Industrial I/O expansion board (4-20mA, 0-10V, contactor)

I have been working on scratching a personal itch with the BeagleBoard
and thought I would make an announcement to see if there are any other
people interested or with the same problem.

The expansion board (dubbed the Hardhat) is an industrial analog I/O
board, for interfacing with various "process control" pieces of
equipment (RTD transmitters, VFDs, etc). Its an all-inclusive board
with 4-20mA and 0-10V inputs and outputs (sourcing 4-20mA
transmitters), an RS485 half duplex port (for MODBUS) as well as
accepting a 24V power input to run the whole thing (BeagleBoard

I'm busy documenting the design as is and awaiting prototype boards.
The design will be under an Open Source Hardware license (likely CC-SA-

More information can be found here:

Hi Yann,

Your Hardhat board will solve a few problems for me. I will follow
your progress with interest.



Isolated 4-20mA would be really useful, together with switchable (or link select-able) 24V loop power!


Im also interested in that project. Can you provide some more details?
We are also working on an extension board with 3x isolated rs485, 2x CAN Bus, analogue inputs, digital inputs and power relay.

Hi, did anything ever come of this?

I have a complete design. 4 channel, optically isolated, and accurate. I need help writing the driver. loop power is totally isolated to protect the beagle.