== Using 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 link:https://www.sparkfun.com/products/9914[JST Jumper 2 Wire Assembly] [WARNING] 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. [WARNING] 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.