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Blog
Notes, thoughts and things I learned.
- ESP32 core 3.x - pinMode() can break your SPI bus
In the Arduino core for ESP32 3.x, calling pinMode() on a pin the SPI bus already uses disconnects it from the bus. Here is how to add a pull-up safely.
- ESP32 won't boot with an SD card on GPIO12
Why an ESP32 stops booting when an SD card module is wired to GPIO12, and three ways to fix it, the simplest being one pin change.
- ESP32 SD card speed - why it stops at 20 MHz
Real SD card speeds on an ESP32 over SPI with the Arduino SD library, why asking for 25 MHz gives 20 MHz, and why bigger reads don't get faster.
- ILI9341 white screen - find the cause in one minute
A white screen on an ILI9341 display means the backlight works but the controller gets no commands. Reading the chip's ID over SPI tells you where to look.
- XPT2046 touch not working - test it without touching
The XPT2046 touch chip has a built-in temperature sensor. Reading it tells you in one second whether the chip is wired right, before any calibration.