====== LamaPLC: AHT20 / BMP280 Modul ======
{{ :sensor:aht20_bmp280_1.png?200|AHT20 / BMP280 Modul}}
This compact module integrates an AHT20 sensor for air temperature and humidity with a BMP280 sensor for air pressure, offering a complete overview of environmental conditions. Both sensors are popular for their accuracy and small size. Communication is straightforward through the [[com:basic_i2c|I²C]] interface, compatible with various microcontrollers, with an operating voltage range of 2-5V.

**Technical Details**

  * Operating voltage: DC 2..5V
  * Sensors: AHT20, BMP280
  * Dimensions: 16 x 16.5 x 3 mm
  * Weight: 4 g

  * //I²C Addresses//
    * BMP280: 0x77
    * AHT20:  0x38

  * //Air pressure//
    * Measurement range: 300 to 1100 hPa
    * Resolution: 0.18 Pa
    * Accuracy: ±1 Pa

  * //Humidity//
    * Resolution: 0.024 %RH
    * Tolerance: ±2 %RH
    * Reproducibility: ±0.1 %RH
    * Response time: 8 seconds
    * Measurement range: 0-100 %RH
    * Long-term drift: ＜0.5 %RH/year

  * //Temperature//
    * Resolution: 0.01℃
    * Tolerance: ±0.3℃
    * Reproducibility: ±0.1℃
    * Response time: minimum 5 seconds, maximum 30 seconds
    * Measurement range: -40℃ to 85℃
    * Long-term drift: ＜0.04℃/year

{{page>:tarhal}}

==== Arduino wiring ====
  * SCL: A5
  * GND: GND
  * SDA: A4
  * Vdd: 5V
==== Arduino code ====

<color red>For some reason, the Adafruit BMP280 library doesn't work reliably. It eventually freezes so severely that it only functions when the Arduino is powered off. I tried different parameter settings, but it didn't make a difference. It seems that the [[https://bitbucket.org/christandlg/bmx280mi/src/master/|BMx280MI library]] written by Gregor Christandl works better.</color>

<code c>
// lamaPLC AHT20+BMP280 module test
// 2025.10.08. free code

#include <Arduino.h>
#include <Wire.h>
#include <Adafruit_AHTX0.h>
#include <BMx280I2C.h>

#define I2C_ADDRESS 0x77

Adafruit_AHTX0 aht;

BMx280I2C bmx280(I2C_ADDRESS);

void(* resetFunc) (void) = 0; //declare reset function @ address 0

void setup() {
  Serial.begin(9600);
  Wire.begin();
  Serial.println("AHT20+BMP280 module test");

  if  (!aht.begin()) {
    Serial.println("Could not find a valid AHT20 sensor, check wiring!"); 
    while (1);
  }

  if  (!bmx280.begin()) {
    Serial.println("Could not find a valid BMP280 sensor, check wiring!"); 
    while (1);
  }   
	bmx280.resetToDefaults();

	//set an oversampling setting for pressure and temperature measurements. 
	bmx280.writeOversamplingPressure(BMx280MI::OSRS_P_x16);
	bmx280.writeOversamplingTemperature(BMx280MI::OSRS_T_x16);

  Serial.println("AHT20 / BMP280 module ok");
}

void loop() {
  Serial.println("check ----------------------------------------------------------");

  //start AHT20 measurement
  sensors_event_t humidity, temp;
  aht.getEvent(&humidity, &temp);
  Serial.print("AHT 20 Temperature: "); Serial.print(temp.temperature); Serial.println(" degrees C");
  Serial.print("AHT 20 Humidity: "); Serial.print(humidity.relative_humidity); Serial.println("% rH");

	//start BMP280 measurement
	if (!bmx280.measure())
	{
		Serial.println("could not start measurement, is a measurement already running?");
		return;
	}

	//wait for the measurement to finish
	do
	{
		delay(100);
	} while (!bmx280.hasValue());

	Serial.print("BMP280 Pressure: "); Serial.print(bmx280.getPressure()); Serial.println(" Pa");
	Serial.print("BMP280 Pressure (64 bit): "); Serial.print(bmx280.getPressure64()); Serial.println(" Pa");
	Serial.print("BMP280 Temperature: "); Serial.print(bmx280.getTemperature()); Serial.println(" degrees C");

  Serial.println();
  delay(5000);
}

</code>

code in github: https://github.com/lamaPLC/AHT20-BMP280-Modul-Arduino-code

**Output on the serial monitor:**
<code>
check ----------------------------------------------------------
AHT 20 Temperature: 22.12 degrees C
AHT 20 Humidity: 62.55% rH
BMP280 Pressure: 99128.00 hPa
BMP280 Pressure (64 bit): 99125.84 hPa
BMP280 Temperature: 23.17 degrees C
</code>

==== Example codes ====
[[arduino:projects:oled_sh1106_with_aht20_bmp280|Arduino - OLED SH1106 with AHT20/BMP280 Sensor]] \\

===== I²C topics on lamaPLC =====
{{topic>i2c}}

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{{tag>BMP280 AHT20 Adafruit temperature humidity pressure sensor arduino code i2c}}

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