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