CCS811 eCO2 + TVOC (CJMCU-811) with ESP32

Supply 3.3 V Bus I2C I2C address 0x5A / 0x5B Measures eco2, tvoc

Pins and ESP32 wiring

Pin	Role	ESP32 pin	Notes
VCC	Power	3V3
GND	Ground	GND
SCL	I2C clock (SCL)	D22
SDA	I2C data (SDA)	D21
WAK	Input (the ESP32 drives it)	D25	Wake, active LOW. Tie to GND to keep it awake
INT	Interrupt	D35	Interrupt output, optional
RST	Input (the ESP32 drives it)	D26	Reset, active LOW. Optional
ADD	Not wired to the ESP32	—	Address select: LOW = 0x5A, HIGH = 0x5B

Suggested wiring for the 30-pin ESP32 DevKit, avoiding flash, input-only and strapping pins. BoardPilot checks it for you as you wire.

Check it is the real chip

Read register 0x20: a genuine part answers 0x81. BoardPilot does this automatically in “Debug a problem”.

Starter code (Arduino)

#include <Wire.h>

void setup() {
  Serial.begin(115200);
  Wire.begin(21, 22);  // SDA = GPIO 21, SCL = GPIO 22
  Wire.beginTransmission(0x5A);
  bool found = Wire.endTransmission() == 0;
  Serial.println(found ? "CCS811 eCO2 + TVOC (CJMCU-811) found at 0x5A" : "Not found: check power, GND and SDA/SCL");
}

void loop() {}

Sources

ams CCS811 datasheet, Register 0x20 HW_ID (reads 0x81)
ams CCS811 datasheet, I2C address 0x5A (ADDR LOW) / 0x5B (ADDR HIGH)

Try it in 3D in BoardPilot

BoardPilot Part data (JSON)

Part data: CC BY 4.0, free to reuse with credit to BoardPilot.