Thorlabs MDT69xx USB Configuration¶

Problem

The USB chip in the Thorlabs MDT69xx series (e.g., MDT693B) may identify as a Human Interface Device (HID). If the usbhid kernel driver binds to it, the device cannot be accessed via a serial interface, rendering it non-functional.

Solution: udev Rule

Identify Vendor and Product IDs

Run the following command to list all USB devices and locate the Thorlabs device:
```
lsusb
```
Example output:
```
Bus 001 Device 003: ID xxxx:xxxx Thorlabs MDT693B
```
Note the xxxx values for idVendor and idProduct.
Find the USB Kernel Path

Use udevadm to inspect the device attributes and locate the kernel path (e.g., 1-8:1.0):
```
udevadm info -a -p $(udevadm info -q path -n /dev/bus/usb/XXX/YYY)
```
Replace XXX and YYY with the bus and device numbers from lsusb. This command will print a lot of information. You are looking for a line like:
```
looking at device '/devices/pci0000:00/0000:00:14.0/usb1/1-8/1-8:1.0/0003:046A:B090.0002/hidraw/hidraw1':
```
Here, the 1-8:1.0 is what you are looking for.
Create the udev Rule

Edit or create a new udev rules file (e.g., /etc/udev/rules.d/99-thorlabs-piezo.rules) and add the following rule:
```
# Thorlabs piezo controller MDT693B
ACTION=="add", DRIVERS=="usb", ATTRS{idVendor}=="xxxx", ATTRS{idProduct}=="xxxx", SYMLINK+="USB_PIEZO_CTRL_1", RUN+="echo -n 'kernel_path' > /sys/bus/usb/drivers/usbhid/unbind"
```
Replace:
- xxxx with the Vendor and Product IDs from Step 1.
- kernel_path with the USB kernel path from Step 2 (e.g., 1-5.1.2.3:1.0).

Reload udev Rules

Apply the changes by reloading the udev rules:

sudo udevadm control --reload-rules
sudo udevadm trigger --action add