Ok, so we are new to programming for the M600 with the A3.  We are looking to control onboard devices (servos) with an onboard Raspberry Pi and also send sensing back to remote control tablet.  

We came across this information:

https://developer.dji.com/onboard-sdk/documentation/development-workflow/hardware-setup.html

We are looking for best practice.  What is the difference between using STM32 board vs direct cabling to the Pi  (PC/Linux ) with a FT232 USB Cable TTL?

Can anyone provide some suggestions or best practices? We would greatly appreciate any input.

For the M600, only OSDK features are compared, STM32 and PC/Linux support features are the same, there is not much difference.
But if you need to do some advanced algorithmic processing and add custom cameras, then PC/Linux is more appropriate; If you want to do low cost, small size, and low power consumption, then STM32 is the first choice.

Thank you for your input. This has helped us very much.

With much respect!

Alan