Hi all,

I just bought an FrSky Taranis for my quad copter and needed to get the Mavlink data up on the Taranis LCD telemetry display. So here is my solution using a Teensy3.1 as a converter between MavLink and the S.Port on FrSky X8R.

See attached file below...

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Hi Rolf,

is it possible to get the RSSI info into the pixhawk? I can't get this out of my minimosd, and im wonding if I need to have the teensy TX going into the minimosd?


Hey can you please make a simple tutorial on hot to set up the taranis for this, i have flasheed the teensy and soldered the pins and plugged the teensy into telem port and smart port but there is no telemetry displaying on the taranis???

It is in your radio manual setup section. Just set up you telemetry pages by adding new parameters to display.

I posted exactly the same question here but figured it out in 5 minutes later and removed my question.

In FrSkySPort.ino the integer ap_longitude and ap_latitude are divided by 100 and the result multiplied by 6 before sending to the SPort. I understand oring with 0x80000000 to set bit 31 high, but why the arithmetic? The photo of the Taranis shows the Lat and Long displays as degrees and MM.MMMM. Is the Taranis taking an integer and doing the conversion internally?


Yes, thank you Kent.
Unfortunately, I'm not so good in C.
Perhaps Rolf can help me.

regards Peter


I have added every single choice to my taranis screen all but rssi display data that is changing.

A1 says 4.76

and T1 and T2 say 32 but even say this when the teensy is disconnnected

Hey guys there is a flaw in the Teensy that is another hit to APM users, it was soeculated by the OP

Basically the teensy is 3.3v but the APM is 5v, the problem is that the teensy wont communicate with APM at this significantly higher voltadge, i wont pretend to know why?#

Simply put, if i power the apm from 3.3v it works, if i power it from 5v, it doesnt

Is there any advice and how to overcome this, also the APM i am testing on has a fried voltage regulator which is passing through 5v, is the telemetry port supposed to output 3.3v?

Permalink Reply by Rolf Blomgren on March 3, 2014 at 11:52am

There could be a problem with the signal levels from Teensy because it is 3,3V on TX output and the APM is 5V or even higher depending on the voltage you supply the APM with.

All inputs to the Teensy is 5V tolerant but it can only drive up to 3.3V.  You can try to use a level converter or lower the voltage to  the APM a little.

My APM is working with Teensy without a problem with a voltage supply from the 3DR Power module of 4,9V measured at the IO pins, the threshold level on ATMega2560 is ~3V @ 5.5V or ~2.8V @ 5V Vcc.

Which telemetry port are you talking about?? Is it the Mavlink or S.Port.

The APM sends the Mavlink data  to the Teensy at 5V and all digital pins are 5 volt tolerant on Teensy.

The Teensy sends  Mavlink data to the APM at 3.3V and as long as you don't supply the APM with more than 5V (max. for the APM) there should normaly not be a problem receiving  this signal at the APM. 

Check the APM you are using (you say there is a faulty regulator on it)

This is the code on the Taranis for the conversion:


             gps_long_lati_b1w = (gps_long_lati_data&0x3fffffff)/10000;

            gps_long_lati_a1w = (gps_long_lati_data&0x3fffffff)%10000;

      switch ((gps_long_lati_data & 0xc0000000)>>30) {

      case 0: {

                frskyData.hub.gpsLatitude_bp = (gps_long_lati_b1w/60*100)+(gps_long_lati_b1w%60);

                frskyData.hub.gpsLatitude_ap = gps_long_lati_a1w;

        frskyData.hub.gpsLatitudeNS = 'N';


      case 1: {

                frskyData.hub.gpsLatitude_bp = (gps_long_lati_b1w/60*100) + (gps_long_lati_b1w%60);

                frskyData.hub.gpsLatitude_ap = gps_long_lati_a1w;

        frskyData.hub.gpsLatitudeNS = 'S';




okay so i have an apm wich had a blow regulator that outputted 5v.

but after replacing it, i have found that even with 3v, the teensy still wont communicate with my APM when powered via 4.9v from USB

however when i power it with 4.95v via a UBEC it works, so that assumption is wrong, sorry, but this is noe confusing, what is it that when powered via USB the Teensy wont communicat ewith the APm and flashed red, but the moment IT is powered via a UBEC, 3v or 5V it works?

Does telemetry not work when connected via USB?

i think it is pretty normal that the usb connection prevents the telemtry connection from running.

tested it today and could not connect while powered via usb.

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