Saturday, May 9, 2015

The New Bosch BME280 (Temp, Humidity, BMP)

Bosch has a new, very accurate all in one sensor chip that does Temperature, Humidity, and Barometric Pressure readings. It's called the BME280. Embedded Adventures has put that chip on a handy breakout board with signal conditioning (MOD-1022) and priced it fairly at $17. It's a 3v I2C unit, so to use it with a Arduino UNO, you will need a bi-directional level shifter, which they also have as the MOD-1003S for an additional $10.

This is the most accurate unit I have found, and is very easy to use. The library and sample code are available on the MOD-1022 page above, and the MOD-1003S level shifter requires no code to use.

There are only 4 wires to connect from the MOD-1022 to the MOD-1003S (VDD -> +3.3v, SCL -> B2), SDA -> B1, Gnd), and 4 wires from the MOD-1003S to the Arduino (+5v, SCL(B2 ->A5), SDA(B1->A4), Gnd). Download and install the library, and upload the example sketch included with the library, and you are on your way (in metric). For US measurements, you will have to convert Celsius to Fahrenheit, and hPa to InHg.

The example sketch communicates with serial defaulting to 115200, so make sure your serial monitor is set accordingly.

See schematic after the code.



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// BME280 MOD-1022 weather multi-sensor Arduino demo
// Written originally by Embedded Adventures

#include <BME280_MOD-1022.h>

#include <Wire.h>

// Arduino needs this to pring pretty numbers

void printFormattedFloat(float x, uint8_t precision) {
char buffer[10];

  dtostrf(x, 7, precision, buffer);


// print out the measurements

void printCompensatedMeasurements(void) {

float temp, humidity,  pressure, pressureMoreAccurate;
double tempMostAccurate, humidityMostAccurate, pressureMostAccurate;
char buffer[80];

  temp      = BME280.getTemperature();
  humidity  = BME280.getHumidity();
  pressure  = BME280.getPressure();
  pressureMoreAccurate = BME280.getPressureMoreAccurate();  // t_fine already calculated from getTemperaure() above
  tempMostAccurate     = BME280.getTemperatureMostAccurate();
  humidityMostAccurate = BME280.getHumidityMostAccurate();
  pressureMostAccurate = BME280.getPressureMostAccurate();
  Serial.println("                Good  Better    Best");
  Serial.print("Temperature  ");
  printFormattedFloat(temp, 2);
  Serial.print("         ");
  printFormattedFloat(tempMostAccurate, 2);
  Serial.print("Humidity     ");
  printFormattedFloat(humidity, 2);
  Serial.print("         ");
  printFormattedFloat(humidityMostAccurate, 2);

  Serial.print("Pressure     ");
  printFormattedFloat(pressure, 2);
  Serial.print(" ");
  printFormattedFloat(pressureMoreAccurate, 2);
  Serial.print(" ");
  printFormattedFloat(pressureMostAccurate, 2);

// setup wire and serial

void setup()

// main loop

void loop()

  uint8_t chipID;
  Serial.println("Welcome to the BME280 MOD-1022 weather multi-sensor test sketch!");
  Serial.println("Embedded Adventures (");
  chipID = BME280.readChipId();
  // find the chip ID out just for fun
  Serial.print("ChipID = 0x");
  Serial.print(chipID, HEX);
  // need to read the NVM compensation parameters
  // Need to turn on 1x oversampling, default is os_skipped, which means it doesn't measure anything
  BME280.writeOversamplingPressure(os1x);  // 1x over sampling (ie, just one sample)
  // example of a forced sample.  After taking the measurement the chip goes back to sleep
  while (BME280.isMeasuring()) {
  // read out the data - must do this before calling the getxxxxx routines
  Serial.println(BME280.getTemperature());  // must get temp first
  Serial.println(BME280.getPressureMoreAccurate());  // use int64 calculcations
  Serial.println(BME280.getTemperatureMostAccurate());  // use double calculations
  Serial.println(BME280.getHumidityMostAccurate()); // use double calculations
  Serial.println(BME280.getPressureMostAccurate()); // use double calculations
  // Example for "indoor navigation"
  // We'll switch into normal mode for regular automatic samples
  BME280.writeStandbyTime(tsb_0p5ms);        // tsb = 0.5ms
  BME280.writeFilterCoefficient(fc_16);      // IIR Filter coefficient 16
  BME280.writeOversamplingPressure(os16x);    // pressure x16
  BME280.writeOversamplingTemperature(os2x);  // temperature x2
  BME280.writeOversamplingHumidity(os1x);     // humidity x1
  while (1) {
    while (BME280.isMeasuring()) {

    // read out the data - must do this before calling the getxxxxx routines
    delay(5000); // do this every 5 seconds

1 comment:

  1. Can you please tell me if there going to be an Ethernet shield added to this sketch and or 4 x 20 display?