Screens
Heart Rate
The Heart Rate screen shows your current heart rate in beats per minute (bpm), along with a timestamp for when the reading was taken. Tap the Raw PPG button at the bottom to switch into a live photoplethysmography waveform view.
Trends
On-device trend graphs aren’t shipped yet — they’re planned for a future firmware update. In the meantime, the HealthyPi Move app shows daily, weekly, and monthly heart-rate trends after you sync. See Sync your Move.
Streaming raw PPG
Tap Raw PPG at the bottom of the Heart Rate screen to enter the live PPG waveform view. The screen continuously updates the heart rate from the raw signal, giving a real-time view of the pulse waveform.
To exit: swipe down on the screen to return to the Heart Rate view.
How PPG works
Photoplethysmography (PPG) is a non-invasive optical technique that measures changes in blood volume in the microvasculature. An LED shines light into the skin and a photodetector measures how much is reflected back — as blood pulses through the vessels with each heartbeat, the absorbed-vs-reflected ratio changes.
The raw signal has two components:
- AC — the pulsatile portion, caused by the volume change with each heartbeat. This is where heart rate, SpO₂, and (with calibration) blood-pressure trends are extracted.
- DC — the steady absorption from skin, muscle, bone, and other tissue. Useful only as a reference; high-pass filtering removes it.
HealthyPi Move runs two PPG paths — a finger sensor (MAX30101 via MAX32664-D) on the underside of the watch and a wrist sensor (MAX86141 via MAX32664-C) on a separate cable. See Know your sensors for the full signal chain.
Only one PPG path streams at a time.