Some good news regarding the NVMPG for the EC500. It is now working. I had to modify the version of the EC500 I have to remove the opto couplers between the MCU and MAX232 IC. Serial would work a 9600 baud but nothing higher, the optos were just not fast enough. The newer version of the board does not have these so I was pretty sure they were the culprit.
A bit fiddly to remove, but well worth it.With the optos removed I was able to get the serial comms working and noted that I had not updated the DMA RX interrupt handlers from the NVEM version of the code.
So all working now and ready for testing.I've got issues pushing updates to the Remora-Novusun repo so have had to create a new Remora-EC500 repo temporarily. The latest bin file is here
github.com/scottalford75/Remora-EC500/tree/main/Firmware