Differences between ST7789 170x320 LCDs

[Fujix1]

I'm using an ESP32 S3 SPI + ST7789 170x320 LCD, which is available at:
https://ja.aliexpress.com/item/1005007187107245.html.

I ordered the same product one year ago and last week. This time I received a slightly different LCD on the same PCB.

The one on the left is the new one. The PCBs look identical.

The new LCD display colors are darker and may be operating at a lower gamma value.

Is it possible to configure LovyanGFX options for this LCD?

Thank you.

FYI, my current configration is here:
https://github.com/Fujix1/NanoDrive7/blob/main/src/disp.cpp

[tobozo]

hi,

thanks for your feedback 👍

you can either use a copy of Panel_ST7789 struct (e.g. rename it to Panel_ST7789_19 and alter the gamma settings manually, or use tft.writeCommand() with the gamma control registers (0xE0, 0xE1) followed by looping tft.writeData() with their respective gamma values

    bool writeCommand(uint32_t data, uint_fast8_t bit_length) override;
    void writeData(uint32_t data, uint_fast8_t bit_length) override;

Going further and being able to distinguish one display model from the other would require to read the device id, as it is done with well-known devices in the autodetect:

LovyanGFX/src/lgfx/v1_autodetect/LGFX_AutoDetect_ESP32_all.hpp

Lines 707 to 735 in 5438181

	static uint32_t _read_panel_id(lgfx::IBus* bus, int32_t pin_cs, uint_fast16_t cmd = 0x04, uint8_t dummy_read_bit = 1) // 0x04 = RDDID command
	{
	size_t dlen = 8;
	uint_fast16_t read_cmd = cmd;
	if (bus->busType() == bus_type_t::bus_parallel16)
	{
	dlen = 16;
	read_cmd = getSwap16(read_cmd);
	}
	bus->beginTransaction();
	_pin_level(pin_cs, true);
	bus->writeCommand(0, dlen);
	bus->wait();
	_pin_level(pin_cs, false);
	bus->writeCommand(read_cmd, dlen);
	bus->beginRead(dummy_read_bit);
	uint32_t res = 0;
	for (size_t i = 0; i < 4; ++i)
	{
	res += ((bus->readData(dlen) >> (dlen - 8)) & 0xFF) << (i * 8);
	}
	bus->endTransaction();
	_pin_level(pin_cs, true);
	ESP_LOGV(LIBRARY_NAME, "[Autodetect] read cmd:%02x = %08x", (unsigned int)cmd, (unsigned int)res);
	return res;
	}

However, your configuration uses cfg.readable = false;, which is somehow confusing since it also specifies cfg.freq_read = 40000000;, but hints at the possibility that this panel is not readable.

[Fujix1]

Thank you for qurick response!

I changed

cfg.readable = true;
cfg.spi_3wire = true;

but I can't get the device id yet. I'm using the Arduino IDE.

I'll also try tweaking use the gamme control registers.

[Fujix1]

I adjusted the gamma settings and now I got fairly good display now:

        CMD_PVGAMCTRL, 14, 0xd0, 0x00, 0x00, 0x02, 0x05, 0x18, 0x25, 0x35, 0x35, 0x03, 0x08, 0x0c, 0x0e, 0x11,
        CMD_NVGAMCTRL, 14, 0xd0, 0x00, 0x00, 0x02, 0x04, 0x18, 0x25, 0x40, 0x38, 0x08, 0x12, 0x0e, 0x12, 0x15,

Thank you again.