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Welcome to the MavlinkToPassthru wiki RELEASED v1.00 - 2018-07-05

This program is free software. You may redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation. See here <http://www.gnu.org/licenses>

The application was written in the hope that it will be useful, but it comes
without any warranty or implied warranty of merchantability or fitness 
for a particular purpose 

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Inspired by original S.Port firmware by Rolf Blomgren

Written from scratch by Eric Stockenstrom - April/May 2018

Acknowledgements and thanks to Craft and Theory (http://www.craftandtheoryllc.com/) for
the Mavlink / Frsky Passthrough protocol

Thank you to yaapu for advice and testing, and his excellent LUA scrip

Thank you florent for advice on working with my FlightDeck

Thank you athertop for advice and extensive testing

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Whereas the Orange (and some other) UHF Long Range RC and telemetry radio systems deliver 
19.2kb/s two-way Mavlink link, the FrSky Taranis and Horus hand-held RC controllers expect
to receive FrSky S.Port protocol telemetry for display on their screen.  While excellent 
firmware is available to convert Mavlink to the native S.Port protocol, the author is 
unaware of a suitable solution to convert to the Passthrough protocol. 

Recently some excellent Lua scripts for Taranis displays, like this one by yaapu 
https://github.com/yaapu/FrskyTelemetryScript 

This firmware converts APM or PX4 Mavlink telemetry to FrSky SPort passthrough telemetry, 
and is designed to run on a Teensy 3.2, or cheap STM32F103 (with some small mods and a signal 
inverter). The Mavlink procol telemetry can still be fed on to Mission Planner or other GCSs.

For now the Teensy 3.2 is prefered to the STM32 because of it's small size. It fits snugly 
into the Orange LRS UHF RX/TX enclosure in the back bay of the Taranis, and requires no 
external inverter.

FrSky telemetry is unlike regular telemetry. It evolved from a simple system to poll sensors on a 'plane, and as the number of sensors grew over time so too did the temetry requirements. Synchromous sensor polling is central to the telemetry, and timing is critical.

On the other hand, most flight control computers manage internal and external sensors so that the polling is handled internally. Telemetry is organised into meaningful records or frames and sent asynchronously (whenever you like).

Originally written for use with ULRS UHF, which delivers Mavlink to the back bay of the Taranis X9D Plus to provide Frsky Passthrough compatible telemetry to yaapu's outstanding LUA script.