Hardware SPI don't work with ILI9341 - 3 bugs and 3 solutions here

[electroremy]

Hi,

I'm use the Adafruit_ILI9341 and the GFX library to drive a ILI9341 TFT SPI touch screen on a Arduino UNO with an Ethernet Shield 2 (for the touch pad I use URTouch.h)

I've found some bugs and also solutions :

1st : If you use Adafruit_ILI9341 tft = Adafruit_ILI9341(TFT_CS, TFT_DC, TFT_RST) you've got an error "call of overloaded 'Adafruit_ILI9341(int, int, int)' is ambiguous" So you have to edit Adafruit_ILI9341.h and Adafruit_ILI9341.cpp to comment Adafruit_ILI9341() fonctions for ESP8266 I think you have to change function names to avoid this.

2nd : ILI9341 use SPI MODE 3 and cannot work with the default SPI MODE the library uses with hardware SPI Curiously, the software SPI use the good mode. Thus, you have to edit Adafruit_ILI9341.cpp and replace initSPI(freq); by initSPI(freq, SPI_MODE3);

3rd When you have quite long wires (eg. 20cm dupont wire) and slow 5V/3.3V level converter (or just 10K resistors !) from the Arduino UNO and the TFT you've got a speed limitation. Remember that in electronics :

• long wire = coil = low pass filter
• resistor + logical input capacitance = low pass filter Indeed, in the sketch, you have to use tft.begin(3000000); instead of tft.begin();

You can also use a fast SPI speed with short wires and a hi-speed level converter.

I found that a lot of people don't know these problems and use Adafruit_ILI9341 tft = Adafruit_ILI9341(TFT_CS, TFT_DC, TFT_MOSI, TFT_CLK, TFT_RST, TFT_MISO); with the hardware SPI pins... that's very very bad... that's very slow... and it doesn't work with other SPI devices...

I wonder that the constructor have explicit names as "tftHardwareSPI" and "tftSoftwareSPI"

Please, can you update your library and also your documentation and sample codes ?

Bests regards.