ESP-IDF GPIO pin error when TFT_CS is not defined

[alba-ado]

Hello, Thank you for making this library.

I am using your library on my project with the esp-idf. The library works fine but there is an error raised from the GPIO controller inside esp when I don't define the TFT_CS pin in the code (or define it to -1 as you did). My board doesn't have a CS pin since it is fixed in the PCB and there are no other free pins to use in place of this pin.

As I said, the code compiles just fine and works as expected when configured correctly. It only raises a trivial error in the logs when I try to monitor the board.

Here is my setup:
MCU: ESP32-S3-WROOM-1-N16R2
ESP-IDF: v4.4

Flash and RAM mode: QIO
Flash and RAM speed: 120 MHz
CPU Speed: 240 MHz

Here is the LCD Configuration:

#ifndef __OCM_LCD_SETUP__
#define __OCM_LCD_SETUP__

#define USER_SETUP_ID 146
#define TFT_PARALLEL_8_BIT
#define ILI9488_DRIVER

#include "BoardDefinitions.h"

// ESP32 S3 pins used for the parallel interface TFT
//#define TFT_CS          PIN_LCD_CS  //  Not used if the CS pin is fixed on the PCB.
#define TFT_DC          PIN_LCD_DC  // Data Command control pin - must use a GPIO in the range 0-31
#define TFT_RST         PIN_LCD_RST

#define TFT_WR          PIN_LCD_WR  // Write strobe control pin - must use a GPIO in the range 0-31
#define TFT_RD          PIN_LCD_RD

#define TFT_D0          PIN_LCD_D0  // Must use GPIO in the range 0-31 for the data bus
#define TFT_D1          PIN_LCD_D1  // so a single register write sets/clears all bits
#define TFT_D2          PIN_LCD_D2
#define TFT_D3          PIN_LCD_D3
#define TFT_D4          PIN_LCD_D4
#define TFT_D5          PIN_LCD_D5
#define TFT_D6          PIN_LCD_D6
#define TFT_D7          PIN_LCD_D7

#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_GFXFF  // FreeFonts. Include access to the 48 Adafruit_GFX free fonts FF1 to FF48 and custom fonts

#define SMOOTH_FONT

#endif

Here is the error log:

[   708][E][esp32-hal-gpio.c:102] __pinMode(): Invalid pin selected
E (714) gpio: gpio_set_level(226): GPIO output gpio_num error
I (721) gpio: GPIO[6]| InputEn: 1| OutputEn: 1| OpenDrain: 0| Pullup: 0| Pulldown: 0| Intr:0 
I (730) gpio: GPIO[5]| InputEn: 1| OutputEn: 1| OpenDrain: 0| Pullup: 0| Pulldown: 0| Intr:0 
I (739) gpio: GPIO[4]| InputEn: 1| OutputEn: 1| OpenDrain: 0| Pullup: 0| Pulldown: 0| Intr:0 
I (748) gpio: GPIO[7]| InputEn: 1| OutputEn: 1| OpenDrain: 0| Pullup: 0| Pulldown: 0| Intr:0 
I (758) gpio: GPIO[15]| InputEn: 1| OutputEn: 1| OpenDrain: 0| Pullup: 0| Pulldown: 0| Intr:0 
I (767) gpio: GPIO[16]| InputEn: 1| OutputEn: 1| OpenDrain: 0| Pullup: 0| Pulldown: 0| Intr:0 
I (776) gpio: GPIO[17]| InputEn: 1| OutputEn: 1| OpenDrain: 0| Pullup: 0| Pulldown: 0| Intr:0 
I (785) gpio: GPIO[18]| InputEn: 1| OutputEn: 1| OpenDrain: 0| Pullup: 0| Pulldown: 0| Intr:0 
I (795) gpio: GPIO[12]| InputEn: 1| OutputEn: 1| OpenDrain: 0| Pullup: 0| Pulldown: 0| Intr:0 
I (804) gpio: GPIO[11]| InputEn: 1| OutputEn: 1| OpenDrain: 0| Pullup: 0| Pulldown: 0| Intr:0 
I (813) gpio: GPIO[10]| InputEn: 1| OutputEn: 1| OpenDrain: 0| Pullup: 0| Pulldown: 0| Intr:0 
I (823) gpio: GPIO[9]| InputEn: 1| OutputEn: 1| OpenDrain: 0| Pullup: 0| Pulldown: 0| Intr:0 
[   827][E][esp32-hal-gpio.c:102] __pinMode(): Invalid pin selected
E (838) gpio: gpio_set_level(226): GPIO output gpio_num error
I (844) gpio: GPIO[5]| InputEn: 1| OutputEn: 1| OpenDrain: 0| Pullup: 0| Pulldown: 0| Intr:0 
I (853) gpio: GPIO[4]| InputEn: 1| OutputEn: 1| OpenDrain: 0| Pullup: 0| Pulldown: 0| Intr:0

I know this error is indeed caused by the TFT_CS pin since I tried to temporarily replace it with another pin that is used for something else and the error disappeared from the logs.

I found the root of this issue to be the definitions in the: TFT_eSPI_ESP32_S3.h file and the other board files where you defined the TFT_CS as -1 if there aren't any other definitions like so:

#ifndef TFT_CS
  #define TFT_CS -1  // Keep DMA code happy
  #define CS_L       // No macro allocated so it generates no code
  #define CS_H       // No macro allocated so it generates no code
#else

I understand this is needed for some other parts of the code, but the error is raised when the TFT_eSPI.cpp calls the pinMode method without checking whether the pin is negative. Thus resulting in a GPIO number error:

#ifdef TFT_CS
  pinMode(TFT_CS, OUTPUT);
  digitalWrite(TFT_CS, HIGH); // Chip select high (inactive)
#endif

#if defined (TFT_CS) && !defined(RP2040_PIO_INTERFACE)
  // Set to output once again in case MISO is used for CS
  pinMode(TFT_CS, OUTPUT);
  digitalWrite(TFT_CS, HIGH); // Chip select high (inactive)
#elif defined (ARDUINO_ARCH_ESP8266) && !defined (TFT_PARALLEL_8_BIT) && !defined (RP2040_PIO_SPI)
  spi.setHwCs(1); // Use hardware SS toggling
#endif

I tried to add #if TFT_CS >= 0 like in the other places you used it and the errors disappeared. Here is how I did it:

#if defined(TFT_CS) && TFT_CS >= 0
  pinMode(TFT_CS, OUTPUT);
  digitalWrite(TFT_CS, HIGH); // Chip select high (inactive)
#endif

#if defined (TFT_CS) && TFT_CS >= 0 && !defined(RP2040_PIO_INTERFACE)
  // Set to output once again in case MISO is used for CS
  pinMode(TFT_CS, OUTPUT);
  digitalWrite(TFT_CS, HIGH); // Chip select high (inactive)
#elif defined (ARDUINO_ARCH_ESP8266) && !defined (TFT_PARALLEL_8_BIT) && !defined (RP2040_PIO_SPI)
  spi.setHwCs(1); // Use hardware SS toggling
#endif

But I didn't know if it would interfere with the other parts of the library. So, I didn't create a pull request.
If this fixes this pin, the same change might also be needed for other non-essential pins if any.

Thank you for your help and time,
Best Regards.