# How to use the RaspberryPi with MCP2518FD to debug UAVCAN

**URL:** <https://forum.opencyphal.org/t/how-to-use-the-raspberrypi-with-mcp2518fd-to-debug-uavcan/1091>\
**Category:** General\
**Created:** [January 27, 2021, 5:15pm UTC](https://forum.opencyphal.org/t/how-to-use-the-raspberrypi-with-mcp2518fd-to-debug-uavcan/1091 "2021-01-27T17:15:07Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![generationmake](https://forum.opencyphal.org/user_avatar/forum.opencyphal.org/generationmake/32/611_2.png) [@generationmake](https://forum.opencyphal.org/u/generationmake)\
**Post date:** [January 27, 2021, 5:15pm UTC](https://forum.opencyphal.org/t/how-to-use-the-raspberrypi-with-mcp2518fd-to-debug-uavcan/1091/1 "2021-01-27T17:15:07Z")

</div>

We will have to do a lot of testing to get the Viper quadcopter flying and to [107-Arduino-UAVCAN](https://github.com/107-systems/107-Arduino-UAVCAN) library. So we need a proper test system. I think most of the users here use a computer or a notebook and some type of slcan adapter.

I didn’t want to risk to corrupt my working system by installing lots of software so I decided to use a Raspberry Pi and set up the system there. There are some CAN boards on the market but most of them use a MCP2515 CAN controller which has no CAN FD and they also don’t have the connector specified by the dronecode standard.

That’s why my first step was to design a new HAT with the MCP2518FD controller. This controller supports CAN FD and it is has also drivers in the mainline raspbian distribution.

This is how the board looks in CAD:

 ![CANFDZeroHAT_rendering](https://forum.opencyphal.org/uploads/default/original/1X/75bf879e4dc656ade59e3ab63696eafeafecf923.png)  
The board has only a few components:

- the MCP2518FD CAN controller
- a TCAN332 CAN transceiver which also supports CAN FD
- a switch to enable the termination resistor
- the JST GH connectors
- a terminal header to connect other CAN devices
- and a few LEDs to show the status

In reality it looks like this:

 ![IMG_2686_k](https://forum.opencyphal.org/uploads/default/original/1X/a0c868f2c79a530e242aaaad134220946e444866.jpeg)  
It plugs directly ontop of a Raspberry Pi. In my case I used a Raspberry Pi 4.

The HAT is open source hardware and all the data is available on github:  
[https://github.com/generationmake/CANFDZeroHAT](https://github.com/generationmake/CANFDZeroHAT)

To enable the HAT and the CAN controller in raspbian you simply have to edit `/boot/config.txt` and add line:

`dtoverlay=mcp251xfd,spi0-0,oscillator=20000000,interrupt=25`

keep care that you choose the right interrupt and SPI CE line and populate the corresponding resistor.

To enable CAN after boot up you have to enter:

`sudo ip link set can0 up type can bitrate 250000`

And that’s it. Now the interface is available as `can0`. You can show all CAN traffic by typing `candump -decaxta can0` or use `yakut` to transmit and receive UAVCAN messages.

The whole test setup with DUT looks like this:

 ![IMG_2685_k](https://forum.opencyphal.org/uploads/default/original/1X/ab72a9894586abe4a935629743de5f6d3c844c56.jpeg)

The Raspberry Pi can be accessed via WiFi so no more cables are necessary. You could also use cable LAN or directly connect a screen and a keyboard.

The HAT has also the possibility to supply power into the CAN systems. So small sensor nodes wouldn’t even require additional wiring.

I hope this helps to setup a proper test environment.

But I also have to confess that there is still a little problem: it seems like the MCP2518FD is sometimes missing some frames. Especially when there is a high load on the system. Maybe the receive interrupt isn’t handled properly. I will have to dig deeper into that but I think this could be only a minor issue.