STM32 SPI Display Demo

• Author: Douglas P. Fields, Jr.
• Date: 2024-11-09
• Copyright 2024 Douglas P. Fields, Jr.
• License: MIT (as per original SPI code)
  • Portions from STM/STM code generation

Goals:

• Make an ILI9341 display work on a Nucleo-F767ZI board.
• Improve performance of original code

Software Used

• STM ILI9341 Display by Aleksander Alekseev under MIT License
• STM32 Cube IDE 1.16

Hardware

• Nucleo F767ZI
• ILI9341

Other possibilities:

• ST7796S

Nucleo-144 Pinout

See STM UM1974 Rev 10 page 32 section 6.13

D13 PA5  SPI1_SCK
D12 PA6  SPI1_MISO
D51 PD7  SPI1_MOSI
D10 PD14 SPI1_DC
D9  PD15 SPI1_CS
D8  PF12 SPI1_RESET

Display non-data connections

• VCC - 5V
• GND - GND
• LED - 3.3V (backlight, instructions say use 100 ohm resistor)

Software Notes

Chip configuration

• NVIC
  • SPI1 Global Interrupt: Enable
• SPI1

Doug's notes

• This is really slow
  • Area fills call the HAL 2 bytes at a time
  • There is no DMA or sending buffer
• The image dump is really fast due to a single HAL call
• I don't readily see how this can be easily done with DMA given the need to toggle the CS and CD GPIOs occasionally and in sync with the SPI data

TODO

• Figure out how to use 8-bit color so we can double the speed of the I/O we do with bitmaps
  • DOesn't seem to be a way to do this
• Use a smaller pixel buffer than 320x240x2 bytes (150k)
  • Maybe use an Nk buffer and loop through it when needed
  • But at least big enough for a decent font size like 16x26 which is 832 bytes
  • I was thinking more like 16k or 8k pixels
    • This would require 19 writes to blank the whole screen
• Rewrite this all with queues and DMA
  • Have reusable buffers
  • Have callbacks when requests are completed