ESP32 SPI display issue with high Frequency

jojojijijojo
Posts: 2
Joined: Thu Feb 20, 2020 8:18 am

ESP32 SPI display issue with high Frequency

Postby jojojijijojo » Thu Feb 20, 2020 8:53 am

Hi,

Im having this weird issue, if I set my CPU frequency to anything higher than 10MHz(40MHz XTAL), SPI driving an ST7735 just stops working, it freezes and glitches. If I set the CPU frequency to the lowest setting, the display works fine. I can't figure out whats the issue exactly. Im using VSPI.

Tried different displays, same problem, tried to refresh the display only 1 frame per second, same problem, 1 frame per 10 seconds same problem, reduced SPI clock speed to 10Mhz from 27mhz, same problem.

ST7735 library im using is https://github.com/Bodmer/TFT_eSPI
#define TFT_CS 5
#define TFT_RST 15
#define TFT_DC 2


Thanks!

mikemoy
Posts: 450
Joined: Fri Jan 12, 2018 9:10 pm

Re: ESP32 SPI display issue with high Frequency

Postby mikemoy » Fri Feb 21, 2020 4:21 am

The first thing to check is what is the max speed in MHZ that panel can receive data at.
The next thing is how long your wires are to the LCD. The longer the wires the slower you can run MHZ

chegewara
Posts: 968
Joined: Wed Jun 14, 2017 9:00 pm

Re: ESP32 SPI display issue with high Frequency

Postby chegewara » Thu Feb 27, 2020 4:16 am

I don't remember now all details, but it's related to clock source in SPI and/or which SPI is used VSPI or HSPI.
I'm pretty sure you can find more info on forum if you dig a bit.

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