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| − | [[文件:02s03702.jpg|400px|缩略图|右]]
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| − | ==产品概述==
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| − | ADXL345 数字三轴加速度计是一款小而薄的超低功耗3轴加速度计，分辨率高达(13位)，测量范围达± 16g。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。其高分辨率(3.9mg/LSB)，能够测量不到1.0°的倾斜角度变化。该器件提供多种特殊检测功能。活动和非活动检测功能通过比较任意轴上的加速度与用户设置的阈值来检测有无运动发生。敲击检测功能可以检测任意方向的单振和双振动作。自由落体检测功能可以检测器件是否正在掉落。这些功能可以独立映射到两个中断输出引脚中的一个。正在申请专利的集成式存储器管理系统采用一个32级先进先出(FIFO)缓冲器，可用于存储数据，从而将主机处理器负荷降至最低，并降低整体系统功耗。低功耗模式支持基于运动的智能电源管理，从而以极低的功耗进行阈值感测和运动加速度测量。
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| − | ==规格参数==
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| − | # 工作电压：3.3-5v
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| − | # 超低功耗：测量模式下40uA电流损耗，待机模式下0.1uA@2.5v
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| − | # 通讯接口：I2C、SPI(3线or4线)
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| − | # 接口类型：0.1"插针孔
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| − | ==接口定义==
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| − | * VCC：电源引脚
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| − | * GND：该引脚必须接地
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| − | * CS：片选端，低电平有效
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| − | * INT1：中断1输出
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| − | * INT2：中断2输出
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| − | * SDO：备用I2C地址选择
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| − | * SDA：I2C接口数据端
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| − | * SCL：I2C接口时钟端
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| − | ==使用方法==
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| − | ===接线方法===
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| − | [[文件:b1.png|423px|缩略图|居中]]
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| − | 接线图：
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| − | [[文件:Adxl345jiexian.jpg|700px|缩略图|居中]]
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| − | ===例子程序===
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| − | [http://pan.baidu.com/s/1o6CI1ZG wire库文件下载]
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| − | <pre style='color:blue'>#include <Wire.h>
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| − | #define DEVICE (0x53) //ADXL345 device address
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| − | #define TO_READ (6) //num of bytes we are going to read each time (two bytes for each axis)
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| − |
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| − | byte buff[TO_READ] ; //6 bytes buffer for saving data read from the device
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| − | char str[512]; //string buffer to transform data before sending it to the serial port
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| − | int regAddress = 0x32; //first axis-acceleration-data register on the ADXL345
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| − | int x, y, z; //three axis acceleration data
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| − | double roll = 0.00, pitch = 0.00; //Roll & Pitch are the angles which rotate by the axis X and y
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| − | //in the sequence of R(x-y-z),more info visit
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| − | void setup() {
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| − | Wire.begin(); // join i2c bus (address optional for master)
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| − | Serial.begin(9600); // start serial for output
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| − |
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| − | //Turning on the ADXL345
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| − | writeTo(DEVICE, 0x2D, 0);
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| − | writeTo(DEVICE, 0x2D, 16);
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| − | writeTo(DEVICE, 0x2D, 8);
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| − | }
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| − | void loop() {
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| − | readFrom(DEVICE, regAddress, TO_READ, buff); //read the acceleration data from the ADXL345
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| − | //each axis reading comes in 10 bit resolution, ie 2 bytes. Least Significat Byte first!!
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| − | //thus we are converting both bytes in to one int
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| − | x = (((int)buff[1]) << 8) | buff[0];
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| − | y = (((int)buff[3])<< 8) | buff[2];
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| − | z = (((int)buff[5]) << 8) | buff[4];
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| − | //we send the x y z values as a string to the serial port
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| − | Serial.print("The acceleration info of x, y, z are:");
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| − | sprintf(str, "%d %d %d", x, y, z);
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| − | Serial.print(str);
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| − | Serial.write(10);
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| − | //Roll & Pitch calculate
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| − | RP_calculate();
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| − | Serial.print("Roll:"); Serial.println( roll );
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| − | Serial.print("Pitch:"); Serial.println( pitch );
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| − | Serial.println("");
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| − | //It appears that delay is needed in order not to clog the port
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| − | delay(50);
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| − | }
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| − |
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| − | //---------------- Functions
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| − | //Writes val to address register on device
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| − | void writeTo(int device, byte address, byte val) {
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| − | Wire.beginTransmission(device); //start transmission to device
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| − | Wire.write(address); // send register address
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| − | Wire.write(val); // send value to write
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| − | Wire.endTransmission(); //end transmission
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| − | }
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| − | //reads num bytes starting from address register on device in to buff array
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| − | void readFrom(int device, byte address, int num, byte buff[]) {
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| − | Wire.beginTransmission(device); //start transmission to device
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| − | Wire.write(address); //sends address to read from
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| − | Wire.endTransmission(); //end transmission
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| − | Wire.beginTransmission(device); //start transmission to device
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| − | Wire.requestFrom(device, num); // request 6 bytes from device
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| − | int i = 0;
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| − | while(Wire.available()) //device may send less than requested (abnormal)
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| − | {
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| − | buff[i] = Wire.read(); // receive a byte
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| − | i++;
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| − | }
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| − | Wire.endTransmission(); //end transmission
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| − | }
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| − | //calculate the Roll&Pitch
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| − | void RP_calculate(){
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| − | double x_Buff = float(x);
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| − | double y_Buff = float(y);
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| − | double z_Buff = float(z);
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| − | roll = atan2(y_Buff , z_Buff) * 57.3;
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| − | pitch = atan2((- x_Buff) , sqrt(y_Buff * y_Buff + z_Buff * z_Buff)) * 57.3;
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| − | }</pre>
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| − | ===程序效果===
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| − | 打开串口监视窗口，可以看到类似下图的数据，分别为：三轴加速度的数据，按照R-xyz旋转顺序时的姿态角。按各轴旋转可以观测到相应的数据变化。
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