[Sugestion / Request] APM 2.5 - use ATMega32-U2 as MAVLink to Frsky Telemetry translator

[Igor Campos]

Hello,

It would be really cool if we could use the APM 2.5 to directly talk to the FrSKY telemetry enabled receivers (or through a TTL-RS232 level shifter). Of course the ATMega2560 on the APM is already lacking CPU resources, and it wouldn't be possible to use it for such task. On the other hand, the ATMega32-U2 isn't working that hard, and there is plenty of room for doing that in it.

First I thought it would be great if we could listen to the UART0 TX used for telemetry on the APM to get the MAVLink packages, translate them to Frsky telemetry and transmit them through an APM input line using it as output with SoftwareSerial. But then I checked the APM 2.5 schematics and the MUX between ATMega2560 and the telemetry/ATMega32-U2 simply makes it impossible to do so.

The other alternative I came up with is:

1. If there is a jumper enabling a CPPM receiver, we would get 5 free I/O ports for the ATMega32-U2 on the APM inputs and processing power.
2. We could use a jumper from UART0 TX to a free APM input line
3. Use SoftwareSerial on the ATMega32-U2 to read the MAVLink packages and output them as FrSKY telemetry through another APM input line
4. Connect the FrSKY telemetry output to a TTL-RS232 level shifter and to the receiver RX  OR  modify the receiver to connect the TTL level output of the ATMega32-U2 directly to the receiver microprocessor RX line, similarly to what is described here (this one on the transmitter): http://www.rcgroups.com/forums/showpost.php?p=21127788&postcount=13. 

What do you guys think of it? Is it doable? How hard is it? Would it be a cool idea?

Sincerely,

Igor Campos

[Matthias Badaire]

Hi
I do not think that the current frsky implementation of frsky for pixhawk consume that much ressources.

I did not look into it yet but the only issue on apm indeed is to find a free serial port.

However the current implementation works only for D receiver not X receiver( s port) . sport is a bit more challenging but I am working on it.
M

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[Igor Campos]

I thought the current implementation was only for pixhawk, according to what I've seen on the wiki. but if it is possible to run on the ATMega2560 itself, even better.

Isn't the UART2 on the APM free?

[Matthias Badaire]

Hey
I have not looked at APM for a very long time but if uart2 is available, I will have a look. Limitation about d port is OK with you ?
M

[Nils Högberg]

Uart2 should be available. I have used it as a second mavlink port to get telemetry to my taranis like this: http://vizual54.github.io/APM-Mavlink-to-FrSky/

[Igor Campos]

No problems regarding d port. My receiver is a d8r-xp, so it should work fine for me.

Thanks very much for your attention.

[Daniel Frenzel]

I am not entirely sure whether I understood correctly. 

However I think the third option would be to use uart2 and shift the signal in the firmware part of the radio.

3DR radios (which you likely connect over uart2 on the APM2.*) should be based on ATMegas too. 

[Luis Vale Gonçalves]

Hi

There's a project based on the concepts that started at DIYDrones at http://diydrones.com/forum/topics/amp-to-frsky-x8r-sport-converter and has evolved to a project based on GitHub at https://github.com/chsw/MavLink_FrSkySPort.

Current implementation is working perfectly with Taranis X9D and X8R receivers via SPort and includes custom designed telemetry screens for the radio.

See if it is appropriate for you.

best regards

Luis