chitram

ESP32 firmware: Waveshare 2.4" ILI9341 LCD + INMP441 mic → Deepgram live speech-to-text → OpenRouter image generation on the display.

Requirements

• PlatformIO Core (python3 -m platformio)
• ESP32 DevKit, USB cable
• Waveshare 2.4" LCD (ILI9341 SPI)
• INMP441 I2S MEMS microphone
• WiFi + Deepgram API key + OpenRouter API key

Secrets

cp include/secrets.h.example include/secrets.h

Edit include/secrets.h with your WiFi SSID/password, DEEPGRAM_API_KEY, and OPENROUTER_API_KEY. That file is gitignored.

Wiring

LCD (Waveshare 2.4" ILI9341)

LCD	ESP32
VCC	3.3V
GND	GND
DIN	GPIO 23 (MOSI)
CLK	GPIO 18 (SCK)
CS	GPIO 5
DC	GPIO 16
RST	GPIO 17
BL	GPIO 4

Mic (INMP441)

INMP441	ESP32	Notes
VDD	3.3V	Never 5V
GND	GND
SCK (BCLK)	GPIO 26
WS (LRCL)	GPIO 25
SD (DOUT)	GPIO 33	Data in
L/R	GND	Left channel

Button (listen / stop toggle)

Button	ESP32
one side	GPIO 27
other side	GND

Press and hold GPIO 27 to talk; release to stop and show the transcript. Serial listen / stop still work.

Usage

1. Wire LCD + mic
2. Fill in include/secrets.h
3. Flash and open serial:

python3 -m platformio run --target upload --upload-port /dev/cu.usbserial-0001
python3 -m platformio device monitor

4. Wait for Ready on the LCD / commands: listen | stop | help on serial
5. Hold the GPIO 27 button to talk (release to stop), or use serial listen / stop:
   • hold — stream mic audio to Deepgram live
   • release — finalize and show the transcript
6. Live partial transcripts appear on the LCD while you speak
7. After stop: transcript briefly, then OpenRouter generates a JPEG and draws it full-screen
8. Auto-stops after 5 minutes if you keep holding

Image gen is memory-optimized: requests 1K / 4:3 from Gemini, stream-decodes base64 straight into LittleFS (no large RAM buffer — avoids ESP32 heap fragmentation OOM), then paints with TJpg_Decoder / PNGdec.

Mic I2S is only on between listen and stop. Audio is streamed as raw PCM (linear16 @ 16 kHz) — no multi‑MB RAM buffer.

Build only

python3 -m platformio run

Layout

Path	Role
include/config.h	Pins + constants
include/display.h + src/display.cpp	ILI9341 UI
include/mic.h + src/mic.cpp	I2S mic, DSP, VU
include/deepgram.h + src/deepgram.cpp	Live STT WebSocket
include/net_services.h + src/net_services.cpp	WiFi + OpenRouter image gen
include/app.h + src/app.cpp	Button/serial flow
src/main.cpp	setup() / loop() only
include/secrets.h	WiFi + API keys (gitignored)