adxl345-sensor
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A Node.js I2C module for the Analog Devices ADXL345 three-axis digital accelerometer
333 lines (287 loc) • 11.5 kB
JavaScript
/*
ADXL345.js
A Node.js I2C module for the Analog Devices ADXL345 three-axis digital accelerometer.
*/
'use strict';
class ADXL345 {
constructor(options) {
const i2c = require('i2c-bus');
this.i2cBusNo = (options && options.hasOwnProperty('i2cBusNo')) ? options.i2cBusNo : 1;
this.i2cBus = i2c.openSync(this.i2cBusNo);
this.i2cAddress = (options && options.hasOwnProperty('i2cAddress')) ? options.i2cAddress : ADXL345.I2C_ADDRESS_ALT_GROUNDED();
this.ADXL345_REG_DEVID = 0x00; // Device ID
this.ADXL345_REG_OFSX = 0x1E; // X-axis offset
this.ADXL345_REG_OFSY = 0x1F; // Y-axis offset
this.ADXL345_REG_OFSZ = 0x20; // Z-axis offset
this.ADXL345_REG_BW_RATE = 0x2C; // Data rate and power mode control
this.ADXL345_REG_POWER_CTL = 0x2D; // Power-saving features control
this.ADXL345_REG_DATA_FORMAT = 0x31; // Data format control
this.ADXL345_REG_DATAX0 = 0x32; // read 6 bytes from ADXL345_REG_DATAX0 for all three axes
this.ADXL345_REG_DATAX1 = 0x33;
this.ADXL345_REG_DATAY0 = 0x34;
this.ADXL345_REG_DATAY1 = 0x35;
this.ADXL345_REG_DATAZ0 = 0x36;
this.ADXL345_REG_DATAZ1 = 0x37;
this.ADXL345_MG2G_SCALE_FACTOR = 0.004; // 4mg per lsb
this.EARTH_GRAVITY_MS2 = 9.80665;
}
init() {
return new Promise((resolve, reject) => {
// Read and validate expected device ID
//
this.i2cBus.writeByte(this.i2cAddress, this.ADXL345_REG_DEVID, 0, (err) => {
if(err) {
return reject(err);
}
this.i2cBus.readByte(this.i2cAddress, this.ADXL345_REG_DEVID, (err, deviceId) => {
if(err) {
return reject(err);
}
else if(deviceId !== ADXL345.DEVICE_ID()) {
return reject(`Unexpected ADXL345 device ID: 0x${deviceId.toString(16)}`);
}
else {
console.log(`Found ADXL345 device id 0x${deviceId.toString(16)} on bus i2c-${this.i2cBusNo}, address 0x${this.i2cAddress.toString(16)}`);
// Enable measurement, disable AUTO_SLEEP
//
this.i2cBus.writeByte(this.i2cAddress, this.ADXL345_REG_POWER_CTL, 0x8, (err) => {
if(err) {
return reject(err);
}
resolve(deviceId);
});
}
});
});
});
}
getAcceleration(gForce) {
return new Promise((resolve, reject) => {
// Request/read all three axes at once
//
this.i2cBus.writeByte(this.i2cAddress, this.ADXL345_REG_DATAX0, 0, (err) => {
if(err) {
return reject(err);
}
this.i2cBus.readI2cBlock(this.i2cAddress, this.ADXL345_REG_DATAX0, 6, new Buffer(6), (err, bytesRead, buffer) => {
if(err) {
return reject(err);
}
let x = this.int16(buffer[1], buffer[0]) * this.ADXL345_MG2G_SCALE_FACTOR;
let y = this.int16(buffer[3], buffer[2]) * this.ADXL345_MG2G_SCALE_FACTOR;
let z = this.int16(buffer[5], buffer[4]) * this.ADXL345_MG2G_SCALE_FACTOR;
resolve({
x : gForce ? x : x * this.EARTH_GRAVITY_MS2,
y : gForce ? y : y * this.EARTH_GRAVITY_MS2,
z : gForce ? z : z * this.EARTH_GRAVITY_MS2,
units : gForce ? 'g' : 'm/s²'});
});
});
});
}
setMeasurementRange(range) {
return new Promise((resolve, reject) => {
if(!ADXL345.isValidRange(range)) {
return reject(`Invalid range (${range})`);
}
// Update the measurement range within the current ADXL345_REG_DATA_FORMAT register
//
this.i2cBus.readByte(this.i2cAddress, this.ADXL345_REG_DATA_FORMAT, (err, format) => {
if(err) {
return reject(err);
}
format &= ~0b1111;
format |= range;
format |= 0b1000; // Enable FULL-RESOLUTION mode for range scaling
this.i2cBus.writeByte(this.i2cAddress, this.ADXL345_REG_DATA_FORMAT, format, (err) => {
err ? reject(err) : resolve();
});
});
});
}
getMeasurementRange() {
return new Promise((resolve, reject) => {
this.i2cBus.readByte(this.i2cAddress, this.ADXL345_REG_DATA_FORMAT, (err, format) => {
if(err) {
return reject(err);
}
resolve(format & 0b11);
});
});
}
setDataRate(dataRate) {
return new Promise((resolve, reject) => {
if(!ADXL345.isValidDataRate(dataRate)) {
return reject(`Invalid data rate (${dataRate})`);
}
// We'll always clear the LOW_POWER bit and the remaining MSBs are unused,
// so no need to read ADXL345_REG_BW_RATE before writing.
//
this.i2cBus.writeByte(this.i2cAddress, this.ADXL345_REG_BW_RATE, dataRate & 0b1111, (err) => {
err ? reject(err) : resolve();
});
});
}
getDataRate() {
return new Promise((resolve, reject) => {
this.i2cBus.readByte(this.i2cAddress, this.ADXL345_REG_BW_RATE, (err, bwRate) => {
if(err) {
return reject(err);
}
resolve(bwRate & 0b1111);
});
});
}
/* The OFSX, OFSY, and OFSZ registers are each eight bits and offer user-set offset
adjustments in twos complement format with a scale factor of 15.6 mg/LSB
(that is, 0x01 = 0.0156 g, 0x7F = 2 g). The value stored in the offset registers
is automatically added to the acceleration data, and the resulting value is
stored in the output data registers. For additional information regarding offset
calibration and the use of the offset registers, refer to the Offset Calibration
section in the ADXL345 datasheet.
*/
setOffsetX(value) {
return new Promise((resolve, reject) => {
this.i2cBus.writeByte(this.i2cAddress, this.ADXL345_REG_OFSX, value, (err) => {
err ? reject(err) : resolve();
});
});
}
setOffsetY(value) {
return new Promise((resolve, reject) => {
this.i2cBus.writeByte(this.i2cAddress, this.ADXL345_REG_OFSY, value, (err) => {
err ? reject(err) : resolve();
});
});
}
setOffsetZ(value) {
return new Promise((resolve, reject) => {
this.i2cBus.writeByte(this.i2cAddress, this.ADXL345_REG_OFSZ, value, (err) => {
err ? reject(err) : resolve();
});
});
}
getOffsets() {
return new Promise((resolve, reject) => {
this.i2cBus.readI2cBlock(this.i2cAddress, this.ADXL345_REG_OFSX, 3, new Buffer(3), (err, bytesRead, buffer) => {
if(err) {
return reject(err);
}
resolve({
x : buffer[0],
y : buffer[1],
z : buffer[2]
});
});
});
}
uint16(msb, lsb) {
return msb << 8 | lsb;
}
int16(msb, lsb) {
let val = this.uint16(msb, lsb);
return val > 32767 ? (val - 65536) : val;
}
static isValidRange(range) {
switch(range) {
// Could simply check for range >= 0 && range <= 0x3 but to be padantic...
case ADXL345.RANGE_2_G():
case ADXL345.RANGE_4_G():
case ADXL345.RANGE_8_G():
case ADXL345.RANGE_16_G():
return true;
default:
return false;
}
}
static isValidDataRate(dataRate) {
switch(dataRate) {
// Could simply check for dataData >= 0 && dataRate <= 0xF but to be padantic...
case ADXL345.DATARATE_0_10_HZ():
case ADXL345.DATARATE_0_20_HZ():
case ADXL345.DATARATE_0_39_HZ():
case ADXL345.DATARATE_0_78_HZ():
case ADXL345.DATARATE_1_56_HZ():
case ADXL345.DATARATE_3_13_HZ():
case ADXL345.DATARATE_6_25HZ():
case ADXL345.DATARATE_12_5_HZ():
case ADXL345.DATARATE_25_HZ():
case ADXL345.DATARATE_50_HZ():
case ADXL345.DATARATE_100_HZ():
case ADXL345.DATARATE_200_HZ():
case ADXL345.DATARATE_400_HZ():
case ADXL345.DATARATE_800_HZ():
case ADXL345.DATARATE_1600_HZ():
case ADXL345.DATARATE_3200_HZ():
return true;
default:
return false;
}
}
static stringifyMeasurementRange(range) {
switch(range) {
case ADXL345.RANGE_2_G() : return 'RANGE_2_G';
case ADXL345.RANGE_4_G() : return 'RANGE_4_G';
case ADXL345.RANGE_8_G() : return 'RANGE_8_G';
case ADXL345.RANGE_16_G(): return 'RANGE_16_G';
default:
return 'UNKNOWN';
}
}
static stringifyDataRate(dataRate) {
switch(dataRate) {
case ADXL345.DATARATE_0_10_HZ() : return 'DATARATE_0_10_HZ';
case ADXL345.DATARATE_0_20_HZ() : return 'DATARATE_0_20_HZ';
case ADXL345.DATARATE_0_39_HZ() : return 'DATARATE_0_39_HZ';
case ADXL345.DATARATE_0_78_HZ() : return 'DATARATE_0_78_HZ';
case ADXL345.DATARATE_1_56_HZ() : return 'DATARATE_1_56_HZ';
case ADXL345.DATARATE_3_13_HZ() : return 'DATARATE_3_13_HZ';
case ADXL345.DATARATE_6_25HZ() : return 'DATARATE_6_25HZ';
case ADXL345.DATARATE_12_5_HZ() : return 'DATARATE_12_5_HZ';
case ADXL345.DATARATE_25_HZ() : return 'DATARATE_25_HZ';
case ADXL345.DATARATE_50_HZ() : return 'DATARATE_50_HZ';
case ADXL345.DATARATE_100_HZ() : return 'DATARATE_100_HZ';
case ADXL345.DATARATE_200_HZ() : return 'DATARATE_200_HZ';
case ADXL345.DATARATE_400_HZ() : return 'DATARATE_400_HZ';
case ADXL345.DATARATE_800_HZ() : return 'DATARATE_800_HZ';
case ADXL345.DATARATE_1600_HZ() : return 'DATARATE_1600_HZ';
case ADXL345.DATARATE_3200_HZ() : return 'DATARATE_3200_HZ';
default:
return 'UNKNOWN';
}
}
static I2C_ADDRESS_ALT_GROUNDED() {
return 0x53; // The SDO/ALT ADDRESS pin is grounded
}
static I2C_ADDRESS_ALT_HIGH() {
return 0x1D; // The SDO/ALT ADDRESS pin is high
}
static DEVICE_ID() {
return 0xE5;
}
// Measurement ranges used with setMeasurementRange/getMeasurementRange (ADXL345_REG_DATA_FORMAT)
//
static RANGE_2_G() { return 0b00; } // +/- 2g (default)
static RANGE_4_G() { return 0b01; } // +/- 4g
static RANGE_8_G() { return 0b10; } // +/- 8g
static RANGE_16_G() { return 0b11; } // +/- 16g
// Data rates used with setDataRate/getDataRate (ADXL345_REG_BW_RATE)
//
static DATARATE_0_10_HZ() { return 0b0000; } // 0.05Hz Bandwidth 23µA IDD
static DATARATE_0_20_HZ() { return 0b0001; } // 0.10Hz Bandwidth 23µA IDD
static DATARATE_0_39_HZ() { return 0b0010; } // 0.20Hz Bandwidth 23µA IDD
static DATARATE_0_78_HZ() { return 0b0011; } // 0.39Hz Bandwidth 23µA IDD
static DATARATE_1_56_HZ() { return 0b0100; } // 0.78Hz Bandwidth 34µA IDD
static DATARATE_3_13_HZ() { return 0b0101; } // 1.56Hz Bandwidth 40µA IDD
static DATARATE_6_25HZ() { return 0b0110; } // 3.13Hz Bandwidth 45µA IDD
static DATARATE_12_5_HZ() { return 0b0111; } // 6.25Hz Bandwidth 50µA IDD
static DATARATE_25_HZ() { return 0b1000; } // 12.5Hz Bandwidth 60µA IDD
static DATARATE_50_HZ() { return 0b1001; } // 25Hz Bandwidth 90µA IDD
static DATARATE_100_HZ() { return 0b1010; } // 50Hz Bandwidth 140µA IDD // default reset value
static DATARATE_200_HZ() { return 0b1011; } // 100Hz Bandwidth 140µA IDD
static DATARATE_400_HZ() { return 0b1100; } // 200Hz Bandwidth 140µA IDD
static DATARATE_800_HZ() { return 0b1101; } // 400Hz Bandwidth 140µA IDD
static DATARATE_1600_HZ() { return 0b1110; } // 800Hz Bandwidth 90µA IDD
static DATARATE_3200_HZ() { return 0b1111; } // 1600Hz Bandwidth 140µA IDD
}
module.exports = ADXL345;