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

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Please login the Matrix git and enter the matrix-nanopi branch
 
Please login the Matrix git and enter the matrix-nanopi branch
 
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Revision as of 05:56, 16 September 2015

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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

重力加速度PCB

  • 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 工作原理

  • ADXL345 是一款小巧纤薄的低功耗三轴加速度计,可以对高达±16 g的加速度进行高分辨率(13 位)测量。数字输出数据为 16 位二进制补码格式,可通过SPI (3 线或 4 线)或者I2C数字接口访问。
  • ADXL345 非常适合移动设备应用。它可以在倾斜检测应用中测量静态重力加速度,还可以测量运动或冲击导致的动态加速度。它具有高分辨率(4 mg/LSB),能够测量约 0.25°的倾角变化。
  • 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。
  • 这里采用I2C通信,接线方式如下图:

三轴重力加速度

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
matrix-3_axis_digital_accelerometer_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. Test utilities are under the "install/usr/bin" directory. The application 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 代码展示

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 与Tiny4412连接使用

6.1 准备工作

参考Tiny4412光盘里的《友善之臂Ubuntu使用手册》,在Tiny4412上运行UbuntuCore系统,然后在主机PC上安装并使用相应的编译器。
注意:只能使用Tiny4412SDK-1506的底板。

6.2 硬件连接

参考下图连接模块Matrix-3_Axis_Digital_Accelerometer和Tiny4412
matrix-3_axis_digital_accelerometer_tiny4412

连接说明:

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

6.3 编译测试程序

进入Matrix代码仓库,切换到matrix-tiny4412分支

$ cd matrix
$ git checkout matrix-tiny4412

编译Matrix配件代码

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

注意:请确保你的主机PC当前使用的交叉编译器为Tiny4412-UbuntuCore配套的arm-linux-gnueabihf-gcc-4.7.3。
编译出来的库文件位于install/lib目录下,而测试程序则位于install/usr/bin目录下,模块Matrix-3_Axis_Digital_Accelerometer对应的测试程序为matrix-3_axis_digital_accelerometer。

6.4 运行测试程序

拷贝库文件和测试程序到Tiny4412的UbuntuCore的文件系统上

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

然后启动Tiny4412,在UbuntuCore的shell终端中执行如下命令运行模块Matrix-3_Axis_Digital_Accelerometer的测试程序
注意:此模块并不支持热插拔,启动系统前需要确保硬件正常连接。

$ matrix-3_axis_digital_accelerometer

6.5 代码展示

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;
}

7 与RaspberryPi连接使用

8 与Arduino连接使用

9 相关资料

ADXL345.pdf