ProtoCentral HealthyPi 4
ESP32 health monitor board with ECG, PPG, and respiration sensors - great for wearable biomedical projects.
ProtoCentral HealthyPi 4 Pinout
25 pins · 2.54 mm pitch| Pin | GPIO | Labels | Status | Capabilities | Notes |
|---|---|---|---|---|---|
| 1 | 0 | A11T1 | strapping | adc · touch | |
| 2 | 1 | TXPWM | uart | uart | |
| 3 | 2 | SSA12T2PWM | strapping | adc · touch · spi | |
| 4 | 3 | RXPWM | uart | uart | |
| 5 | 4 | A10T0AFE4490_PWDN_PINPWM | safe | adc · touch | |
| 6 | 12 | A15T5PWM | strapping | adc · touch | |
| 7 | 13 | A14T4ADS1292_CS_PINPWM | strapping | adc · touch | |
| 8 | 14 | A16T6ADS1292_START_PINPWM | strapping | adc · touch | |
| 9 | 15 | LED_BUILTINA13T3PWM | strapping | adc · touch | |
| 10 | 16 | SLIDE_SWITCHPWM | safe | - | |
| 11 | 17 | KEY_BUILTINPUSH_BUTTONPWM | safe | - | |
| 12 | 18 | SCKPWM | safe | spi | |
| 13 | 19 | MISOPWM | safe | spi | |
| 14 | 21 | SDAAFE4490_CS_PINPWM | safe | i2c | |
| 15 | 22 | SCLPWM | safe | i2c | |
| 16 | 23 | MOSIPWM | safe | spi | |
| 17 | 25 | A18DAC1PWM | safe | adc · dac | |
| 18 | 26 | A19DAC2ADS1292_DRDY_PINPWM | safe | adc · dac | |
| 19 | 27 | A17T7ADS1292_PWDN_PINPWM | safe | adc · touch | |
| 20 | 32 | A4T9PWM | safe | adc · touch | |
| 21 | 33 | A5T8PWM | safe | adc · touch | |
| 22 | 34 | A6 | strapping | adc | |
| 23 | 35 | A7 | strapping | adc | |
| 24 | 36 | A0 | strapping | adc | |
| 25 | 39 | A3AFE4490_DRDY_PIN | strapping | adc |
Start with these
13 pins with no boot or system involvementFreely assignable - no strapping, flash, USB or JTAG duties. Ideal first picks for buttons, sensors and LEDs.
Fine - with a little care
12 pins · 11 things to knowA11GPIO0 Bootstrapping pin (enter bootloader when low); internal pull-up. Strapping
Must be HIGH during boot for normal startup; if held LOW on reset, forces flash programming mode.
TXGPIO1 Default UART0 TX pin for USB-serial programming and console. UART
Connected to on-board USB-UART for uploading and logs; drives serial output at boot, so using as GPIO can disrupt programming or console.
SSGPIO2 Bootstrapping pin (must be low or floating at reset); internal pull-down. Strapping
If driven HIGH on reset (while IO0 is LOW), selects an unsupported SDIO boot mode, causing boot failure.
RXGPIO3 Default UART0 RX pin for USB-serial programming (console input). UART
Used for receiving data from USB-UART (programming); also pulled HIGH at boot for console communication, so using as GPIO can disrupt uploads.
A15GPIO12 Bootstrapping pin; JTAG TDI; sets flash voltage (VDD_SDIO); also HSPIQ (flash data line). Strapping
Keep LOW during boot (internal PD); pulling HIGH at reset selects 1.8V flash mode, causing flash brownout if 3.3V flash is used.
A14GPIO13 JTAG clock pin (TCK); also ADC2 channel 4 / Touch4 input. JTAG
Used for JTAG debugging (TCK); avoid using as GPIO if JTAG is needed.
A16GPIO14 JTAG mode select pin (TMS); also HSPI CLK and PWM-capable GPIO. JTAG
Used for JTAG debugging (TMS); driving it as GPIO may interfere with JTAG or produce spurious signals at boot.
LED_BUILTINGPIO15 Bootstrapping pin; JTAG TDO; controls UART0 boot log output; also HSPICS0 (secondary SPI CS). Strapping
Keep HIGH during boot (internal PU); if LOW on reset, bootloader log is silenced and boot mode may change.
A6GPIO34 Input-only GPIO (no output driver); ADC1 channel 6. Other
Cannot be used as output (no drive capability); only suitable for analog/digital input.
A7GPIO35A3GPIO39 Input-only GPIOs with ADC1 channels - no output driver Other
Cannot be used as output; only suitable for input.
- A7Input-only GPIO (no output driver); ADC1 channel 7.
- A3Input-only GPIO (no output); ADC1 channel 3, Hall sensor VN.
A0GPIO36 Input-only GPIO (no output); ADC1 channel 0, Hall sensor VP. Other
Cannot be used as output; only suitable for input (e.g., analog read).
The ProtoCentral HealthyPi 4 pinout brings out 25 GPIO pins at a 2.54 mm pitch - every one of them usable in your project.
For peripherals, I²C is mapped to SDA on GPIO21 and SCL on GPIO22; the SPI bus (MOSI, MISO, SCK, SS) is broken out in full; TX/RX on GPIO1 and GPIO3 cover serial logging and flashing.
On the analog side there are 16 ADC-capable pins for sensors and battery monitoring, 10 capacitive-touch inputs and 2 true DAC outputs.
If you want zero surprises, A10, SLIDE_SWITCH, KEY_BUILTIN, SCK and 9 more are free of any such role - the safest first picks. 12 of the exposed pins carry boot-time or system duties on the ESP32 (A11, TX, SS and 9 more).
Getting started
flash your first firmware in ~2 minutesBoard: ESP32 Dev Module Flash Size: 4MB (32Mb) Flash Mode: DIO Partition Scheme: Default 4MB with spiffs (1.2MB APP/1.5MB SPIFFS) Upload Speed: 921600
// toggle GPIO4 - wire an LED and resistor to it
void setup() {
pinMode(4, OUTPUT);
}
void loop() {
digitalWrite(4, HIGH); delay(500);
digitalWrite(4, LOW); delay(500);
}[env:healthypi4]
platform = espressif32
board = esp32dev
framework = arduino
monitor_speed = 115200
upload_speed = 921600esp32dev - or type it after board =.esp32:
board: esp32dev
variant: esp32
framework:
type: esp-idf
# blink - GPIO4
output:
- platform: gpio
pin: 4
id: led_out
light:
- platform: binary
name: "LED"
output: led_outesp32dev (same ids as PlatformIO).esptool.py --chip esp32 --port /dev/ttyACM0 \
--baud 921600 write_flash 0x1000 firmware.bin--port = your /dev/tty* (macOS/Linux) or COMx (Windows).Specifications
ESP32 · 65 × 56 mm · vs other ESP32 chips →Dimensions
About this board
At its core is the ESP32 - a dual-core Xtensa with both Bluetooth Classic and BLE.
Expect to pay about $199.00 - above the ~$20 typical for ESP32 boards.
Onboard you'll find a Qwiic connector and battery charging via JST-PH 2.0.
- ECG & respiration: TI ADS1292R 24-bit analog front-end (107 dB SNR)
- Pulse oximetry (PPG/SpO2): TI AFE4400 front-end with integrated LED driver and 22-bit ADC
- Skin temperature: Maxim MAX30208 digital body-temperature sensor
- Raspberry Pi HAT form factor with 40-pin GPIO header
- 1000 mAh LiPo battery with onboard charging and power management
- Slide switch toggles between HAT (continuous) and standalone wearable mode
- DB9 connector for ECG electrode cable and 3.5 mm jack for the SpO2 finger sensor
- 2x SparkFun Qwiic I2C connectors for sensor expansion
- Fully open-source hardware and firmware (Arduino IDE and ESP-IDF)
Where to buy
prices are typical street pricesResources
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