Matrix - 3-Axis Digital Accelerometer

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1 Introduction

3-Axis Digital Accelerometer

• This module measures the static acceleration of gravity in three axis x, y and z resulting from motion or shock.
• Its digital interface is IIC or SPI.
• It is integrated with an ADXL345 chip with high resolution (13-bit) measurement at ±2g, ±4g, ±8g and ±16g.
• The module is powered by 5V and converts 5V to 3.3V to ADXL345.

2 Features

• I2C, 3.3V
• 13-bit, up to +-16g
• 2.54mm spacing pin interface
• PCB dimension(mm): 16 x 32

• Pin Description:
  

Pin	Description
INT2	Interrupt
INT1	Interrupt
CS	Enable
SCL	I2C SCL
SDA	I2C SDA
SDO	Set Slave Address
5V	Supply Voltage 5V
GND	Ground

3 Basic Device Operation

• The ADXL345 is a small, thin, ultralow power, 3-axis accelerometer with high resolution (13-bit) measurement at up to ±16 g. Digital output data is formatted as 16-bit twos complement and is acces-sible through either a SPI (3- or 4-wire) or I2C digital interface.
• The ADXL345 is well suited for mobile device applications. It measures the static acceleration of gravity in tilt-sensing appli-cations, as well as dynamic acceleration resulting from motion or shock. Its high resolution (3.9 mg/LSB) enables measurement of inclination changes less than 1.0°.
• The ADXL345 conforms to the UM1024 I2C Specification. It supports standard (100 kHz) and fast (400 kHz) data transfer modes. If the CS is tied high it will be in the I2C mode. If the CS or ALT ADDRESS pin is floating or unconnected the state will be unknown.
• The module's I2C connection diagram is as follows:

4 Applications

4.1 Connect to NanoPi M1

Please refer to the following connection diagram to connect the module to the NanoPi M1:

Connection Details:

Matrix-3_Axis_Digital_Accelerometer	NanoPi M1
INT2	NC
INT1	NC
CS	Pin2
SCL	Pin5
SDA	Pin3
SDO	High, it is connected to the GPIO pin-header's 3.3V
5V	Pin4
GND	Pin6

4.2 Connect to NanoPi 2

Please refer to the following connection diagram to connect the module to the NanoPi 2:

Connection Details:

Matrix-3_Axis_Digital_Accelerometer	NanoPi 2
INT2	NC
INT1	NC
CS	Pin2
SCL	Pin5
SDA	Pin3
SDO	High, it is connected to the GPIO pin-header's 3.3V
5V	Pin4
GND	Pin6

4.3 Connect to NanoPi M2 / NanoPi 2 Fire

Please refer to the following connection diagram to connect the module to the NanoPi M2/ NanoPi 2 Fire:

Connection Details:

Matrix-3_Axis_Digital_Accelerometer	NanoPi M2
INT2	NC
INT1	NC
CS	Pin2
SCL	Pin5
SDA	Pin3
SDO	High, it is connected to the GPIO pin-header's 3.3V
5V	Pin4
GND	Pin6

4.4 Connect to NanoPC-T2

Please refer to the following connection diagram to connect the module to the NanoPC-T2:
Matrix-3_Axis_Digital_Accelerometer_NanoPC-T2

Connection Details:

Matrix-3_Axis_Digital_Accelerometer	NanoPC-T2
INT2	NC
INT1	NC
CS	USB Host 5V
SCL	Pin5
SDA	Pin6
SDO	USB Host 5V
5V	Pin29
GND	Pin30

4.5 Compile Test Program

Please login the matrix hub and enter the nanopi2 branch

$ cd matrix
$ git checkout nanopi2

Compile the Matrix code

$ make CROSS_COMPILE=arm-linux- clean
$ make CROSS_COMPILE=arm-linux-
$ make CROSS_COMPILE=arm-linux- install

Note: please make sure to install the cross compiler "arm-linux-gcc-4.9.3" on your PC, which is used to compile files for the NanoPi 2.
Generated library files are under the "install/lib" directory. The test program is under the "install/usr/bin" directory. The modules are under the "modules" directory.
The modules are under the "modules" directory. The driver's source code is in github: https://github.com/friendlyarm/linux-3.4.y.git

5 Compile & Run Test Program

Boot your ARM board with Debian and copy the matrix code:

$ apt-get update && apt-get install git
$ git clone https://github.com/friendlyarm/matrix.git

If your cloning is done successfully a "matrix" directory will be generated.

Compile and install Matrix:

$ cd matrix
$ make && make install

Run test program:

$ matrix-accelerometer

Note: this module is not plug and play therefore before running the module please make sure it is connected to an ARM board.
Here is what you should observe:

The position is (-6, 3, 236)

6 Code Sample

This Matrix code sample can work with all the ARM boards mentioned in this module's wiki. The name of this code sample is "matrix-3_axis_digital_accelerometer". Here is its source code:

int main(int argc, char ** argv) 
{
    char position[BUF_SIZE];
    int board;
 
    if ((board = boardInit()) < 0) {
        printf("Fail to init board\n");
        return -1;
    }
 
    system("modprobe adxl34x");
    system("modprobe adxl34x-i2c");
    memset(position, 0, BUF_SIZE);
    if (adxl34xRead(position) > 0) {
        printf("The position is %s", position);
    } else {
        printf("Fail to get position\n");        
    }
    system("rmmod adxl34x-i2c");
    system("rmmod adxl34x");
 
    return 0;
}

For more details about this APIs called in this code sample refer to Matrix API reference manual

7 Resources

ADXL345.pdf

8 Update Log

8.1 Feb-23-2016

• Changed CS pin spec in Section 5.1
• Added driver's source code location in Section 5.2

8.2 June-17-2016

• Re-organized and simplified wiki