Hi there,
So, I wanted a Basic Color Forum Activity & Weather or Rain Display for the desk. These E-paper displays are made for Low Power apps, So cool to have the device off but a display is still vizable (including a last check time is key too) at a glance you can see the status of things as of X minutes ago.
It’s a Nice Display… SO I put this together and it is a WIP! 
I started with the Basic color cycle test… Seeed and Good_Display have these displays.
Hardware Used
- Seeed Studio XIAO ESP32-C3
- 2.9" Quad-Color ePaper (128×296)
- Seeed ePaper Breakout Board
This is the professional embedded approach, especially for e-ink.
Use a Full framebuffer with Correct timing.
Single refresh (no flashing)
Quad-color mapping
How text works here;
You render text into a buffer, then refresh once.
// 1/21/26
// Quad Color 2.9" ePaper (JD79667) Full-Screen Color + Image Test
// Minimal-flash sequencing: init once, run sequence, sleep once.
// Rev 1.1 - 2026-01-24
// Pj Glasso & EAILLM
// Tested with Breakout Board AOK with Xiao ESP32C3, C5, S3, BSP 3.3.5
// be sure to place demo.h & IMAGE.h files in the directory with skecth
// Use the image2hex tool to create bitmaps.
// https://www.seeedstudio.com/2-9-Quadruple-Color-ePaper-Display-with-128x296-Pixels-p-5783.html
// https://www.seeedstudio.com/ePaper-Breakout-Board-p-5804.html
//
#include <SPI.h>
#include"demo.h" //Seeed Studio Graphic
//#include"AP_29demo.h" //Good displays Graphic
#include"IMAGE.h" // Graphic basic 2.9 one.
//SCLK--GPIO23
//MOSI---GPIO18
int BUSY_Pin = 7; //D5; //23 //works with S3 too...change the GPIO's
int RES_Pin = 2; //D0; //0
int DC_Pin = 5; //D3; //21
int CS_Pin = 3; //D1; //01
#define EPD_W21_CS_0 digitalWrite(CS_Pin,LOW)
#define EPD_W21_CS_1 digitalWrite(CS_Pin,HIGH)
#define EPD_W21_DC_0 digitalWrite(DC_Pin,LOW)
#define EPD_W21_DC_1 digitalWrite(DC_Pin,HIGH)
#define EPD_W21_RST_0 digitalWrite(RES_Pin,LOW)
#define EPD_W21_RST_1 digitalWrite(RES_Pin,HIGH)
#define isEPD_W21_BUSY digitalRead(BUSY_Pin)
//2bit
#define black 0x00 /// 00
#define white 0x01 /// 01
#define yellow 0x02 /// 10
#define red 0x03 /// 11
#define Source_BITS 128
#define Gate_BITS 296
#define ALLSCREEN_BYTES Source_BITS*Gate_BITS/4
////////FUNCTION//////
void SPI_Write(unsigned char value);
void EPD_W21_WriteCMD(unsigned char command);
void EPD_W21_WriteDATA(unsigned char datas);
//EPD
//EPD
void EPD_init(void);
void Acep_color(unsigned char color);
void PIC_display (const unsigned char* picData);
void Display_All_White(void);
void EPD_sleep(void);
void EPD_refresh(void);
void lcd_chkstatus(void);
void setup() {
Serial.begin(115200);
delay(600);
Serial.println("\n=== PJ Forum Basic E-Paper test ===");
pinMode(BUSY_Pin, INPUT);
pinMode(RES_Pin, OUTPUT);
pinMode(DC_Pin, OUTPUT);
pinMode(CS_Pin, OUTPUT);
//SPI
SPI.begin();
SPI.beginTransaction(SPISettings(10000000, MSBFIRST, SPI_MODE0));
}
//Tips//
/*When the electronic paper is refreshed in full screen, the picture flicker is a normal phenomenon, and the main function is to clear the display afterimage in the previous picture.
When the local refresh is performed, the screen does not flash.*/
/*When you need to transplant the driver, you only need to change the corresponding IO. The BUSY pin is the input mode and the others are the output mode. */
void loop() {
///////////////////////////Normal picture display/////////////////////////////////////////////////////////////////
/************Normal picture display*******************/
//EPD_init(); //EPD init
//PIC_display(gImage_1);//EPD_picture1
//EPD_sleep();//EPD_sleep,Sleep instruction is necessary, please do not delete!!!
//delay(1000); //5s
EPD_init();
PIC_display(gImage_2); // one refresh
EPD_sleep();
while(1); // stop (no repeated refreshes)
}
///////////////////EXTERNAL FUNCTION////////////////////////////////////////////////////////////////////////
/////////////////////delay//////////////////////////////////////
//////////////////////SPI///////////////////////////////////
void SPI_Write(unsigned char value)
{
SPI.transfer(value);
}
void EPD_W21_WriteCMD(unsigned char command)
{
EPD_W21_CS_0;
EPD_W21_DC_0; // command write
SPI_Write(command);
EPD_W21_CS_1;
}
void EPD_W21_WriteDATA(unsigned char datas)
{
EPD_W21_CS_0;
EPD_W21_DC_1; // command write
SPI_Write(datas);
EPD_W21_CS_1;
}
/////////////////EPD settings Functions/////////////////////
//////////////////////////////////////////////////////////////////////////////////////////////////
//JD
void EPD_init(void)
{
delay(20);//At least 20ms delay
EPD_W21_RST_0; // Module reset
delay(40);//At least 40ms delay
EPD_W21_RST_1;
delay(50);//At least 50ms delay
lcd_chkstatus();
EPD_W21_WriteCMD(0x4D);
EPD_W21_WriteDATA(0x78);
EPD_W21_WriteCMD(0x00); //PSR
EPD_W21_WriteDATA(0x0F);
EPD_W21_WriteDATA(0x29);
EPD_W21_WriteCMD(0x01); //PWRR
EPD_W21_WriteDATA(0x07);
EPD_W21_WriteDATA(0x00);
EPD_W21_WriteCMD(0x03); //POFS
EPD_W21_WriteDATA(0x10);
EPD_W21_WriteDATA(0x54);
EPD_W21_WriteDATA(0x44);
EPD_W21_WriteCMD(0x06); //BTST_P
EPD_W21_WriteDATA(0x05);
EPD_W21_WriteDATA(0x00);
EPD_W21_WriteDATA(0x3F);
EPD_W21_WriteDATA(0x0A);
EPD_W21_WriteDATA(0x25);
EPD_W21_WriteDATA(0x12);
EPD_W21_WriteDATA(0x1A);
EPD_W21_WriteCMD(0x50); //CDI
EPD_W21_WriteDATA(0x37);
EPD_W21_WriteCMD(0x60); //TCON
EPD_W21_WriteDATA(0x02);
EPD_W21_WriteDATA(0x02);
EPD_W21_WriteCMD(0x61); //TRES
EPD_W21_WriteDATA(Source_BITS/256); // Source_BITS_H
EPD_W21_WriteDATA(Source_BITS%256); // Source_BITS_L
EPD_W21_WriteDATA(Gate_BITS/256); // Gate_BITS_H
EPD_W21_WriteDATA(Gate_BITS%256); // Gate_BITS_L
EPD_W21_WriteCMD(0xE7);
EPD_W21_WriteDATA(0x1C);
EPD_W21_WriteCMD(0xE3);
EPD_W21_WriteDATA(0x22);
EPD_W21_WriteCMD(0xB4);
EPD_W21_WriteDATA(0xD0);
EPD_W21_WriteCMD(0xB5);
EPD_W21_WriteDATA(0x03);
EPD_W21_WriteCMD(0xE9);
EPD_W21_WriteDATA(0x01);
EPD_W21_WriteCMD(0x30);
EPD_W21_WriteDATA(0x08);
EPD_W21_WriteCMD(0x04);
lcd_chkstatus();
}
//////////////////////////////All screen update////////////////////////////////////////////
/////////////////////////////////////////////////////////////////////////////////////////
void EPD_refresh(void)
{
EPD_W21_WriteCMD(0x12); //Display Update Control
EPD_W21_WriteDATA(0x00);
lcd_chkstatus();
}
void EPD_sleep(void)
{
EPD_W21_WriteCMD(0X02); //power off
EPD_W21_WriteDATA(0x00);
lcd_chkstatus(); //waiting for the electronic paper IC to release the idle sign
EPD_W21_WriteCMD(0X07); //deep sleep
EPD_W21_WriteDATA(0xA5);
}
void lcd_chkstatus(void)
{
while (isEPD_W21_BUSY == 0) {
delay(3);
}
}
unsigned char Color_get(unsigned char color)
{
unsigned datas;
switch(color)
{
case 0x00:
datas=white;
break;
case 0x01:
datas=yellow;
break;
case 0x02:
datas=red;
break;
case 0x03:
datas=black;
break;
default:
break;
}
return datas;
}
void PIC_display(const unsigned char* picData)
{
unsigned int i,j;
unsigned char temp1;
unsigned char data_H1,data_H2,data_L1,data_L2,datas;
EPD_W21_WriteCMD(0x10);
for(i=0;i<Gate_BITS;i++) //Source_BITS*Gate_BITS/4
{
for(j=0;j<Source_BITS/4;j++)
{
temp1=picData[i*Source_BITS/4+j];
data_H1=Color_get(temp1>>6&0x03)<<6;
data_H2=Color_get(temp1>>4&0x03)<<4;
data_L1=Color_get(temp1>>2&0x03)<<2;
data_L2=Color_get(temp1&0x03);
datas=data_H1|data_H2|data_L1|data_L2;
EPD_W21_WriteDATA(datas);
}
}
//Refresh
EPD_refresh();
}
void Display_All_White(void)
{
unsigned long i;
EPD_W21_WriteCMD(0x10);
{
for(i=0;i<ALLSCREEN_BYTES;i++)
{
EPD_W21_WriteDATA(0x55);
}
}
EPD_refresh();
}
//////////////////////////////////END//////////////////////////////////////////////////
This code shows ways to do that:
Pre-render text → bitmap (easy, reliable)
Minimal bitmap font renderer (lightweight)
Hybrid (icons static + small dynamic text)
No GFX stack required.
No library dependency hell.
No surprise flicker.
This is how: ,Kindle, Shelf labels and Industrial HMI do it.
Here is the Serial Output for the basic test.
EPD Seq Rev 1.1
[EPD] WHITE
[EPD] BLACK
[EPD] YELLOW
[EPD] RED
[EPD] gImage_1
[EPD] CLEAR
[EPD] gImage_2
[EPD] IDLE BLANK
[EPD] WHITE
[EPD] BLACK
[EPD] YELLOW
[EPD] RED
[EPD] gImage_1
[EPD] CLEAR
[EPD] gImage_2
[EPD] IDLE BLANK
Basic_demo.zip (15.2 KB)
I ended up with this
Forum Activity & Rain Monitor
Next…
GL 
PJ 
Forum Activity (Seeed Studio Discourse)
Weather Status (top-left)
Connectivity / Heartbeat Indicator (bottom-left)
Timestamp
Wake → Connect → Fetch
Activity Detection (not polling spam)
Daily Reset Logic
Change-Detection Display Updates (ePaper-friendly)
Custom Graphics Pipeline (no display libraries)