LVGL compatible DMA enabled LCD drivers for Teensy 4.x

[honey_the_codewitch]

I noticed the existing drivers require an entire framebuffer to be used to support DMA.
I retooled and stripped these drivers so that they can do partial updates to the display, the way libraries like LVGL and htcw_uix expect.
They don't do anything but initialize, rotate, and send bitmaps to the display.

The SSD1351 currently can't be rotated to 1 or 3 without scrambling the output. Not sure why yet, but it works otherwise, and since it's 128x128 i don't consider it a show stopper.

One nice thing is the lcd_spi_driver_t4 makes it easy to implement new displays, complete with DMA support.

Shared Lib Code: https://github.com/codewitch-honey-crisis/lcd_spi_driver_t4
SSD1351 https://github.com/codewitch-honey-crisis/ssd1351_t4
ST7789 https://github.com/codewitch-honey-crisis/st7789_t4

To use, initialize with the pins (I haven't tested software SPI yet, so use a CS pin for your DC line and use the hardware pins for maximum speed and reliability)
Then set your flush complete callback off the class. You'll use this to notify a library like LVGL that the most recent DMA transfer was completed
Then call begin() - the order of this and the above doesn't really matter, you can set callbacks any time
You can call rotation(x) to change the rotation of the display. Works like the T3 drivers, or adafruit drivers
You can then call flush() to send a bitmap to the display. Usually libs like LVGL will call this.

Note that these are NOT general purpose graphics libraries. They are display drivers meant to be used with libraries like LVGL that don't drive hardware directly.

Also, these libraries are structured to be Arduino and PlatformIO ready, but I have not registered them with either of those repos. To use them presently, you'll have to download them manually from the above links.

 

[honey_the_codewitch]

I added this driver for the ILI9341 https://github.com/codewitch-honey-crisis/ili9341_t4

also changed the interface a bit so now there's flush() and flush_async() - async uses DMA and takes an optional argument to flush the cache which you'll want to do if your transfer buffers are malloc'd. no need if they are in DTCM memory.

 

[Rezo]

This is neat, I might give it a go with a 320*320 ST7796s display I have (I've written an 8080 async driver for it, but might try SPI first)

Would be great if you could provide an example sketch on your main repo.

 

[honey_the_codewitch]

This is neat, I might give it a go with a 320*320 ST7796s display I have (I've written an 8080 async driver for it, but might try SPI first)

Would be great if you could provide an example sketch on your main repo.

https://github.com/codewitch-honey-crisis/teensy_lcd_dma

Here's the benchmark I've been using. It's using htcw_uix instead of LVGL but the concept is the same

 

[honey_the_codewitch]

I added some LVGL 9.2 boilerplate code to the READMEs for each of the drivers (not the base class)

 

[honey_the_codewitch]

Folks I found a bug with the DMA that I didn't catch before. It's corrupting once you stop updating the display. As long as you continue to update it works fine. I'm running it down, but I'm waiting on some hardware i need first that should get here any day.