Template: Pico e-Paper 7.5 Spec

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Overview

7.5-inch EPD (Electronic Paper Display) Module For Raspberry Pi Pico, 800 × 480 Pixels, Black / White, SPI Interface.

Features

  • No backlight keeps displaying the latest content for a long time even when powered down.
  • Ultra-low power consumption, basically power is only required for refreshing.
  • SPI interface requires minimal IO pins.
  • 2 x user buttons and 1 x reset button for easy interaction.

Specification

  • Dimension: 7.5inch
  • Outline dimensions(raw panel): 170.2mm x 111.2mm x 1.18mm
  • Outline dimensions(driver board): 65mm x 31mm
  • Display Size: 163.2mm x 97.92mm
  • Operating voltage: 3.3V
  • Interface: SPI
  • Dot pitch: 0.205x 0.204
  • Display color: Black, White
  • Resolution: 800 x 480
  • Greyscale: 2
  • Full refresh time: 5s
  • Refresh power: 26.4mW (typ.)
  • Standby current: <0.01uA (almost none)

【Note】: Refresh time: The refresh time is the experimental test data, the actual refresh time will have errors, and the actual effect shall prevail. There will be a flickering effect during the global refresh process, this is a normal phenomenon.
Power consumption: The power consumption data is the experimental test data. The actual power consumption will have a certain error due to the existence of the driver board and the actual use situation. The actual effect shall prevail.

SPI Timing

1.54inch-e-paper-manual-1.png
Note: Different from the traditional SPI protocol, the data line from the slave to the master is hidden since the device only has a display requirement.

  • CS is slave chip select, when CS is low, the chip is enabled.
  • DC is data/command control pin, when DC = 0, write command, when DC = 1, write data.
  • SCLK is the SPI communication clock.
  • SDIN is the data line from the master to the slave in SPI communication.
  • Timing: CPHL=0, CPOL=0 (SPI0)

[Remarks] For specific information about SPI, you can search for information online.

Working principle

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 suspended 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. Under ambient light, the E-paper screen still has high visibility with a wide viewing angle of 180 degrees. It is the ideal choice for E-reading.

Pixel & Byte

For black and white pictures, we can specify that if it is black we define it as 0 and if it is white we define it as 1. Then there is the way to represent the color:
White: □, corresponds to 1
Black: ■, corresponds to 0

  • A point on the graph is generally called a pixel, and the color is either 1 or 0, which means that 1 bit can identify the color: 1 pixel = 1 bit, so a byte contains 8-pixel points.
  • Taking 16 pixels as an example, let's assume that the first 8 pixels are black and the last 8 pixels are white, so we can consider that pixels 1-16, corresponding to bits 0 to 15, 0 means black and 1 means white:

Pico e-paper 5.83 spec09.png
For a computer, it stores data in such a way that the high bits come first and the low bits come second, and there are only 8 bits in a byte, so it is stored in the byte as follows:
Pico e-paper 5.83 spec10.png
This requires only 2 bytes to represent 16-pixel points.