ILI9341 reset pin held high problem

[adamalfath]

Hi,

I'm designing my custom display board based on this ILI9341 TFT Display. Aiming to have minimum wire, I decided not to broken-out the RESET, CS & MISO pin like the schematic below:

RESET pulled high to always enable the display, CS pulled low for always active SPI connection, and MISO left floating since I'm not using read command (?). No other SPI device is connected on this bus other than the display itself.

During testing, I've got issues when sometimes the display is responding to the command (firmware) and sometimes (most of the time) is not. Sometimes disconnecting the display, plugging it back, then hit MCU reset solve it, but it is not reproducible since right now that method is not working. Also my mistake of not having a "working" module to test around first before making my own -_-.

Here's what I've done:

1. Set Setup70c_ESP32_C3_ILI9341.h inside User_Setup_Select.h file
2. Define TFT_MOSI=7, TFT_SCLK=6, TFT_DC=5 inside Setup70c_ESP32_C3_ILI9341.h, anything else is commented
3. Trying ILI9341_DRIVER or ILI9341_2_DRIVER
4. Test code:

   tft.init();
   delay(500);
   tft.fillScreen(TFT_RED);
   delay(500);
   tft.fillScreen(TFT_GREEN);
   delay(500);
   tft.fillScreen(TFT_BLUE);
   delay(500);
   tft.fillScreen(TFT_WHITE);
   delay(500);
   

Maybe someone can give me an insight whether this is hardware due to another necessary pin needed for communication or firmware (library config) issue. Any help is appreciated. Thank you.

[TangerineDreamer]

When RST goes to 3,3V, i suggest you write :
TFT_RST -1

[adamalfath]

Hi, thanks for the response.

From my understanding, I think using TFT_RST -1 or commenting it would be the same as later it treated the same:

TFT_eSPI/TFT_eSPI.cpp

Lines 560 to 565 in 2b576dc

	#ifdef TFT_RST
	if (TFT_RST >= 0) {
	pinMode(TFT_RST, OUTPUT);
	digitalWrite(TFT_RST, HIGH); // Set high, do not share pin with another SPI device
	}
	#endif

TFT_eSPI/TFT_eSPI.cpp

Lines 673 to 689 in 2b576dc

	#ifdef TFT_RST
	#if !defined(RP2040_PIO_INTERFACE)
	// Set to output once again in case MISO is used for TFT_RST
	pinMode(TFT_RST, OUTPUT);
	#endif
	if (TFT_RST >= 0) {
	writecommand(0x00); // Put SPI bus in known state for TFT with CS tied low
	digitalWrite(TFT_RST, HIGH);
	delay(5);
	digitalWrite(TFT_RST, LOW);
	delay(20);
	digitalWrite(TFT_RST, HIGH);
	}
	else writecommand(TFT_SWRST); // Software reset
	#else
	writecommand(TFT_SWRST); // Software reset
	#endif

My problem is line 686/688 I mentioned above didn't have an affect to the display module. The module won't responding to the next command the MCU sent.

[adamalfath]

Update, after RTFM (duh), turns out my problem is clearly documented on the datasheet:

The current workaround is to add delay to the reset signal by implementing RC circuit:

The caveat is that this method only works during the first power-up since the reset pin is only triggered then. If I implement software reset to the main MCU (like ESP.reset/ESP.restart), the next initialization (during init function call) will make the display not respond to any command after.

[adamalfath]

This maybe became self-answered. I leave it here in case somebody needed it later.

Solution	Note
Add delay circuit	Only works during first power-up
Tied display reset line to MCU reset line	Won't be responding to MCU soft reset
Dedicated HW reset signal from MCU IO	The best option

[TangerineDreamer]

I find it such complicated to drive a tft 9341 with a esp32XX,have you tried with a simple esp32?
this setup works for me:

//--------------------------------------------------------------------------

//ILI9341 & ESP32

#define ILI9341_DRIVER

#define TFT_MISO 19 (better on the air)
#define TFT_MOSI 23
#define TFT_SCLK 18
#define TFT_CS 15 // Chip select control pin
#define TFT_DC 2 // Data Command control pin
//#define TFT_RST 4 // Reset pin (could connect to RST pin)
#define TFT_RST -1 // Set TFT_RST to -1 if display RESET is connected to ESP32 board RST

//#define TOUCH_CLK 18
#define TOUCH_CS 27 // Chip select pin (T_CS) of touch screen (if you don't have touch,comment it)
//#define TOUCH_DIN 23
//#define TOUCH_DO 19

#define LOAD_GLCD // Font 1. Original Adafruit 8 pixel font needs ~1820 bytes in FLASH
#define LOAD_FONT2 // Font 2. Small 16 pixel high font, needs ~3534 bytes in FLASH, 96 characters
#define LOAD_FONT4 // Font 4. Medium 26 pixel high font, needs ~5848 bytes in FLASH, 96 characters
#define LOAD_FONT6 // Font 6. Large 48 pixel font, needs ~2666 bytes in FLASH, only characters 1234567890:-.apm
#define LOAD_FONT7 // Font 7. 7 segment 48 pixel font, needs ~2438 bytes in FLASH, only characters 1234567890:-.
#define LOAD_FONT8 // Font 8. Large 75 pixel font needs ~3256 bytes in FLASH, only characters 1234567890:-.
//#define LOAD_FONT8N // Font 8. Alternative to Font 8 above, slightly narrower, so 3 digits fit a 160 pixel TFT
#define LOAD_GFXFF // FreeFonts. Include access to the 48 Adafruit_GFX free fonts FF1 to FF48 and custom fonts

#define SMOOTH_FONT

#define SPI_FREQUENCY 20000000

#define SPI_READ_FREQUENCY 20000000

#define SPI_TOUCH_FREQUENCY 2500000

//-------------------------------------------------------------------------------

In this way you can define if your tft is alright,and maybe if there is bugs in the lastest esp32 packages,the 2.05 have some bugs,the
2.04 too,i had to downgrade to 2.02,that still support esp32sx series,i think.