E-Paper ESP32 Driver Board

Universal e-Paper Driver HAT, supports various Waveshare SPI e-Paper raw panels

Introduction

Universal e-Paper Driver HAT features ESP32, supports various Waveshare SPI interface in e-Paper raw panels. It also supports refreshing image to e-paper via WIFI or Bluetooth and Arduino.

More

Parameter

WiFi Standard: 802.11b/g/n
Communication Interface: SPI
Bluetooth Standard: 4.2, BR/EDR and BLE included
Communication Interface: 3-Wire SPI, 4-wire SPI (default)
Working voltage: 5V
Working Current: 50mA-150mA
Outline dimension: 29.46mm x 48.25mm

Pin

Pin	ESP32	Description
VCC	3.3V	Power input
GND	GND	Power ground
SCK	P13	SPI CLK, Clock Signal Input
DIN	P14	SPI MOSI, Data Input
CS	P15	Chip Select, active-low
BUSY	P25	Busy Output Pin (means busy)
RST	P26	Reset, active-low
DC	P27	Reset, Data/Demand, low level means to demand, high level means data

PS: The above is the board fixed connection, no additional operation by the user

Feature

Onboard ESP32, support Arduino development
Provide Android mobile APP program, which can update the display content through Bluetooth EDR, easy to use
Provide HTML host computer program, which can remotely update the display content through the web page, which is convenient to integrate into various network applications
Supports Floyd-Steinberg dithering algorithm for more color combinations and better shadow of the original image
Supports many common image formats (BMP, JPEG, GIF, PNG, etc.)
Factory built-in e-ink screen driver (open source)
5V pin supports 3.6V to 5.5V voltage input, can be powered by lithium battery
Provide complete supporting information manual

Application

This product cooperates with the ink screen and is suitable for the application scenario of wireless brushing.

Supermarket electronic price tag
Electronic name card
Serial information display board, etc.

Preparation

Hardware Connection

This product is shipped with an ESP32 network driver board, an adapter board, and an FFC extension cable.
When using it, you can directly connect the screen to the driver board, or connect it through extension cables and adapter boards.
Direct access to the driver board:

Access via extension cord:

Set the mode switch: Set the No. 1 switch according to the model of the EPD used. There are many screens. If it is not listed, please use 'A' to try. If the display effect is poor or cannot be driven, please try switching the switch.

Turn on the serial port module: Toggle the No. 2 switch to "ON", this switch controls the power supply of the CP2102 (USB to UART module). When you don't need to use it, you can manually turn off the module to save power (if the switch 2 is in the OFF state, you cannot upload the program)
Use a micro USB cable to connect the ESP32 driver board to a computer or 5V power supply

Download Demo

We provide three kinds of demos: local, bluetooth, and WiFi. The sample program can be found in the "Information" tab of this page, or click the sample program to download
Unzip the downloaded compressed package, you can get the following files:demo example

ePape_Esp32_Loader_APP: Bluetooth App source code (Android Studio)
examples: local demo
Loader_esp32bt: Bluetooth demos
Loader_esp32wf: WiFi demo
app-release.apk: Bluetooth demo App installation package

Environment Configuration

If the Arduino IDE is not installed on your computer before, or the version of the IDE is older. It is recommended to go to the Arduino official website to download the latest IDE and install it according to your own system.

Official link: https://www.arduino.cc/en/Main/Software
Download the ESP32 Dev Module management tool: 1. Open the preferences of the arduino software and add a link to the add-on board manager URL: https://dl.espressif.com/dl/package_esp32_index.json

After the addition is complete, open Tools -> Development Board -> Development Board Management Tool, and manually search for "ESP32" to download and install the latest version.

3. After the installation is complete, you can find the model option of ESP32 Dev Module in Tools - Boards of IDE.

If the installation cannot be completed due to repeated errors, please contact the after-sales technicians.

Image Processing Algorithms

In the Bluetooth and WiFi demos, two image processing algorithms are provided, namely Level and Dithering

color scale method

An image can be divided into several large color gamuts, and each pixel on the image is divided into these color gamuts according to how close the color is to these color gamuts. This method is more suitable for images with few colors, such as bright or tri-color shapes or text images. Taking the black and white and red ink screen as an example, when processing the image, we hope to process it into black, white and red, so for an image, we can divide all the colors of the image into three large color areas: the black area , white area, red area.
For example, according to the figure below, if the value of a pixel in the grayscale image is equal to or less than 127, we regard this pixel as a black pixel, otherwise, it is white

For color images, we all know that RGB has three color channels. Compared with the red channel, we can refer to blue and green as the blue-green channel, or the non-red channel. According to the figure below, a pixel on a color image, if it has a high value in the red channel, but a low value in the blue-green channel, we classify it as a red pixel; if its red channel and blue- If the green channel has low values, we classify it as a black pixel; if the red and blue-green channel values are high, we classify it as white.

In the algorithm, the color definition is calculated based on the difference between the RGB value and the sum of the squares of the expected color value. The expected color value refers to the color value that the pixel is closest to, and these values are stored in the curPal array

Dithering

For those images with more colors or more gradient areas, the above gradation method is not suitable. In many cases, the pixels in the gradient area in the image may be very close to all color gamuts. If you use the gradation method to draw The image will lose a lot of image details. Many images taken by cameras, by mixing colors to paint shadows and transition areas, in these images, the gradient area accounts for the majority For the human eye, it is easy to confuse a particularly small color. For example, two colors, red and blue, are juxtaposed. If you reduce it to a small enough hand, it will appear to the human eye as a mixture of red and blue. into color. The defect of the human eye means that we can deceive the human eye and use the "mixing" method to obtain more colors that can be expressed. The dithering algorithm uses this phenomenon. The routine we provide uses the Floyd-Steinberg dithering algorithm - based on error diffusion (published by Robert Floy and Louis Steinberg in 1976). The formula is for error diffusion according to the image below

X is the error (a scalar (vector) difference between the original color and the gray value (color value)), this error will spread to the right, lower right, lower, and lower left four directions, respectively 7/16, 1/16, 5/16 and 3/16 weights are added to the values of these four pixels. Interested users can go to understand the algorithm, there are many resources on the Internet.

Comparison

Original image

"Black and white grading" and "Multicolor grading"

"Black and White Dithering" and "Multicolor Dithering"

Bluetooth Examples

Bluetooth Demo

Download example

Go to the Loader_esp32bt directory, double click the Loader_esp32bt.ino file to open the example.
Choose Tools->Boards->ESP32 Dev Module and select the correct Port according to Device Manager: Tools -> Port.

Click the Upload icon to build the project and upload it to the ESP32 driver board.
Install the APP to the Android board and open it:

APP has five buttons on the main page:
- BLUETOOTH CONNECTION: This button is used to connect the ESP32 device via Bluetooth.
- SELECT DISPLAY TYPE: This button is used to select the type of display according to what you buy.
- LOAD IMAGE FILE: Click it and choose a picture to open. It is only available after choosing the display type.
- SELECT IMAGE FILTER: This button is used to choose the image process method.
- UPLOAD IMAGE: Upload the processed image to ESP32 driver board and update to e-Paper display.
Please first open the Bluetooth function of your phone. Click the BLUETOOTH CONNECTION button -> Click the SCAN icon on the top-right to scan the Bluetooth device.
Find the ESP32 device and connect. If your phone is the first time to connect this device, it requires pairing, complete the pairing process according to the prompt. (Note: The APP cannot work with pairing.)
Click "SELECT DISPLAY TYPE" to choose the display type.
Click "LOAD IMAGE FILE" To choose a picture from your phone and cut it.
Click " SELECT IMAGE FILTER" to choose a process algorithm and confirm.
- "LEVEL: MONO": This option will process the picture to a monochrome image.
- "LEVEL" COLOR": This option will process the picture to the tricolor image according to the display colors of the display (only valid for colorful displays).
- "DITHERING: MONO": This option will process the picture to a monochrome image.
- "DITHERING: COLOR": This option will process the picture to the tricolor image according to the display colors of the display (only valid for colorful displays).
Click "UPLOAD IMAGE" to upload the image to the ESP32 device and display it.

WiFi Examples

WiFi Demo

Provide WiFi demos with an HTML host computer.
Note: The module only supports the 2.4G network band.

How to Use

Go to the Loader_esp32wf directory, double click Loader_esp32wf.ino file to open the project.
Choose Tools -> Boards -> ESP32 Dev Module in the IDE menu, and select the correct COM port: Tools -> Port.

Open the srvr.h file and change the ssid and password to the actual WiFi username and password used.

Press win + R and type CMD to open the command line and get the IP of your computer.

Open the srvr.h file, modify the network segment in the location shown in the picture to the corresponding network segment. Note: the IP address of ESP32 (that is, the fourth bit) should not be the same as the address of the computer, and the rest should be exactly the same as the IP address of the computer.

Then click upload to compile and download the demo to the ESP8266 driver board.
Open the serial monitor and set the baud rate to 115200, you can see the serial port print out the IP address of the ESP32 driver board as follows:

Open the browser on your computer or cell phone (note that the network you are accessing needs to be on the same network segment as the wifi connected to the ESP8266), enter the IP address of the ESP8266 in the URL input field, and open it, you can see the operation interface as follows.

The entire operation interface is divided into five areas:
- Image Operation Area:
  Select Image file: Click to choose an image from your computer or phone
  Level: mono: Black and white image processing algorithm
  Level: color: Multi-color image processing algorithm (only effective for multi-color screens)
  Dithering: mono: Black dithering image processing algorithm
  Dithering: color: Multi-color dithering image processing algorithm (only effective for multi-color screens)
  Update image: Upload image
- IP information display area: This displays the IP address information of the module you are currently connected to
- Image size setting area: Here, x and y can be set to specify the starting position of the display, which is relative to the image file you have selected. For example, if you choose an 800x480 image but the e-ink screen you are connected to is 2.9 inches, the screen will not be able to display the entire image. In this case, the processing algorithm will automatically crop the image from the upper left corner and send a portion of it to the e-ink screen for display. You can set x and y to customize the starting position of the cropping. W and h represent the resolution of the current e-ink screen. Note: If you modify the x and y coordinates, you need to click on the processing algorithm again to generate a new image.
- Model selection area: Here, you can choose the e-ink screen model you are connected to.
- Image display area: Here, the selected image and the processed image will be displayed.
- PS: During image upload, the upload progress will be displayed at the bottom.
Area ①: Click "Select Image file" to choose an image, or drag and drop the image directly into the "Original image" area.
Area ④: Choose the corresponding e-ink screen model, for example, 1.54b.
Area ①: Click on an image processing algorithm, for example, "Dithering: color".
Area ①: Click "Upload image" to upload the image to the e-ink screen display.

Offline Examples

Offline Demo

Provides offline ESP32-based demos without WiFi, Bluetooth, and other devices.

Demo Usage

Open Arduino IDE to view the project file folder location (please do not modify it).

Go to the E-Paper_ESP32_Driver_Board_Code\examples directory and copy the entire esp32-waveshare-epd folder to the libraries directory in the project folder.

Close all Arduino IDE windows, reopen the Arduino IDE, and select the corresponding example demo as shown:

Choose the corresponding board and COM port.

Resources

Documentation

Schematic

Demo Code

Demo code

Related Resources

This is a post in Arduino Form about our SPI e-Paper thanks to ZinggJM, maybe you want to refer to.

Waveshare e-Paper display with SPI

FAQ

Question:If you don't have a V2 logo on the back of your 2.13inch e-paper screen, how do I use it?

Answer:

Open epd1in13.h in the project and change the following value to 1

Question:If you don't have a V2 logo on the back of your 1.54inch e-paper screen, how do I use it?

Answer:

* Open epd1in54.h in the project and change the following value to 1

Question:ESP32 downloads the Bluetooth demo, and the module reports an error: "Guru Meditation Error: Core 0 panic'ed (LoadProhibited). Exception was unhandled." and the Bluetooth cannot be turned on successfully. What should I do?

Answer:

Download Arduino-ESP32 Package，Unzip the files in the compressed package to the hardware\espressif\esp32 path in the Arduino IDE installation directory, select "OK to overwrite the file" (remember to back up the original file), and then re-run the routine after power off. (Note: If the path does not exist in the installation directory, you can create it manually)

Question:Downloading ESP32 program with Arduino sometimes succeeds and sometimes fails, how to solve it?

Answer:

Try to reduce the baud rate, you can try to adjust to 115200, as shown in the figure below

Question:The wifi routine upload is normal, the serial port outputs the ip address, but the computer input IP address cannot be accessed, it is necessary to check that the network segment of the ip is consistent with the network segment value of the wifi, and the IP does not conflict

Answer:

Modify the ip network segment, as shown in the following figure

Question:If the computer does not recognize the driver board, first confirm whether the serial port driver has been installed, and then try to replace the USB cable and USB interface as much as possible.

Answer:

mac serial driver: https://www.silabs.com/documents/public/software/Mac_OSX_VCP_Driver.zip

Windows serial port driver: https://www.silabs.com/documents/public/software/CP210x_Universal_Windows_Driver.zip

Question:Burning and uploading program error:

Answer:

Connecting........................................................................................................................................................................_____....._____.... .____Error uploading project_A fatal error occurred: Failed to connect to ESP32: Timed out waiting for packet header

You need to press and hold the boot button on the ESP32 baseboard when the Connecting... prompt appears