+x

 

john123 - 2/23/2025 10:19:04 PM

Hi Sean I would be interested in your spare BT758

+x

 

Petertel - 2/20/2025 1:39:06 PM

Hello, first I introduce myself since it is my first intervention in this forum. My name is Pedro, I am from Spain, I have an ultralight plane and I like to fly and program my own instruments for my plane.

I am building the Bluetooth adapter to be able to send the autopilot information from Skydemon to an old TRUTRAK DIGIFLIGHT II autopilot but it is not capable of recognizing the NMEA sentences that the Skydemon sends it.

I have been analyzing the NMEA sentences that the Garmin GPSMAP 296 GPS sends and they are like this:

$GPRMC,111231,A,4041.3941,N,00036.84755,W,0.0,227.3,190225,0.8,W,D*11
$GPRMB,A,0.00,R,,EDNT,4859.7560,N,01053.0926,E,656.923,44.7,,V,D*41
$GPRMC,111232,A,4041.3941,N,00036.84755,W,0.0,227.3,190225,0.8,W,D*12
$GPRMB,A,0.00,R,,EDNT,4859.7560,N,01053.0926,E,656.923,44.7,,V,D*41
$GPRMC,111233,A,4041.3941,N,00036.84755,W,0.0,227.3,190225,0.8,W,D*13
$GPRMB,A,0.00,R,,EDNT,4859.7560,N,01053.0926,E,656.923,44.7,,V,D*41

However, the NMEA sentences that Skydemon currently throws are like this:

$GPRMC,111343,A,41$GPRMB,A,0.76,R,OR$GPRMC,111344,A,41$GPRMB,A,0.76,R,OR$GPRMC,111345,A,41$GPRMB,A,0.76,R,OR$GPRMC,111346,A,41$GPRMB,A,0.76,R

That is, the NMEA frames of the Skydemon are missing all the information fields and also do not end with CR+LF (0x0D + 0x0A) so the TRUTRAK autopilot is not able to interpret the NMEA sentences correctly.

Could you please check and correct it.

PD.-
Thank you very much Tim for having implemented the new Bluetooth functions, it is something that has been needed for a long time to be able to use Skydemon as the main route planning source.

+x

 

Tim Dawson - 2/24/2025 11:49:45 AM

Petertel and Ben, SkyDemon is sending full sentences but clearly they are being truncated somewhere. Are you on Android or iOS?

Petertel I look forward to hearing the results of your test. It's possible there is a MTU related problem where everything we send after the first X characters is simply being discarded.

+x

 

Tim Dawson - 2/24/2025 11:49:45 AM

Petertel and Ben, SkyDemon is sending full sentences but clearly they are being truncated somewhere. Are you on Android or iOS?

Petertel I look forward to hearing the results of your test. It's possible there is a MTU related problem where everything we send after the first X characters is simply being discarded.

+x

 

Petertel - 2/25/2025 10:42:17 AM

+x

 

Tim Dawson - 2/24/2025 11:49:45 AM

Petertel and Ben, SkyDemon is sending full sentences but clearly they are being truncated somewhere. Are you on Android or iOS?

Petertel I look forward to hearing the results of your test. It's possible there is a MTU related problem where everything we send after the first X characters is simply being discarded.

  Hello, I am using a Samsung Galaxy S20 mobile with Android 13 but I have also tried with 2 older Android tablets and the results are the same.
     I have been finding out that the MTU of the CC2541 bluetooth modules that are used by the HM-10 is 20 bytes, but the datasheet clearly indicates that the data packet that can be sent is larger and the module is responsible for packetizing and sending all the data on its own, so this should not be the problem. And the truncated data is exactly 18 bytes in all error frames.

  Additionally, I have tried using an app like nRF to send a data packet much larger than 20 bytes to the HM-10, and it receives all the data perfectly.

   And finally, with the tests that Michael has been able to do with various HM-10 models and Android and iPad, it is very curious how the MLT-08 works well with Android and iPad.

  Michael, can you look at what Bluetooth chip have each of the 3 modules you have tested have?. It is possible that the problem is there.

Regards, Peter.