Original Post by Neil Fitch at diydrones here
If you are like me and have ditched the 3DR radios in favor of the OrangeRX OpenLRS hardware then you will need to modify the APM settings in order to make this work.
The default baud rate for the APM when using the 3DR radios in 57600bps but that is too fast for the OpenLRS setup. I have configured mine to be 19200bps but haven’t had much time to test it yet, it seems to work well though.
First things first, i tried to use the openlrsng firmware by kh4 here but it didn’t work very well with Mavlink so i did some googling and found this by Martin and i must say it works well. Kh4 has said that he is re-writing some of the code and will eventually merge it into his branch. There is also a Mavlink bug fix listed here for his version.
So with Martin’s openlrsng installed on my APM 2.5 board we need to change some settings to be able to connect to the APM through the OrangeRX hardware:
With the APM connected to your computer fire up mission planner and navigate to Config / Tuning > Full Parameter List.
Set SERIAL1_BAUD to 19 which is 19200bps
set SR0_PARAMS to 5
set SR0_EXT_STAT to 2
set SR0_POSITION to 1
set SR0_EXTRA_1 to 1
set SR0_EXTRA_2 to 1
set SR0_EXTRA_3 to 1
At this point MinimOSD will be able to receive telemetry with the lower baudrate (Once you flash it with my firmware here)
When you’ve set those, press Write Params then change to the Config / Tuning > Standard Params and change Telemetry Baud Rate to: 19200
Write the parameters and disconnect mission planner and physically disconnect your USB connection to the APM.
at this point you will be able to connect to the PAM using Mission Planner through the OrangeRX hardware.