ESP32 Forum

Posted: **Sat Feb 15, 2020 7:22 am**

Hi ALL,

In my app for some purposes I need not only to draw on TFT but also read some registers of ILI9341. There is an example in ESP-IDF which demonstartes of how to use ILI9341: https://github.com/espressif/esp-idf/tr ... spi_master In this example there is a function to Read Display Identification Information:

Code: [Select all] [Expand/Collapse]

uint32_t lcd_get_id(spi_device_handle_t spi)
{
    //get_id cmd
    lcd_cmd(spi, 0x04);
 
    spi_transaction_t t;
    memset(&t, 0, sizeof(t));
    t.length=8*3;
    t.flags = SPI_TRANS_USE_RXDATA;
    t.user = (void*)1;
 
    esp_err_t ret = spi_device_polling_transmit(spi, &t);
    assert( ret == ESP_OK );
 
    return *(uint32_t*)t.rx_data;
}

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but it always returns zeros and thats OK, but if I change port for example to 0x0A (Read Display Power Mode) it also always returns zeros....

I tried to test my hardware with Arduino and it works excellent:

Code: [Select all] [Expand/Collapse]

#include "SPI.h"
#include "Adafruit_GFX.h"
#include "Adafruit_ILI9341.h"
 
#define TFT_CS   27
#define TFT_DC   18
#define TFT_MOSI 15
#define TFT_CLK  14
#define TFT_RST  25
#define TFT_MISO 2
#define TFT_LED   26  // GPIO not managed by library
 
Adafruit_ILI9341 tft = Adafruit_ILI9341(TFT_CS, TFT_DC, TFT_MOSI, TFT_CLK, TFT_RST, TFT_MISO);
 
void setup() {
  Serial.begin(115200);
  Serial.println("ILI9341 Test!"); 
 
  tft.begin();
  pinMode(TFT_LED, OUTPUT);
 
  uint8_t x = tft.readcommand8(ILI9341_RDMODE, 0);
  Serial.print("Display Power Mode: 0x"); Serial.println(x, HEX);
  x = tft.readcommand8(ILI9341_RDMADCTL, 0);
  Serial.print("MADCTL Mode: 0x"); Serial.println(x, HEX);
  x = tft.readcommand8(ILI9341_RDPIXFMT, 0);
  Serial.print("Pixel Format: 0x"); Serial.println(x, HEX);
  x = tft.readcommand8(ILI9341_RDIMGFMT, 0);
  Serial.print("Image Format: 0x"); Serial.println(x, HEX);
  x = tft.readcommand8(ILI9341_RDSELFDIAG, 0);
  Serial.print("Self Diagnostic: 0x"); Serial.println(x, HEX);
  x = tft.readcommand8(ILI9341_RDDID, 0);
  Serial.print("Identification information: 0x"); Serial.println(x, HEX); 
}
 
void loop(void){}

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Using this code I'm finally got registers:

Code: [Select all] [Expand/Collapse]

02:17.198 -> load:0x3fff001c,len:1216
02:17.198 -> ho 0 tail 12 room 4
02:17.198 -> load:0x40078000,len:9720
02:17.198 -> ho 0 tail 12 room 4
02:17.198 -> load:0x40080400,len:6364
02:17.198 -> entry 0x400806b8
02:17.367 -> ILI9341 Test!
02:18.084 -> Display Power Mode: 0x94
02:18.084 -> MADCTL Mode: 0x48
02:18.084 -> Pixel Format: 0x5
02:18.084 -> Image Format: 0x80
02:18.084 -> Self Diagnostic: 0xC0
02:18.084 -> Identification information: 0x0

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In Arduino libs reading registers realized the following way:

Code: [Select all] [Expand/Collapse]

 
uint8_t Adafruit_ILI9341::readcommand8(uint8_t commandByte, uint8_t index) {
  uint8_t data = 0x10 + index;
  Adafruit_SPITFT::sendCommand(0xD9, &data, 1); // Set Index Register
  return Adafruit_SPITFT::readcommand8(commandByte);
}
 
void Adafruit_SPITFT::sendCommand(uint8_t commandByte, uint8_t *dataBytes,
                                  uint8_t numDataBytes) {
  SPI_BEGIN_TRANSACTION();
  if (_cs >= 0)
    SPI_CS_LOW();
 
  SPI_DC_LOW();          // Command mode
  spiWrite(commandByte); // Send the command byte
 
  SPI_DC_HIGH();
  for (int i = 0; i < numDataBytes; i++) {
    spiWrite(*dataBytes); // Send the data bytes
    dataBytes++;
    if ((connection == TFT_PARALLEL) && tft8.wide) {
      SPI_WRITE16(*(uint16_t *)dataBytes);
      dataBytes += 2;
    } else {
      spiWrite(*dataBytes); // Send the data bytes
      dataBytes++;
    }
  }
 
  if (_cs >= 0)
    SPI_CS_HIGH();
  SPI_END_TRANSACTION();
}
 
uint8_t Adafruit_SPITFT::readcommand8(uint8_t commandByte, uint8_t index) {
  uint8_t result;
  startWrite();
  SPI_DC_LOW(); // Command mode
  spiWrite(commandByte);
  SPI_DC_HIGH(); // Data mode
  do {
    result = spiRead();
  } while (index--); // Discard bytes up to index'th
  endWrite();
  return result;
}

So the question is: How to read ILI9341 registers using ESP-IDF SPI API?

Thanks in advance!

Posted: **Thu Jun 10, 2021 2:19 am**

The situation is similar with the display on ILI9488. Please clarify this issue.

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