ILI9341 TFT display in XIAO ESP32 Seeeduino MISO issue

Projects General Guidance
1

I am using a XIAO ESP32 Seeeduino with an ILI9341 TFT display that is working great. The touch screen is also working well.

The problem is that I have to disconnect the MISO connection ( TFT_MISO to GPIO9 ) every time I power on the ESP32. When I power on the ESP32 the display is blank, but when I disconnect MISO and power back on the ESP32 I do get the image. Then I connect back MISO and it works as it should (the touch doesn't work leaving MISO disconnected). I don't know if it is a hardware or software issue.
I tried connecting MISO to GND with a 10k ohm resistor and setting pinMode(TFT_MISO, INPUT_PULLUP), but none worked.

Pin connections:

VCC -> 5 V
GND -> GND
CS  -> GPIO3
RST -> GPIO4
DC  -> GPIO5
MOSI -> GPIO10
SCK -> GPIO8
LED -> 5 V
MISO -> GPIO9
T_CLK -> TFT_SCK
T_CS -> GPIO21
T_DIN -> TFT_MOSI
T_DO -> TFT_MISO

Arduino setup:

#include <Adafruit_ILI9341.h>
#include <XPT2046_Touchscreen.h>

#include <SPI.h>

#define CS_PIN 21
#define TFT_CS 3      // TFT CS  pin is connected to esp pin 3
#define TFT_RST 4     // TFT RST pin is connected to esp pin 4
#define TFT_DC 5      // TFT DC pin is connected to esp pin 5
#define TFT_MISO 9

XPT2046_Touchscreen ts(CS_PIN);

Adafruit_ILI9341 tft = Adafruit_ILI9341(TFT_CS, TFT_DC, TFT_RST);

void setup() {
  pinMode(TFT_MISO, INPUT_PULLUP);
  Serial.begin(38400);
  pinMode(TFT_CS, OUTPUT);
  pinMode(CS_PIN, OUTPUT);
  digitalWrite(TFT_CS, HIGH);
  digitalWrite(CS_PIN, HIGH);
  esp_sleep_enable_timer_wakeup(1000000);
  
  tft.begin();
  tft.setRotation(1);
  ts.begin();
  ts.setRotation(1);

  tft.fillScreen(ILI9341_BLACK);
  tft.fillCircle(160, 120, 120, ILI9341_RED);
  tft.setTextColor(ILI9341_WHITE);
  tft.setTextSize(3);
  tft.setCursor(20, 110);
  tft.fillScreen(ILI9341_BLACK);
  tft.fillCircle(160, 120, 120, ILI9341_GREEN);
  tft.setTextColor(ILI9341_BLACK);
  tft.setTextSize(4);
  tft.setCursor(100, 110);
  tft.print("Start");
}
2

I suspect the problem is your choice of GPIO9 for MISO. Can you assign MISO to a different pin?

3

Well I'm connecting the tft MISO to the esp MISO. I'm not really defining MISO to GPIO9, so I don't know if I can assign MISO to another pin. I looked in different posts and couldn't find a way of assigning it to another pin. I do found that the MISO pin enters bootloading mode after resetting the device.

4

I connected a 7.3 kOhm resistor from the esp to the TFT MISO and it worked good. I tested it out a couple of days and worked normally. I noticed that adding a higher resistance value would also work, but slowed the touch functionality or not work, and adding a smaller resistor would still leave the screen blank.

5

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