LM75A temperature (CJMCU-75) with ESP32

Supply 3.3-5 V Bus I2C I2C address 0x48 / 0x49 / 0x4A / 0x4B / 0x4C / 0x4D / 0x4E / 0x4F Measures temperature

Pins and ESP32 wiring

Pin	Role	ESP32 pin	Notes
VCC	Power	3V3	Use 3V3 so the I2C lines stay at 3.3 V
GND	Ground	GND
SDA	I2C data (SDA)	D21
SCL	I2C clock (SCL)	D22
OS	Interrupt	D35	Over-temperature output (open drain), optional
A0	Not wired to the ESP32	—	Address bit 0. Check the board: some leave A0 to A2 floating
A1	Not wired to the ESP32	—	Address bit 1
A2	Not wired to the ESP32	—	Address bit 2

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

Starter code (Arduino)

#include <Wire.h>

void setup() {
  Serial.begin(115200);
  Wire.begin(21, 22);  // SDA = GPIO 21, SCL = GPIO 22
  Wire.beginTransmission(0x48);
  bool found = Wire.endTransmission() == 0;
  Serial.println(found ? "LM75A temperature (CJMCU-75) found at 0x48" : "Not found: check power, GND and SDA/SCL");
}

void loop() {}

Sources

NXP LM75A datasheet, Slave address 1001 A2 A1 A0 = 0x48 to 0x4F; supply 2.8 to 5.5 V
NXP LM75A datasheet, No ID register; the pin order here is one common board layout

Try it in 3D in BoardPilot

BoardPilot Part data (JSON)

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

LM75A temperature (CJMCU-75) with ESP32

Pins and ESP32 wiring

Starter code (Arduino)

Sources

Try it in 3D in BoardPilot

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