Template: Pico e-Paper 2.7 Spec
Overview
2.7inch EPD (Electronic Paper Display) Module For Raspberry Pi Pico, 264 × 176 Pixels, Black / White, SPI Interface.
Version Description
The V2 version has several differences compared to the V1 version (please note the differences if you are making a second purchase):
- The V2 version has added functions for local and quick refreshing.
- The display of grayscale colors is slightly different.
- There are changes in the wiring, so please check whether the holes/slots in your self-made PCB are compatible.
Specification
- Size: 2.7 inch
- Outline dimensions (bare screen): 70.42mm × 45.8mm × 0.98mm
- Outline dimensions (driver board): 73.5mm × 47mm
- Display size: 57.288mm × 38.192mm
- Operating voltage: 3.3V
- Communication interface: SPI
- Pitch: 0.217 X 0.217
- Resolution: 264 X 176
- Display color: Black, white
- Greyscale: 4
- Full refresh: 6s
- Partial refresh: 0.3s (V2)
- Refreshing power: 26.4mW(typ.)
- Sleep current: <0.01uA (almost 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 circumstances, 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.
- Timing: CPHL=0, CPOL=0 (SPI0)
【Note】: for more details about SPI communication, you can search on the Internet.
Refreshinh Principle
Working Protocol
The electronic paper used in this product uses "microencapsulated electrophoresis display" technology for image display, the basic principle of which is the migration of charged nanoparticles suspended in liquid by an electric field. The e-paper display relies on the reflection of ambient light to display patterns and does not require a backlight, making the e-paper display clearly visible in ambient light with a viewing angle of almost 180°. Therefore, e-paper displays are ideal for reading.
Pixel & Byte
We define the pixels in a monochrome picture, 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 the computer, the data is saved in MSB format:
So we can use two bytes for 16 pixels.
- In addition to bicolor displaying, the 3.7-inch e-Paper also supports four grayscale.
- To display grey pixels, we need to define data for gray
- Black: 00b
- Dark Grey: 01b
- Light Grey: 10b
- White: 11b
| Pixel | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | ||||||||
| Bit | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
| Data | 0 | 0 | 0 | 0 | 0 | 1 | 0 | 1 | 1 | 0 | 1 | 0 | 1 | 1 | 1 | 1 |
| Color | Black | Black | Dark Grey | Dark Grey | Light Grey | Light Grey | White | White | ||||||||
| Byte | 0x05 | 0xAF | ||||||||||||||
The display divides a four-grayscale picture into two pictures. The pixels in the same position of pictures are combined into one pixel.
| Register | White | Light Grey | Dark Grey | Black |
| 0x10 | 0x01 | 0x01 | 0x00 | 0x00 |
| 0x13 | 0x01 | 0x00 | 0x01 | 0x00 |
With the tables above, you can define the data which can be used to display grayscale pixels in the 3.7inch e-Paper
| Pixel | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | ||||||||
| Bit | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
| Data | 0 | 0 | 0 | 0 | 0 | 1 | 0 | 1 | 1 | 0 | 1 | 0 | 1 | 1 | 1 | 1 |
| Color | Black | Black | Dark Grey | Dark Grey | Light Grey | Light Grey | White | White | ||||||||
| Byte | 0x05 | 0xAF | ||||||||||||||
| Bit in 0x10 register | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 0 | 1 | 0 | 1 | 0 | 1 |
| Bit in 0x13 register | 0 | 0 | 0 | 0 | 0 | 1 | 0 | 1 | 0 | 0 | 0 | 0 | 0 | 1 | 0 | 1 |
| Data sent to 0x10 register | 0x00 | 0x55 | ||||||||||||||
| Data sent to 0x13 register | 0x05 | 0x05 | ||||||||||||||