Capture signals between MCU and display controller

[kelchm]

Given that the CGG1 is using an unknown display controller, we need to capture and try to reverse engineer the communication between the MCU and the display controller. As a first step, it will also be necessary to map out the test points on the reverse of the PCB.

Relevant Links

• https://github.com/znanev/MHO-C401#components (a similar controller may be being used)

[kelchm]

Display FCP Pinout (WIP)

Note: numbered from left-to-right with the PCB inverted. The first pin is marked on the PCB itself with a vertical white line.

FPC Pin	MCU Pin	Purpose	Test Point	Notes
Pin 1	10 [PO.08]		TP5
Pin 2	37 [P0.25]		TP1
Pin 3	9 [P0.07]		TP6
Pin 4	27 [P0.22]		TP2
Pin 5	39 [P0.27]		TP21
Pin 6	38 [P0.26]		TP22
Pin 7		VDD	TP20
Pin 8		Ground	GND
Pin 9		VDH (?)		Measured max of ~10V
Pin 10		VDL (?)		Measured max of ~5V

[kelchm]

I'm still getting up to speed with how to use a logic analyzer, but here is a raw initial capture in for ~10 seconds after power on for the six relevant test points (TP5, TP1, TP6, TP2, TP21, TP22).

~cgg1-10s-after-power-on.sal.zip~

EDIT: This is the same capture as the file above, but has been updated to add an SPI analyzer. cgg1-10s-after-power-on-fixed.sal.zip

[pvvx]

EDIT: This is the same capture as the file above, but has been updated to add an SPI analyzer.

CMD  DATA

0x04 POWER_ON

0x00 0x0F PANEL_SETTING
0x01 0x32 0x32 POWER_SETTING 
0x03 0x00 POWER_OFF_SEQUENCE_SETTING
0x30 0x03 PLL_CONTROL
0x20 0x47 0x47 0x01 0x87 0x87 0x01 0x47 0x47 0x01 0x87 0x87 0x01 0x81 0x81 0x01 LUT_FOR_VCOM // T_LUTV_init
0x23 0x87 0x87 0x01 0x87 0x87 0x01 0x47 0x47 0x01 0x47 0x47 0x01 0x81 0x81 0x01 LUT_CMD_0x23 // T_LUT_KK_init
0x26 0x47 0x47 0x01 0x47 0x47 0x01 0x87 0x87 0x01 0x87 0x87 0x01 0x81 0x81 0x01 LUT_CMD_0x26 // T_LUT_KW_init

0x18 0xF9 0x20 0xB5 0xAB 0x3C 0x00 0x00 0x40 0x05 0x0C 0x0F 0xFF 0xFF 0xF8 0xF2 0x3E 0x8F 0xFF DATA_START_TRANSMISSION_1

0x12 DISPLAY_REFRESH

0x04 POWER_ON

0x00 0x0F PANEL_SETTING
0x01 0x32 0x32 POWER_SETTING
0x03 0x00 POWER_OFF_SEQUENCE_SETTING
0x30 0x07 PLL_CONTROL
0x15 0x00 0x87 0x01 PARTIAL_DISPLAY_REFRESH
0x03 0x06 POWER_OFF_SEQUENCE_SETTING
0x20 0x47 0x47 0x01 0x87 0x87 0x01 0x47 0x47 0x01 0x87 0x87 0x01 0x81 0x81 0x01 // T_LUTV_init
0x23 0x47 0x47 0x01 0x87 0x87 0x01 0x47 0x47 0x01 0x87 0x87 0x01 0x81 0x81 0x01 // T_LUTV_init
0x26 0x47 0x47 0x01 0x87 0x87 0x01 0x47 0x47 0x01 0x87 0x87 0x01 0x81 0x81 0x01 // T_LUTV_init
0x24 0x87 0x87 0x01 0x87 0x87 0x01 0x87 0x87 0x01 0x87 0x87 0x01 0x81 0x81 0x01 // T_LUT_KK_update
0x25 0x47 0x47 0x01 0x47 0x47 0x01 0x47 0x47 0x01 0x47 0x47 0x01 0x81 0x81 0x01 // T_LUT_KW_update

0x18 0xF9 0x20 0xB5 0xAB 0x3C 0x00 0x00 0x40 0x05 0x0C 0x0F 0xFF 0xFF 0xF8 0xF2 0x3E 0x8F 0xFF DATA_START_TRANSMISSION_1

0x12 DISPLAY_REFRESH

0x02 0x03 POWER_OFF

0x04 POWER_ON

0x00 0x0F PANEL_SETTING
0x01 0x32 0x32 POWER_SETTING 
0x03 0x00 POWER_OFF_SEQUENCE_SETTING
0x30 0x07 PLL_CONTROL
0x15 0x00 0x87 0x01 PARTIAL_DISPLAY_REFRESH
0x03 0x06 POWER_OFF_SEQUENCE_SETTING
0x20 0x47 0x47 0x01 0x87 0x87 0x01 0x47 0x47 0x01 0x87 0x87 0x01 0x81 0x81 0x01 // T_LUTV_init
0x23 0x47 0x47 0x01 0x87 0x87 0x01 0x47 0x47 0x01 0x87 0x87 0x01 0x81 0x81 0x01 // T_LUTV_init 
0x26 0x47 0x47 0x01 0x87 0x87 0x01 0x47 0x47 0x01 0x87 0x87 0x01 0x81 0x81 0x01 // T_LUTV_init 
0x24 0x87 0x87 0x01 0x87 0x87 0x01 0x87 0x87 0x01 0x87 0x87 0x01 0x81 0x81 0x01 // T_LUT_KK_update
0x25 0x47 0x47 0x01 0x47 0x47 0x01 0x47 0x47 0x01 0x47 0x47 0x01 0x81 0x81 0x01 // T_LUT_KW_update

0x18 0xF8 0x20 0x00 0x00 0x1C 0x00 0x40 0x80 0x41 0xA1 0x7F 0xFF 0xFF 0xF8 0x02 0x3E 0x8F 0xFF DATA_START_TRANSMISSION_1 

0x12 DISPLAY_REFRESH

0x02 0x03 POWER_OFF

[pvvx]

I didn't solder to the EPD connector pins. To CGG1-"M" made a driver based on your scan-capture and previous knowledge. Could you scan-capture for longer? Interested in the EPD update-refresh cycle.

Having changed the GPIO in source the MHO-C401, I added js function (in TelinkMiFlasher.html) a bit output for segments diagnostics:

var lcdb = new Uint8Array(19);
var lcdb_stage = 0;
var lcdb_cnt = 0;
function lcd_tst_segmets() {
    if(lcdb_stage == 0xff) return;
    switch(lcdb_stage) {
        case 0:
            lcdb.fill(0);
            lcdb_stage++;
            break;
        case 1:
            lcdb.fill(0xff);
            lcdb_cnt = 0;
            lcdb_stage++;
            break;
        case 2:
            lcdb.fill(0);
            lcdb[lcdb_cnt + 1] = 0xff;
            lcdb_cnt++;
            if(lcdb_cnt > 18) {
                lcdb_cnt = 1;
                lcdb_stage++;
            }
            break;
        case 3:
            lcdb.fill(lcdb_cnt);
            lcdb_cnt *= 2;
            if(lcdb_cnt > 0xff) {
                lcdb_cnt = 0;
                lcdb_stage = 0;
            }
            break;
        default:
            lcdb_stage = 0;
    }
    lcdb[0] = 0x60;
    addClog("Stage: "+lcdb_stage+"Send cmd (60): Set LCD data");
    settingsCharacteristics.writeValue(lcdb).then(_ => {addClog('Send data ok'); setTimeout(lcd_tst_segmets, 5000);});
}

Filmed the work on a video camera and did https://pvvx.github.io/CGG1/img/EPD_segments.gif

For further optimization, I would like to refine the EPD refresh cycle code.

[kelchm]

I didn't solder to the EPD connector pins.

To CGG1-"M" made a driver based on your scan-capture and previous knowledge.

Could you scan-capture for longer?

Interested in the EPD update-refresh cycle.

Sure! I'll post another capture later this week.

[pvvx]

@kelchm Thanks for attention. I have already read everything I need in the logic analyzer: https://github.com/pvvx/pvvx.github.io/tree/master/CGG1/SaleaeLogic