2.8" round USB screen (rebranded by SAMA) not detected: different VID/PID (1a86:ca21)

Title

2.8" round USB screen (rebranded by SAMA) not detected: different VID/PID (1a86:ca21) than the one hardcoded for this model (1cbe:0028)

Description

I have a SAMA AIO liquid cooler with an integrated 2.8" round LCD screen. The device identifies itself to the OS as "Turing" / "UsbMonitor", so I assumed it matched the recently added "2.8" round (V1.X new HW rev.)" support from PR #995.

However, after selecting this screen size in configure.py and running main.py, I always get:

Import error: USB device not found

Investigation

I checked library/lcd/lcd_comm_turing_usb.py and found:

VENDOR_ID = 0x1cbe
PRODUCT_ID = {0x0028: (480, 480),  # Turing 2.8" round (USB)

But my actual device, confirmed via lsusb -v, reports:

Bus 001 Device 007: ID 1a86:ca21 QinHeng Electronics UsbMonitor
  idVendor           0x1a86 QinHeng Electronics
  idProduct          0xca21 UsbMonitor
  iManufacturer      1 Turing
  iProduct           2 UsbMonitor
  iSerial            3 CT21INCH
  bDeviceClass       2 Communications
  bNumConfigurations 1
  bNumInterfaces     2
  MaxPower           500mA

So it seems there are (at least) two different hardware variants of the "2.8" round" screen circulating, using different USB controller chips:

• 1cbe:0028 — currently supported by this project
• 1a86:ca21 (QinHeng) — my device, reported by SAMA AIO coolers, NOT currently supported

Environment

• OS: Fedora Linux 44 (KDE Plasma)
• Kernel: 6.19.10-300.fc44.x86_64
• Python: 3.14
• turing-smart-screen-python version: commit a3a375d (main, includes PR #995)
• Hardware: SAMA AIO liquid cooler with integrated 2.8" round LCD (sold under SAMA branding, screen itself reports manufacturer "Turing", serial "CT21INCH")

Additional note

I also found and fixed a small unrelated bug while testing: in configure.py, SIZE_2_8_INCH_NEWREV is defined on line 80, but the code further down referenced it as SIZE_2_8_ROUND_USB (an apparent leftover from a rename), causing a NameError on startup. I fixed this locally with sed -i 's/SIZE_2_8_ROUND_USB/SIZE_2_8_INCH_NEWREV/g' configure.py to get past that step. Happy to confirm if this needs a separate issue.

Windows confirmation

The screen works perfectly on Windows using TURZX v3.1.0 (the official Windows software for this type of screen). This confirms that:

1. The hardware is fully functional and genuine Turing/TURZX compatible hardware
2. A working communication protocol with chip 1a86:ca21 exists — it is implemented in TURZX v3.1.0 for Windows
3. This is purely a missing implementation on the Linux side, not a hardware limitation

This also means that if someone wanted to add support, capturing USB traffic with Wireshark + USBPcap on Windows while TURZX v3.1.0 communicates with the screen would be a viable path to reverse-engineer the protocol for the QinHeng chip.

Further testing — manually adding VID/PID

To go further, I manually patched lcd_comm_turing_usb.py to add my device:

VENDOR_ID = 0x1a86
PRODUCT_ID = {0xca21: (480, 480),  # SAMA/Turing 2.8" round (QinHeng USB)
    0x0028: (480, 480),  # Turing 2.8" round (USB)

After this change, running sudo python3 main.py produced a different result — the device was now found, but failed with:

Warning: set_configuration() failed: [Errno 16] Resource busy
AssertionError: Could not find USB endpoints

The kernel also confirms the device is detected correctly:

[ 7.805627] usb 1-10.2: New USB device found, idVendor=1a86, idProduct=ca21, bcdDevice=1.00
[ 7.805639] usb 1-10.2: Product: UsbMonitor

This confirms that:

1. The device IS detected by Linux and by the program when the correct VID/PID is added
2. The failure is at the USB endpoint level — the QinHeng chip (1a86:ca21) has a different internal USB structure than the 1cbe:0028 chip currently supported
3. A specific protocol implementation for the QinHeng chip is needed — not just a VID/PID addition

Request

Could support for VID 0x1a86 / PID 0xca21 be added with its own protocol implementation? The device is detected by Linux, works perfectly on Windows with TURZX v3.1.0, and has a 480x480 resolution. I'm happy to capture USB traffic with Wireshark + USBPcap on Windows while TURZX v3.1.0 is running, run any test scripts, or provide any other debug info needed to implement support for this QinHeng variant.

Start with library/lcd/lcd_comm_turing_usb.py and compare the existing 1cbe:0028 handling with the 1a86:ca21 device's USB endpoints. Capture USB traffic with Wireshark and USBPcap while TURZX v3.1.0 communicates with the screen, then use those observations to define the QinHeng protocol. Done means the 480x480 SAMA/Turing variant is detected and communicates successfully on Linux.