70 lines
4.2 KiB
Markdown
70 lines
4.2 KiB
Markdown
# eInk API for Raspberry Pi Pico
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This firmware drives a Waveshare 4.2" e-Paper display from a Raspberry Pi Pico / Pico W. It launches the e-paper driver on core 1 while core 0 acts as a simple serial command processor, giving you an interactive API for drawing primitives, text, and editor-mode logs over USB.
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## Features
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- Lightweight C implementation built on the official Pico SDK and Waveshare e-Paper drivers.
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- Core 1 renders directly to a framebuffer and updates the display with both full and partial refreshes.
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- Serial command queue exposes operations such as clearing, drawing geometry, writing text, and entering an editor mode.
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- Automatic display shutdown after 30 seconds of inactivity to preserve the panel.
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## Requirements
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- Raspberry Pi Pico or Pico W (project sets `PICO_BOARD` to `pico_w`).
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- Waveshare 4.2" e-Paper V2 display, wired to SPI + compatible GPIOs defined in `DEV_Config.h`.
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- Pico SDK (2.2.0) installed and available via `PICO_SDK_PATH`.
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- `cmake`, `ninja`, and `picotool` (or the Pico toolchain) for flashing.
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## Building
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```sh
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# configure the build
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cmake -S . -B build
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# build the UF2 image
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cmake --build build
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```
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After building, flash the firmware to your Pico (e.g. by copying `build/eink_api.uf2` to the Pico's mass storage device or using `picotool load build/eink_api.uf2`).
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### Build/Flash Helper Script
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Run `scripts/flash_and_connect.sh [/dev/ttyACM0]` to configure CMake, compile the firmware, optionally flash it with `picotool`, and open a serial session (defaults to `screen` at 115200 baud). Set `PICO_SERIAL` to override the port, `PICO_BAUD` for a different baud rate, and `SERIAL_CLIENT` if you prefer `picocom` or `minicom`. If `picotool` is missing, the script will remind you to copy the UF2 to the board manually.
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## Usage
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1. Open a serial terminal (115200 baud) over the Pico's USB CDC interface.
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2. Type commands followed by `Enter`. The firmware echoes the command buffer and executes the operation on core 1.
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3. Most commands require the display to be initialized (`init`). The device automatically turns off the screen after ~30 seconds of inactivity, so send another command to revive it.
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4. If `editor` mode is enabled, keystrokes are batched and rendered directly on the display until inactivity ends the mode.
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### Supported Commands
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| Command | Description |
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| --- | --- |
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| `init` | Initializes the e-Paper panel and allocates the framebuffer. |
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| `clear` | Clears the current framebuffer to white (requires display on). |
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| `display` | Pushes the framebuffer to the panel (requires display on). |
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| `draw_test` | Draws a hard-coded Waveshare demo pattern. |
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| `draw_text x y text` | Writes `text` at `(x,y)` using the current font. |
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| `draw_text_white x y text` | Writes inverted white text at `(x,y)` with a black background. |
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| `draw_point x y` | Draws a black point at the given coordinates. |
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| `draw_line x1 y1 x2 y2` | Draws a black line between two points. |
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| `draw_sine x y length amplitude frequency` | Draws a sine-wave curve of `length` pixels starting at `(x,y)`, oscillating by `amplitude`, with the given number of cycles. |
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| `draw_rectangle x1 y1 x2 y2` | Draws an empty rectangle. |
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| `draw_rectangle_fill x1 y1 x2 y2` | Draws a filled rectangle. |
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| `draw_circle x y r` | Draws an empty circle with radius `r`. |
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| `draw_circle_fill x y r` | Draws a filled circle with radius `r`. |
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| `draw_num x y num` | Draws `num` using the default numeric font. |
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| `set_pixel x y color` | Sets a single pixel to `color` (0=white, 1=black). |
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| `close` | Sends the panel to deep sleep and frees the framebuffer. |
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| `editor [0|1]` | Enables editor mode; default uses white background, non-zero switches to white text on black. Press Enter to run typed commands. |
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## Notes
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- The project imports the Waveshare e-Paper libraries from `Pico_ePaper_Code/c/lib/*` for configuration, fonts, GUI primitives, and the panel driver.
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- USB serial I/O is enabled (`pico_enable_stdio_usb`), while UART stdio is disabled to avoid conflicts (`pico_enable_stdio_uart` set to `0`).
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- The firmware allocates the framebuffer via `malloc` and frees it when the display goes to sleep; avoid running out of heap on severely constrained Pico builds.
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- Editor-mode inactivity is 10 seconds before automatically exiting back to command mode.
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