Template: Pico e-Paper 4.2 B Spec
Overview
This is a 4.2inch e-Paper display module for Raspberry Pi Pico, 400 x 300 pixels, supports red, black, white colors. SPI interface.
Features
- No backlight, keeps displaying last content for a long time even when power down
- Ultra low power consumption, basically power is only required for refreshing
- SPI interface, requires minimal IO pins
- Onboard voltage translator, compatible with 3.3V / 5V MCUs
- 2x user buttons for easy interacting
Specifications
- Operating voltage: 3.3V/5V
- Display color: red, black, white
- Resolution: 400 x 300 pixels
- Grey scale: 2
- Interface: 3-wire SPI, 4-wire SPI
- Viewing angle: >170°
- Partial refresh time: N/A
- Full refresh time: 15s
- Outline dimensions: 93.5 x 78.5mm
- Display size: 84.8 x 63.6mm
- Refresh power: 26.4mW (typ.)
- Standby current: <0.01uA (almost none)
- Dot pitch: 0.212 x 0.212mm
Working Protocol
This product is an E-paper device adopting the image display technology of Microencapsulated Electrophoretic Display, MED. The initial approach is to create tiny spheres, in which the charged color pigments are suspending in the transparent oil and would move depending on the electronic charge. The E-paper screen displays patterns by reflecting the ambient light, so it has no background light requirement. (Note that the e-Paper cannot support updating directly under sunlight).
How to define pixels
In a monochrome picture we define the pixels, 0 is black and 1 is white.
White：□，Bit 1
Black：■：Bit 0
- The dot in the figure is called a pixel. As we know, 1 and 0 are used to define the color, therefore we can use one bit to define the color of one pixel, and 1 byte = 8pixels
- For example, If we set the first 8 pixels to black and the last 8 pixels to white, we show it by codes, they will be 16 bit as below:
For computer, the data is saved in MSB format:
So we can use two bytes for 16 pixels.
For 2.13inch e-paper B, the display colors are red, black, and white. We need to split the picture into 2 pictures, one is the black and white picture, another is the red and white picture. When transmitting, because one register controls a black or white pixel, one controls Red or white display. The black and white part of 2.13 use 1 byte to control 8 pixels, and the red and white part use 1 byte to control 8 pixels.
For example, suppose there are 8 pixels, the first 4 are red, and the back 4 are black:
They need to be disassembled into a black and white picture and a red and white picture. Both pictures have 8 pixels, but the first four pixels of the black and white picture are white, the last 4 pixels are black, and the first 4 pixels of the red and white picture One pixel is red, and the last four pixels are white.
If you define that the data of white pixel is 1 and the black is 0, then we can get:
So that we can use 1 byte to control every eight pixels.
Pinout
