V0.3 - 41bdceb

Main new features:

• heart-rate sensor (PPG, TYHX HX3918) streamed over BLE, with the heart rate computed on the ring (only with a clear pulse and a still hand) and an experimental SpO2 mode (red + IR, not calibrated)
• new web demos: Heart Rate, HRV & SpO2 (pulse, heart rate variability, session trends) and Webcam Pulse (heart rate from the laptop webcam)
• outside indicators: red heart while an app uses the heart-rate sensor, green steps while it streams the accelerometer
• charging indicators: dim red heart while charging, dim green when nearly full (also with the display off)

Extra:

• faster, more reliable connections (advertising every 100 ms instead of 687.5 ms: ~1.5 s instead of 3-10 s); the web apps retry, warn when a connection fails, and keep working after a reconnection (Chrome on Linux)
• fluid display twice as fast (200 steps/s, with half the CPU time), display at 50 % brightness
• make scan shows the firmware commit of each ring; make flash LibRing_XX flashes rings by name
• MIDI app: the touch sensor is sent as a note (or CC); all the apps use one plot library (no Chart.js)
• rings already running this firmware (V0.1 or later) accept any of the 2 binaries, whatever their model. Stock rings only accept the binary of their product ID:
  • output_41bdceb_0x4C_2026_rings.bin: 2026 rings (product ID 0x4C)
  • output_41bdceb_0x17_older_rings.bin: original SR08 rings (product ID 0x17)

Notes:

• the accelerometer range is now set to +-16 g on every ring (it was never set, and rings differed); the accelerometer demos read the range from the ring, so update the rings to this version
• a stock ring that was used with the vendor app refuses the computer: flash it once with the Android SUOTA app
• SpO2 is experimental and not a medical measurement