ADXL345 Tutorial

Today, I have started to set up my ADXL345 tutorial as I had promised. I wanted to go ahead and share the YouTube video of it working. Click here to see what the end result could look like if you hook it up properly.

Video:   http://www.youtube.com/watch?v=4eyQJgTIFNE


If you haven't gotten your ADXL345 triple-axis accelerometer yet, click here!

The way of getting this little guy to work with your Arduino is very similar to the tutorial I posted earlier (below) regarding the IDG500. So if you get stuck here, just scroll down for more detailed steps!


You should hook your ADXL345 up to your Arduino following the below pin configuration so that the example code (below) will work without any modifications. Of course, you are welcome to make modifications as necessary if you feel comfortable, and you are experienced enough to get them to work the way you want. This pin configuration will work with almost any Arduino. Leave a comment below if you have any questions or need help!

Pin configuration:

For those of you who are visual learners, I provide you with the following wiring diagram:

Make sure your wires are hooked up right! I have burned out quite a few Arduinos because of careless mistakes. If you find yourself hooking things up too fast because you just want the darn thing to work, SLOW DOWN and double check everything! Numerous times I was SO sure I had everything hooked up right and then found out nothing worked. Even worse - you think you have everything right and then fry your brand new Arduino! If you're in the same boat, please read my original post below to find out how you can make your own Arduino for super cheap! I digress.

Here is the sample code that corresponds to the above wiring (thanks to sparkfun.com):

//Add the SPI library so we can communicate with the ADXL345 sensor#include <SPI.h>//Assign the Chip Select signal to pin 10.int CS=10;//This is a list of some of the registers available on the ADXL345.//To learn more about these and the rest of the registers on the ADXL345, read the datasheet!char POWER_CTL = 0x2D; //Power Control Registerchar DATA_FORMAT = 0x31;char DATAX0 = 0x32; //X-Axis Data 0char DATAX1 = 0x33; //X-Axis Data 1char DATAY0 = 0x34; //Y-Axis Data 0char DATAY1 = 0x35; //Y-Axis Data 1char DATAZ0 = 0x36; //Z-Axis Data 0char DATAZ1 = 0x37; //Z-Axis Data 1//This buffer will hold values read from the ADXL345 registers.char values[10];//These variables will be used to hold the x,y and z axis accelerometer values.int x,y,z;

void setup(){   //Initiate an SPI communication instance.  SPI.begin();  //Configure the SPI connection for the ADXL345.  SPI.setDataMode(SPI_MODE3);  //Create a serial connection to display the data on the terminal.  Serial.begin(9600);    //Set up the Chip Select pin to be an output from the Arduino.  pinMode(CS, OUTPUT);  //Before communication starts, the Chip Select pin needs to be set high.  digitalWrite(CS, HIGH);    //Put the ADXL345 into +/- 4G range by writing the value 0x01 to the DATA_FORMAT register.  writeRegister(DATA_FORMAT, 0x01);  //Put the ADXL345 into Measurement Mode by writing 0x08 to the POWER_CTL register.  writeRegister(POWER_CTL, 0x08);  //Measurement mode  }void loop(){  //Reading 6 bytes of data starting at register DATAX0 will retrieve the x,y and z acceleration values from the ADXL345.  //The results of the read operation will get stored to the values[] buffer.  readRegister(DATAX0, 6, values);  //The ADXL345 gives 10-bit acceleration values, but they are stored as bytes (8-bits). To get the full value, two bytes must be combined for each axis.  //The X value is stored in values[0] and values[1].  x = ((int)values[1]<<8)|(int)values[0];  //The Y value is stored in values[2] and values[3].  y = ((int)values[3]<<8)|(int)values[2];  //The Z value is stored in values[4] and values[5].  z = ((int)values[5]<<8)|(int)values[4];    //Print the results to the terminal.  Serial.print(x, DEC);  Serial.print(',');  Serial.print(y, DEC);  Serial.print(',');  Serial.println(z, DEC);        delay(10); }

//This function will write a value to a register on the ADXL345.//Parameters://  char registerAddress - The register to write a value to//  char value - The value to be written to the specified register.void writeRegister(char registerAddress, char value){  //Set Chip Select pin low to signal the beginning of an SPI packet.  digitalWrite(CS, LOW);  //Transfer the register address over SPI.  SPI.transfer(registerAddress);  //Transfer the desired register value over SPI.  SPI.transfer(value);  //Set the Chip Select pin high to signal the end of an SPI packet.  digitalWrite(CS, HIGH);}//This function will read a certain number of registers starting from a specified address and store their values in a buffer.//Parameters://  char registerAddress - The register addresse to start the read sequence from.//  int numBytes - The number of registers that should be read.//  char * values - A pointer to a buffer where the results of the operation should be stored.void readRegister(char registerAddress, int numBytes, char * values){  //Since we're performing a read operation, the most significant bit of the register address should be set.  char address = 0x80 | registerAddress;  //If we're doing a multi-byte read, bit 6 needs to be set as well.  if(numBytes > 1)address = address | 0x40;    //Set the Chip select pin low to start an SPI packet.  digitalWrite(CS, LOW);  //Transfer the starting register address that needs to be read.  SPI.transfer(address);  //Continue to read registers until we've read the number specified, storing the results to the input buffer.  for(int  SPI.transfer(0x00);  }  //Set the Chips Select pin high to end the SPI packet.  digitalWrite(CS, HIGH);}

Compile and upload this example code to your Arduino, and presto! If you have any issues or questions, please leave a comment below. I check my blogs daily.

Now that you have it working, challenge yourself to build a similar project as seen in the YouTube video.