also sell lithium polymer batteries with this same connector. All that we have found use the opposite polarity, and if you use them that way, you will damage or destroy TeleGPS.
TeleGPS logs GPS data at a user-configurable rate. Data are logged to a 2MB on-board flash memory part, which can be partitioned into several equal-sized blocks, one for each flight. 64kB of this storage are reserved to hold configuration data, leaving 1984kB for flight data.
The on-board flash is partitioned into separate flight logs, each of a fixed maximum size. Increase the maximum size of each log and you reduce the number of flights that can be stored. Decrease the size and you can store more flights.
To compute the amount of space needed for a single log, you can divide the expected time (in seconds) by the sample period (by default, 1 second per sample) and then multiply the result by 32 bytes per sample. For instance, a sample period of 1 second and a flight lasting one hour will take 32 * 3600 = 115200 bytes. TeleGPS does try to reduce log space used by not recording position information when it isn’t moving, so actual space consumed may be less than this.
The default size allows for four flights of 496kB each, which provides over four hours of logging at 1 sample per second.
TeleGPS will not overwrite existing flight data, so be sure to download flight data and erase it from the onboard flash before it fills up. TeleGPS will still report telemetry even if memory is full, so the only thing you will lose is the on-board data log.
The battery connectors are a standard 2-pin JST connector and match batteries sold by Spark Fun. These batteries are single-cell Lithium Polymer batteries that nominally provide 3.7 volts. Other vendors sell similar batteries for RC aircraft using mating connectors, however the polarity for those is generally reversed from the batteries used by Altus Metrum products. In particular, the Tenergy batteries supplied for use in Featherweight flight computers are not compatible with Altus Metrum flight computers or battery chargers.
Check polarity and voltage before connecting any battery not purchased from Altus Metrum or Spark Fun.
TeleGPS uses an integrate GPS patch antenna and won’t receive GPS signals if installed inside a metal or carbon fiber compartment. Test GPS reception and telemetry transmission with the system installed and all other electronics powered up to verify signal reception and make sure there isn’t any interference from other systems.
The TeleGPS application provides a graphical user interface for interacting with the Altus Metrum product family. TeleGPS can monitor telemetry data, configure devices and many other tasks. The primary interface window is for displaying data received over the telemetry link. There are additional tasks available from the main window menu bar.
This is the window brought up when you start the application. If you have a TeleDongle device connected to the computer, it will automatically be selected for telemetry monitoring
All telemetry data received are automatically recorded in suitable log files. The name of the files includes the current date and TeleGPS serial and flight numbers.
The radio frequency being monitored by the TeleDongle device is displayed at the top of the window. You can configure the frequency by clicking on the frequency box and selecting the desired frequency. The TeleGPS application remembers the last frequency selected for each TeleDongle and selects that automatically the next time you use that device.
Below the TeleDongle frequency selector, the window contains a few significant pieces of information about the altimeter providing the telemetry data stream:
Finally, the largest portion of the window contains a set of tabs, each of which contain some information about the TeleGPS board. The final table tab displays many of the raw telemetry values in one place in a spreadsheet-like format.
The Map tab shows the TeleGPS track over time on top of map data making it easy to locate the device.
The map’s default scale is approximately 3m (10ft) per pixel. The map can be dragged using the left mouse button. The map will attempt to keep the rocket roughly centered while data is being received.
You can adjust the style of map and the zoom level with buttons on the right side of the map window. You can draw a line on the map by moving the mouse over the map with a button other than the left one pressed, or by pressing the left button while also holding down the shift key. The length of the line in real-world units will be shown at the start of the line.
Images are fetched automatically via the Google Maps Static API, and cached on disk for reuse. If map images cannot be downloaded, the rocket’s path will be traced on a dark gray background instead.
You can pre-load images for your favorite launch sites before you leave home; check out Section 3.5, “Load Maps”.
The Location tab shows the raw GPS data received from TeleGPS.
The Status tab shows data relative to the location of TeleGPS when the application first received telemetry from it.
TeleGPS has three or four menus at the top of the window:
The Graph tab shows a plot of the the GPS data collected. The X axis is time in seconds; there are a variety of Y axes available for different kinds of data. This window also allows you to see some statistics computed from the data, and an overall map of the entire data record.
This selects which graph elements to show, and, at the bottom, lets you switch between metric and imperial units
Shows a map of the area overlaid with the GPS track. As with the telemetry monitoring window, you can select the style of map and zoom level using buttons along the side; you can scroll the map by dragging within the map pressing the left button and you can draw a line to measure distances using either the left button with the shift key, or any other button.
This tool takes the raw data files and makes them available for external analysis. When you select this button, you are prompted to select a data file, which can be either a .eeprom or .telem. The .eeprom files contain higher resolution and more continuous data, while .telem files contain receiver signal strength information. Next, a second dialog appears which is used to select where to write the resulting file. It has a selector to choose between CSV and KML file formats.
This is a text file containing the data in a form suitable for import into a spreadsheet or other external data analysis tool. The first few lines of the file contain the version and configuration information from TeleGPS, then there is a single header line which labels all of the fields. All of these lines start with a # character which many tools can be configured to skip over.
The remaining lines of the file contain the data, with each field separated by a comma and at least one space. All of the sensor values are converted to standard units, with the barometric data reported in both pressure, altitude and height above pad units.
Before heading out to a new launch site, you can use this to load satellite images in case you don’t have internet connectivity at the site.
There’s a drop-down menu of launch sites we know about; if your favorites aren’t there, please let us know the lat/lon and name of the site. The contents of this list are actually downloaded from our server at run-time, so as new sites are sent in, they’ll get automatically added to this list. If the launch site isn’t in the list, you can manually enter the lat/lon values
There are four different kinds of maps you can view; you can select which to download by selecting as many as you like from the available types:
You can specify the range of zoom levels to download; smaller numbers show more area with less resolution. The default level, 0, shows about 3m/pixel. One zoom level change doubles or halves that number. Larger zoom levels show more detail, smaller zoom levels less.
The Map Radius value sets how large an area around the center point to download. Select a value large enough to cover any plausible flight from that site. Be aware that loading a large area with a high maximum zoom level can attempt to download a lot of data. Loading hybrid maps with a 10km radius at a minimum zoom of -2 and a maximum zoom of 2 consumes about 120MB of space. Terrain and road maps consume about 1/10 as much space as satellite or hybrid maps.
Clicking the Load Map button will fetch images from Google Maps; note that Google limits how many images you can fetch at once, so if you load more than one launch site, you may get some gray areas in the map which indicate that Google is tired of sending data to you. Try again later.
TeleGPS provides voice announcements during flight so that you can keep your eyes on the sky and still get information about the current flight status. However, sometimes you don’t want to hear them.
TeleGPS logs all telemetry data and saves all flash data to this directory. This directory is also used as the staring point when selecting data files for display or export.
Click on the directory name to bring up a directory choosing dialog, select a new directory and click Select Directory to change where TeleGPS reads and writes data files.
This value is transmitted in each command packet sent from TeleDongle and received from an altimeter. It is not used in telemetry mode, as the callsign configured in the altimeter board is included in all telemetry packets. Configure this with the TeleGPS operators call sign as needed to comply with your local radio regulations.
Note that to successfully command a flight computer over the radio (to configure the altimeter, monitor idle, or fire pyro charges), the callsign configured here must exactly match the callsign configured in the flight computer. This matching is case sensitive.
This switches between metric units (meters) and imperial units (feet and miles). This affects the display of values use during flight monitoring, configuration, data graphing and all of the voice announcements. It does not change the units used when exporting to CSV files, those are always produced in metric units.
This causes all communication with a connected device to be dumped to the console from which TeleGPS was started. If you’ve started it from an icon or menu entry, the output will simply be discarded. This mode can be useful to debug various serial communication issues.
Selects the set of fonts used in the flight monitor window. Choose between the small, medium and large sets.
Switches between the available Java user interface appearances. The default selection is supposed to match the native window system appearance for the target platform.
Selects the initial position for the main TeleGPS window that includes all of the command buttons.
Sets the number of map tiles kept in memory while the application is running. More tiles consume more memory, but will make panning around the map faster.
This brings up a dialog where you can configure the set of frequencies shown in the various frequency menus. You can add as many as you like, or even reconfigure the default set. Changing this list does not affect the frequency settings of any devices, it only changes the set of frequencies shown in the menus.
This closes the current window, leaving any other windows open and the application running.
Selecting this item brings up a dialog box listing all of the connected TeleDongle devices. When you choose one of these, AltosUI will display telemetry data as received by the selected TeleDongle device.
Scans the configured set of frequencies looking for telemetry signals. A list of all of the discovered signals is show; selecting one of those and clicking on Monitor will select that frequency in the associated TeleGPS application window.
TeleGPS records data to its internal flash memory. On-board data is recorded at the same rate as telemetry but is not subject to radio drop-outs. As such, it generally provides a more complete and precise record. The Download Data menu entry allows you to read the flash memory and write it to disk.
Select the Download Data menu entry to bring up a list of connected TeleGPS devices. After the device has been selected, a dialog showing the data stored in the device will be shown allowing you to select which entries to download and which to delete. You must erase flights in order for the space they consume to be reused by another track. This prevents accidentally losing data if you neglect to download data before starting TeleGPS again. Note that if there is no more space available in the device, then no data will be recorded.
The file name for each data log is computed automatically from the recorded date, altimeter serial number and flight number information.
Select this button and then select any connected TeleGPS device from the list provided.
The first few lines of the dialog provide information about the connected device, including the product name, software version and hardware serial number. Below that are the individual configuration entries.
At the bottom of the dialog, there are four buttons:
The rest of the dialog contains the parameters to be configured.
This configures which of the frequencies to use for both telemetry and packet command mode. Note that if you set this value via packet command mode, the TeleDongle frequency will also be automatically reconfigured to match so that communication will continue afterwards.
The radios in every Altus Metrum device are calibrated at the factory to ensure that they transmit and receive on the specified frequency. If you need to you can adjust the calibration by changing this value. Do not do this without understanding what the value means, read the appendix on calibration and/or the source code for more information. To change a TeleDongle’s calibration, you must reprogram the unit completely.
Enables the radio for transmission during flight. When disabled, the radio will not transmit anything during flight at all.
This sets the modulation bit rate for data transmission for both telemetry and packet link mode. Lower bit rates will increase range while reducing the amount of data that can be sent and increasing battery consumption. All telemetry is done using a rate 1/2 constraint 4 convolution code, so the actual data transmission rate is 1/2 of the modulation bit rate specified here.
How often to transmit GPS information via APRS (in seconds). When set to zero, APRS transmission is disabled. Note that a single APRS packet takes nearly a full second to transmit, so enabling this option will prevent sending any other telemetry during that time.
Which SSID to report in APRS packets. By default, this is set to the last digit of the serial number, but can be configured to any value from 0 to 9.
Whether to send APRS data in Compressed or Uncompressed format. Compressed format is smaller and more precise. Uncompressed format is older, but may work better with your device. The Kenwood TH-D72 only displays altitude information with Uncompressed format, while the Yaesu FT1D only displays altitude with Compressed format. Test before you fly to see which to use.
This sets the call sign included in each telemetry packet. Set this as needed to conform to your local radio regulations.
This sets the amount of motion that TeleGPS needs to see before logging the new position. Motions smaller than this are skipped, which saves storage space.
This reprograms TeleGPS devices with new firmware. Please read the directions for flashing devices in Appendix D, Updating Device Firmware.
TeleGPS’s native telemetry system doesn’t use a normal packet radio mode like APRS because it’s not very efficient. The GFSK modulation we use is FSK with the base-band pulses passed through a Gaussian filter before they go into the modulator to limit the transmitted bandwidth. When combined with forward error correction and interleaving, this allows us to have a very robust 19.2 kilobit data link with only 10-40 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 great reception, and calculations suggest we should be good to well over 40k feet AGL with a 5-element yagi on the ground with our 10mW units and over 100k feet AGL with the 40mW devices.
TeleGPS can send APRS if desired, and the interval between APRS packets can be configured. As each APRS packet takes a full second to transmit, we recommend an interval of at least 5 seconds to avoid consuming too much battery power or radio channel bandwidth. You can configure the APRS interval using TeleGPS; that process is described in Section 3.13, “Configure Device”.
AltOS supports both compressed and uncompressed APRS position report data formats. The compressed format provides for higher position precision and shorter packets than the uncompressed APRS format. We’ve found some older APRS receivers that do not handle the compressed format. The Kenwood TH-72A requires the use of uncompressed format to display altitude information correctly. The Yaesu FT1D requires the use of compressed format to display altitude information.
APRS packets include an SSID (Secondary Station Identifier) field that allows one operator to have multiple transmitters. AltOS allows you to set this to a single digit from 0 to 9, allowing you to fly multiple transmitters at the same time while keeping the identify of each one separate in the receiver. By default, the SSID is set to the last digit of the device serial number.
The APRS packet format includes a comment field that can have arbitrary text in it. AltOS uses this to send status information as shown in the following table.
Table A.1. Altus Metrum APRS Comments
Field | Example | Description |
---|---|---|
1 | L | GPS Status U for unlocked, L for locked |
2 | 6 | Number of Satellites in View |
3 | B4.0 | Altimeter Battery Voltage |
4 | 1286 | Device Serial Number |
Here’s an example of an APRS comment showing GPS lock with 6 satellites in view and a primary battery at 4.0V from device 1876.
L6 B4.0 1876
Make sure your primary battery is above 3.8V and GPS is locked with at least 5 or 6 satellites in view before flying. If GPS is switching between L and U regularly, then it doesn’t have a good lock and you should wait until it becomes stable.
If the GPS receiver loses lock, the APRS data transmitted will contain the last position for which GPS lock was available. You can tell that this has happened by noticing that the GPS status character switches from L to U. Before GPS has locked, APRS will transmit zero for latitude, longitude and altitude.
Configuring TeleGPS is very simple; the few configurable parameters can all be set using the TeleGPS application over USB. Check out Section 3.13, “Configure Device”.
All Altus Metrum products are sophisticated electronic devices. When handled gently and properly installed in an air-frame, they will deliver impressive results. However, as with all electronic devices, there are some precautions you must take.
The Lithium Polymer rechargeable batteries 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 air-frame. We often wrap them in suitable scraps of closed-cell packing foam before strapping them down, for example.
The barometric sensors used on all of our flight computers are sensitive to sunlight. In normal mounting situations, the baro sensor 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 when designing an installation in an air-frame with a see-through plastic payload bay. It is particularly important to consider this with TeleMini v1.0, both because the baro sensor is on the “top” of the board, and because many model rockets with payload bays use clear plastic for the payload bay! Replacing these with an opaque cardboard tube, painting them, or wrapping them with a layer of masking tape are all reasonable approaches to keep the sensor out of direct sunlight.
The 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, and also by having a suitable static vent to outside air.
As with all other rocketry electronics, Altus Metrum altimeters must be protected from exposure to corrosive motor exhaust and ejection charge gasses.
TeleGPS uses an NXP LPC11U14 micro-controller. This tiny CPU contains 32kB of flash for the application and 4kB of RAM for temporary data storage.
Shipping restrictions may prevent us from including a battery battery with TeleGPS.
TeleGPS is designed to be rugged enough for typical rocketry applications. The 4 mounting holes on the board are sized for use with 4-40 or M3 screws.
TeleGPS is programmed directly over its USB connectors.
You may wish to begin by ensuring you have current firmware images. These are distributed as part of the TeleGPS software bundle that also includes the TeleGPS 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/
Version 1.6.3 adds idle mode to AltosDroid and has bug fixes for our host software on desktops, laptops an android devices along with BlueTooth support for Windows.
AltOS fixes:
AltosUI and TeleGPS New Features:
AltosUI and TeleGPS Fixes:
AltosDroid new features:
AltosDroid bug fixes:
Version 1.6.2 includes support for our updated TeleMega v2.0 product and bug fixes in in the flight software for all our boards and ground station interfaces.
AltOS New Features:
AltOS Fixes:
AltosUI and TeleGPS Fixes:
We spent a bunch of time trying to improve our documentation
Version 1.6.1 includes support for our updated TeleBT v3.0 product and bug fixes in in the flight software for all our boards and ground station interfaces.
AltOS New Features:
AltOS Fixes:
AltosUI and TeleGPS New Features:
AltosUI and TeleGPS Fixes:
AltosDroid New Features:
AltosDroid Fixes:
Version 1.6 includes support for our updated TeleDongle v3.0 product and bug fixes in in the flight software for all our boards and ground station interfaces.
AltOS New Features
AltOS Fixes
AltosUI and TeleGPS New Features
AltosUI Fixes
Version 1.5 is a major release. It includes support for our new EasyMega product, new features and bug fixes in in the flight software for all our boards and the AltosUI ground station
AltOS New Features
AltOS Fixes
AltosUI and TeleGPS New Features
AltosUI Fixes
Version 1.4.2 is a minor release. It fixes Java-related install issues on Windows
Version 1.4.1 is a minor release. It fixes install issues on Windows and provides the missing TeleMetrum V2.0 firmware. There aren’t any changes to the firmware or host applications at all. All Windows users will want to upgrade to get the signed driver, but Mac and Linux users who do not need the TeleMetrum V2.0 firmware image will not need to upgrade.
Windows Install Fixes
Other Fixes
Version 1.4 is a major release. It includes support for our new TeleGPS product, new features and bug fixes in in the flight software for all our boards and the AltosUI ground station
AltOS new features:
AltOS fixes:
AltosUI new features:
AltosUI fixes:
Documentation changes: