Raspberry Pi 4.01inch e-Paper HAT (F) User Guide

This 4.01inch Colorful E-Paper E-Ink Display HAT For Raspberry Pi, 640×400 Pixels, ACeP 7-Color, SPI Interface

Specifications

Operating voltage: 3.3V/5V
Display color: ACep 7-Color
Interface: 3-wire SPI, 4-wire SPI
Crey scale: 2
Display size: 86.40 × 54.00mm
Dot pitch: 0.135 × 0.135mm
Resolution: 640 × 400 pixels
Viewing angle: >170°
Full refresh time: 15s
Refresh power: 50mW(typ.)
Standby current: <0.01uA(almost none)
Outline dimension: 98.50 × 70.00mm

Interfaces

VCC	3.3V/5V
GND	GND
DIN	SPI MOSI
CLK	SPI SCK
CS	SPI chip select (Low active)
DC	Data/Command control pin (High for data, and low for a command)
RST	External reset pin (Low for reset)
BUSY	Busy state output pin

SPI timing

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. 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. (Note that the e-Paper cannot support updating directly under sunlight)

Communication protocol

Note: Different from the traditional SPI protocol, the data line from the slave to the master is hidden since the device only has display requirement.

CS is the 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.

SPI communication has data transfer timing, which is combined with CPHA and CPOL.

CPOL determines the level of the serial synchronous clock at idle state. When CPOL = 0, the level is Low. However, CPOL has little effect to the transmission.
CPHA determines data is collected at the first clock edge or at the second clock edge of the serial synchronous clock; when CPHL = 0, data is collected at the first clock edge.

There are 4 SPI communication modes. SPI0 is commonly used, in which CPHL = 0, CPOL = 0.

As you can see from the figure above, data transmission starts at the first falling edge of SCLK, and 8 bits of data are transferred in one clock cycle. In here, SPI0 is in used, and data is transferred by bits, MSB first.

Color of e-Paper

An image is made of pixels. The sizes of every pixel defined how many kinds of color are supported by the e-Paper. Monochrome image use one bit for one pixel (0 and 1, black and white), in this case, if we want to display more colors, we should use more bits for every pixel.
We need at least 3bits to display severe color. For easy programming, we and an 0 bit in front of it. In this case, we use 4 bits for every pixel.

Color	BIN	HEX	The color (reference)
Black	0b0000	0x0
White	0b0001	0x1
Green	0b0010	0x2
Blue	0b0011	0x3
Red	0b0100	0x4
Yellow	0b0101	0x5
Orange	0b0110	0x6

For example, if you want to display four colors, green, yellow, red and orange, it should be like as below:

Pixel	1				2				3				4
Bit	0	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15
Data	0	0	1	0	0	1	0	1	0	1	0	0	0	1	1	0
Color

Data is saved in MSB formate and 1byte is equal to 8 bits.

Pixel	1				2				3				4
Bit	7	6	5	4	3	3	1	0	7	6	5	4	3	2	1	0
Data	0	0	1	0	0	1	0	1	0	1	0	0	0	1	1	0
Color
Byte	0x25								0x46

You can refer to the "Make BMP file for e-Paper" guide and make the image yourself for this module.

Documentation

Demo code

Question:

What is the Operation temperature?

Answer:

The Operating temperature range of ACep e-Paper is 15~35°C. The color fade if you use it out of the range.

To：

Dear Customers, There may be a lag of several hours before we could process your order, depending on the time difference between your location and ours. Sincerely hoping your understanding!