PulseLink turns the pocket-sized M5Stack StickS3 into a self-contained PulseSensor display with a live waveform, honest signal-confidence coaching, and beat-synced BPM. No phone, cloud, router, breadboard, or second processor is required.
- Hackster build guide: PulseLink: Watch Your Heartbeat on M5Stack StickS3
- M5Stack controller: StickS3 documentation
- Sensor: PulseSensor Amped kit
The PulseSensor kit plugs directly into the StickS3. The black lead connects to GND, while the paired red and purple connector plugs into the adjacent 3V3 and G2 pins. No breadboard, adapter harness, or extra jumper wires are required.
| PulseSensor lead | StickS3 |
|---|---|
| Signal / purple | G2 / GPIO2 |
| VCC / red | 3V3 |
| GND / black | GND |
Disconnect USB power before wiring. Power the PulseSensor from 3.3 V only in this build; do not connect it to 5 V.
Before skin contact, apply the included transparent vinyl dot to the sensor face and completely insulate the electronics on the back. Do not place exposed electronics against skin.
The StickS3 combines the parts this project needs in one polished controller: an ESP32-S3, a sharp 1.14-inch display, battery power, programmable buttons, accessible GPIO, and UIFlow2 MicroPython. It samples the PulseSensor on GPIO2, runs adaptive beat detection and confidence logic, and renders the complete 240 × 135 interface at the same time.
The front button becomes RESYNC, the side button performs a detector reset, and the battery makes the experience portable. StickS3 also offers Wi-Fi, an IMU, audio, and a much broader development platform, but PulseLink deliberately keeps the verified build local and focused: sensing, interpretation, feedback, and display all happen on the controller.
Many heartbeat projects jump directly from a noisy signal to a confident-looking number. PulseLink keeps the waveform visible and makes uncertainty part of the interface:
| State | Meaning |
|---|---|
| Blue | Collecting data; nothing trustworthy yet |
| Yellow | A pulse-like waveform is present; confidence is building |
| Green | The signal is qualified and BPM is ready |
The waveform, heart, confidence state, and BPM tile share this color language. Every accepted beat animates the heart and BPM tile. RESYNC lets the user retune detection to the signal already visible on screen.
| Quantity | Component | Purpose |
|---|---|---|
| 1 | M5Stack StickS3 | Samples, processes, and displays the signal |
| 1 | PulseSensor Amped kit | Captures the optical pulse waveform |
That is the complete electronics list. The PulseSensor kit's black, red, and purple leads plug directly onto the StickS3 header; no breadboard, adapter harness, or additional jumper wires are needed.
The verified build uses UIFlow2 v2.4.9 on StickS3 and one readable
MicroPython application: pulselink.py.
-
Install or restore UIFlow2 v2.4.9 with M5Burner.
-
Install Python 3 and
mpremote:python3 -m pip install mpremote
-
Clone this repository and copy the application to the StickS3 as
main.py:git clone https://github.com/yury-g/pulsesensor-m5sticks3.git cd pulsesensor-m5sticks3 python3 -m mpremote connect auto fs cp pulselink.py :main.py -
Reset the StickS3. PulseLink should start automatically.
If UIFlow2 opens its launcher instead of main.py, set the UIFlow2 boot option
to run the downloaded program, then reset again.
Rest a fingertip lightly on the prepared PulseSensor and hold still while the detector builds confidence. Small changes in pressure or motion will be visible in the waveform.
| Control | Action |
|---|---|
| Front blue button / BtnA | RESYNC — retune to the live waveform and open a short fast-lock period |
| Side button / BtnB | Perform a full detector reset |
The StickS3 samples the analog signal at 50 Hz and reduces its 12-bit ADC reading to the 10-bit range used by the detector. The detector follows the running peak and trough, places an adaptive threshold between them, and uses a refractory gate to prevent one physical pulse from being counted more than once.
Possible beats must fall within the educational demo's interval, rate, and amplitude limits. A confidence score rises for consistent beats and falls when the signal becomes uncertain. BPM appears only after the score passes the 10-of-12 lock threshold, then uses up to ten recent qualified intervals for smoothing.
The current code corresponds to the real-hardware-verified v1.1-resync build.
The finished application is pulselink.py. Earlier experiments
and filenames remain available through the public Git history and tags.
Motion and changing contact pressure can disrupt the optical signal. This project has not been compared against a calibrated reference instrument.
PulseLink is an educational biofeedback project. It is not a medical device and must not be used for diagnosis, treatment, or health decisions.
PulseLink is an original StickS3 and MicroPython implementation by Yury Gitman.
It adapts beat-detection concepts from the MIT-licensed
PulseSensor Playground,
whose copyright and license notice are preserved in
THIRD_PARTY_NOTICES.md.
Disclosure: Yury is a co-founder of World Famous Electronics, the company that makes PulseSensor.
MIT. See LICENSE.