Hi guys,
Using 4.0" TFT display. ST7796 driver. TFT_eSPI library.
Concerning the SPI frequency. First off using 55MHz and short wires to connect the display (6" or so) and all seems fine. Ran without issue for a couple of hours.
Now I want to mount the project in my car and have used 5m of 28 AWG 8 wire shielded cable from the PCB to the display. Uses a JST connector on the PCB and I've soldered the wires to the display.
It worked fine for about 10 mins and then the screen colours inverted and the display updates stopped. Upon reset it just went white screen.
After I left it a while and jiggle the wires it started working again, but after checking the wires there's continuity so no problem there I don't think.
I slowed the SPI frequency down to 40MHz thinking that may be the problem as the cable length is the only difference but still went white screen after a while.
I can try a lower frequency but just wondered what you guys think. Does this sound like a frequency thing? Or something else is going on.
Its not vibration as it's just been siting in the parked car.
Cheers
Matt
Did you change both of the SPI frequencies?
I found the "setup file" I use "Setup28_RPi_ST7796_ESP8266.h" redefines the SPI back to 400000.
OR
It could be electrical noise from the vehicle. What other connections to the vehicle do you have in addition to (I assume) power?
@JohnRob
Thanks for your reply.
copied from the User_Setup.h file:
// #define SPI_FREQUENCY 1000000
// #define SPI_FREQUENCY 5000000
// #define SPI_FREQUENCY 10000000
// #define SPI_FREQUENCY 20000000
// #define SPI_FREQUENCY 27000000
#define SPI_FREQUENCY 40000000
// #define SPI_FREQUENCY 55000000 // STM32 SPI1 only (SPI2 maximum is 27MHz)
// #define SPI_FREQUENCY 80000000
// #define SPI_FREQUENCY 100000000
// Optional reduced SPI frequency for reading TFT
#define SPI_READ_FREQUENCY 15000000
// The XPT2046 requires a lower SPI clock rate of 2.5MHz so we define that here:
#define SPI_TOUCH_FREQUENCY 2500000
As for electrical noise. I'm running stand alone for testing, so not connected to the car battery. Using a separate 12V battery.
In the first case, yes I thought maybe electrical noise, but today it is in the car, with the engine and ignition off, and the screen went blank, so not related.
When I have a mo, I'll drop the frequency to 27MHz and see if that makes a difference.
Oh, I forgot to mention that I've already run it in the car once before at 55MHz, but with the display on the 6" wires, and it worked fine for a good half hour as I drove home from work.
Cheers,
Matt
Re: SPI frequency. I could see in the compiler warnings where different files redefined the SPI frequency. May not be your issue but just a note.