CYD – Cheap Yellow Display Emotion Player

This sub-project runs on the Cheap Yellow Display (CYD) — an ESP32 development board with a built-in 2.8 inch ILI9341 TFT display and an SD card slot. It receives plain-text emotion commands from the RSC Raspberry Pi over hardware UART and plays the matching MJPEG animation loop on the screen.

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Hardware

Component	Details
MCU	ESP32 (Dual-core Xtensa LX6, 240 MHz)
Display	ILI9341 2.8" TFT, 240 × 320 px, 16-bit colour
Storage	microSD card (FAT32, connected via VSPI)
Interface	Hardware UART to Raspberry Pi (TX/RX)
Skip button	Boot button on GPIO 0

Pin mapping

Display (HSPI)

Signal	GPIO
DC	2
CS	15
SCK	14
MOSI	13
MISO	12
Backlight	21 (some variants use 27)

SD card (VSPI)

Signal	GPIO
CS	5
MISO	19
MOSI	23
SCK	18

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How it works

1. On boot, setup() initialises the display, SD card, and memory buffers, then switches to the /pride folder.
2. loop() listens for UART commands and calls updateAnimationPlayer() each iteration.
3. updateAnimationPlayer() plays the next .mjpeg file in the active folder and advances the index, looping continuously.
4. A UART command switches the active folder and restarts the file index so the new emotion begins immediately after the current animation ends.
5. Pressing the physical boot button (GPIO 0) skips the current animation and starts the next one.

UART command protocol

Command	Folder switched to	Emotion shown
caring	/caring	Caring / nurturing
surprised	/surprised	Surprised
pride	/pride	Pride / happy

Commands are plain ASCII strings terminated with a newline (\n). They are case-insensitive — leading and trailing whitespace is ignored. Any unrecognised command is echoed back on Serial with "Unknown command".

Example (sent from the Raspberry Pi):

echo "caring" > /dev/ttyUSB0

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SD card layout

Format the card as FAT32 and create one folder per emotion. Each folder contains .mjpeg animation files. Up to 20 files per folder are supported (configurable via MAX_FILES in AnimationPlayer.cpp).

SD card root/
├── caring/
│   ├── idle.mjpeg
│   └── loop.mjpeg
├── surprised/
│   └── surprise.mjpeg
└── pride/
    ├── happy01.mjpeg
    └── happy02.mjpeg

Tip: Convert GIF or video clips to MJPEG using FFmpeg:

ffmpeg -i input.gif -vf "scale=240:320" -q:v 5 output.mjpeg

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Dependencies & toolchain

Library	Source	Tested version
Arduino core for ESP32 (Espressif)	espressif/arduino-esp32	v3.2.0
GFX Library for Arduino	Arduino Library Manager (Arduino_GFX_Library)	v1.6.0
JPEGDEC	Arduino Library Manager (JPEGDEC)	v1.8.2
SD (built-in)	Included with Espressif Arduino Core	v3.2.0
MjpegClass	Included in this project (MjpegClass.h)	—

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Building & flashing

1. Install Arduino IDE 2 or PlatformIO.
2. Add the Espressif ESP32 board package (URL: https://raw.githubusercontent.com/espressif/arduino-esp32/gh-pages/package_esp32_index.json).
3. Select board "ESP32 Dev Module".
4. Install the libraries listed above via the Library Manager.
5. Open main.cpp (or the .ino wrapper if using Arduino IDE), compile, and upload.
6. Open the Serial Monitor at 115200 baud — you should see Ready for UART commands after boot.

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File structure

CYD/
├── AnimationPlayer.cpp   # Display driver, SD reader, MJPEG playback engine
├── AnimationPlayer.h     # Public API: used_to_be_setup(), updateAnimationPlayer(), switchFolder()
├── MjpegClass.h          # Lightweight MJPEG streaming helper (included in project)
├── main.cpp              # Arduino setup()/loop() + UART command handler
└── README.md             # This file

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Credits

The MJPEG playback core is based on the tutorial by atomic14:

• Video: https://youtu.be/jYcxUgxz9ks

Code has been edited to suit the RSC project's needs (UART command interface, folder-based emotion switching, boot-button skip).