BME680 Environment sensor

This module reads temperature, humidity, pressure and gas quality from Bosch Sensortec's BME680 sensor.

Wiring

To wire for I2C:

BME680 Pin	Espruino
1 (GND)	GND
2 (CSB)	3.3v (forces I2C mode)
3 (SDI)	SDA pin (A6 in example)
4 (SCK)	SCL pin (A7 in example)
5 (SDO)	GND (default address)
6 (VDDIO)	3.3v
7 (GND)	GND
8 (VDD)	3.3v

The BME680 can run off 1.8v to 3.6v so can be connected directly to 3.3v (however some breakout boards contain a voltage regulator).

Software

BME680 Reset

Creating a new BME680 class - either by calling connectI2C, connectSPI, or directly calling new BME680() - issues a reset to the BME680 device, and it won't be available for roughly 10ms. The error is Cannot read property 'cal_t' of undefined... Use the setInterval method like in the examples, or a setTimeout with more than 10ms, it will work.

I2C

We're using software I2C here so you can use any pins, but you could easily use a hardware I2C device such as I2C1.

var i2c = new I2C();
i2c.setup({sda:A6,scl:A7});
var bme = require("BME680").connectI2C(i2c);

setInterval(function() {
  var data = bme.get_sensor_data();
  console.log(JSON.stringify(data,null,2));
  bme.perform_measurement();
}, 1000);

Prints data of the form:

{
  "new": true,             // is this a new measurement?
  "temperature": 20.9,     // degrees C
  "pressure": 990.7,       // hPa
  "humidity": 52.425,      // % rH
  "gas_resistance": 95197  // Ohms
 }

The first reading is done automatically, but subsequent readings must be performed by calling bme.perform_measurement(). The result will then be available 1 second later.

Different I2C addresses

The BME680's default address is 0x76 (which you get when SDO is connected to GND). If SDO is connected to VDD the address can be forced to 0x77.

You can specify this new address with:

var bme = require("BME680").connectI2C(i2c, {addr:0x77});

SPI

For usage with SPI, the BME680 module can be intialised as follows:

var spi = new SPI();
spi.setup({miso : ..., mosi : ..., sck: ...});
var bme = require("BME680").connectSPI(spi, cs_pin);

setInterval(function() {
  var data = bme.get_sensor_data();
  console.log(JSON.stringify(data,null,2));
  bme.perform_measurement();
}, 1000);

Low-level

The BME680 class is also exposed via require("BME680").BME680 so that you can initialise it with your own read/write functions if needed.

Reference

BME680.prototype.soft_reset = function (callback) { ... }

BME680.prototype.get_calib_data = function () { ... }

BME680.prototype.set_sensor_mode = function (mode) { ... }

// filter, heatr_ctrl, os_temp, os_pres, os_hum, run_gas, nb_conv
BME680.prototype.set_sensor_settings = function (options) { ... }

BME680.prototype.set_heating_settings = function (tmp, dur, cnv) { ... }

// get duration in milliseconds needed before a reading
BME680.prototype.get_profile_dur = function (options) { ... }

/* Return data:
  new             // is this a new measurement?
  temperature     // degrees C
  pressure        // hPa
  humidity        // % rH
  gas_resistance  // Ohms
*/
BME680.prototype.get_sensor_data = function () { ... }

// Request the sensor takes another reading
BME680.prototype.perform_measurement = function () { ... }

BME680.prototype.calc_temperature = function (temp_adc) { ... }

BME680.prototype.calc_pressure = function (pres_adc) { ... }

BME680.prototype.calc_humidity = function (hum_adc) { ... }

BME680.prototype.calc_gas_resistance = function (gas_res_adc, gas_range) { ... }

BME680.prototype.calc_heater_resistance = function (temperature) { ... }

BME680.prototype.calc_heater_duration = function (duration) { ... }

function (options, read, write) { ... }

exports.connectI2C = function (i2c, options) { ... }

exports.connectSPI = function (spi, cs, options) { ... }

Using

(No tutorials are available yet)

Buying

BME680 ICs are too small to easily hand-solder, so we'd recommend buying them on a breakout board:

• eBay
• Pimoroni
• Adafruit