fdcanusb

One of the necessary pieces for bringing up the moteus brushless controller and for ongoing development with it is being able to communicate with the device on the desk.  There aren’t many options for desktop FDCAN communication currently, and certainly none that are in the affordable range occupied by the CANUSB family of devices which I’ve used before and was very happy with.  Thus I created “fdcanusb”, a USB to FDCAN converter that allows one to communicate with FDCAN devices via a USB interface using a documented protocol, no drivers necessary.

The notable features:

  • USB 2.0 full speed host interface
  • ISO 11898-1: 2015 FDCAN interface on industry standard DB9 connector
  • Standards compliant bitrates up to 1/5Mbps supported
  • Software controllable termination
  • Frame sizes up to 64 bytes
  • Non-standards compliant bitrates allowed
  • Documented CDC ACM based host protocol (virtual COM port)
  • Apache 2.0 licensed firmware based on the STM32G474 controller

All for an expected sales prices of around $100.

This does come with some caveats: For one there is no galvanic or optoisolation, you get a common mode range of around +- 12V.  Another is that using just a USB 2.0 full speed interface means it may not be able to keep a FDCAN bus fully saturated at high bitrates.  Finally, the firmware will start out with just the bare bones capabilities, but can be extended to support features such as error injection, triggers, buffering, and more compact protocols in the future.

I’ve got the first functioning prototypes of these boards in hand now:

fdcanusb_r2
PCB render
dsc_2026
Set up for test

Next up I’ll describe bringing up this board.

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