使用ni USB 8451适配器使用ADXL345加速度计芯片进行TAP检测

此示例显示了如何使用Ni®USB8451 I2C适配器从ADXL345 I2C启用加速度计芯片中编写和读取数据。加速度计将配置为检测双击，MATLAB®将用于显示芯片已检测到的消息。

仪表控制工具箱™支持通过接口和驱动程序与仪器进行通信。金宝app

For a complete list of supported hardware, visit the Instrument Control Toolboxproduct page。

Requirements

This example requires a Microsoft® Windows® system and NI845x driver 2.1.1 or higher installed. Make sure the Measurement & Automation Explorer recognizes the NI845x device before you use this example. In addition, ensure the Measurement & Automation Explorer™ is closed prior to accessing the device form MATLAB.

该示例使用AnalogDevices®ADXL345加速度计，该加速度计安装在SparkFun™的9DOF传感器棒上。加速度计具有可以连接到适配器I2C总线线输入的I2C总线线路。由于NI USB 8451没有可编程的内拉电阻器，因此需要用外部拔下电阻将公交线抬高。请注意，液位变速器用于分离V_S和V_DD。

Introduction

仪表控制工具箱™支持通过I2C适配器（例如Ni USB 金宝app8451）与I2C设备进行通信。该工具箱允许您创建一个I2C接口，该接口可用于配置适配器以与I2C外围芯片进行通信。

This example will demonstrate how to configure an I2C based accelerometer to respond to tapping the breadboard twice with your finger. When the double tap is detected, a message will be displayed in the MATLAB command window.

验证NI845X安装

使用乐器命令检查是否正确安装了NI845X驱动程序，并且该仪器控制工具箱可以正确检测到它。

董事会序列号应帮助您识别设备

instrreset i2cinfo = instrhwinfo（'i2c'，，，，'ni845x');disp（i2cInfo);

adaptorDlllname：[1x94 char] adaptorDlllllllllversion：'版本3.4'adaptorName：'ni845x'boardIdsInuse：[1x0 double] installed hosted dobledboards：0检测boardserials：{'0180d47a）;'vendordllname：'ni845x.dll'vendordriverDescription：“国家仪器NI USB 845X驱动程序”

Create the I2C Interface and set the bus speed (BitRate property)

accelerometerAddress = hex2dec('53');i2cinterface = i2c（'ni845x'，0，加速度计）;fopen（i2Cinterface）;i2cinterface.bitrate = 100;

设置TAP阈值，第二点延迟，第二点TAP窗口和TAP持续时间寄存器值

Set the register values according to the datasheet of the device. Read the value back from the device to confirm that the value is indeed set.

threshtapregisteraddress = hex2dec（'1d');valueToWrite = hex2dec ('50');％5G值disp（[[“写作价值：”num2str（valueTowrite）]）;fwrite（i2Cinterface，[threshtapregisteraddress valuetOwrite]）;fwrite（i2Cinterface，threshTapRegisterAddress）;registerValue = fread（i2Cinterface，1，'uint8');disp（[['Thresh_tap寄存器的值是：'num2str（registerValue）]）;latentRegisterAddress = hex2dec('22');valueToWrite = hex2dec ('5');disp（[[“写作价值：”num2str（valueTowrite）]）;fwrite(i2cInterface, [latentRegisterAddress valueToWrite]);％确认价值返回到寄存器fwrite(i2cInterface, latentRegisterAddress); registerValue = fread(i2cInterface, 1,'uint8');disp（[[“潜在寄存器的价值是：”num2str（registerValue）]）;WindowRegisterAddress = hex2dec（'23');valueToWrite = hex2dec ('FF');disp（[[“写作价值：”num2str（valueTowrite）]）;fwrite(i2cInterface, [windowRegisterAddress valueToWrite]);％确认价值返回到寄存器fwrite（i2Cinterface，windowRegisterAddress）;registerValue = fread（i2Cinterface，1，'uint8');disp（[['The value of the WINDOW register is :'num2str（registerValue）]）;durationRegisterAddress = hex2dec('21');valueToWrite = hex2dec ('10');disp（[[“写作价值：”num2str（valueTowrite）]）;fwrite（i2Cinterface，[durationRegisterAddress valuetOwrite]）;fwrite（i2Cinterface，durationRegisterAddress）;registerValue = fread（i2Cinterface，1，'uint8');disp（[[“ DUR寄存器的价值为：”num2str（registerValue）]）;tapaxesRegisterAddress = hex2dec（'2a');valueToWrite = bin2dec('00000111');disp（[[“写作价值：”num2str（valueTowrite）]）;fwrite（i2Cinterface，[tapaxesRegisterAddress valuetWrite]）;fwrite（i2 cinterface，tapaxesRegisterAddress）;registerValue = fread（i2Cinterface，1，'uint8');disp（[['The value of the TAP_AXES register is :'num2str（registerValue）]）;InterruptEnableregisterAddress = hex2dec（'2e');valueToWrite = bin2dec('01100000');disp（[[“写作价值：”num2str（valueTowrite）]）;fwrite（i2Cinterface，[InterruptEnableRegisterAddress valuetOwrite]）;fwrite（i2 -cinterface，intrupteNablEregisterAddress）;registerValue = fread（i2Cinterface，1，'uint8');disp（[['The value of the INT_ENABLE register is :'num2str（registerValue）]）;

Writing Value: 80 The value of the THRESH_TAP register is :80 Writing Value: 5 The value of the LATENT register is :5 Writing Value: 255 The value of the WINDOW register is :255 Writing Value: 16 The value of the DUR register is :16 Writing Value: 7 The value of the TAP_AXES register is :7 Writing Value: 96 The value of the INT_ENABLE register is :96

通过写入power_ctl寄存器来启用操作

根据数据表编写到power_ctl寄存器将导致芯片从待机模式转变为正常操作模式。

powerControlregisterAddress = hex2dec（'2d');valueToWrite = bin2dec('00001000');disp（[[“写作价值：”num2str（valueTowrite）]）;fwrite(i2cInterface, [powerControlRegisterAddress valueToWrite]); fwrite(i2cInterface, powerControlRegisterAddress); registerValue = fread(i2cInterface, 1,'uint8');disp（[['The value of the POWER_CTL register is :'num2str（registerValue）]）;

写作值：8 power_ctl寄存器的值是：8

调查中断登记册

中断源寄存器将包含与特定源生成的中断标志相对应的位。检查是否生成双击中断

interruptSourceRegisterAddress = hex2dec('30');disp（'Waiting for double tap...');while(1) fwrite(i2cInterface, interruptSourceRegisterAddress); InterruptValues = fread(i2cInterface, 1); TapInterrupt = bitand(InterruptValues, bin2dec('00100000'));ifTapInter Rupt Disp（“双击检测到！”);break;结尾结尾

Waiting for double tap... Double tap detected!