Hi,
Having a bit of an issue with the SCLK pin assignment.
Using the TFT_eSPI library (V2.5.0).
ST7796 4" display.
I currently have the pins set as follows, and everything is working correctly:
//#define TFT_MISO 10
#define TFT_MOSI 23
#define TFT_SCLK 18
#define TFT_CS 16// Chip select control pin
#define TFT_DC 5// Data Command control pin
#define TFT_RST 27// Reset pin (could connect to RST pin)
Now it seems that I can move the TFT_SCLK pin around to other gpio pins and all still functions correctly, but if I choose gpio 19 as the TFT_SCLK pin then it doesn't work. Just the white screen of death!
This is particularly annoying as I already have my PCB layout pretty much sorted and I want to use gpio 19 as the TFT_SCLK pin.
I tried two different dev boards (prototyping on a bread board) and get the same results.
Tried a ILI9341 display.....same result. gpio 19 doesn't seem to work with the display.
Turned the frequency down to 10MHz, but doesn't work.
The strange thing is that yesterday I was testing the MCP3202 ADC with gpio 19 as the clk pin and all was working great. That was at 1MHz clock, but I'm not sure that'll make a difference.
Also tried a different jumper wire. Didn't think that it would make a difference and it didn't.
Can anyone offer some insight into what is going on here?
Why does the clock work on gpio 19 for the MCP3202 and also an ADXL345 that I tested in SPI mode, but the TFT display doesn't work?
Confused 
Any and all tips greatly appreciated.
Oh, and I haven't tried up or downgrading the TFT_eSPI version.
Cheers,
Matt