50 lines
2.0 KiB
Markdown
50 lines
2.0 KiB
Markdown
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# Telemetry
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Telemetry allows you to know what is happening on your aircraft while you are flying it. Among other things you can receive battery voltages and GPS positions on your transmitter.
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Two telemetry providers are currently supported, FrSky (the default) and Graupner HoTT V4.
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## FrSky telemetry
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See the Configuration examples in the documentation for details on how to enable it.
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FrSky telemetry is transmit only and just requires a single connection from the TX pin of a serial port to the RX pin on an FrSky telemetry receiver.
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FrSky telemetry signals are inverted. To connect a cleanflight capable board to an FrSKy receiver you have some options.
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1. A hardware inverter - Built in to some flight controllers.
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2. Use software serial and enable frsky_inversion.
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3. Use a flight controller that has software configurable hardware inversion (e.g. STM32F30x).
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For 1, just connect your inverter to a usart or software serial port.
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For 2 and 3 use the cli command as follows:
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```
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set frsky_inversion = 1
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```
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## HoTT telemetry
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See the Configuration examples in the documentation for details on how to enable it.
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HoTT telemetry can be used when the TX and RX pins of a serial port are connected using a diode and a single wire to the T port on a HoTT receiver.
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Serial ports use two wires but HoTT uses a single wire so some electronics are required so that the signals don't get mixed up.
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Connect as follows:
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```
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HoTT TX/RX -> Serial RX (connect directly)
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Serial TX -> 1N4148 Diode -(| )-> HoTT TX/RX (connect via diode)
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```
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The diode should be arranged to allow the data signals to flow the right way
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```
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-(| )- == Diode, | indicates cathode marker.
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```
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As noticed by Skrebber the GR-12 (and probably GR-16/24, too) are based on a PIC 24FJ64GA-002, which has 5V tolerant digital pins.
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Note: The softserial ports are not listed as 5V tolerant in the STM32F103xx data sheet pinouts and pin description section. Verify if you require a 5v/3.3v level shifters.
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