CSB (CS): Slave chip select signal, active at low level. When it is at low level, the chip is enabled.
SCL (SCK/SCLK): Serial clock signal.
D/C (DC): Data/command control signal, write command (Command) when the level is low; write data (Data/parameter) when the level is high.
SDA (DIN): Serial data signal.
Timing: CPHL=0, CPOL=0, i.e. SPI mode 0.
Note: For specific information about SPI communication, you can search for information online on your own.

The e-paper used in this product uses "microcapsule electrophoresis display" technology for image display. The basic principle is that charged nanoparticles suspended in a liquid migrate under the action of an electric field. The e-paper display screen displays patterns by reflecting ambient light and does not require a backlight. Under ambient light, the e-paper display screen is clearly visible, with a viewing angle of almost 180°. Therefore, e-paper displays are ideal for reading.

• For black and white images, we can define it as 0 if it is black and 1 if it is white, so there is a way to represent colors:
  
  • White: □, corresponding to 1
    
  • Black: ■, corresponding to 0
    
• A dot is generally called a pixel on the graph, and the color is either 1 or 0, that is, 1 bit can identify the color: 1Pixel = 1bit, then a byte contains 8 pixels.
  
• Take 16 pixels as an example. We assume that the first 8 pixels are black and the last 8 pixels are white. Then it can be thought that pixels 1-16 correspond to bits 0 to 15, and 0 means black. 1 means white:
  

• For the computer, the way it stores data is that the high bits come first and the low bits come last, and each byte only has 8 bits, so there may be a slight change:
  

• In this way, only 2 bytes are required to represent 16 pixels.
  
• For the 2.15inch e-paper B, which has three colors of red, black, and white, we need to split the image into two parts: one black and white image, and one red and white image. During transmission, one register controls the black and white display, while the other controls the red and white display. One byte for the black and white part controls 8 pixels, and one byte for the red and white part controls 8 pixels
  
• Suppose there are 8 pixels, the first 4 are red and the back 4 are black, then you need to split them into a black and white picture, a red and white picture. Both of which are 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 are red, and the last four pixels are white.
  

• If we specify that white is stored as 1 and red or black is stored as 0, then we have the following representation:
  

• One byte for the black and white part controls 8 pixels, and one byte for the red and white part controls 8 pixels, then it can be expressed as follows:
  

Note: This section is a general template. Please check and confirm if it matches your device.

1. For screens that support partial refresh, note that you should not continuously use partial refresh to update the screen. After using partial refresh several times, you need to perform a full screen refresh to clear the screen. Otherwise, it may cause abnormal display effects on the screen.
2. When three-color or multi-color e-Paper screens are produced in batches, there will be a certain color difference. This is a normal phenomenon. It is recommended to store the screen with the white side facing up. Before use, power on and do several whitening operations.
3. Note that the screen cannot be powered on for a long time. When the screen does not refresh, the screen must be set to sleep mode or power off. Otherwise, the screen will remain in a high voltage state for a long time, which will damage the diaphragm and cannot be repaired.
4. When using the e-paper screen, it is recommended that the refresh interval is at least 180s, and refreshed at least every 24 hours. If the e-paper screen is not used for a long time, it should be whitened and stored. (Refer to the data sheet for specific storage environment requirements)
5. After the screen enters sleep mode, the image data sent will be ignored, and it can only be refreshed normally after re-initialization.
6. Control the 0x3C or 0x50 (refer to the data sheet for details) register to adjust the border color. In the example demo, you can adjust the Border Waveform Control register or VCOM AND DATA INERTVAL SETTING to set it.
7. If you find that the data of the created image is displayed incorrectly on the screen, it is recommended to check whether the image size is set correctly, and try again by changing the width and height settings.
8. The working voltage requirement for an e-Paper screen is 3.3V. If you purchase a raw display and need to work in a 5V environment when designing the circuit, it is recommended to perform level conversion processing. The new version of the driver board (Rev2.1 and subsequent versions) has added a level processing circuit, which can support both 3.3V and 5V working environments simultaneously. The old version can only support 3.3V working environment. When using it, you can first confirm the version number (which is under the board name).
9. The FPC cable of the screen is relatively fragile. Please note: do not bend the cable in the vertical direction of the screen to avoid the cable being torn; do not repeatedly bend the cable excessively to avoid the cable breaking; do not bend the cable toward the front of the screen to prevent the cable from being disconnected from the panel. During debugging and R&D, it is recommended to fix the wiring before use.
10. The e-Paper screen is relatively fragile, so be careful to avoid falling, colliding, or pressing hard.
11. We recommend that customers first use the sample demo we provide and use the corresponding development board to test after getting the screen.