The traditional paper price tag in grocery stores is on the verge of becoming a relic of the past. This innovative switch to e-ink displays offers a multitude of benefits for both stores and customers. Firstly, it promotes sustainability by eliminating the need for constantly printing and discarding paper tags. Secondly, the system utilizes XIAO's USB for serial communication, allowing for quick and efficient updates to prices and other label information, eliminating the time-consuming task of manually changing paper tags. Finally, e-ink displays offer superior readability compared to paper — their clear, high-contrast text ensures that customers can easily see prices and other relevant information, even under bright store lighting.

In this tutorial, we will explore a tiny device — the Seeeduino XIAO SAMD21. Despite its size, XIAO offers ample pins for various components and supports multiple communication protocols. Its user-friendly Arduino compatibility makes it perfect for beginners and makers alike to explore the world of electronics.

This project is for makers, small retailers, or students who want a low-power, easily updatable alternative to printed shelf labels — updating a price becomes a quick reflash instead of printing and swapping paper tags.

Gather everything below before you start.

The XIAO SAMD21, a tiny but mighty board from Seeed Studio, is the first in a line of powerful Arduino-compatible development boards. Despite its small size, it packs a punch with a low-power processor that excels at processing tasks, making it perfect for wearable devices and other projects where space is limited and battery life is important.

The XIAO SAMD21 is packed with features, offering 14 pins for connecting various components like sensors and lights. It also includes a built-in LED for debugging and a modern USB-C port for both power and uploading code. With its versatility and compact design, the XIAO SAMD21 is a great tool for creating all sorts of electronic projects.

The ePaper Breakout Board is an extension board built with a 24-pin FPC connector, designed for Seeed Studio XIAO series boards, allowing you to drive an ePaper display seamlessly. It also comes with an 8-pin 2.54mm header, letting you connect to any microcontroller like an Arduino Uno or Raspberry Pi.

It is suitable for a wide range of ePaper displays, from small to large sizes. Supported by different functional Seeed Studio XIAO boards and requiring no soldering, this extension board can be easily deployed in various scenarios.

This 2.13-inch e-paper display offers a high-quality, low-power option for various uses. It's clear, readable in sunlight, and uses minimal energy, making it ideal for e-readers, shelf labels, and more.

Follow the step-by-step build guide below.

Align the pins and gently insert your XIAO into the XIAO socket on the board.

Carefully slide your e-paper display into the 24-pin FPC connector on the ePaper Breakout Board.

The recommended programming tool is the Arduino IDE. You will need to configure the Arduino environment for the XIAO and add the on-board package.

Add your board model to the Arduino IDE.

This avoids the port disappearing when the program fails to upload.

1. Connect the Seeed Studio SAMD21 to your computer.
2. Use tweezers or short lines to short the RST pins in the diagram twice.
3. The orange LED lights flicker on and light up.

Go to Tools → Board Manager, then search for SEEEDUINO SAMD Boards and click Install.

Click the Board selection dropdown menu, then click on "Select other board and port..."

Select the communication port for your XIAO, then search for and select "COM7 Serial Port (USB)" or whatever appears on your side.

Go to File → Examples → Basics → Blink for testing.

Change all instances of LED_BUILTIN to 10.

Connect the LED to GND and A10/D10 (MOSI) for checking.

Before developing a sketch, here are the ePaper library functions available.

• void EPD_HW_Init() — Full screen refresh initialization.
• void EPD_HW_Init_180() — Display rotation 180 degrees initialization.
• void EPD_WhiteScreen_ALL(const unsigned char *datas) — Full screen refresh display function.
  Input Parameter: datas — the image data that needs to be refreshed.
• void EPD_WhiteScreen_White() — Clear screen display.
• void EPD_WhiteScreen_Black() — Display all black.
• void EPD_DeepSleep() — Deep sleep function.
  Warning: Enter sleep mode and do not remove this call — skipping it will reduce the lifespan of the screen.
• void EPD_Init_Part() — Partial refresh display.
• void EPD_SetRAMValue_BaseMap(const unsigned char * datas) — Partial refresh of background display.
  Input Parameter: datas — the image data that needs to be refreshed.
• void EPD_Dis_PartAll(const unsigned char *datas) — Full screen partial refresh display.
• void EPD_Dis_Part(unsigned int x_start, unsigned int y_start, const unsigned char * datas, unsigned int PART_COLUMN, unsigned int PART_LINE) — Partial refresh display.
  Input Parameters:

  • x_start — the x value of the starting point.
  • y_start — the y value of the starting point.
  • datas — data that needs to be changed.
  • PART_COLUMN — the length of the area to be changed.
  • PART_LINE — the width of the area to be changed.
• void EPD_HW_Init_Fast() — Fast refresh display.
• void EPD_WhiteScreen_ALL_Fast(const unsigned char *datas) — Fast refresh display function.
  Input Parameter: datas — the image data that needs to be refreshed.
• void EPD_HW_Init_Fast2() — Fast refresh display function.

Use the built-in Paint software in Windows to create a picture with the same resolution as the screen you are using, and save it as a BMP or JPG file.

Open Image2Lcd.7z (https://files.seeedstudio.com/wiki/eInk/xiao-expansion/Image2Lcd.7z), extract it, and open the application.

Open the picture, select the "Output file type" as "C array (*.c)", and select the "Scan mode" as "Horizon Scan". The other parameter settings for a 2.13-inch Monochrome ePaper are as follows:

Click "Save" to save the LCD output array as a .h file.

Download the demo code (https://github.com/Allen-Kuang/e-ink_Demo/tree/main/2.13-inch%20E-paper%20-%20monocolor%20122x250/example) for the 2.13-inch E-paper - monocolor 122x250.

Once you have downloaded and extracted the demo code, navigate to and open the "2.13-inch E-paper - monocolor 122x250" folder. Move your files to this folder, then open the "example" folder and use Arduino IDE to open the "example.ino" file.

Delete the demo.h file and replace it with the .h file you outputted from Image2Lcd, then include it in the code.

Click the Board selection dropdown menu, then click on "Select other board and port..."

Select the communication port for your XIAO, then search for and select "COM7 Serial Port (USB)" or whatever appears on your side.

Don't forget to include your outputted .h file from Image2Lcd in the following line of code:

EPD_WhiteScreen_ALL(gImage_pricetag);

Click "Upload" to flash the firmware onto the XIAO.

You should see the ePaper display refreshing with the image, as shown below:

Go to Canva or wherever you did your ePaper image design.

Change it to your desired price.

Repeat the Bitmap Conversion and Downloading and Setting Up the Code steps above, and you're good to go.

As shown above, the price changed from PHP 500 to PHP 1000.

Video Demonstration

Tired of endless paper price tags? This project explores a revolutionary idea: using e-ink displays in grocery stores. These low-power, easy-to-read screens can replace paper tags, saving money and reducing waste. The Seeeduino XIAO, a tiny powerhouse, allows for quick price updates via USB — no reprinting, no paper waste, just a reflash. This project points to a smoother, more sustainable way to handle grocery store labeling using e-ink technology.

• XIAO eInk Expansion Board Wiki
  (https://wiki.seeedstudio.com/XIAO-eInk-Expansion-Board/)
• Seeeduino XIAO Wiki
  (https://wiki.seeedstudio.com/Seeeduino-XIAO/)
• e-ink_Demo — GitHub
  (https://github.com/Allen-Kuang/e-ink_Demo)

• Christian Kyle Mari Arcamo

• Lukie-Mar Lonzaga
• Miles Darren Bagnol
• Elijah Joseph Orias