useful_linux_scripts/set_up_can_usb.md

Example binding slcan to a USB tty serial port

sudo slcand -o -s3 -t hw -S 3000000 /dev/ttyACM3 sudo ip link set dev can0 up type can bitrate 100000

Example seting up can0 for an SDS CAN HAT for Raspberry pi

sudo ip link set can0 down sudo ip link set can0 type can bitrate 100000 sjw 128 sudo ip link set can0 up

to upgrade usb devices in chromium

Creating a udev rule to grant write permissions to a USB device and automate updating a dongle involves the following steps:

1. Identify the USB Device

Plug in the USB device or dongle and identify its attributes using lsusb or udevadm. Using lsusb:

Run:

lsusb

Find your device in the list. It will look something like this:

Bus 001 Device 004: ID 1234:5678 Vendor_Name Product_Name

Vendor ID: 1234
Product ID: 5678

Using udevadm:

Run:

udevadm info --query=all --name=/dev/bus/usb/001/004

(Replace 001 and 004 with the values from lsusb.)

This command provides detailed information about the device, such as the idVendor and idProduct. 2. Create a udev Rule

Create a new file for your custom udev rules in /etc/udev/rules.d/.

For example:

sudo nano /etc/udev/rules.d/99-usb-dongle.rules

Add the following rule:

SUBSYSTEM=="usb", ATTR{idVendor}=="1234", ATTR{idProduct}=="5678", MODE="0666"

Replace 1234 and 5678 with your device's Vendor and Product IDs.
MODE="0666" grants read and write permissions to all users. For more restricted access, specify a group and set group ownership (e.g., GROUP="usbusers" and MODE="0660").

3. Reload udev Rules

After saving the rule, reload udev rules and trigger them:

sudo udevadm control --reload-rules sudo udevadm trigger

4. Test Permissions

Unplug and replug your device, then check the permissions:

ls -l /dev/bus/usb/001/004

(Replace 001 and 004 with the actual bus and device numbers.)

It should now show the updated permissions. 5. Automate Dongle Updates

If you have a script or tool to update the dongle, ensure it runs as the user with proper permissions. For example, create an update script:

#!/bin/bash echo "Updating dongle..."

Replace with the actual command to update your dongle

your-update-command --device=/dev/bus/usb/001/004

Make it executable:

chmod +x update_dongle.sh

Run the script after ensuring permissions are correct. 6. Optional: Match by Serial Number or Other Attributes

If multiple devices share the same Vendor/Product IDs, you can refine the rule by matching additional attributes like serial, idProduct, or idVendor.

Example:

SUBSYSTEM=="usb", ATTR{idVendor}=="1234", ATTR{idProduct}=="5678", ATTR{serial}=="ABCDEFG12345", MODE="0666"

You can find these attributes using:

udevadm info --attribute-walk --name=/dev/bus/usb/001/004