TeleGPS Owner's Manual
A recording GPS tracker
Keith
Packard
2015
Bdale Garbee and Keith Packard
This document is released under the terms of the
Creative Commons ShareAlike 3.0
license.
1.6
8 January 2015
Major release adding TeleDongle v3.0 support.
1.4.1
20 June 2014
Minor release fixing some installation bugs.
1.4
13 June 2014
Initial release
Acknowledgements
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
Quick Start Guide
TeleGPS is designed to be easy to use. Requiring no external
components, flying takes just a few steps.
First, download and install the software from . This will make sure that
you have the right device drivers installed.
Next, plug in the battery and USB cable and connect TeleGPS to
your computer. This will charge the battery and allow you to
configure the device.
Start the TeleGPS application and set the callsign and frequency
on your TeleGPS device; refer to the Configure TeleGPS section
in the TeleGPS Application chapter for instructions.
Unplug TeleGPS when the battery charger light goes green. This
will enable the radio and logging portions of the TeleGPS
firmware.
Connect TeleDongle to your computer and start TeleGPS or start
AltosDroid on your android device and connect to TeleBT. Set the
frequency to match the TeleGPS and you should be receiving telemetry.
Handling Precautions
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 batteries have an
extraordinary power density. This is great because we can fly with
much less battery mass... but if they are punctured
or their contacts are allowed to short, they can and will release their
energy very rapidly!
Thus we recommend that you take some care when handling TeleGPS
to keep conductive material from coming in contact with the exposed metal elements.
As with all other rocketry electronics, Altus Metrum devices must
be protected from exposure to corrosive motor exhaust and ejection
charge gasses.
TeleGPS Hardware
Hooking Up Lithium Polymer Batteries
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.
On-board Data Recording
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.
Installation
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.
System Operation
GFSK Telemetry
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.
APRS
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 AltosUI; that process is described in
the Configure Altimeter section of the AltosUI chapter.
AltOS uses the APRS compressed position report data format,
which provides for higher position precision and shorter
packets than the original APRS format. It also includes
altitude data, which is invaluable when tracking rockets. We
haven't found a receiver which doesn't handle compressed
positions, but it's just possible that you have one, so if you
have an older device that can receive the raw packets but
isn't displaying position information, it's possible that this
is the cause.
The APRS packet format includes a comment field that can have
arbitrary text in it. AltOS uses this to send status
information about the flight computer. It sends four fields as
shown in the following table.
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
Battery Voltage
Here's an example of an APRS comment showing GPS lock with 6
satellites in view and a battery at 4.0V.
L6 B4.0
Make sure your primary battery is above 3.8V and GPS is locked
with at least 5 or 6 satellites in view before starting. 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.
Configurable Parameters
Configuring TeleGPS is very
simple; the few configurable parameters can all be set
using the TeleGPS application over USB. Read
the Configure TeleGPS section in the TeleGPS Software chapter below
for more information.
Radio Frequency
Altus Metrum boards support radio frequencies in the 70cm
band. By default, the configuration interface provides a
list of 10 “standard” frequencies in 100kHz channels starting at
434.550MHz. However, the firmware supports use of
any 50kHz multiple within the 70cm band. At any given
launch, we highly recommend coordinating when and by whom each
frequency will be used to avoid interference. And of course, both
TeleGPS and the receiver must be configured to the same
frequency to successfully communicate with each other.
Callsign
This sets the callsign used for telemetry and APRS to
identify the device.
Telemetry/RDF/APRS Enable
You can completely disable the radio, if necessary, leaving
TeleGPS only logging data to internal memory.
APRS Interval
This selects how often APRS packets are transmitted. Set
this to zero to disable APRS without also disabling the
regular telemetry and RDF transmissions. As APRS takes a
full second to transmit a single position report, we
recommend sending packets no more than once every 5 seconds.
Maximum Flight Log
Changing this value will set the maximum amount of flight
log storage that an individual flight will use. The
available storage is divided into as many flights of the
specified size as can fit in the available space. You can
download and erase individual flight logs. If you fill up
the available storage, future flights will not get logged
until you erase some of the stored ones.
Logging Trigger Motion
If TeleGPS moves less than this distance over a long period
of time, it will not log that location, saving storage space.
Position Reporting Interval
This sets how often TeleGPS reports position information via
telemetry and to the on-board log. Reducing this value will
save power and logging memory consumption.
TeleGPS Application
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 chapter
is split into sections, each of which documents one of the tasks
provided from the top-level toolbar.
Telemetry Monitoring
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:
The configured call-sign
The device serial number
The flight number. TeleGPS remembers how many
times it has flown.
The Received Signal Strength Indicator value. This lets
you know how strong a signal TeleDongle is receiving. The
radio inside TeleDongle operates down to about -100dBm;
weaker signals may not be receivable. The packet link uses
error detection and correction techniques which prevent
incorrect data from being reported.
The age of the displayed data, in seconds since the last
successfully received telemetry packet. In normal operation
this will stay in the low single digits. If the number starts
counting up, then you are no longer receiving data over the radio
link from the flight computer.
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.
Map
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 the 'Preload Maps' section below.
Location
The Location tab shows the raw GPS data received from TeleGPS.
Status
The Status tab shows data relative to the location of
TeleGPS when the application first received telemetry from
it.
Table
The Table tab shows detailed information about the GPS
receiver
TeleGPS Menus
TeleGPS has three or four menus at the top of the window:
File
New Window, Graph Data, Export Data, Load Maps, Preferences, Close and Exit
Monitor
Connect Device, Disconnect and Scan Channels
Device
Download Data, Configure Device and Flash Device
Frequency
This shows the current monitoring frequency with a
drop-down menu listing other configured
frequencies. You can change the set of frequencies
shown here from the Preferences dialog. This menu is
only shown when the TeleGPS application is connected
to a TeleDongle or TeleBT device.
New Window
This creates another telemetry monitoring window, in case
you have multiple TeleDongle devices connected to the
computer.
Graph Data
This brings up a file dialog to load a saved log, either
a .telem file of recorded telemetry or .eeprom of saved
data from on-board memory. It looks a bit like the flight
monitoring window, using a selection of tabs to show
different views of the saved data.
Graph
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.
Configure Graph
This selects which graph elements to show, and, at the
bottom, lets you switch between metric and imperial units
Statistics
Shows overall data computed from the flight.
Map
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.
Export Data
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.
Comma Separated Value Format
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.
Keyhole Markup Language (for Google Earth)
This is the format used by Google Earth to provide an overlay
within that application. With this, you can use Google Earth to
see the whole flight path in 3D.
Load Maps
Before using TeleGPS, you can use Load Maps to load map data
in case you don't have access to the internet while
receiving telemetry.
There's a drop-down menu of rocket 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:
Hybrid
A combination of satellite imagery and road data. This
is the default view.
Satellite
Just the satellite imagery without any annotation.
Roadmap
Roads, political boundaries and a few geographic features.
Terrain
Contour intervals and shading that show hills and
valleys.
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.
The Tile Radius value sets how large an area around the center
point to download. Each tile is 512x512 pixels, and the
'radius' value specifies how many tiles away from the center
will be downloaded. Specify a radius of 0 and you get only the
center tile. A radius of 1 loads a 3x3 grid, centered on the
specified location.
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.
Preferences
Voice Settings
AltosUI 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.
Enable
Turns all voice announcements on and off
Test Voice
Plays a short message allowing you to verify
that the audio system is working and the volume settings
are reasonable
Log Directory
AltosUI logs all telemetry data and saves all TeleMetrum 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 AltosUI reads and writes data files.
Callsign
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 AltosUI 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.
Imperial Units
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.
Serial Debug
This causes all communication with a connected device to be
dumped to the console from which AltosUI 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.
Font Size
Selects the set of fonts used in the flight monitor
window. Choose between the small, medium and large sets.
Look & Feel
Adjust the style of the windows. By default, the TeleGPS
application attempts to blend in with the native style.
Manage Frequencies
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.
Close
This closes the current window, leaving any other windows
open and the application running.
Exit
This closes all TeleGPS windows and terminates the application.
Connect Device
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.
Disconnect
Disconnects the currently connected TeleDongle or TeleBT
Scan Channels
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.
Download Data
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.
Configure Device
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:
Save
This writes any changes to the
configuration parameter block in flash memory. If you don't
press this button, any changes you make will be lost.
Reset
This resets the dialog to the most recently saved values,
erasing any changes you have made.
Reboot
This reboots the device. This will restart logging for
a new flight number, if any log information has been
saved for the current flight.
Close
This closes the dialog. Any unsaved changes will be
lost.
The rest of the dialog contains the parameters to be configured.
Frequency
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.
RF Calibration
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.
Telemetry/RDF/APRS Enable
Enables the radio for transmission during flight. When
disabled, the radio will not transmit anything during flight
at all.
APRS Interval
How often to transmit GPS information via APRS (in
seconds). When set to zero, APRS transmission is
disabled. This option is available on TeleMetrum v2 and
TeleMega boards. TeleMetrum v1 boards cannot transmit APRS
packets. 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.
Callsign
This sets the call sign included in each telemetry packet. Set this
as needed to conform to your local radio regulations.
Maximum Log Size
This sets the space (in kilobytes) allocated for each data
log. The available space will be divided into chunks of this
size. A smaller value will allow more logs to be stored,
a larger value will record data for longer times.
Logging Trigger Motion
If TeleGPS moves less than this distance over a long period
of time, it will not log that location, saving storage space.
Position Reporting Interval
This sets how often TeleGPS reports position information via
telemetry and to the on-board log. Reducing this value will
save power and logging memory consumption.
Flash Device
This reprograms TeleGPS devices with new firmware. Please
read the directions for flashing devices in the Updating
Device Firmware chapter below.
Updating Device Firmware
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 .
Updating TeleGPS Firmware
Attach a battery and power switch to the target
device. Power up the device.
Using a Micro USB cable, connect the target device to your
computer's USB socket.
Run TeleGPS, and select 'Flash Device' from the Device menu.
Select the target device in the Device Selection dialog.
Select the image you want to flash to the device, which
should have a name in the form
<product>-v<product-version>-<software-version>.ihx, such
as TeleGPS-v1.0-1.4.0.ihx.
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 device with new firmware, showing a progress bar.
Verify that the device is working by using the 'Configure
Altimeter' item to check over the configuration.
Technical Information
GPS Receiver
TeleGPS uses the u-Blox Max-7Q GPS receiver.
Micro-controller
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.
Lithium Polymer Battery
Shipping restrictions may prevent us from including a battery
battery with TeleGPS.
Mechanical Considerations
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.
On-board data storage
TeleGPS has 2MB of non-volatile storage, separate from the
code storage memory. The TeleGPS firmware uses this to log
information during flight.
Release Notes
Version 1.6
Version 1.4.1
Version 1.4