Template: Pico e-Paper 2.9 D Spec
Overview
2.9inch EPD (Electronic Paper Display) Module For Raspberry Pi Pico, 296 × 128 Pixels, Black / White, 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.
- 2 x user buttons and 1 x reset button for easy interaction.
Specification
- Size: 2.9inch
- Dimensions (screen only): 79.0mm × 36.7mm × 0.34mm
- Dimensions (driver): 65mm × 31mm
- Display size: 66.9mm x 29.06mm
- Working voltage: 3.3V
- Communication interface: SPI
- Dot pitch: 0.226 × 0.227mm
- Resolution: 296 x 128
- Display color: Black, White
- Grayscale: 2
- Partial refresh: 0.3s
- Global refresh: 2s
- Refresh power consumption: 26.4mW(typ.)
- Sleep current: <0.01uA (close to 0)
【Note】: Refresh time: refresh time for the experimental test data, the actual refresh time will be inaccurate, subject to the actual effect. The global refresh process will have a flickering effect, this is a normal phenomenon.
Power consumption: power consumption data for the experimental test data, the actual power consumption due to the existence of the driver board and the actual use of different conditions, there will be a certain error, subject to the actual effect.
SPI Timing
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 a 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.
- Sequence: CPHL=0, CPOL=0 (SPI0)
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 display 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.