Dive Computer

Based on the previous bottom timer project. Pressure sensor and housing remains the same.

• Add dive computer mode with Bühlmann ZHL-16C algorithm
• Add tilt compensated digital compass with soft and hard iron calibration Compass function removed, too unstable for navigation, strong interference from the motor.
• Backlight auto adjustment

Hardware

• Change MCU from ESP32-C3 to ESP32-S3 (Waveshare ESP32-S3-LCD-2)
• Change display from 1.54 inch OLED to onboard 2 inch IPS LCD
• Offboard BH1750 light sensor (GY-302, solder to GY-273 back to back)

Software

• Common

  • Dive time starts at 1m depth, stops after 60 seconds when less than 1m depth
  • Depth turns red if stop violated
  • Long press boot button to enable/disable demo
  • Hold boot button for 5 seconds to upload JPEG image via WiFi AP
  • Long press main button to enter menu
  • In menu, short press main button to scroll down, long press to confirm

• Surface

  • Short press main button to display a JPEG image (map, note, etc.)
  • Hold main button for 5 seconds to power off

• Underwater

  • Short press boot button to power off (forced power off incase of depth sensor failure and stuck in dive)
  • Short press main button to start/stop timer
  • Hold main button for 5 seconds to display image, short press to exit

Decompression model assumptions

• Fixed gradient factor 60/85 (optional overide)
• OC/CC switch in menu
• Close circuit with selectable set points of 1.3 and 0.7, default 0.7
• OC gas: 21%, 50%, 99%
• Selectable last stop: 3m or 6m
• Ascent rate 9 m/min
• Sea level 1 atm
• No prior dives
• No helium penalty