Moving telemetry documentation to it's own file.

docs/Configuration.md

@@ -132,22 +132,6 @@ set telemetry_provider = 1
 save
 ```
 
-## FrSky telemetry
-
-FrSky telemetry signals are inverted.  To connect a cleanflight capable board to an FrSKy receiver you have some options.
-
-1. A hardware inverter - Built in to some flight controllers.
-2. Use software serial and enable frsky_inversion.
-3. Use a flight controller that has software configurable hardware inversion (e.g. STM32F30x).
-
-For 1, just connect your inverter to a usart or software serial port.
-
-For 2 and 3 use the cli command as follows:
-
-```
-set frsky_inversion = 1
-```
-
 ## CLI command differences from baseflight
 
 ### gps_type

docs/Telemetry.md

@@ -0,0 +1,49 @@
+# Telemetry
+
+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.
+
+Two telemetry providers are currently supported, FrSky (the default) and Graupner HoTT V4.
+
+## FrSky telemetry
+
+See the Configuration examples in the documentation for details on how to enable it.
+
+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.
+
+FrSky telemetry signals are inverted.  To connect a cleanflight capable board to an FrSKy receiver you have some options.
+
+1. A hardware inverter - Built in to some flight controllers.
+2. Use software serial and enable frsky_inversion.
+3. Use a flight controller that has software configurable hardware inversion (e.g. STM32F30x).
+
+For 1, just connect your inverter to a usart or software serial port.
+
+For 2 and 3 use the cli command as follows:
+
+```
+set frsky_inversion = 1
+```
+
+## HoTT telemetry
+
+See the Configuration examples in the documentation for details on how to enable it.
+
+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.
+
+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.
+
+Connect as follows:
+```
+HoTT TX/RX -> Serial RX (connect directly)
+Serial TX -> 1N4148 Diode -(|  )-> HoTT TX/RX (connect via diode)
+```
+
+The diode should be arranged to allow the data signals to flow the right way
+
+```
+-(|  )- == Diode, | indicates cathode marker.
+```
+
+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.
+
+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.