bme280 Archives

In this example we look at the enviro:bit which is an add on from pimoroni which has a BME280 temperature, pressure, and humidity sensor fitted to it a long with a TCS3472 light and colour sensor and a MEMS microphone

Lets look at the enviro:bit fitted to a bpi:bit

enviro:bit and bpi:bit

Features:

Comes fully-assembled and ready to use.
BME280 temperature, pressure, and humidity sensor.
TCS3472 light and colour sensor.
MEMS microphone.
Compatible with micro:bit.
Microsoft MakeCode and MicroPython support.
No soldering required!

Lets look at the BME280 sensor now

The BME280 is an integrated environmental sensor developed specifically for mobile applications where size and low power consumption are key design constraints. The unit combines individual high linearity, high accuracy sensors for pressure, humidity and temperature in an 8-pin metal-lid 2.5 x 2.5 x 0.93 mm³ LGA package, designed for low current consumption (3.6 μA @1Hz), long term stability and high EMC robustness.

The humidity sensor features an extremely fast response time which supports performance requirements for emerging applications such as context awareness, and high accuracy over a wide temperature range. The pressure sensor is an absolute barometric pressure sensor with features exceptionally high accuracy and resolution at very low noise. The integrated temperature sensor has been optimized for very low noise and high resolution. It is primarily used for temperature compensation of the pressure and humidity sensors, and can also be used for estimating ambient temperature.

The BME280 supports a full suite of operating modes which provides the flexibility to optimize the device for power consumption, resolution and filter performance.

Parts List

Name	link
Banana PI Bit board	Banana PI Bit board with EPS32
envirobit	Pimoroni enviro:bit for BBC micro:bit

Code

You need to import the BME280 and sensor libraries into the Arduino IDE. The BME280 sensor is set to 0x76 on the envirobit

[codesyntax lang=”cpp”]

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

#define SEALEVELPRESSURE_HPA (1013.25)

Adafruit_BME280 bme; // I2C


unsigned long delayTime;

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

    unsigned status;
    
    // default settings
    // (you can also pass in a Wire library object like &Wire2)
    status = bme.begin(0x76);  
    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);
    }
    
    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();
}

[/codesyntax]

Output

Open the serial monitor window and you will see something like this

Temperature = 21.40 *C
Pressure = 1009.94 hPa
Approx. Altitude = 27.61 m
Humidity = 41.04 %

Temperature = 21.40 *C
Pressure = 1009.92 hPa
Approx. Altitude = 27.74 m
Humidity = 41.03 %

Temperature = 21.39 *C
Pressure = 1009.90 hPa
Approx. Altitude = 27.90 m
Humidity = 41.04 %

The BME280 is a great new chip which was originally designed for the next generation of smartphones. It is made up of a very accurate pressure sensor and an associated temperature sensor which helps calibrate the pressure readings.

And just for fun they threw in a pretty solid humidity sensor in there as well! So with an I2C connection you have access to enough weather data to make some pretty good predictions for your local area.

Or you can just use the pressure sensor with it’s abililty to discern the difference in 7.5cm in altitude.

The chip contains smarts to smooth out measurements

Parameter	Technical data
Operation range	Pressure: 300…1100 hPa Temperature: -40…85°C
Supply voltage VDDIO Supply voltage VDD	1.2 … 3.6 V 1.71 … 3.6 V
Interface	I²C and SPI
Average current consumption (typ.) (1Hz data refresh rate)	1.8 μA @ 1 Hz (H, T) 2.8 μA @ 1 Hz (P, T) 3.6 μA @ 1 Hz (H, P, T) T = temperature
Average current consumption in sleep mode	0.1 μA
Humidity sensor Response time (τ63%) Accuracy tolerance Hysteresis	1 s ±3% relative humidity ≤2% relative humidity
Pressure sensor RMS Noise Sensitivity Error Temperature coefficient offset	0.2Pa (equiv. to 1.7cm) ±0.25% (equiv. to 1m at 400m height change) ±1.5Pa/K (equiv. to ±12.6cm at 1 °C temperature change)

Parts Required

Here are the parts I used

The sensor you can pick up in the $6 price range – you can connect to the sensor using a standard header the classic dupont style jumper wire.

Name	Link
ESP32		Aliexpress link Amazon Ebay
BME280		Aliexpress link Ebay link Amazon Link
Connecting cables		Aliexpress link Amazon Ebay

Connection:

vin—————-3v3
GND————–GND
SCL—————-22
SDA—————-21

Just like this

esp32 and bme280

Code

No libraries required

/ Distributed with a free-will license.
// Use it any way you want, profit or free, provided it fits in the licenses of its associated works.
// BME280
// This code is designed to work with the BME280_I2CS I2C Mini Module available from ControlEverything.com.
// https://www.controleverything.com/content/Humidity?sku=BME280_I2CS#tabs-0-product_tabset-2

#include<Wire.h>

// BME280 I2C address is 0x76(108)
#define Addr 0x76

void setup()
{
// Initialise I2C communication as MASTER
Wire.begin();
// Initialise Serial communication, set baud rate = 9600
Serial.begin(9600);
}

void loop()
{
unsigned int b1[24];
unsigned int data[8];
unsigned int dig_H1 = 0;
for(int i = 0; i < 24; i++)
{
// Start I2C Transmission
Wire.beginTransmission(Addr);
// Select data register
Wire.write((136+i));
// Stop I2C Transmission
Wire.endTransmission();

// Request 1 byte of data
Wire.requestFrom(Addr, 1);

// Read 24 bytes of data
if(Wire.available() == 1)
{
b1[i] = Wire.read();
}
}

// Convert the data
// temp coefficients
unsigned int dig_T1 = (b1[0] & 0xff) + ((b1[1] & 0xff) * 256);
int dig_T2 = b1[2] + (b1[3] * 256);
int dig_T3 = b1[4] + (b1[5] * 256);

// pressure coefficients
unsigned int dig_P1 = (b1[6] & 0xff) + ((b1[7] & 0xff ) * 256);
int dig_P2 = b1[8] + (b1[9] * 256);
int dig_P3 = b1[10] + (b1[11] * 256);
int dig_P4 = b1[12] + (b1[13] * 256);
int dig_P5 = b1[14] + (b1[15] * 256);
int dig_P6 = b1[16] + (b1[17] * 256);
int dig_P7 = b1[18] + (b1[19] * 256);
int dig_P8 = b1[20] + (b1[21] * 256);
int dig_P9 = b1[22] + (b1[23] * 256);

// Start I2C Transmission
Wire.beginTransmission(Addr);
// Select data register
Wire.write(161);
// Stop I2C Transmission
Wire.endTransmission();

// Request 1 byte of data
Wire.requestFrom(Addr, 1);

// Read 1 byte of data
if(Wire.available() == 1)
{
dig_H1 = Wire.read();
}

for(int i = 0; i < 7; i++)
{
// Start I2C Transmission
Wire.beginTransmission(Addr);
// Select data register
Wire.write((225+i));
// Stop I2C Transmission
Wire.endTransmission();

// Request 1 byte of data
Wire.requestFrom(Addr, 1);

// Read 7 bytes of data
if(Wire.available() == 1)
{
b1[i] = Wire.read();
}
}

// Convert the data
// humidity coefficients
int dig_H2 = b1[0] + (b1[1] * 256);
unsigned int dig_H3 = b1[2] & 0xFF ;
int dig_H4 = (b1[3] * 16) + (b1[4] & 0xF);
int dig_H5 = (b1[4] / 16) + (b1[5] * 16);
int dig_H6 = b1[6];

// Start I2C Transmission
Wire.beginTransmission(Addr);
// Select control humidity register
Wire.write(0xF2);
// Humidity over sampling rate = 1
Wire.write(0x01);
// Stop I2C Transmission
Wire.endTransmission();

// Start I2C Transmission
Wire.beginTransmission(Addr);
// Select control measurement register
Wire.write(0xF4);
// Normal mode, temp and pressure over sampling rate = 1
Wire.write(0x27);
// Stop I2C Transmission
Wire.endTransmission();

// Start I2C Transmission
Wire.beginTransmission(Addr);
// Select config register
Wire.write(0xF5);
// Stand_by time = 1000ms
Wire.write(0xA0);
// Stop I2C Transmission
Wire.endTransmission();

for(int i = 0; i < 8; i++)
{
// Start I2C Transmission
Wire.beginTransmission(Addr);
// Select data register
Wire.write((247+i));
// Stop I2C Transmission
Wire.endTransmission();

// Request 1 byte of data
Wire.requestFrom(Addr, 1);

// Read 8 bytes of data
if(Wire.available() == 1)
{
data[i] = Wire.read();
}
}

// Convert pressure and temperature data to 19-bits
long adc_p = (((long)(data[0] & 0xFF) * 65536) + ((long)(data[1] & 0xFF) * 256) + (long)(data[2] & 0xF0)) / 16;
long adc_t = (((long)(data[3] & 0xFF) * 65536) + ((long)(data[4] & 0xFF) * 256) + (long)(data[5] & 0xF0)) / 16;
// Convert the humidity data
long adc_h = ((long)(data[6] & 0xFF) * 256 + (long)(data[7] & 0xFF));

// Temperature offset calculations
double var1 = (((double)adc_t) / 16384.0 - ((double)dig_T1) / 1024.0) * ((double)dig_T2);
double var2 = ((((double)adc_t) / 131072.0 - ((double)dig_T1) / 8192.0) *
(((double)adc_t)/131072.0 - ((double)dig_T1)/8192.0)) * ((double)dig_T3);
double t_fine = (long)(var1 + var2);
double cTemp = (var1 + var2) / 5120.0;
double fTemp = cTemp * 1.8 + 32;

// Pressure offset calculations
var1 = ((double)t_fine / 2.0) - 64000.0;
var2 = var1 * var1 * ((double)dig_P6) / 32768.0;
var2 = var2 + var1 * ((double)dig_P5) * 2.0;
var2 = (var2 / 4.0) + (((double)dig_P4) * 65536.0);
var1 = (((double) dig_P3) * var1 * var1 / 524288.0 + ((double) dig_P2) * var1) / 524288.0;
var1 = (1.0 + var1 / 32768.0) * ((double)dig_P1);
double p = 1048576.0 - (double)adc_p;
p = (p - (var2 / 4096.0)) * 6250.0 / var1;
var1 = ((double) dig_P9) * p * p / 2147483648.0;
var2 = p * ((double) dig_P8) / 32768.0;
double pressure = (p + (var1 + var2 + ((double)dig_P7)) / 16.0) / 100;

// Humidity offset calculations
double var_H = (((double)t_fine) - 76800.0);
var_H = (adc_h - (dig_H4 * 64.0 + dig_H5 / 16384.0 * var_H)) * (dig_H2 / 65536.0 * (1.0 + dig_H6 / 67108864.0 * var_H * (1.0 + dig_H3 / 67108864.0 * var_H)));
double humidity = var_H * (1.0 - dig_H1 * var_H / 524288.0);
if(humidity > 100.0)
{
humidity = 100.0;
}
else if(humidity < 0.0)
{
humidity = 0.0;
}

// Output data to serial monitor
Serial.print("Temperature in Celsius : ");
Serial.print(cTemp);
Serial.println(" C");
Serial.print("Temperature in Fahrenheit : ");
Serial.print(fTemp);
Serial.println(" F");
Serial.print("Pressure : ");
Serial.print(pressure);
Serial.println(" hPa");
Serial.print("Relative Humidity : ");
Serial.print(humidity);
Serial.println(" RH");
delay(1000);
}

Output

In the serial monitor you should see something along these lines

Temperature in Celsius : 34.20 C
Temperature in Fahrenheit : 93.56 F
Pressure : 903.94 hPa
Relative Humidity : 0.00 RH
Temperature in Celsius : 34.51 C
Temperature in Fahrenheit : 94.11 F
Pressure : 893.48 hPa
Relative Humidity : 0.00 RH
Temperature in Celsius : 33.74 C
Temperature in Fahrenheit : 92.73 F
Pressure : 919.16 hPa
Relative Humidity : 0.00 RH

Links

bme280