LIS2DW12 v2 Accelerometer

This library is a built-in class that provides functions to control the STMicroelectronics LIS2DW12 Accelerometer.

Library usage requirements
Type	I2C
Name	LIS2DW12_V2
Version	2020-12-10
Code size used	3.7KB
Resources used	I2C x 1, Timers x 1

Abstracts

Methods()/Properties	Summary
`new LIS2DW12()`	Creates an `LIS2DW12` instance using an activated I2C object.

{LIS2DW12} Instance

Methods()/Properties	Summary
`.write()`	Writes 1 byte of data to the specified register of the I2C device.
`.read()`	Reads 1 byte of data from the specified register of the I2C device.
`.readBuff()`	Reads data of specified length from the specified register of the I2C device.
`.init()`	Initializes the sensor.
`.measOn()`	Powers on the sensor and starts the measurement.
`.measOff()`	Powers off the sensor.
`.getFifoNum()`	Retrieves the number of stored samples in FIFO buffer.
`.readFifo()`	Retrieves the linear acceleration measurement results for the X, Y, and Z axes.
`.readFifoMaxAcc()`	Retrieves the magnitude of the maximum acceleration measurement of the X, Y, and Z axes, and the linear acceleration values for that sample.

Details

`new LIS2DW12(i2c)`

Creates an LIS2DW12 instance using an activated I2C object.

Instance Methods

`.write(reg,data)`

Writes 1 byte of data to the specified register of the I2C device.
This method is used to access the sensor registers directly.

Name	Type	Default	Summary
`reg`	number	MANDATORY	Target register Range: 0x00-0xFF
`data`	number	MANDATORY	Write data Range: 0x00-0xFF
return	boolean	-	true: Success false: Failure

`.read(reg)`

Reads 1 byte of data from the specified register of the I2C device.
This method is used to access the sensor registers directly.

Name	Type	Default	Summary
`reg`	number	MANDATORY	Target register Range: 0x00-0xFF
return	number, undefined	-	Read data If the read function fails, `undefined` will be returned.

`.readBuff(reg,len)`

Reads data of specified length from the specified register of the I2C device.
This method is used to access the sensor registers directly.

Name	Type	Default	Summary
`reg`	number	MANDATORY	Target register Range: 0x00-0xFF
`len`	number	MANDATORY	Length of data to be read (in bytes) The maximum length that can be specified is 255 bytes.
return	ArrayBuffer, undefined	-	Read data If the read function fails, `undefined` will be returned.

`.init()`

Initializes the sensor.
This method must be called first after the instance is created.

Name	Type	Default	Summary
return	boolean	-	true: Success false: Failure

`.measOn(odr,mode,bwfilter,fs,fds,lownoise)`

Powers on the sensor and starts the measurement.
Various acceleration measurement modes can be selected. For more information, please refer to the sensor datasheet.

Name	Type	Default	Summary
`odr`	number	MANDATORY	Output data rate [ value: At High-Performance Mode / At Low-Power Mode ] 1: 12.5 / 1.6 Hz 2: 12.5 / 12.5 Hz 3: 25 / 25 Hz 4: 50 / 50 Hz 5: 100 / 100 Hz 6: 200 / 200 Hz 7: 400 / 200 Hz
`mode`	number	MANDATORY	Power mode and resolution 0: High-Performance Mode (14-bit) 1: Low-Power Mode 1 (12-bit) 2: Low-Power Mode 2 (14-bit) 3: Low-Power Mode 3 (14-bit) 4: Low-Power Mode 4 (14-bit)
`bwfilter`	number	MANDATORY	Filter bandwidth 0: ODR/2 1: ODR/4 2: ODR/10 3: ODR/20
`fs`	number	MANDATORY	Full-scale 0: ±2g 1: ±4g 2: ±8g 3: ±16g
`fds`	boolean	MANDATORY	Filter type true: High-pass filter false: Low-pass filter
`lownoise`	boolean	MANDATORY	Low noise operation mode true: Enabled false: Disabled
return	boolean	-	true: Success false: Failure

`.measOff()`

Powers off the sensor, reducing power consumption.

Name	Type	Default	Summary
return	undefined	-	-

`.getFifoNum()`

Retrieves the number of stored samples in FIFO buffer.
The sensor's FIFO buffer can store up to 32 samples of 3-axis acceleration data.
Therefore, if the method returns the number of samples as 32, this may indicate that some samples have been overwritten and the data was lost.
To prevent data loss, optimal output data rate and distributed application processing must be implemented.

Name	Type	Default	Summary
return	number	-	Number of stored samples

`.readFifo(num)`

Retrieves the linear acceleration measurement results for the X, Y, and Z axes.

Name	Type	Default	Summary
`num`	number	MANDATORY	The number of samples to be read. The number of samples that can be specified must be less than or equal to the value obtained by the `.getFifoNum()` method.
return	array	-	Returns a two-dimensional number array of the 3-axis linear acceleration (g) measurements in the `[ x[], y[], z[] ]` format. The elements of the array are of type `number`. If the reading fails, an empty array `[ [], [], [] ]` will be returned.

`.readFifoMaxAcc(num)`

Retrieves the magnitude of the maximum acceleration measurement of the X, Y, and Z axes, and the linear acceleration values for that sample.
Of the num samples read, the sample with the highest magnitude of acceleration is returned.

Name	Type	Default	Summary
`num`	number	MANDATORY	The number of samples to be read. The number of samples that can be specified must be less than or equal to the value obtained by the `.getFifoNum()` method.
return	array	-	Returns an array containing the maximum magnitude `m` of acceleration (g) and the 3-axis linear acceleration (g) measurement results in the `[m, x, y, z]` format. The elements of the array are of type `number`. If the reading fails, a maximum magnitude of acceleration of `-1` will be returned.

Usage Examples

Sample 1: Continuous measurement with exponential smoothing

// IMPORTED LIBRARIES
// - LIS2DW12_V2

// Logging setup
log.setLevel(0,2); //-1:NONE 0:ERROR 1:WARNING 2:DEBUG 3:TRACE, 0:DISABLE 1:LOG 2:CONSOLE 3:BOTH
log.printLevel(2); //0:DISABLE 1:LOG 2:CONSOLE 3:BOTH

// I2C Configuration
var i2c;
if('nqBridge' in this){
    if(nqEx.getBoardType()){
        // Using NEQTO Bridge IO Board or NEQTO Bridge Digital IO Board.
        nqEx.enI2CS(true);
        nqEx.enI2CL(true);
    }
    i2c = new I2C(1);
} else if('nqSpresense' in this){
    i2c = new I2C(0);
} else if('nqDiscovery' in this){
    i2c = new I2C(1);
} else{
    throw("Incompatible device.");
}

i2c.open(400000); // Baudrate: 400000
var lis2dw12 = new LIS2DW12(i2c);
var ready = lis2dw12.init();

var results;
var ewmaVals = []; // Smoothed results (Exponential Weighted Moving Average)
var prevVals = []; // Stored previous results
var isFirstRun = true;
var alpha = 0.5;

var count = 0;
var maxCount = 100;
var loopFlag = true;

if (!ready) {
    print("Error: Unable to connect to LIS2DW12");
}
else{
    // 100 Hz, High Perf, ODR/2, +-2g, Low pass filter, Low noise enabled
    var ready2 = lis2dw12.measOn(5, 0, 0, 0, false, true);
    if(!ready2) print('measOn unsuccessful');
    else {
        print('measOn successful');
        while(loopFlag){
            var num = lis2dw12.getFifoNum();
            // print('accnum: '+num);
            if(num == 32) print('Warning: Fifo buffer possible overrun!');

            if(num!=0){
                results = lis2dw12.readFifo(num);

                for(var i=0; i<num; i++) {
                    if(isFirstRun){
                       isFirstRun = false;
                       print('|  cnt  |   x  |   y  |   z  |  smx |  smy |  smz |');
                       print(`|   ${count}   | ${results[0][0].toFixed(2)} | ${results[1][0].toFixed(2)} | ${results[2][0].toFixed(2)} |  { } |  { } |  { } |`);
                        count++;
                    } else {
                        for (var j = 0; j < 3; j++) { // 3-Axis X, Y, Z
                            if (ewmaVals.length < 3) { // Initial values for ewmaVals
                                ewmaVals[j] = results[j][0];
                            } else {
                                ewmaVals[j] = (alpha * prevVals[j]) + ((1-alpha) * ewmaVals[j]);
                            }
                            prevVals[j] = results[j][i];
                        }
                        print(`|   ${count}   | ${results[0][i].toFixed(2)} | ${results[1][i].toFixed(2)} | ${results[2][i].toFixed(2)} | ` +
                              `${ewmaVals[0].toFixed(2)} | ${ewmaVals[1].toFixed(2)} | ${ewmaVals[2].toFixed(2)} |`);
                        if(count++ >= maxCount){
                            loopFlag = false;
                            break;
                        }
                    }
                }
            }
        }
    }
    lis2dw12.measOff();
}
i2c.close();

Sample 2: Shock detection

// IMPORTED LIBRARIES
// - LIS2DW12_V2

// Logging setup
log.setLevel(0,2); //-1:NONE 0:ERROR 1:WARNING 2:DEBUG 3:TRACE, 0:DISABLE 1:LOG 2:CONSOLE 3:BOTH
log.printLevel(2); //0:DISABLE 1:LOG 2:CONSOLE 3:BOTH

// I2C Configuration
var i2c;
if('nqBridge' in this){
    if(nqEx.getBoardType()){
        // Using NEQTO Bridge IO Board or NEQTO Bridge Digital IO Board.
        nqEx.enI2CS(true);
        nqEx.enI2CL(true);
    }
    i2c = new I2C(1);
} else if('nqSpresense' in this){
    i2c = new I2C(0);
} else if('nqDiscovery' in this){
    i2c = new I2C(1);
} else{
    throw("Incompatible device.");
}

i2c.open(400000); // Baudrate: 400000
var lis2dw12 = new LIS2DW12(i2c);
var ready = lis2dw12.init();
var dateTime;

var results;
var highThreshold = 2.00; // Shock threshold engage
var lowThreshold = 0.50; // Shock threshold release
var detection = false;
var maxShock = [0, 0, 0, 0];
var maxShockTime;

var count = 0;
var maxCount = 100;
var loopFlag = true;

if (!ready) {
    print("Error: Unable to connect to LIS2DW12");
}
else{
    // 400 Hz, High Perf, ODR/2, +-16g, High pass filter, Low noise enabled
    var ready2 = lis2dw12.measOn(7, 0, 0, 3, true, true);
    if(!ready2) print('measOn unsuccessful');
    else {
        print('measOn successful');
        while(loopFlag){
            var num = lis2dw12.getFifoNum();
            // print('accnum: '+num);
            if(num == 32) print('Warning: Fifo buffer possible overrun!');

            if(num!=0){
                results = lis2dw12.readFifoMaxAcc(num);

                if(!detection && results[0] > highThreshold){
                    print("Warning: Shock detected!");
                    detection = true;
                    if(maxShock[0] <= results[0]){
                      maxShock = results.slice();
                      maxShockTime = Date.now();
                    }
                } else if(detection && results[0] < lowThreshold){
                    detection = false;
                    print(`[Max Shock] ${maxShockTime}, Magnitude: ${maxShock[0].toFixed(2)}, X: ${maxShock[1].toFixed(2)}, Y: ${maxShock[2].toFixed(2)}, Z: ${maxShock[3].toFixed(2)}`);
                    // loopFlag = false; // One-shock detection
                    var maxShock = [0, 0, 0, 0]; // Reset
                }
            }
        }
    }
    lis2dw12.measOff();
}
i2c.close();

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Updated: 2021-10-06

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LIS2DW12 v2 Accelerometer

Related Documents

Abstracts

{LIS2DW12} Instance

Details

`new LIS2DW12(i2c)`

Instance Methods

`.write(reg,data)`

`.read(reg)`

`.readBuff(reg,len)`

`.init()`

`.measOn(odr,mode,bwfilter,fs,fds,lownoise)`

`.measOff()`

`.getFifoNum()`

`.readFifo(num)`

`.readFifoMaxAcc(num)`

Usage Examples

Sample 1: Continuous measurement with exponential smoothing

Sample 2: Shock detection