I’m not sure I was clear in what I said previously. The V6 board is set up to ‘supposedly’ have 5 UARTS. The v5.1 only has 3
UARTS. Now in theory it might might be possible to have more UARTS on the 5.1 board as the ARM STM32F405 chip can support more. However this is dependent upon which pinouts on the board are connected to which pins on the chip. In all likeliness it would mean sacrificing other functions (like pwm, buzzer, etc) by remapping the board for extra UARTS. However, to do this is currently above my knowledge level and not something I am looking to do.
The reason I say that the V6 ‘supposedly’ has 5 UARTS is because one UART is Rx only and another is Tx only. So not the most helpful. I think that the v6 board will work with the v6 nano hwdef target. However this will only give 4 pwm not 6 pwm. I will eventually get around to adding the last two pwm on the full size v6 board.