Driving a 6-colour e-paper display is not like driving a monochrome panel. Seeed Studio’s reTerminal E1002 carries a 7.3-inch ACeP with 800×480 resolution, and a XIAO ESP32-S3 runs underneath it. Mariusz Jurgielewicz has put together a set of Arduino examples tested on exactly this combination, so newcomers don’t have to reinvent pinout, polarity and refresh sequences.

The practical value of the collection lies in the details the official drivers don’t tell you. The GDEP073E01 panel uses the ED2208 controller and is wired to the carrier through an internal FPC. So the pins are not the ones you’d expect from a breakout module: SCK is on GPIO 7, MOSI on GPIO 9, CS on GPIO 10, DC on GPIO 11, RST on GPIO 12 and BUSY on GPIO 13. Logging is also duplicated across two serials, Serial1 on GPIO 43 and GPIO 44 through the USB-UART bridge, plus the XIAO ESP32-S3’s native USB CDC Serial.

BUSY active-low and SPI clock at 2 MHz

Trap number one is the BUSY polarity. On the ED2208 the signal is active-low: 0 means refresh in progress, 1 means ready. Inverting it locks up the driver or corrupts subsequent writes, and the symptom isn’t a clear error but a panel that stays half-drawn.

The second trap is the clock. The SPI bus runs reliably at 2 MHz, and this also applies to the upload speed set in the Arduino IDE, fixed at 115200. The log serial runs at 115200 baud. Higher frequencies on the internal flex risk clock distortion, with pixel dropouts or corrupted command bytes. Finally there’s the watchdog: during a cold refresh the 40-second timeout can fire, so the sequence has to be handled accordingly.

• SCK on GPIO 7, MOSI on GPIO 9, CS on GPIO 10
• DC on GPIO 11, RST on GPIO 12, BUSY on GPIO 13
• BUSY active-low: 0 refresh in progress, 1 ready
• Reliable SPI clock at 2 MHz
• Serial1 on GPIO 43 (TX) and GPIO 44 (RX), plus native USB CDC
• 192,000 bytes of frame buffer in OPI PSRAM

A full frame buffer of 800×480 pixels at 4 bits per pixel, two pixels per byte, requires 192,000 bytes. It doesn’t fit in the ESP32-S3’s internal RAM, so it has to be buffered in OPI PSRAM. The panel exposes 6 native solid colour fields: black, white, red, green, blue and yellow. So each pixel is not a grey value but a colour index, and dithering has to be planned accordingly.

On the software side the collection covers three driver stacks. The first is Jean-Marc Zingg’s GxEPD2, the upstream one you get from the Library Manager. The second is the Good Display vendor driver. The third is Waveshare’s GUI_Paint graphics framework, sitting on top of Adafruit_GFX. Watch out for one detail: the Seeed_GxEPD2 fork should not be installed, because it conflicts with the upstream GxEPD2.

Besides the display, the examples cover the carrier board’s onboard peripherals. There’s the PCF8563 real time clock and the SHT4x environmental sensor, so a complete project can show the time plus temperature and humidity data without adding external modules. Anyone who wants to rebuild everything from scratch will find Mariusz Jurgielewicz’s repository with the sketches ready to upload.

To work on it you need the Arduino IDE with XIAO ESP32-S3 support, the GxEPD2 library from the Library Manager, and the panel connected to the carrier.

Source: https://github.com/melastmohican/reTerminal-E1002-arduino-examples

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