LMT01 Temperature Sensor Library (ESP32 + Arduino)

An Arduino-compatible library for the ESP32 platform that interfaces with the Texas Instruments LMT01 digital temperature sensor using a pulse-counting method and hardware timer.

Key Features

• Works with ESP32 (Arduino framework)
• No analog pins required — digital pulses are counted instead
• Hardware timer-based measurement window
• Temperature output in Celsius
• Ultra-low power consumption: typically 34 µA to 125 µA during the temperature-to-digital conversion process.
• High accuracy: ±0.5 °C (–20 °C to 90 °C), ±0.625 °C (90 °C to 150 °C), ±0.7 °C (–50 °C to –20 °C)

Basic Usage

#include "LMT01.h"

#define LMT01_PULSES_PIN 41
#define LMT01_PWR_PIN 2

LMT01 sensor(LMT01_PULSES_PIN, LMT01_PWR_PIN, 130); // 130ms window

void setup() {
    Serial.begin(19200);
    sensor.begin();
}

void loop() {
    if (sensor.ready()) {
        float temp = sensor.read();
        Serial.printf("%.2f %cC\n", temp, 176);
    }
}

Note: This library is designed specifically for ESP32 boards using the Arduino framework. It uses hw_timer_t and attachInterrupt for reliable pulse measurement.

Basic Circuit

Internal pull-up enabled by the library.

Serial Output

Temperature variation from an ambient temperature of around 25 °C up to approximately 60 °C (achieved by placing the sensor in contact with water preheated in the microwave for about 40 seconds).

Concepts (Datasheet)

Time Window Definition

Transfer Function

The output transfer function is approximately linear and can be expressed as:

$$ \text{Temp} = \left( \frac{\text{PC}}{4096} \times 256^\circ\text{C} \right) - 50^\circ\text{C} $$

Where:

• PC is the number of pulses counted within the defined time window.
• Temp is the resulting temperature in degrees Celsius.

Compatibility

This library was tested with:

• ESP32 Arduino Core v3.2.0
  Based on ESP-IDF v5.4.1
  🔗 GitHub Release: espressif/arduino-esp32 v3.2.0

For best results, ensure you are using this version or later of the ESP32 Arduino core.