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PulseSensor Waveshare RLCD Prototype

Prototype Tutorial

PulseSensor on Waveshare ESP32-S3-RLCD-4.2

Try the monochrome version: Flash a Waveshare ESP32-S3-RLCD-4.2, wire the PulseSensor to the rear 2 x 8 female header, and watch a live pulse dashboard on the 400 x 300 reflective LCD. No WiFi, no IDE after flashing, and no backlight needed.

Rendered screenshot of the Waveshare ESP32-S3-RLCD-4.2 showing the monochrome PulseSensor dashboard with large labels

This software is an educational biofeedback demo and is not intended for medical use.

Flash Your RLCD Board

Plug the Waveshare board into USB-C. Use Chrome, Edge, or Brave on a computer. Mobile browsers do not support WebSerial yet.

This browser does not support WebSerial. Open this page in Chrome, Edge, or Brave on a desktop or laptop. WebSerial is blocked. Make sure the page is loaded over HTTPS.

First time? After you click Install, your browser will ask which serial port to use. Pick the USB-C serial port for the Waveshare ESP32-S3 board.

What Is Different From The CYD?

The CYD version is a color touchscreen project. This version is intentionally smaller: a black-and-white live PulseSensor dashboard for the Waveshare reflective LCD board.

CYD tutorial Waveshare RLCD tutorial
ESP32-2432S028 "Cheap Yellow Display" Waveshare ESP32-S3-RLCD-4.2
320 x 240 ILI9341 color TFT 400 x 300 ST7305 monochrome reflective LCD
Touch controls, sound, rear LED First milestone: screen dashboard only
Purple wire on P3 IO35 Purple wire on rear header GP1
Red wire on CYD P3/CN1 power Red wire on rear header 3V3

Wire Your PulseSensor

The Waveshare board exposes a rear 2 x 8 female header. Use the printed labels on the board, not cable colors from any other kit.

Line art of Waveshare rear header with GP1 highlighted for the purple PulseSensor signal wire
Purple signal wire goes to lower-row GP1
Schematic showing PulseSensor red to 3V3, black to GND, purple to GPIO1 ADC1_CH0
Three-wire schematic
PulseSensor Wire Waveshare Rear Header Connection
Red (+V) 3V3
Black (GND) GND
Purple (Signal) GP1 / GPIO1 / ADC1_CH0
Important: Use 3V3, not VBUS. The firmware reads the PulseSensor signal from GPIO1, so the purple wire must go to the lower-row GP1 socket.

What You'll See

After flashing and wiring, hold the PulseSensor gently against a fingertip or earlobe. The RLCD dashboard shows the same signal state as the CYD firmware, simplified for monochrome.

  • SIGNAL SEARCH while the firmware looks for clean beats.
  • QUALIFIED BEAT once the quality meter locks.
  • A live scrolling waveform across the center of the 400 x 300 display.
  • Lower panels for BPM, IBI, and SIG GPIO1.
  • A pulsing heart in the header when qualified beats arrive.
  • Monochrome light/dark mode toggle with the board's KEY/GPIO18 button.

Features

Reflective display. The 400 x 300 ST7305 RLCD is readable without a backlight and works well for black-and-white line art.
Small firmware. This is a focused prototype, not a full CYD app port.
Signal-first loop. readPulseSensor() remains the first meaningful foreground call.
Known pinout. Display pins are SCK=11, MOSI=12, DC=5, CS=40, RST=41.
ADC1 signal. PulseSensor signal uses GPIO1 / ADC1_CH0 on the rear header.
Monochrome modes. Use KEY/GPIO18 to switch between light and dark display modes.

PulseSensor Playground Tie-Ins

Every reading on the display comes from the PulseSensor Playground library, just like the CYD version.

What you see on screen Playground call behind it
Live waveform getLatestSample()
Beat event / heart pulse sawStartOfBeat()
Inside-beat state isInsideBeat()
BPM number getBeatsPerMinute()
IBI number getInterBeatIntervalMs()
Amplitude meter getPulseAmplitude()
Dotted threshold line setThreshold(550)
Success looks like:
  • Smooth waveform. Clear peaks matching your heartbeat.
  • BPM stabilizes. A real reading usually settles after a few clean beats.
  • Quality rises. The signal meter fills as the waveform becomes usable.
  • Header changes. SIGNAL SEARCH becomes QUALIFIED BEAT.

Quick Troubleshooting

Problem Fix
Install button does nothing Use Chrome, Edge, or Brave on a desktop or laptop. Mobile browsers do not support WebSerial yet.
No serial port appears Use a data-capable USB-C cable and plug directly into the computer.
Screen stays blank Confirm this is the Waveshare ESP32-S3-RLCD-4.2. This firmware is for the ST7305 RLCD pins listed below.
Flat or clipped waveform Confirm purple is on GP1, red is on 3V3, and black is on GND. Do not use VBUS for sensor power.
BPM stays 0 Hold the sensor with gentle, steady pressure and give it a few clean beats. Try an earlobe if fingertip readings are jumpy.
Display mode is hard to read Tap the board's KEY/GPIO18 button to switch monochrome light/dark mode.

Get The Source / Get A Sensor

The Source Code

This version is a standalone PlatformIO Arduino/C++ project for the Waveshare RLCD board.

github.com/yury-g/PulseSensor_RLCD

MIT licensed. This is the first known-working RLCD milestone.

Need a PulseSensor?

The PulseSensor Kit ships with a Stabilizer Ring, color-coded cable, ear clip, finger strap, and vinyl insulation dots.

Get the Kit

Hardware details and pinout

The firmware targets the Waveshare ESP32-S3-RLCD-4.2 board with ESP32-S3, 16 MB flash, 8 MB PSRAM, and ST7305 reflective LCD.

PULSE_PIN       = 1
RLCD_SCK        = 11
RLCD_MOSI       = 12
RLCD_DC         = 5
RLCD_CS         = 40
RLCD_RST        = 41
BUTTON_BOOT     = 0
BUTTON_KEY      = 18

PulseSensor Playground expects 10-bit samples, so the firmware calls analogReadResolution(10) during startup.

This software is an educational biofeedback demo and is not intended for medical use.

Made by World Famous Electronics. Source on GitHub. MIT licensed. Heartbeats in your project, lickety-split.