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 Spec:
  

Pin	Comment
INT2	Interrupt
INT1	Interrupt
CS	Enable
SCL	I2C SCL
SDA	I2C SDA
SDO	Set Slave Address
5V	Power 5V
GND	Ground

3 General Description

• 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°.
• 由于这里使用的是I2C通信方式，所以只简单的介绍I2C的工作原理，具体时序的实现可自行去查看芯片手册。ADXL345遵循UM1024 I2C-总线规格，它支持标准的数据传输模式（100KHz），并且支持快速传输模式（400KHz），采用I2C模式，需要把CS引脚上拉，I2C引脚无连接时，默认模式不存在。
• The module's I2C connection is as follows:

4 Download Matrix Source Code

Matrix family members' code samples are open source which are maintained at: git://github.com/friendlyarm/matrix.git
In this warehouse each branch represents an ARM board that this matrix member can work with

• matrix-nanopi includes code samples for Matrix members that can work with the NanoPi;
• matrix-tiny4412 includes code samples for Matrix members that can work with the Tiny4412;
• matrix-raspberrypi includes code samples for Matrix members that can work with the RaspberryPi;

Here are the steps for installing git on a PC running Ubuntu14.04

$ sudo apt-get install git

Clone Matrix code warehouse

$ git clone git://github.com/friendlyarm/matrix.git

If this is a success a matrix directory will be generated, which will contain all available Matrix code samples.

5 Connect to NanoPi

5.1 Preparations

You need to install a Debian on the NanoPi and have a PC which has an appropriate cross compiler ready. For details you can refer to wiki:NanoPi

5.2 Hardware Connection

Please refer to the following diagrams to connect "Matrix-3_Axis_Digital_Accelerometer" to the NanoPi

Connection Details:

Matrix-3_Axis_Digital_Accelerometer	NanoPi
INT2	Floating
INT1	Floating
CS	Pin1
SCL	Pin5
SDA	Pin3
SDO	Pin2
5V	Pin4
GND	Pin6

5.3 Compile Test Program

Please login the Matrix git and enter the matrix-nanopi branch

$ cd matrix
$ git checkout matrix-nanopi

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-4.4.3" on your PC, which is used to compile files for the NanoPi-Debian.
Generated library files are under the "install/lib" directory. Applications are under the "install/usr/bin" directory. The test program for the "Matrix-3_Axis_Digital_Accelerometer" module is "matrix-3_axis_digital_accelerometer".

5.4 Run Test Program

Please copy the library files and test program to the NanoPi

$ cp install/usr/bin/* nanopi_rootfs/usr/bin/
$ cp install/lib/* nanopi_rootfs/lib/ -d

Power on the NanoPi and run the following command in Debian's terminal
Note: this module is not plug and play therefore before running the module please make sure it is connected to a NanoPi.

$ matrix-3_axis_digital_accelerometer

5.5 Code Sample

int main(int argc, char ** argv) 
{
    char position[BUF_SIZE];
    memset(position, 0, BUF_SIZE);
 
    if (adxl34xRead(position) > 0) {
        printf("Get position: %s", position);
    } else {
        printf("Fail to get position\n");        
    }
    return 0;
}

6 Connect to Tiny4412

6.1 Preparations

Please refer to the Tiny4412's user's manual to install a UbuntuCore on the Tiny4412 and install an appropriate cross compiler on a PC.
Note: only the Tiny4412SDK-1506 carrier board can work with this module.

6.2 Hardware Connection

Please refer to the following diagrams to connect the Matrix-3_Axis_Digital_Accelerometer to the Tiny4412

Connection Details:

Matrix-3_Axis_Digital_Accelerometer	Tiny4412
INT2	Floating
INT1	Floating
CS	CON16 5V
SCL	CON18 SCL
SDA	CON18 SDA
SDO	CON14 5V
5V	CON18 5V
GND	CON18 GND

6.3 Compile Test Program

Please login the Matrix git and enter the matrix-tiny4412 branch

$ cd matrix
$ git checkout matrix-tiny4412

Compile the Matrix code

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

Note: please make sure to install the cross compiler "arm-linux-gnueabihf-gcc-4.7.3" on your PC, which is used to compile files for the Tiny4412-UbuntuCore.
Generated library files are under the "install/lib" directory. Applications are under the "install/usr/bin" directory. The test program for the "Matrix-3_Axis_Digital_Accelerometer" module is "matrix-3_axis_digital_accelerometer".

6.4 Run Test Program

Please copy the library files and test program to the Tiny4412

$ cp install/usr/bin/* tiny4412_rootfs/usr/bin/
$ cp install/lib/* tiny4412_rootfs/lib/ -d

Power on the Tiny4412 and run the following command in UbuntuCore's terminal
Note: this module is not plug and play therefore before running the module please make sure it is connected to a Tiny4412.

$ matrix-3_axis_digital_accelerometer

6.5 Code Sample

int main(int argc, char ** argv) 
{
    char position[BUF_SIZE];
    memset(position, 0, BUF_SIZE);
 
    if (adxl34xRead(position) > 0) {
        printf("Get position: %s", position);
    } else {
        printf("Fail to get position\n");        
    }
    return 0;
}

9 Resources

ADXL345.pdf