[FAQ] SK-TDA4VM: How do I use the CAN bus headers on SK-TDA4VM using Edge AI SDK?

Prerequisite: Download and flash Edge AI SDK prebuilt micro SD card image. This FAQ was made using 8.2 version of SDK: https://www.ti.com/tool/download/PROCESSOR-SDK-LINUX-SK-TDA4VM/08.02.00.02.

The Edge AI SDK's prebuilt SD card image comes packaged with the same Linux driver for CAN as used in PSDK Linux. The CAN bus can be enabled and used as documented here: https://software-dl.ti.com/jacinto7/esd/processor-sdk-linux-jacinto7/08_02_00_03/exports/docs/linux/Foundational_Components/Kernel/Kernel_Drivers/MCAN.html

Linux discovers the CAN bus instances with the following names:

can0=J1=MCU_CAN0
can1=J5=CAN0
can2=J6=CAN5
can3=J2=CAN9

The header pins are defined like so (taken from SK userguide https://www.ti.com/lit/ug/spruj21b/spruj21b.pdf?ts=1651850889758&ref_url=https%253A%252F%252Fwww.google.com%252F):

Running "ifconfig -a" should show available CAN interfaces like below logs:

root@am69a-sk:/opt/edgeai-gst-apps# ifconfig -a
can0: flags=128<NOARP>  mtu 16
        unspec 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00  txqueuelen 10  (UNSPEC)
        RX packets 0  bytes 0 (0.0 B)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 0  bytes 0 (0.0 B)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0
        device interrupt 235

can1: flags=128<NOARP>  mtu 16
        unspec 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00  txqueuelen 10  (UNSPEC)
        RX packets 0  bytes 0 (0.0 B)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 0  bytes 0 (0.0 B)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0
        device interrupt 236

can2: flags=128<NOARP>  mtu 16
        unspec 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00  txqueuelen 10  (UNSPEC)
        RX packets 0  bytes 0 (0.0 B)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 0  bytes 0 (0.0 B)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0
        device interrupt 237

can3: flags=128<NOARP>  mtu 16
        unspec 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00  txqueuelen 10  (UNSPEC)
        RX packets 0  bytes 0 (0.0 B)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 0  bytes 0 (0.0 B)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0
        device interrupt 238

eth0: flags=4099<UP,BROADCAST,MULTICAST>  mtu 1500
        ether 08:04:b4:2e:8f:39  txqueuelen 1000  (Ethernet)
        RX packets 0  bytes 0 (0.0 B)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 0  bytes 0 (0.0 B)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

lo: flags=73<UP,LOOPBACK,RUNNING>  mtu 65536
        inet 127.0.0.1  netmask 255.0.0.0
        inet6 ::1  prefixlen 128  scopeid 0x10<host>
        loop  txqueuelen 1000  (Local Loopback)
        RX packets 92  bytes 7642 (7.4 KiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 92  bytes 7642 (7.4 KiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

root@am69a-sk:/opt/edgeai-gst-apps#

To test CAN driver, we can do a loopback by connecting two CAN bus on SK board, then running the following commands:

root@j721e-eaik:~# ip link set can0 type can bitrate 500000
root@j721e-eaik:~# ip link set can1 type can bitrate 500000
root@j721e-eaik:~#
root@j721e-eaik:~#
root@j721e-eaik:~#
root@j721e-eaik:~# ip link set up can0
root@j721e-eaik:~# ip link set up can1
root@j721e-eaik:~#
root@j721e-eaik:~#
root@j721e-eaik:~# candump can0 &
[2] 1220
root@j721e-eaik:~# cansend can1 123#1122334455667788
  can0  123   [8]  11 22 33 44 55 66 77 88
root@j721e-eaik:~#

Regards,

Takuma

UPDATE - June 5, 2024

In 9.x SDK, CAN device tree nodes have been removed. They can be re-enabled by applying this patch:

4760.0001-Enable-MCAN-for-SK-TDA4VM-on-6.1-kernel.patch

1. The patch can be applied to the kernel source in Linux SDK 9.x version installable from here: https://www.ti.com/tool/download/PROCESSOR-SDK-LINUX-J721E
2. Kernel source is located within installed Linux SDK under board-support/ti-linux-kernel-6.1.*. It can be applied with "git apply /path/to/patch/0001-Enable-MCAN-for-SK-TDA4VM-on-6.1-kernel.patch". 
3. Build and installation can be done following the "Usage Examples" section here: https://software-dl.ti.com/jacinto7/esd/processor-sdk-linux-jacinto7/09_02_00_05/exports/docs/linux/Overview_Top_Level_Makefile.html 

*Note: this new patch changes name of CAN interface to main_mcan0, main_mcan5, main_mcan9, and mcu_mcan0, so update commands to initialize these interfaces to use these new names.

Regards,

Takuma