Grove - 3-Axis Digital Accelerometer(±16g)

From Wiki 来自痴汉的爱
Jump to: navigation, search

[中文]

Contents

Introduction

3-axis Accelerometer ADXL345.jpg
Grove-3-Axis (16g) v1.3.jpg
Grove - 3-Axis Digital Accelerometer(16g) v1.2
Grove - 3-Axis Digital Accelerometer(16g) v1.3


This is a high resolution digital accelerometer providing you at max 3.9mg/LSB resolution and large ±16g measurement range. It's base on an advanced 3-axis IC ADXL345. Have no worry to implement it into your free-fall detection project, cause it's robust enough to survive up to 10,000g shock. Meanwhile, it's agile enough to detect single and double taps. It's ideal for motion detection, Gesture detection as well as robotics.




Specifications

  • Input Voltage: 3.3V, 5V
  • Test Range: ±16
  • High sensitivity
  • Large measurement range
  • Low power 0.1 μA in standby mode at VS = 2.5 V (typical)
  • 10,000 g shock survival
  • RoHS/WEEE lead-free compliant
  • Suli-compatible Library


Note: More details about Suli-compatible Library, please refer to Suli




Demonstration

With Arduino

Every accelerometer has been individually tested before shipping to you. But in rare cases, you might need to reset the zero-offset by yourself.

Here below we show you how to read the raw data and obtain data in the unit of g, AKA g-force, from this accelerometer.
Grove - 3-Axis Digital Accelerometer ADXL345 connect photo.JPG

1. Plug it onto the I2C port of your Grove - Base Shield.

2. Download the Digital Accelerometer(±16g) Library .zip and unpack it into arduino-1.0\libraries in your Arduino installation folder.

3. Open the demo code directly by the path:File -> Example ->DigitalAccelerometer_ADXL345->ADXL345_demo_code.

4. Upload the code and open the serial monitor. Please click here if you do not know how to upload.

5. Open the serial monitor to check the result.
Digital Accelerometer.jpg

The outputs of this sensor consist of two parts: raw data and 3-axis acceleration info converted into the unit of gravity, "g".





With Raspberry Pi

1.You should have got a raspberry pi and a grovepi or grovepi+.
2.You should have completed configuring the development enviroment, otherwise follow here.
3.Connection

  • Plug the sensor to grovepi socket i2c-x(1~3) by using a grove cable.

4.Navigate to the demos' directory:

   cd yourpath/GrovePi/Software/Python/
  • To see the code
   nano grovepi_tilt_switch.py   # "Ctrl+x" to exit #
import smbus
from time import sleep

# select the correct i2c bus for this revision of Raspberry Pi
revision = ([l[12:-1] for l in open('/proc/cpuinfo','r').readlines() if l[:8]=="Revision"]+['0000'])[0]
bus = smbus.SMBus(1 if int(revision, 16) >= 4 else 0)

# ADXL345 constants
EARTH_GRAVITY_MS2   = 9.80665
SCALE_MULTIPLIER    = 0.004

DATA_FORMAT         = 0x31
BW_RATE             = 0x2C
POWER_CTL           = 0x2D

BW_RATE_1600HZ      = 0x0F
BW_RATE_800HZ       = 0x0E
BW_RATE_400HZ       = 0x0D
BW_RATE_200HZ       = 0x0C
BW_RATE_100HZ       = 0x0B
BW_RATE_50HZ        = 0x0A
BW_RATE_25HZ        = 0x09

RANGE_2G            = 0x00
RANGE_4G            = 0x01
RANGE_8G            = 0x02
RANGE_16G           = 0x03

MEASURE             = 0x08
AXES_DATA           = 0x32

class ADXL345:

    address = None

    def __init__(self, address = 0x53):        
        self.address = address
        self.setBandwidthRate(BW_RATE_100HZ)
        self.setRange(RANGE_2G)
        self.enableMeasurement()

    def enableMeasurement(self):
        bus.write_byte_data(self.address, POWER_CTL, MEASURE)

    def setBandwidthRate(self, rate_flag):
        bus.write_byte_data(self.address, BW_RATE, rate_flag)

    # set the measurement range for 10-bit readings
    def setRange(self, range_flag):
        value = bus.read_byte_data(self.address, DATA_FORMAT)

        value &= ~0x0F;
        value |= range_flag;  
        value |= 0x08;

        bus.write_byte_data(self.address, DATA_FORMAT, value)
    
    # returns the current reading from the sensor for each axis
    #
    # parameter gforce:
    #    False (default): result is returned in m/s^2
    #    True           : result is returned in gs
    def getAxes(self, gforce = False):
        bytes = bus.read_i2c_block_data(self.address, AXES_DATA, 6)
        
        x = bytes[0] | (bytes[1] << 8)
        if(x & (1 << 16 - 1)):
            x = x - (1<<16)

        y = bytes[2] | (bytes[3] << 8)
        if(y & (1 << 16 - 1)):
            y = y - (1<<16)

        z = bytes[4] | (bytes[5] << 8)
        if(z & (1 << 16 - 1)):
            z = z - (1<<16)

        x = x * SCALE_MULTIPLIER 
        y = y * SCALE_MULTIPLIER
        z = z * SCALE_MULTIPLIER

        if gforce == False:
            x = x * EARTH_GRAVITY_MS2
            y = y * EARTH_GRAVITY_MS2
            z = z * EARTH_GRAVITY_MS2

        x = round(x, 4)
        y = round(y, 4)
        z = round(z, 4)

        return {"x": x, "y": y, "z": z}

if __name__ == "__main__":
    # if run directly we'll just create an instance of the class and output 
    # the current readings
    adxl345 = ADXL345()
    
    axes = adxl345.getAxes(True)
    print "ADXL345 on address 0x%x:" % (adxl345.address)
    print "   x = %.3fG" % ( axes['x'] )
    print "   y = %.3fG" % ( axes['y'] )
    print "   z = %.3fG" % ( axes['z'] )

5.Run the demo.

   sudo python grove_tilt_switch.py

With Beaglebone Green

To begin editing programs that live on BBG, you can use the Cloud9 IDE.
As a simple exercise to become familiar with Cloud9 IDE, creating a simple application to blink one of the 4 user programmable LEDs on the BeagleBone is a good start.

If this is your first time to use Cloud9 IDE, please follow this link.


Step1: Set the Grove - UART socket as a Grove - GPIO Socket, just follow this link.

Step2: Click the "+" in the top-right to create a new file.

C9-create-tab.png

C9 newfile.jpg

Step3: Copy and paste the following code into the new tab

import smbus
import time
 
bus = smbus.SMBus(1)
 
# ADXL345 device address
ADXL345_DEVICE = 0x53
 
# ADXL345 constants
EARTH_GRAVITY_MS2   = 9.80665
SCALE_MULTIPLIER    = 0.004
 
DATA_FORMAT         = 0x31
BW_RATE             = 0x2C
POWER_CTL           = 0x2D
 
BW_RATE_1600HZ      = 0x0F
BW_RATE_800HZ       = 0x0E
BW_RATE_400HZ       = 0x0D
BW_RATE_200HZ       = 0x0C
BW_RATE_100HZ       = 0x0B
BW_RATE_50HZ        = 0x0A
BW_RATE_25HZ        = 0x09
 
RANGE_2G            = 0x00
RANGE_4G            = 0x01
RANGE_8G            = 0x02
RANGE_16G           = 0x03
 
MEASURE             = 0x08
AXES_DATA           = 0x32
 
class ADXL345:
 
    address = None
 
    def __init__(self, address = ADXL345_DEVICE):        
        self.address = address
        self.setBandwidthRate(BW_RATE_100HZ)
        self.setRange(RANGE_2G)
        self.enableMeasurement()
 
    def enableMeasurement(self):
        bus.write_byte_data(self.address, POWER_CTL, MEASURE)
 
    def setBandwidthRate(self, rate_flag):
        bus.write_byte_data(self.address, BW_RATE, rate_flag)
 
    # set the measurement range for 10-bit readings
    def setRange(self, range_flag):
        value = bus.read_byte_data(self.address, DATA_FORMAT)
 
        value &= ~0x0F;
        value |= range_flag;  
        value |= 0x08;
 
        bus.write_byte_data(self.address, DATA_FORMAT, value)
 
    # returns the current reading from the sensor for each axis
    #
    # parameter gforce:
    #    False (default): result is returned in m/s^2
    #    True           : result is returned in gs
    def getAxes(self, gforce = False):
        bytes = bus.read_i2c_block_data(self.address, AXES_DATA, 6)
 
        x = bytes[0] | (bytes[1] << 8)
        if(x & (1 << 16 - 1)):
            x = x - (1<<16)
 
        y = bytes[2] | (bytes[3] << 8)
        if(y & (1 << 16 - 1)):
            y = y - (1<<16)
 
        z = bytes[4] | (bytes[5] << 8)
        if(z & (1 << 16 - 1)):
            z = z - (1<<16)
 
        x = x * SCALE_MULTIPLIER 
        y = y * SCALE_MULTIPLIER
        z = z * SCALE_MULTIPLIER
 
        if gforce == False:
            x = x * EARTH_GRAVITY_MS2
            y = y * EARTH_GRAVITY_MS2
            z = z * EARTH_GRAVITY_MS2
 
        x = round(x, 4)
        y = round(y, 4)
        z = round(z, 4)
 
        return {"x": x, "y": y, "z": z}
 
if __name__ == "__main__":
    # if run directly we'll just create an instance of the class and output 
    # the current readings
    adxl345 = ADXL345()
 
    while True:
        axes = adxl345.getAxes(True)
        print "ADXL345 on address 0x%x:" % (adxl345.address)
        print "   x = %.3fG" % ( axes['x'] )
        print "   y = %.3fG" % ( axes['y'] )
        print "   z = %.3fG" % ( axes['z'] )
        time.sleep(2)

Step4: Save the file by clicking the disk icon with with the .py extension..


Step5: Connect Grove - 3-Axis Digital Accelerometer(±16g) to Grove I2C socket on BBG.

Step6: Run the code. You'll find that the terminal outputs Gravity info every 2 seconds.

Resources

Personal tools
Namespaces

Variants
Actions
Bazaar
Navigation
Collections
Toolbox