Control Arduino through UART txd rxd

[CapnKernel]

For my prototype, I used a USB cable (look for the blue wire):

      

Since the RPi and nano are in the same box, I felt using the USB cable wouldn't have electrical problems in the short term.

Since then I've made a PCB, and I'm using a chip which provides isolation, and level shifts from RPi's 3.3V to the Arduino nano's 5V (top right corner, circled):

      

@seandepagnier's design uses a CPC5001 (U1 on page 2):

  http://pypilot.org/schematics/hbridge_controller.pdf

I'm using an Si8621, because it's cheaper and easier to get.

  https://au.element14.com/silicon-labs/si...dp/2423245

The RPi and nano are talking through the Si8621 just fine.