•  Hardware
  • MCU : Raspberry Pi Pico (RP2040)
  • Display : ILI9488 480×320 SPI TFT (3.5")
  • Audio : Original CJ-71 piezo buzzer, GPIO driven
  • Power : 2× LR14 → XL6019 boost converter → 5V → Pico VBUS
  • SPI : SPI0 at 40MHz, 18-bit color
  • Consumption : ~55mA at 5V · ~70h estimated battery life

The ILI9488 fits almost perfectly behind the original CJ-71 screen bezel.

• Power
  • The original CJ-71 ran on 2× LR14 C-cell batteries (~3V). An XL6019 boost converter steps this up to stable 5V for the Pico VBUS.