Add custom overlay for MCP2517FD for Raspberry pi 4 for CAN bus FD

dreyplatt · September 20, 2020, 4:23am

So, I am trying to interface with the can bus hat from seeed studio using the raspberry pi 4.

This new board uses the newer mcp2517fd chip instead of the notorious mcp2515 chip which is built into raspbian. I need to now add this overlay to

/resin-boot/overlays

I see the

mcp2515-can0.dtbo

overlay. Of course resin-boot is read only so I have to do something before it starts up, but have no idea what that would be.

phil-d-wilson · September 21, 2020, 8:28am

Hi Drey!

I’m glad to see you’re still fighting! We’re working in the background to try and work out your Beaglebone Green issue with CANbus, but moving over to a more capable device might be a good step anyway.

So to this issue, you can use our special configurable variables to set DT Overlays:

This page gives some guidance for the overlay you’re trying to use:

github.com

raspberrypi/linux/blob/rpi-4.19.y/arch/arm/boot/dts/overlays/README

Introduction
============

This directory contains Device Tree overlays. Device Tree makes it possible
to support many hardware configurations with a single kernel and without the
need to explicitly load or blacklist kernel modules. Note that this isn't a
"pure" Device Tree configuration (c.f. MACH_BCM2835) - some on-board devices
are still configured by the board support code, but the intention is to
eventually reach that goal.

On Raspberry Pi, Device Tree usage is controlled from /boot/config.txt. By
default, the Raspberry Pi kernel boots with device tree enabled. You can
completely disable DT usage (for now) by adding:

    device_tree=

to your config.txt, which should cause your Pi to revert to the old way of
doing things after a reboot.

In /boot you will find a .dtb for each base platform. This describes the

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Hope this helps. Keep going, we’ll get you sorted!

Phil

npetridis · November 5, 2020, 1:03pm

Hello! I also need overlay support for MCP2517FD for raspberry pi 3B+.
Can you provide instructions on how to add the custom overlay?
Thank you in advance

npetridis · November 5, 2020, 1:18pm

Hi there! Did you manage to load the overlay?

acostach · November 5, 2020, 8:31pm

Hi @npetridis,

To include your custom overlay in a BalenaOS image you can open a PR in the balena-raspberrypi repository. Here’s an example PR on how to add your overlay https://github.com/balena-os/balena-raspberrypi/pull/484

npetridis · November 7, 2020, 11:21am

Thank you very much Alexandru! A little more help here.
So the PR has three file changes:

layers/meta-balena-raspberrypi/conf/layer.conf
Seems ok I’m just not sure if I should name my dtbo file 2xmcp2517fd or mcp2517fd. Should this be defined by how it is named in the raspberry kernel system?
layers/meta-balena-raspberrypi/recipes-kernel/linux/linux-raspberrypi_%.bbappend
Is straight forward
layers/meta-balena-raspberrypi/recipes-kernel/linux/linux-raspberrypi/0009-seeed studio-can-bus-v2-Add-dtbo-for-this-can-bus.patch
About my patch file, should it have prefix 0001, 0009 or something else?

Concerning the content of the patch file, the diff is extracted from where? A quick search lead me here but I can’t find arch/arm/boot/dts/overlays/Makefile path
I use raspberry pi 3 model B maybe not the correct branch?
Also I have located 2xMCP2517FD.dtbo and 2xMCP2517FD-overlay.dts files here, should I add these files somehow of are they already located in raspberry os (not balena os).
Sorry for the noob questions first time trying to figure these out! Hopefully I will soon be able to contribute more independently!

robertgzr · November 9, 2020, 6:38am

heyo @npetridis,

the patched makefile is here https://github.com/raspberrypi/linux/blob/rpi-5.4.y/arch/arm/boot/dts/overlays/Makefile - github always struggles with lots of files in a directory but going via url works…