A WiFi-connected ePaper display used as a fancy door sign.
The current door signs in my school are small boring stickers that don't really allow for any creativity, or useful information aside from the room number/code.
I was challenged to create a fun door sign for the Computer Science department rooms that can display a seasonal picture background, along with the room code and additional information. I was allowed to borrow a 7-color ePaper display and controller to develop with over the Christmas holidays for fun.
I used contrasting colors for the text fill and text outline, along with a very large font to ensure it can be read from a distance, and monospaced to ensure it will fit on the screen.
I created a webpage to make it incredibly easy to update the display, and to allow for a preview of the display before it is updated. By using a web page, I can offload the image processing from the microcontroller to the web browser, meaning much faster update times, realtime change preview, and support of more image formats. I also added the ability to set a background color, meaning an image is not required if the user prefers a solid color - or to fill in the background of a transparent image.
I used the color-palette defined by the web client viewing the page, so the page is displayed in light mode, dark mode, or with high contrast, depending on user preference.
Finally, I added an 'identify' button that writes out the IP of the screen to the display, so it can be easily seen when multiple screens are connected to the same network.
The device prints its IP address to the screen when it is first booted up, so it is easy to connect to.
I chose PlatformIO as the build system as it is much quicker and easier to use than the Arduino IDE, which requires a GUI and lots of setup-time, and makes it easier to add new libraries and boards.
The WiFi credentials are hardcoded into the firmware, so access to update the screen's contents is restricted to those who have physical access to the device's USB port, or have the credentials to connect to the same WiFi network that the screen is connected to. Finally, a username/password combo is required to access the web interface, so only those who know the credentials can update the screen.
I read through the (very poorly-written) libraries from WaveShare's website to understand how the display is supposed to be controlled. I renamed many of the functions to make it clearer what each one does, and removed lots of unused and duplicate code, along with code not related to my model of display.
I also ported the library and example code over from using the Arduino IDE to using the PlatformIO build system, making the build+upload process significantly easier (as PlatformIO supports automatically downloading all boards+libraries in one command by reading the platformio.ini file, instead of having to navigate a GUI and copy/paste board+library URLs if using a new machine, making it much easier to build).
Finally, I wrote my own webpage and webserver to allow creating and uploading images to the display. I used one of the examples as source for the 7-color dithering algorithm, but the rest of the code I wrote myself.
demo.mov
Wifi credentials are stored under include/secrets.h which is gitignore'd, see include/secrets_example.h for an example.
Upload the firmware to the ESP32 board.
pio run -e esp32dev --target uploadMonitor the serial output of the ESP32 board.
pio device monitor