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MagTag SSD1680 contrast fix (FPC-7519rev.b only) #10992

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MagTag SSD1680 contrast fix (FPC-7519rev.b only) #10992

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c16d316
MagTag SSD1680 FPC-7519rev.b: use VCOM=0x20 for correct contrast
mikeysklar May 8, 2026
5dd1097
MagTag SSD1680 FPC-7519rev.b: tune VCOM to 0x14 (-1.0V)
mikeysklar May 9, 2026
83576c6
MagTag SSD1680 FPC-7519rev.b: rename vcom20 → vcom14, add OTP note
mikeysklar May 9, 2026
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50 changes: 46 additions & 4 deletions ports/espressif/boards/adafruit_magtag_2.9_grayscale/board.c
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Original file line number Diff line number Diff line change
Expand Up @@ -128,6 +128,41 @@ const uint8_t ssd1680_display_start_sequence[] = {
0x22, 0x00, 0x01, 0xc7 // display update mode
};

// FPC-7519rev.b (User ID byte 0xca) requires lower VCOM for correct contrast.
// VCOM=0x14 (-1.0V) confirmed by reading the panel's OTP register (cmd 0x2D, byte 1 = 0x14).
// The 0x44 panel works correctly with the default VCOM=0x28, so keep them separate.
const uint8_t ssd1680_vcom14_display_start_sequence[] = {
0x12, DELAY, 0x00, 0x14, // soft reset and wait 20ms
0x11, 0x00, 0x01, 0x03, // Ram data entry mode
0x3c, 0x00, 0x01, 0x03, // border color
0x2c, 0x00, 0x01, 0x14, // Set vcom voltage (0x14 = -1.0V, tuned for FPC-7519rev.b)
0x03, 0x00, 0x01, 0x17, // Set gate voltage
0x04, 0x00, 0x03, 0x41, 0xae, 0x32, // Set source voltage
0x4e, 0x00, 0x01, 0x01, // ram x count
0x4f, 0x00, 0x02, 0x00, 0x00, // ram y count
0x01, 0x00, 0x03, 0x27, 0x01, 0x00, // set display size
0x32, 0x00, 0x99, // Update waveforms
0x2a, 0x60, 0x15, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // VS L0
0x20, 0x60, 0x10, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // VS L1
0x28, 0x60, 0x14, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // VS L2
0x00, 0x60, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // VS L3
0x00, 0x90, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // VS L4
0x00, 0x02, 0x00, 0x05, 0x14, 0x00, 0x00, // TP, SR, RP of Group0
0x1E, 0x1E, 0x00, 0x00, 0x00, 0x00, 0x01, // TP, SR, RP of Group1
0x00, 0x02, 0x00, 0x05, 0x14, 0x00, 0x00, // TP, SR, RP of Group2
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // TP, SR, RP of Group3
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // TP, SR, RP of Group4
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // TP, SR, RP of Group5
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // TP, SR, RP of Group6
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // TP, SR, RP of Group7
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // TP, SR, RP of Group8
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // TP, SR, RP of Group9
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // TP, SR, RP of Group10
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // TP, SR, RP of Group11
0x24, 0x22, 0x22, 0x22, 0x23, 0x32, 0x00, 0x00, 0x00, // FR, XON
0x22, 0x00, 0x01, 0xc7 // display update mode
};

const uint8_t ssd1680_display_stop_sequence[] = {
0x10, DELAY, 0x01, 0x01, 0x64
};
Expand All @@ -141,6 +176,7 @@ typedef enum {
DISPLAY_IL0373,
DISPLAY_SSD1680_COLSTART_0,
DISPLAY_SSD1680_COLSTART_8,
DISPLAY_SSD1680_COLSTART_8_VCOM14, // FPC-7519rev.b (User ID 0xca)
} display_type_t;

static display_type_t detect_display_type(void) {
Expand Down Expand Up @@ -218,8 +254,9 @@ static display_type_t detect_display_type(void) {
case 0x00:
return DISPLAY_SSD1680_COLSTART_0;
case 0x44:
case 0xca:
return DISPLAY_SSD1680_COLSTART_8;
case 0xca:
return DISPLAY_SSD1680_COLSTART_8_VCOM14;
}
}

Expand Down Expand Up @@ -268,12 +305,17 @@ void board_init(void) {
} else {
epaperdisplay_construct_args_t args = EPAPERDISPLAY_CONSTRUCT_ARGS_DEFAULTS;
// Default colstart is 0.
if (display_type == DISPLAY_SSD1680_COLSTART_8) {
if (display_type == DISPLAY_SSD1680_COLSTART_8 || display_type == DISPLAY_SSD1680_COLSTART_8_VCOM14) {
args.colstart = 8;
}
args.bus = bus;
args.start_sequence = ssd1680_display_start_sequence;
args.start_sequence_len = sizeof(ssd1680_display_start_sequence);
if (display_type == DISPLAY_SSD1680_COLSTART_8_VCOM14) {
args.start_sequence = ssd1680_vcom14_display_start_sequence;
args.start_sequence_len = sizeof(ssd1680_vcom14_display_start_sequence);
} else {
args.start_sequence = ssd1680_display_start_sequence;
args.start_sequence_len = sizeof(ssd1680_display_start_sequence);
}
args.stop_sequence = ssd1680_display_stop_sequence;
args.stop_sequence_len = sizeof(ssd1680_display_stop_sequence);
args.width = 296;
Expand Down
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