CYD open_echo Display

Ultrasonic echo waterfall display for open_echo using ESP32 CYD (Cheap Yellow Display).

Hardware

• ESP32 CYD - ESP32-WROOM-32 with 2.8" ILI9341 TFT (320×240 pixels)
• Connection: RP2040 TX (GPIO0) → ESP32 GPIO22 (RX), GND → GND
• Baud Rate: 921600

Features

• Full screen waterfall (320×240 pixels, right-to-left scrolling)
• Flicker-free overlays (depth value, vertical scale)
• Automatic normalization (Mean±2σ dynamic range)
• Dead zone (excludes sensor ringing from statistics)
• Dynamic scale (automatically calculated step size)

Configuration

Edit main.cpp (USER CONFIGURATION section):

Serial Communication

#define SERIAL_BAUD 921600         // must match RP2040
#define RXD2 22                    // ESP32 RX pin (connects to RP2040 TX)

Measurement Settings

#define NUM_SAMPLES 5000           // must match RP2040
#define SPEED_OF_SOUND 330         // m/s (330=air, ~1500=water)
#define SAMPLE_TIME 1.554e-6       // must match RP2040 setup

Display Settings

#define COLUMN_WIDTH 2             // pixels per measurement
                                   // 1=320 columns (slow), 2=160, 4=80 (fast)

Normalization Settings

#define NORM_DEADZONE_M 0.30       // exclude first X meters from auto-gain
                                   // typical: 0.3-0.7m (prevents ringing)

Building

pio run -t upload