Difference between revisions of "Matrix - 3-Axis Digital Accelerometer"

Revision as of 08:29, 17 June 2016

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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:
  

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:

4.2 Connect to NanoPi 2

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

Connection Details:

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:

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:

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