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EPD Update Procedure

The update procedure includes 8 steps as shown on the right side.

  1. Power on screen
  2. Reset the CoG driver
  3. Read the OTP data
  4. Initialize the COG driver
  5. Send the image
  6. Update the COG
  7. Stop DC/DC
  8. Power off screen

Power on screen

The initial state before start has VCC/VDD, /RESET, D/C, /CS, SDA, SCL kept at 0V.

In order to the inrush current will cause other issue. It is recommended to add start DC/DC when VCC/VDD is turned on.

Perform in the following order.

Step Pin/Register Data/Value Name/Unit Comment
GPIO POWER HIGH External MOSFET power driver
GPIO D/C HIGH Data if HIGH, command if LOW
GPIO /RESET HIGH Panel reset, active LOW
GPIO Panel /CS HIGH SPI chip select, active LOW
GPIO !BUSY INPUT Input, floating
SPI CLK SPI clock
SPI SDA SPI data

Reset the CoG driver

Note

Included in function COG_reset()

Step Pin/Register Data/Value Name/Unit Comment
GPIO RESET LOW Set RESET HIGH
Delay 20
10 for 1.54", 2.13"		 ms Make sure POWER is stable
GPIO RESET HIGH Set RESET HIGH
Delay 10
10 for 1.54", 2.13"		 ms
GPIO RESET LOW Set RESET LOW
Delay 20
20 for 1.54", 2.13"		 ms
GPIO RESET HIGH Set RESET HIGH
Delay 10
40 for 1.54", 2.13"		 ms
GPIO BUSY HIGH? Proceed to next step when HIGH
Otherwise, continue waiting
Delay 10
10 for 1.54", 2.13"		 ms

Proceed to next step “Read the OTP data”.

If the OTP data is already read and available, proceed to Initialise the COG driver.

Read the OTP data

Note

Included in function COG_getDataOTP()

This step is performed once, as long as the host retains the values. If the host loses the values, the host should perform this step again.

Info

The maximum clock speed of the display is 2.5MHz (Read).

The SPI sequence for reading the OTP follows:

There are two bank spaces in the OTP memory. When the data are read out, the first step is to determine which space is the active space (Bank0 or Bank1).

If the address 0 data is “0xa5”, the active space is Bank0; otherwise, the active space is Bank1.

EPD Size Active bank OTP range
1.54", 2.13", 2.66" bank0 0x1500-150F
bank1 0x1510-152F
2.06” bank0 0xD80-0xD8F
bank1 0xD90-0xDB0
4.2", 4.37" bank0 0x1500-156F
bank1 0x1570-15DF


Step Pin/Register Data/Value Name/Unit Comment
GPIO /CS LOW Select
GPIO D/C LOW Command mode
SPI3 0x70 SPI3 = SCK, SDIO, CS plus D/C
GPIO D/C HIGH Data mode
SPI3 Read 2 bytes Read the chip ID
0x03, 0x02 for 1.54", 2.13"
0x83, 0x02 for 2.66"
0x06, 0x05 for 4.2"
0x0B, 0x04 for 4.37"
SPI3 0xa4 [0x15, 0x00, 0x01] Sets the start address for OTP reading
GPIO BUSY HIGH? Proceed to next step when HIGH
Otherwise, continue waiting
SPI3 0xa1 Assigns the start address for OTP reading
SPI3 1 byte Reads 1 dummy byte
SPI3 48 bytes for 1.54", 2.06", 2.13", 2.66"
112 bytes for 4.2", 4.37"		 Reads OTP data bytes
GPIO RESET LOW Set RESET LOW
Delay 40 ms
GPIO RESET HIGH Set RESET HIGH
Delay 10 ms
GPIO BUSY HIGH? Proceed to next step when HIGH
Otherwise, continue waiting
GPIO /CS HIGH Unselect

Store the OTP data in memory to avoid reading it at each update.

Initialize the COG Driver

Note

Included in function COG_initial()

1.54”, 2.13”, 2.66”

Step Pin/Register Data/Value Name/Unit Comment
SPI 0xe0 0x02 1 byte
SPI 0xe6 Temperature 1 byte
SPI 0xa5 0 byte
GPIO BUSY HIGH? Proceed to next step when HIGH
Otherwise, continue waiting
SPI 0x01 OTP[16] 1 byte
SPI 0x00 OTP[17-18] 2 bytes
SPI 0x03 OTP[30-32] 3 bytes
SPI 0x06 OTP[23-29] 7 bytes
SPI 0x50 OTP[39] 1 byte
SPI 0x60 OTP[40-41] 2 bytes
SPI 0x61 OTP[19-22] 4 bytes
SPI 0xe7 OTP[33] 1 byte
SPI 0xe3 OTP[42] 1 byte
SPI 0x4d OTP[43] 1 byte
SPI 0xb4 OTP[44] 1 byte
SPI 0xb5 OTP[45] 1 byte
SPI 0xe9 0x01 1 byte
SPI 0x30 0x08 1 byte

2.06”

Step Pin/Register Data/Value Name/Unit Comment
SPI 0xe0 0x02 1 byte
SPI 0xe6 Temperature 1 byte
SPI 0xa5 0 byte
GPIO BUSY HIGH? Proceed to next step when HIGH
Otherwise, continue waiting
SPI 0x01 OTP[16-17] 2 bytes
SPI 0x00 OTP[18-19] 2 bytes
GPIO BUSY HIGH? Proceed to next step when HIGH
Otherwise, continue waiting
SPI 0x61 OTP[20-23] 4 bytes
GPIO BUSY HIGH? Proceed to next step when HIGH
Otherwise, continue waiting
SPI 0x06 OTP[24-27] 7 bytes
SPI 0x03 OTP[30] 1 byte
SPI 0xe7 OTP[33] 1 byte
SPI 0x65 OTP[34-37] 4 bytes
SPI 0x30 OTP[38] 1 byte
SPI 0x50 OTP[39] 1 byte
SPI 0x60 OTP[40-41] 2 bytes
SPI 0xe3 OTP[42] 1 byte
SPI 0x62 OTP[43-44] 2 bytes
SPI 0xe9 0x01 1 byte

4.2”

Step Pin/Register Data/Value Name/Unit Comment
SPI 0xe0 0x02 1 byte
SPI 0xe6 Temperature 1 byte
SPI 0x01 OTP[16] 1 byte
SPI 0x00 OTP[17-18] 2 bytes
SPI 0x03 OTP[30-32] 3 bytes
SPI 0x06 OTP[23-25] 3 bytes
SPI 0x50 OTP[39] 1 byte
SPI 0x60 OTP[40-41] 2 bytes
SPI 0x61 OTP[19-22] 4 bytes
SPI 0xe3 OTP[42] 1 byte
SPI 0xe7 OTP[33] 1 byte
SPI 0x65 OTP[34-37] 4 bytes
SPI 0x30 OTP[38] 1 byte
SPI 0xe9 0x01 1 byte
SPI 0x04 0 byte

4.37”

Step Pin/Register Data/Value Name/Unit Comment
SPI 0xe6 Temperature 1 byte
SPI 0xe0 0x02 1 byte
SPI 0xa5 0 byte
GPIO BUSY HIGH? Proceed to next step when HIGH
Otherwise, continue waiting
SPI 0x00 OTP[17-18] 2 bytes
SPI 0x01 OTP[16] 1 byte
SPI 0x03 OTP[30-32] 3 bytes
SPI 0x06 OTP[23-25] 3 bytes
SPI 0x30 OTP[38] 1 byte
SPI 0x50 OTP[39] 1 byte
SPI 0x60 OTP[40-41] 2 bytes
SPI 0x61 OTP[19-22] 4 bytes
SPI 0x65 OTP[34-37] 4 bytes
SPI 0xe7 OTP[33] 1 byte
SPI 0xe3 OTP[42] 1 byte
SPI 0xe9 0x01 1 byte

Send the Image

Note

Included in function COG_sendImageDataNormal()

Step Pin/Register Data/Value Name/Unit Comment
SPI 0x10 Image data The data is the NEW image data that you want displayed next moment

The index of the image buffer is 0x10.

Sending the image data array to this register requires defining the size of the array. To do so, take note of the buffer size according to your EPD screen size, as seen below.

Size 1.54” 2.06” 2.13” 2.66” 4.2” 4.37”
Bytes 5776 7936 5512 11248 30000 21120

There are 2-bit data per pixel to define 4 colors.

Data Colour
00 Black
01 White
10 Yellow
11 Red

Example

The first byte represents the 1st…4th pixels of the first line.

The second byte represents the 5th…8th pixels of the first line, and so on.

Update the COG

Note

Included in function COG_update()

Send the Update Command

For 1.54”, 2.06”, 2.13”, 2.66”

Step Pin/Register Data/Value Name/Unit Comment
SPI 0x04 Power on DC/DC
GPIO !BUSY HIGH? Wait for !BUSY = HIGH
SPI 0x12 0x00 Display refresh
GPIO !BUSY HIGH? Wait for !BUSY = HIGH

For 4.2”

Step Pin/Register Data/Value Name/Unit Comment
SPI 0x12 0x00 Display refresh
GPIO !BUSY HIGH? Wait for !BUSY = HIGH

For 4.37”

Step Pin/Register Data/Value Name/Unit Comment
SPI 0xff 0xa5 1 byte
SPI 0xef OTP[43-50] 8 bytes
SPI 0xc3 OTP[64] 1 byte
SPI 0xdc OTP[59] 1 byte
SPI 0xdd OTP[60] 1 byte
SPI 0xde OTP[61] 1 byte
SPI 0xfd OTP[65] 1 byte
SPI 0xe8 OTP[62] 1 byte
SPI 0xda OTP[63] 1 byte
SPI 0xc9 OTP[67] 1 byte
SPI 0xa8 OTP[66] 1 byte
SPI 0xff 0xe3 1 byte
SPI 0x04 0 byte
GPIO BUSY HIGH? Proceed to next step when HIGH
Otherwise, continue waiting
SPI 0xff 0xa5 1 byte
SPI 0xef OTP[51-58] 8 bytes
SPI 0xc3 OTP[64] 1 byte
SPI 0xdc OTP[59] 1 byte
SPI 0xdd OTP[60] 1 byte
SPI 0xde OTP[61] 1 byte
SPI 0xfd OTP[65] 1 byte
SPI 0xe8 OTP[62] 1 byte
SPI 0xda OTP[63] 1 byte
SPI 0xc9 OTP[67] 1 byte
SPI 0xa8 OTP[66] 1 byte
SPI 0xff 0xe3 1 byte
SPI 0x12 0x00 1 byte
GPIO BUSY HIGH? Proceed to next step when HIGH
Otherwise, continue waiting

Stop DC/DC

Note

Included in function COG_stopDCDC()

All sizes

Step Pin/Register Data/Value Name/Unit Comment
SPI 0x02 0x00 Turn off DC/DC
GPIO !BUSY HIGH? Wait for !BUSY = HIGH

For 2.06”

Step Pin/Register Data/Value Name/Unit Comment
SPI 0x07 0xa5 1 byte

For 4.2”

Step Pin/Register Data/Value Name/Unit Comment
SPI 0x00 OTP[26-27] 2 bytes

Power the screen off

Step Pin/Register Name/Unit Name/Unit Comment
GPIO D/C LOW Data if HIGH, command if LOW
GPIO /RESET LOW Panel reset, active low
GPIO Panel /CS LOW SPI chip select, active low
GPIO !BUSY Input, floating
GPIO POWER LOW External MOSFET power driver
SPI CLK SPI clock
SPI SDA SPI data

The EPD update procedure is completed.