How to add CAN-FD to an SKR v2.0 and connect a CAN-FD Toolboard


From 3.5b2, it is now possible to use one or two toolboards with an STM32F4 based board using the CAN-FD protocol. To do so, you must purchase a separate SPI to CAN-FD module. TeamGloomy have worked with Flymaker/Mellow to produce 2 designs of module to suit the board you are using.

For the SKR v2.0 you can only use the EFD module (which plugs into EXP1/EXP2), which can be purchased from AliExpress.

Connecting the EXP1/EXP2 module (EFD)

The type of module shouldn’t be shared with a 12864 display.
Connect the EXP1 header on the module to EXP1 on the board. Connect the EXP2 header to EXP2 on the board.

Wiring for the driver module

CAN-FD only requires 2 wires to be connected between each board, CAN-H and CAN-L.
We recommend using stranded twisted wire pairs, such as those found in ethernet patch cables.

Using the image below, the CAN-H connection should be connected to CAN-H on the toolboard. The CAN-L connection should be connected to CAN-L. A jumper should be added to the pins highlighted by the red box.

EXP1/EXP2 SPI to CAN-FD Module Connections
EXP1/EXP2 SPI to CAN-FD Module Connections

Board.txt changes

The following two lines should be added to board.txt.
If you do not have a board.txt file in sys (the same location as config.g), create one using DWC.

//CAN-FD Interface
can.csPin = PA_4
can.spiChannel = 0

Config.g Changes

If successful, the toolboard should show in the object model.
See this page for more information about CAN addresses etc.