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PulseSensor on CYD (ESP32-2432S028)

New Tutorial

PulseSensor CyberDeck on the CYD (ESP32-2432S028)

Try it now: Plug your CyberDeck into USB, click Install below, then wire up your PulseSensor. Live heartbeat on a 320×240 TFT in under two minutes — with sound, blinking light, and on-screen volume control. No app to install, no WiFi, no IDE. Just Chrome, Edge, or Brave.

PulseSensor CyberDeck running 1.3.0-launch firmware on an ESP32-2432S028 — live waveform reading 121 BPM next to a finger wearing a red 3D-printed PulseSensor ring

What's a CYD?

"CYD" is the maker community's nickname for the ESP32-2432S028 — short for "Cheap Yellow Display," after the bright yellow PCB the early boards shipped on. For pocket change you get an ESP32 microcontroller, a 2.8″ 320×240 color touchscreen, an SD card slot, and a speaker pin in one tiny package. That bundle is why it exploded in the maker community as the go-to board for portable dashboards, retro mini-games, smart-home displays, and — with this firmware — live heart-rate biofeedback.

Credit where it's due: YouTuber Brian Lough is who put the CYD on the map. His "Cheap Yellow Display" video series, Discord, and stream of starter projects turned a random AliExpress board into a thriving maker community — and gave thousands of people their first taste of building a portable touchscreen device.

We call our build of it the PulseSensor CyberDeck — a CYD running open-source PulseSensor firmware, ready to flash from this page.

⚡ Flash Your CyberDeck

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

Installer firmware: 1.3.0-launch - 2026-05-26. After flashing, the dashboard should show the same version and date under PulseSensor.com.

First time? After you click Install, your browser will ask which serial port to use. Pick the one labeled with your board's USB-serial chip (often CP210x or CH340).

Wire Your PulseSensor

The PulseSensor uses three color-coded wires. Use this two-step guide before you connect the sensor.

Two ESP32-2432S028 boards and two included cable harness examples

Identify your board and harness

Look for the ESP32-2432S028 number in the listing or printed on the board.

  • Single micro-USB style works.
  • Micro-USB plus USB-C style works.
  • Make sure it includes a JST-SH 1.0 mm to Dupont jumper harness.
  • Harness colors vary by seller; the board labels matter most.
Annotated P3 connector on ESP32-2432S028 showing P3, IO35, IO21 power, and GND

Wire P3 by label

Plug the white harness into P3, then match the PulseSensor wires to the board labels.

  • RedIO21 on P3
  • BlackGND on P3
  • PurpleIO35 on P3

Important: Use P3 IO21 as PulseSensor power, not 5V. The firmware reads the PulseSensor signal from P3 IO35.

Two ESP32-2432S028 boards connected with different colored P3 jumper harnesses
Two CyberDecks wired with different seller-supplied harness colors.

What You'll See

After you flash and wire up, press your finger lightly on the sensor. You'll see two states:

ESP32-2432S028 screen searching for signal: yellow waveform, GOOD WAVE header
Searching for signal — yellow waveform
ESP32-2432S028 screen locked on qualified beat: green waveform, BPM, IBI displayed
Locked on qualified beat — green waveform

The dashboard tells you what state it's in at a glance:

  • Yellow → Green. The waveform starts yellow while the firmware searches for clean beats, then turns green once the quality meter locks at 10/12.
  • Header flips. SIGNAL SEARCH becomes QUALIFIED BEAT the moment lock happens.
  • Numbers settle. BPM, IBI (milliseconds between beats), and the animated heart all sync to your rhythm. The pulse amplitude meter rises with stronger signals.

Features

Four feedback channels turn the CyberDeck into a complete biofeedback teaching tool.

Screen. Waveform, BPM, IBI, quality, and lock state on a 320×240 ILI9341 TFT.
Light. The board's rear red LED blinks and fades on every qualified beat.
Sound. Short heartbeat tone on the onboard speaker (GPIO 26) on each qualified beat.
Touch. Header buttons let you change speaker volume in 10 steps. Default 1/10.
Auto re-arm. If the waveform looks alive but the detector isn't producing beats, the firmware quietly resets it.
Change-driven UI. Only the parts of the screen that change get redrawn — no flicker.

PulseSensor Playground Tie-Ins

Every reading on the screen comes directly from the PulseSensor Playground library, so what you see on the ESP32-2432S028 display is what you'd see in your own Arduino sketches.

What you see on screen Playground call behind it
Live waveform getLatestSample()
Heart pulse / LED blink / tone sawStartOfBeat()
"Inside beat" indicator 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 — yellow first, then green once locked.
  • BPM stabilizes. Settles to 60–100 within 5–10 seconds.
  • Heart pulses. The header heart and rear red LED flash on every qualified beat.
  • Sound + light. Short heartbeat tone on each qualified beat.

Quick Troubleshooting

Problem Fix
Install button does nothing Use Chrome, Edge, or Brave on a desktop or laptop. Mobile browsers don't support WebSerial yet.
No serial port appears in the picker Try a different USB cable — many micro-USB cables are charge-only. Plug directly into your computer, not a hub.
Flashes but screen stays blank The CYD backlight is on GPIO 21. If it's truly dark, you may have a different board variant. Open an issue with your board photo.
Flat waveform Confirm the purple wire is on P3 IO35 and the red wire is on P3 IO21. Do not use 5V.
Erratic readings Use gentle, steady finger pressure. Insulate the back of the sensor. Try the Stabilizer Ring for the cleanest signal.
BPM stays at 0 Give it 5–10 seconds. The detector needs a few clean beats before it reports BPM.

Get the Source / Get a Sensor

Prefer to see it in a browser without a screen? Try PulseSensor + WebSerial — same sensor, dashboard runs in Chrome.

📂 The Source Code

The firmware is intentionally one Arduino .ino file so you can open, read, and modify it in the Arduino IDE.

github.com/WorldFamousElectronics/PulseSensor_CYD

MIT licensed. PRs welcome.

🛒 Need a PulseSensor?

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

Get the Kit — $30

Hardware details and pinout (for advanced users)

The firmware targets the ESP32-2432S028 board family, commonly sold under the "Cheap Yellow Display" nickname, with an ILI9341 320×240 TFT and XPT2046 resistive touch.

PULSE_PIN       = 35
BACKLIGHT       = 21
LED_RED_PIN     = 4
LED_GREEN_PIN   = 16
LED_BLUE_PIN    = 17
SPEAKER_PIN     = 26
TOUCH_IRQ       = 36
TOUCH_MISO      = 39
TOUCH_MOSI      = 32
TOUCH_SCLK      = 25
TOUCH_CS        = 33

Why GPIO 35? The PulseSensor signal pin was discovered with a small analog pin scanner on a connected CYD. On this revision the signal was visible on IO35, not the originally documented GPIO 36.

ESP32 analog quirk. PulseSensorPlayground's detector expects 10-bit analog samples (0..1023), but ESP32 defaults to 12-bit (0..4095). The firmware calls analogReadResolution(10) at startup to keep the library's beat-detection math in the range it expects.

Build from source in Arduino IDE
  1. Download PulseSensor_CYD.ino from the repo.
  2. Make a folder named PulseSensor_CYD. Put the .ino inside it.
  3. Open it in Arduino IDE 2.x.
  4. Install the ESP32 board package (Boards Manager).
  5. Install three libraries: TFT_eSPI, PulseSensor Playground, XPT2046_Touchscreen.
  6. Configure TFT_eSPI for the ESP32-2432S028 display (the repo's flash-cyd.sh script shows the exact compile flags — preferred over editing the global User_Setup.h).
  7. Select your ESP32 board and upload at 115200 baud.

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. ♥