1 == Using TeleGPS Hardware
3 === Hooking Up Lithium Polymer Batteries
5 TeleGPS has a two pin JST PH series connector to connect up
6 a single-cell Lithium Polymer cell (3.7V nominal). You can
7 purchase matching batteries from the Altus Metrum store, or
8 other vendors, or you can make your own. Pin 1 of the
9 connector is positive, pin 2 is negative. Spark Fun sells a
10 cable with the connector attached, which they call a
11 link:https://www.sparkfun.com/products/9914[JST Jumper 2 Wire Assembly]
15 Many RC vendors also sell lithium polymer batteries with
16 this same connector. All that we have found use the opposite
17 polarity, and if you use them that way, you will damage or
20 === On-board Data Recording
22 TeleGPS logs GPS data at a user-configurable
23 rate. Data are logged to a 2MB on-board flash memory
24 part, which can be partitioned into several
25 equal-sized blocks, one for each flight. 64kB of this
26 storage are reserved to hold configuration data,
27 leaving 1984kB for flight data.
29 The on-board flash is partitioned into separate flight
30 logs, each of a fixed maximum size. Increase the
31 maximum size of each log and you reduce the number of
32 flights that can be stored. Decrease the size and you
33 can store more flights.
35 To compute the amount of space needed for a single
36 log, you can divide the expected time (in seconds) by
37 the sample period (by default, 1 second per sample)
38 and then multiply the result by 32 bytes per
39 sample. For instance, a sample period of 1 second and
40 a flight lasting one hour will take 32 * 3600 = 115200
41 bytes. TeleGPS does try to reduce log space used by
42 not recording position information when it isn't
43 moving, so actual space consumed may be less than
46 The default size allows for four flights of 496kB
47 each, which provides over four hours of logging at 1
50 TeleGPS will not overwrite existing flight data, so be
51 sure to download flight data and erase it from the
52 onboard flash before it fills up. TeleGPS will still
53 report telemetry even if memory is full, so the only
54 thing you will lose is the on-board data log.
58 TeleGPS v1.0 has a dual greed/red LED along the edge
59 towards the USB connector end of the board. This
60 indicates battery charging status while connected to
61 power over USB. When the red LED is lit, the battery
62 is charging. Once the battery is fully charged, the
63 red LED goes out and the green LED turns on. If both
64 LEDs are lit, something is probably wrong with the battery.
66 TeleGPS v2.0 has the same green/red battery charging
67 status LED and adds another green LED along the same
68 edge, towards end of the board with the 70cm
69 antenna. This green LED indicates GPS lock status — it
70 blinks once every three seconds when the GPS receiver
71 is locked and tracking position.
75 The battery connectors are a standard 2-pin JST
76 connector and match batteries sold by Spark Fun. These
77 batteries are single-cell Lithium Polymer batteries
78 that nominally provide 3.7 volts. Other vendors sell
79 similar batteries for RC aircraft using mating
80 connectors, however the polarity for those is
81 generally reversed from the batteries used by Altus
82 Metrum products. In particular, the Tenergy batteries
83 supplied for use in Featherweight flight computers are
84 not compatible with Altus Metrum flight computers or
88 Check polarity and voltage before connecting any
89 battery not purchased from Altus Metrum or Spark
92 TeleGPS uses an integrate GPS patch antenna and won't
93 receive GPS signals if installed inside a metal or
94 carbon fiber compartment. Test GPS reception and
95 telemetry transmission with the system installed and
96 all other electronics powered up to verify signal
97 reception and make sure there isn't any interference