rule_steps.md

Manual udev rule steps for Rosmaster board

These are the detailed manual steps that add_rule.sh automates. Use them if you prefer not to run the script.

1. Identify the device

Plug the board in and list serial devices:

ls /dev/ttyUSB*

Optionally inspect attributes (adjust ttyUSB0 if different):

udebadm info -a -n /dev/ttyUSB0 | less

Typical CH340 / QinHeng adapters use vendor:product 1a86:7523.

2. Create the udev rule file

sudo nano /etc/udev/rules.d/99-rosmaster.rules

Paste (modify myserial to your desired symlink, keep quotes):

KERNEL=="ttyUSB*", ATTRS{idVendor}=="1a86", ATTRS{idProduct}=="7523", MODE:="0777", SYMLINK+="myserial"

(You can also tighten permissions, e.g. MODE:="0666" or use GROUP="dialout").

3. Reload rules

sudo udevadm control --reload-rules
sudo udevadm trigger

Or unplug and replug the device.

4. Verify

ls -l /dev/myserial

It should show a symlink pointing to something like ttyUSB0.

5. Use in Python

from Rosmaster_Lib import Rosmaster
rm = Rosmaster(com="/dev/myserial")

Because Rosmaster defaults to /dev/myserial (if you keep that name) you can also omit the argument.

6. Custom vendor/product

If your adapter uses a different VID:PID, adapt the rule:

KERNEL=="ttyUSB*", ATTRS{idVendor}=="abcd", ATTRS{idProduct}=="1234", MODE:="0666", SYMLINK+="myros"

Find the correct IDs via:

lsusb

7. Multiple identical adapters

Match by physical path or serial attribute. After running:

udebadm info -a -n /dev/ttyUSB0 | grep -E 'serial|idVendor|idProduct'

Add an extra selector, e.g. ATTRS{serial}=="A50285BI" to distinguish boards.

8. Reverting

Delete the line (or file) and reload rules:

sudo rm /etc/udev/rules.d/99-rosmaster.rules
sudo udevadm control --reload-rules
sudo udevadm trigger

Script alternative

All of the above condensed:

sudo ./add_rule.sh myserial