Enabling GPS using NMEA

[L4ncelot]

Hi,

I would like to use emlid’s reach rtk module with px4 firmware. My current setup is navio2 with raspberry pi 3 to which rtk reach is connected.

I’ve read that px4 doesn’t support emlid’s ERB format but it does support NMEA.

Is there a way to enable this feature in px4 firmware? Is there a way to read NMEA output, then send it to some px4 module (I don’t know if there’s one, but it should exist since px4 supports other RTK systems) to output corrections in RTCM3 format?

Thanks in advance for any advice.

[fulano]

I’m bumping. I’ve been searching the forum, but all post I find about PX4 and NMEA are old or unanswered.

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Thanks!

[sibujacob]

Has this been resolved regarding NMEA messages not being read by Px4 through Pixhawk v2.1 such as the CUBE .
It is a shame we have developers who don’t understand anything technically and are not willing to place a piece of code while we alert them on the issue…
My GPS module outputs GNGGA , GNGSA ,GPGSV , GQGSV , GAGSV , GBGSV , GNSVD,GNRMC , GNGST . i am surprised not one of these messages are detected by Orange CUBE Px4 !

[Justin_Armer]

Looks like the NMEA drivers haven’t been updated since Feb of 2021. The links to the trimble website they reference are dead. it looks the NMEA decoder was hacked at one point to support differential and that broke the health checks for a valid NMEA stream.

[Justin_Armer]

More digging this morning. Both ‘NMEA’ and ‘Ashtech’ have decoders for ingesting NMEA 0813 data in GGA sentence format. However, the decoders are different in each driver which explains why setting GPS device type to Ashtech works for some NMEA devices and the generic NMEA type works for others. In either case it looks like there is no handling of null fields for differential GPS (despite the NMEA spec calling this out) so this is likely leading to the incompatibility issues. More to follow

[sibujacob]

Is there anyway you could fix this GPS NMEA driver issue so that we could rebuild the Px4 firmware with the nmea driver

[Justin_Armer]

Yes but it may be easier to modify the code on my NMEA device to just send what PX4 is expecting. We will see

[sibujacob]

@Justin_Armer
Hello,
Thanks for the feedback.
Please advice here if you succeed in that route.
I tried using the GPS satview software. It does detect the GPS and fills some data but the GPS status always indicates
" status not ok"
Any idea where to look under Px4 folder what PX4 expects as data from a NMEA style GPS .

[Justin_Armer]

same issue on my end. the GPS drivers are here src/drivers/gps/devices/src