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DESTM32S display driver

Copyright 2017 Moddable Tech, Inc.
Revised: September 10, 2024

The DESTM32S display controller drives three different ePaper displays. The displays are available from various sources, including Crystalfontz where we purchased our test units. They use a small adapter board (from good-display.com), though the display controller is part of the ePaper display itself (so called chip-on-glass).

  • 122 x 250 black and white (available here)
  • 128 x 296 black, white, and red (available here)
  • 104 x 212 black, white, gray, and red (available here)

The black and white display uses a different controller from the two displays that support red pixels. The black and white display updates at approximately 4 frames per second, while the displays with red pixels take approximately 20 seconds per frame (e.g. 3 frames per minute).

The ePaper display drivers in the Moddable SDK use the same API as LCD displays. However, because of their relatively slow refresh rate and other update requirements, they are typically used with dedicated applications which are designed to work well with the unique characteristics of the displays.

The love-e-ink example is designed to work with the black and white ePaper display. It demonstrates how to update parts of the display continuously without the need for long full screen refreshes. The redandblack example is designed to work with ePaper displays that have red pixels. It cycles through a slide show of images that contain black, white, and red pixels.

Adding DESTM32 to a project

To add the SSD1351 driver to a project, include its manifest:

"include": [
	/* other includes here */
	"$(MODULES)/drivers/destm32s/manifest.json"
],

If using Commodetto or Piu, set the screen property of the config object in the manifest to destm32s to make SSD1351 the default display driver. Since there is no touch input, set the touch driver name to an empty string to disable it.

"config": {
	"screen": "destm32s",
	"touch": ""
},

Pixel format

The DESTM32S driver requires 8-bit gray or, when the display supports color (e.g. red), 8-bit color pixels as input. When building with mcconfig, set the pixel format to gray256 or rgb332 on the command line:

mcconfig -m -p esp -r 90 -f gray256
mcconfig -m -p esp -r 90 -f rgb332

Defines

In the defines object, declare the pixel width and height. The dimensions of the display specified in the manifest select the display controller that is used, so it is essential to set this correctly.

For 122 x 250 black and white:

"defines": {
	"destm32s": {
		"width": 122,
		"height": 250
	}
}

For 128 x 296 black, white, and red:

"defines": {
	"destm32s": {
		"width": 128,
		"height": 296
	}
}

For 104 x 212 black, white, gray, and red:

"defines": {
	"destm32s": {
		"width": 104,
		"height": 212
	}
}

Configuring SPI

The defines object must contain the spi_port, along with the DC, CS, and BUSY. pin numbers. If a RST pin is provided, the device will be reset when the constructor is invoked. If the cs_port, dc_port, rst_port, or busy_port properties are not provided, they default to NULL.

"defines": {
	"ssd1351": {
		/* other properties here */
		"cs_pin": 4,
		"dc_pin": 2,
		"rst_pin": 0,
		"busy_pin": 5,
		"spi_port": "#HSPI"
	}
}

The hz property, when present, specifies the SPI bus speed. The default value is 500,000 Hz which is near the maximum SPI speed supported by the controllers.