Which board fits our robot best? Please help!

As part of a university project, we are developing a robotic arm that shall operate under water. We would like each joint module along the arm to be controlled by an Arduino board mounted inside a dry and watertight volume. I have no previous experience with Arduino boards so I would be very grateful if someone could provide advise regarding the Arduino board which might be most suitable for us.

Our main requirements to the Arduino board are as follows:

As small as possible. Preferrably smaller than 60x60 mm.


  • Several digital I/O ports
  • Several A/D channels
  • PWM output (at least 4 channels)
  • RS-232 (preferrably two such interfaces)
  • CAN bus
  • Preferrably LEDs on the board which we can use for debugging and status output.
  • Preferrably a real time debugging interface which easily allows us to debug the code.

Which Arduino boards could be suitable for our robotic arm?

Thank you so much for any helpful advice!

You need a custom board to be that small and have RS232 (adds 1 chip, 5 caps, 9 pin connector) and CAN support (2 chips, MCP2515 CAN Bus controller with SPI interface and MCP2551 CAN transceiver, several Rs & Cs, 9 pin connector).
Or an Arduino Uno wit CANBUS shield and RS232 Shield stacked on top. Bulky. Maybe one will have some prototype area for LEDs, and you’ll get lucky and the connectors won’t interfere. Some examples:
(because Sparkfun and Adafruit are taking forever to open):
But you didn’t specify a height, so maybe you can live with that.
If you need it lower, single layer solution, I can do a custom design for you. I have found adding Serial.prints to be enough debug support.
Using a '1284P for a processor will add a 2nd hardware serial port so you have one for RS232 and one for USB for debug back to a PC and code download during development.