LG ACB8300

The LG ACB8300 is a cheap monitor calibration utility. It is designed for LG monitors and is currently only supported by LG's True Color Pro software.

I bought such a device, even though I don't have a LG display. My initial thought was that the device was just another rebranded colorimeter - but it turned out it was wrong.

This page describes the USB protocol as well as the work towards integrating it into Argyll CMS.

I traced parts of the LG_ACB8300.dll with OllyDBG. I built a small C wrapper around the library in order to have access to the funtions and their parameters. The wrapper simply loads the DLL entry points and calls DeviceOpen, Get_ADC, Get_XYZ, etc. in order to reverse engineer the functionality.

Inside the Get_XYZ function, a lot of floating point magic is going on. After reversing all the floating point assembly, it turns out that the conversion from ADC to XYZ is performing as follows:

1. Read ADC value from device
2. Do an offset correction (can be read from calibration)
3. Apply a correction matrix (can be read from calibration)
4. Do an offset correction (can be read from calibration)
5. Apply a monitor correction matrix

The monitor correction matrix is hardcoded in the DLL. The SetMonitorType() function simply loads a different matrix into memory.

The data section contains 7 different monitor types. Monitor Type 1 is a simple unity matrix.

For my DLL, the memory locations are:

The next 9 double numbers at the memory locations define the correction matrices. They are in row-column order.

The USB protocol consists of input reports and output reports, with a fixed length of 43 bytes. The host speaks first, the device responds (most of the time).

Send: 0x01
Response: 0x3

Send: 0x51
Response: 0x53

Send: 0x52
Response: 0x53

Send: 0x54
Response: 0x53

Send: 0x55
Response: 0x53

Send: 0x31
Response: 0x32

Send: 0x80
Response: 0x88

Send: 0x05
Response: 0x03

Whenever the button is pressed, the device sends 0x62.