# SmartPort (SPort) Master

## Overview

With the Taranis, I got a GPS using the "SmartPort" interface from FrSky. It's basically a Serial bus on which you can add many sensors, which are (randomly ?) polled by the master of the bus.

* One wire bus ( => Half Duplex communication )
* Inverted logic
* 57600 bauds

Luckily the Teensy3 can do that. If you don't want to mess with voltage conversion, just use a Teensy3.1.

Most of the information comes from the OpenTX firmware, information on the Internet and direct analysis of the communication bus, so it might not be perfectly accurate.


## Teensy3

I don't have anything permanent, it's all on breadboard for now, so there's no schematic. Just connect the __signal__ pin of the sensor to the pin __ 1__ of the Teensy (__TX1__, __PB17__), Gnd to Gnd and... you're done.
You can power the GPS using the Vin pin of the Teensy, it makes development easier.

Here's the last code: {{:rc:dev:sport_master:tsysportmaster_20140916.tar.gz|}}

<note important>This is experimental work. Do this at your own risks.</note>

## Next ?

* Forge UBX/NMEA packets from SPort GPS data
* Serial/SPI/I2C output (something standard =) )
* Write a TauLabs module, like the existing one for the Hub Telemetry
* Attiny(25/45, or 85 but it might be overkill) port with serial output, with Low power mode so it can be embedded on virtually any other flight controller
* Support more sensors


## Links

I found different projects interfacing the Teensy3.1 with a SmartPort receiver (like the X8R):

* http://code.google.com/p/telemetry-convert/
* https://code.google.com/p/telemetry-convert/wiki/FrSkySPortProtocol
* http://diydrones.com/forum/topics/amp-to-frsky-x8r-sport-converter