Problem with BME280 and I2C

greenrocklee588 · March 23, 2023, 6:31pm

Hello guys,

I have an Arduino uno WiFi rev 2 and I'm trying to run a BME280 sensor on it.

I have it connected as follows:
VCC = 5V
GND = GND
SCL = A5
SDA = A4

The problem is that the sensor can never be found. So I tried to find the I2C address to which the given sensor is connected.

#include <Wire.h>

void setup() {
  Serial.begin(9600);
  Serial.println("\nI2C Scanner");
}

void loop() {
  byte error, address;
  int devices;

  devices = 0;
  for (address = 1; address < 127; address++ ) {
    Wire.beginTransmission(address);
    error = Wire.endTransmission();

    if (error == 0) {
      Serial.print("I2C device found at address 0x");
      if (address < 16)
        Serial.print("0");
      Serial.print(address, HEX);
      Serial.println("  !");
      devices++;
    }
  }
  if (devices == 0)
    Serial.println("No I2C devices found\n");
  else
    Serial.println("done\n");

  delay(5000);
}

the output is that a device is connected to all addresses:

19:35:09.816 -> I2C device found at address 0x66  !
19:35:09.848 -> I2C device found at address 0x67  !
19:35:09.880 -> I2C device found at address 0x68  !
19:35:09.914 -> I2C device found at address 0x69  !
19:35:09.945 -> I2C device found at address 0x6A  !
19:35:10.009 -> I2C device found at address 0x6B  !
19:35:10.046 -> I2C device found at address 0x6C  !
19:35:10.077 -> I2C device found at address 0x6D  !
19:35:10.108 -> I2C device found at address 0x6E  !
19:35:10.140 -> I2C device found at address 0x6F  !
19:35:10.173 -> I2C device found at address 0x70  !
19:35:10.237 -> I2C device found at address 0x71  !
19:35:10.269 -> I2C device found at address 0x72  !
19:35:10.300 -> I2C device found at address 0x73  !
19:35:10.333 -> I2C device found at address 0x74  !
19:35:10.365 -> I2C device found at address 0x75  !
19:35:10.432 -> I2C device found at address 0x76  !
19:35:10.464 -> I2C device found at address 0x77  !
19:35:10.498 -> I2C device found at address 0x78  !
19:35:10.528 -> I2C device found at address 0x79  !
19:35:10.559 -> I2C device found at address 0x7A  !
19:35:10.623 -> I2C device found at address 0x7B  !
19:35:10.656 -> I2C device found at address 0x7C  !
19:35:10.688 -> I2C device found at address 0x7D  !
19:35:10.719 -> I2C device found at address 0x7E  !
19:35:10.753 -> done
19:35:10.785 ->

But this code:

#include "I2CScanner.h"

I2CScanner scanner;

void setup() 
{
	Serial.begin(9600);
	while (!Serial) {};

	scanner.Init();
}

void loop() 
{
	scanner.Scan();
	delay(5000);
}

found this even though I don't have any device connected to the arduino.

19:30:59.176 -> --- Scan started ---
19:30:59.176 -> I2C device found at address 0x60  !
19:30:59.244 -> --- Scan finished ---

I'm so confused about this, what could be wrong please?

Koepel · March 23, 2023, 7:27pm

Welcome to the forum.

Thank you for all the information and the sketch between code tags
That helps a lot to give a short answer: Wire.begin() is missing in the first sketch.

The second sketch has Wire.begin() hidden in Scanner.Init() here.

srnet · March 23, 2023, 7:31pm

Is the 'BME280 sensor' a 3.3V logic level module or a 5V logic level module ?

greenrocklee588 · March 23, 2023, 7:40pm

greenrocklee588:

#include <Wire.h>

void setup() {
  Serial.begin(9600);
  Serial.println("\nI2C Scanner");
}

void loop() {
  byte error, address;
  int devices;

  devices = 0;
  for (address = 1; address < 127; address++ ) {
    Wire.beginTransmission(address);
    error = Wire.endTransmission();

    if (error == 0) {
      Serial.print("I2C device found at address 0x");
      if (address < 16)
        Serial.print("0");
      Serial.print(address, HEX);
      Serial.println("  !");
      devices++;
    }

5V logic module

DrDiettrich · March 23, 2023, 7:40pm

Please use the pins labeled SCL and SDA. These are different from the ordinary Uno.

greenrocklee588 · March 23, 2023, 7:48pm

And after i try to use this code for BME280:

/***************************************************************************
  This is a library for the BME280 humidity, temperature & pressure sensor

  Designed specifically to work with the Adafruit BME280 Breakout
  ----> http://www.adafruit.com/products/2650

  These sensors use I2C or SPI to communicate, 2 or 4 pins are required
  to interface. The device's I2C address is either 0x76 or 0x77.

  Adafruit invests time and resources providing this open source code,
  please support Adafruit andopen-source hardware by purchasing products
  from Adafruit!

  Written by Limor Fried & Kevin Townsend for Adafruit Industries.
  BSD license, all text above must be included in any redistribution
  See the LICENSE file for details.
 ***************************************************************************/

#include <Wire.h>
#include <SPI.h>
#include <Adafruit_Sensor.h>
#include <Adafruit_BME280.h>

#define BME_SCK 13
#define BME_MISO 12
#define BME_MOSI 11
#define BME_CS 10

#define SEALEVELPRESSURE_HPA (1013.25)

Adafruit_BME280 bme; // I2C
//Adafruit_BME280 bme(BME_CS); // hardware SPI
//Adafruit_BME280 bme(BME_CS, BME_MOSI, BME_MISO, BME_SCK); // software SPI

unsigned long delayTime;

void setup() {
    Serial.begin(9600);
    while(!Serial);    // time to get serial running
    Serial.println(F("BME280 test"));

    unsigned status;
    
    // default settings
    status = bme.begin();  
    // You can also pass in a Wire library object like &Wire2
    // status = bme.begin(0x76, &Wire2)
    if (!status) {
        Serial.println("Could not find a valid BME280 sensor, check wiring, address, sensor ID!");
        Serial.print("SensorID was: 0x"); Serial.println(bme.sensorID(),16);
        Serial.print("        ID of 0xFF probably means a bad address, a BMP 180 or BMP 085\n");
        Serial.print("   ID of 0x56-0x58 represents a BMP 280,\n");
        Serial.print("        ID of 0x60 represents a BME 280.\n");
        Serial.print("        ID of 0x61 represents a BME 680.\n");
        while (1) delay(10);
    }
    
    Serial.println("-- Default Test --");
    delayTime = 1000;

    Serial.println();
}


void loop() { 
    printValues();
    delay(delayTime);
}


void printValues() {
    Serial.print("Temperature = ");
    Serial.print(bme.readTemperature());
    Serial.println(" °C");

    Serial.print("Pressure = ");

    Serial.print(bme.readPressure() / 100.0F);
    Serial.println(" hPa");

    Serial.print("Approx. Altitude = ");
    Serial.print(bme.readAltitude(SEALEVELPRESSURE_HPA));
    Serial.println(" m");

    Serial.print("Humidity = ");
    Serial.print(bme.readHumidity());
    Serial.println(" %");

    Serial.println();
}

i recive this response

20:45:35.619 -> BME280 test
20:45:35.625 -> Could not find a valid BME280 sensor, check wiring, address, sensor ID!
20:45:35.689 -> SensorID was: 0x0
20:45:35.722 ->         ID of 0xFF probably means a bad address, a BMP 180 or BMP 085
20:45:35.785 ->    ID of 0x56-0x58 represents a BMP 280,
20:45:35.817 ->         ID of 0x60 represents a BME 280.
20:45:35.850 ->         ID of 0x61 represents a BME 680.

But my question is still why I2C can fund some sensor, even though nothing is connected to the arduino

DrDiettrich · March 23, 2023, 7:55pm

Missing pullup resistors on unconnected SCL/SDA.

greenrocklee588 · March 23, 2023, 8:00pm

Okay and how can I fix that please?

DrDiettrich · March 23, 2023, 8:21pm

Please read a bit about I2C fundamentals and add pullup resistors.

greenrocklee588 · March 23, 2023, 9:17pm

Is this connection of pullup resistors okay please?
*that resistors should be connected into "+". MB sorry

DrDiettrich · March 23, 2023, 9:21pm

Why should anybody respond if you don't follow given instructions?

greenrocklee588 · March 23, 2023, 9:24pm

I am sorry, i found some advice that i should:
Add pull-up resistors (4.7kΩ or 10kΩ) on both the SDA and SCL lines:

Connect a resistor between the SDA (A4) pin on the Arduino and the 3.3V pin
Connect another resistor between the SCL (A5) pin on the Arduino and the 3.3V pin

and I just try to ask if that connection is okay.

Sorry I'm am new in this stuff.

greenrocklee588 · March 23, 2023, 9:54pm

Okey guys, i fiexed it.

I noticed that the arduino I used - Arduino uno Wifi rev 2 have SDA and SCL pins not on A4 and A5 but it has specially designed pins for that, see picture: (right up PA3 and PA2)

So i connect that BPE280 sensor to that pins and also on +5 and GND and use this code:

/***************************************************************************
  This is a library for the BME280 humidity, temperature & pressure sensor

  Designed specifically to work with the Adafruit BME280 Breakout
  ----> http://www.adafruit.com/products/2650

  These sensors use I2C or SPI to communicate, 2 or 4 pins are required
  to interface. The device's I2C address is either 0x76 or 0x77.

  Adafruit invests time and resources providing this open source code,
  please support Adafruit andopen-source hardware by purchasing products
  from Adafruit!

  Written by Limor Fried & Kevin Townsend for Adafruit Industries.
  BSD license, all text above must be included in any redistribution
  See the LICENSE file for details.
 ***************************************************************************/

#include <Wire.h>
#include <SPI.h>
#include <Adafruit_Sensor.h>
#include <Adafruit_BME280.h>

#define BME_SCK 13
#define BME_MISO 12
#define BME_MOSI 11
#define BME_CS 10

#define SEALEVELPRESSURE_HPA (1013.25)

Adafruit_BME280 bme; // I2C
//Adafruit_BME280 bme(BME_CS); // hardware SPI
//Adafruit_BME280 bme(BME_CS, BME_MOSI, BME_MISO, BME_SCK); // software SPI

unsigned long delayTime;

void setup() {
    Serial.begin(9600);
    while(!Serial);    // time to get serial running
    Serial.println(F("BME280 test"));

    unsigned status;
    
    // default settings
    status = bme.begin(0x76);  
    // You can also pass in a Wire library object like &Wire2
    // status = bme.begin(0x76, &Wire2)
    if (!status) {
        Serial.println("Could not find a valid BME280 sensor, check wiring, address, sensor ID!");
        Serial.print("SensorID was: 0x"); Serial.println(bme.sensorID(),16);
        Serial.print("        ID of 0xFF probably means a bad address, a BMP 180 or BMP 085\n");
        Serial.print("   ID of 0x56-0x58 represents a BMP 280,\n");
        Serial.print("        ID of 0x60 represents a BME 280.\n");
        Serial.print("        ID of 0x61 represents a BME 680.\n");
        while (1) delay(10);
    }
    
    Serial.println("-- Default Test --");
    delayTime = 1000;

    Serial.println();
}


void loop() { 
    printValues();
    delay(delayTime);
}


void printValues() {
    Serial.print("Temperature = ");
    Serial.print(bme.readTemperature());
    Serial.println(" °C");

    Serial.print("Pressure = ");

    Serial.print(bme.readPressure() / 100.0F);
    Serial.println(" hPa");

    Serial.print("Approx. Altitude = ");
    Serial.print(bme.readAltitude(SEALEVELPRESSURE_HPA));
    Serial.println(" m");

    Serial.print("Humidity = ");
    Serial.print(bme.readHumidity());
    Serial.println(" %");

    Serial.println();
}

And it is working now. So thanks for help

system · September 19, 2023, 9:55pm

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