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Topic: SOLVED: SPI.h Accelerometer on Duemilanove issue... (Read 1 time) previous topic - next topic


Dec 09, 2012, 11:12 pm Last Edit: Dec 10, 2012, 12:44 am by drewtoby Reason: 1
Hello, I recently bought an accelerometer that works with the Uno through the following code below. However, my uno is taken at the moment (screwed onto my maze robot and covered with an R3 shield) and I have a spare Duemilanove. Only the issue is that this accelerometer will not work on my Duemilanove! I have it set up as it says exactly below (code is from an ebay seller). It uploads perfectly and I am sure that I have no loose wires (it was hard to solder so I covered those areas with silicone).

Do I need to modify the SPI.h file? Is the code below flawed? Or is it something else?

Any help is greatly appreciated.


Code: [Select]

Hooking it Up:

Here is the guide illustrates how to connect an Arduino to the ADXL345 breakout board. The following is a table describing which pins on the Arduino should be connected to the pins on the accelerometer:
Arduino Pin ADXL345 Pin
10 CS
11 SDA
12 SDO
13 SCL

Test Code:

//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 Register
char DATA_FORMAT = 0x31;
char DATAX0 = 0x32;    //X-Axis Data 0
char DATAX1 = 0x33;    //X-Axis Data 1
char DATAY0 = 0x34;    //Y-Axis Data 0
char DATAY1 = 0x35;    //Y-Axis Data 1
char DATAZ0 = 0x36;    //Z-Axis Data 0
char 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.
 //Configure the SPI connection for the ADXL345.
 //Create a serial connection to display the data on the terminal.

 //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(y, DEC);
 Serial.println(z, DEC);      

//This function will write a value to a register on the ADXL345.
//  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.
 //Transfer the desired register value over SPI.
 //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.
//  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.
 //Continue to read registers until we've read the number specified, storing the results to the input buffer.
 for(int i=0; i<numBytes; i++){
   values[i] = SPI.transfer(0x00);
 //Set the Chips Select pin high to end the SPI packet.
 digitalWrite(CS, HIGH);

// code is from: http://www.ebay.com/itm/230743987142?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649


"Pete, it's a fool looks for logic in the chambers of the human heart." Ulysses Everett McGill.
Do not send technical questions via personal messaging - they will be ignored.
I speak for myself, not Arduino.


Dec 09, 2012, 11:31 pm Last Edit: Dec 09, 2012, 11:44 pm by drewtoby Reason: 1
Nothing, as the arduino is not reading the voltage/input. It prints 0,0,0. Nothing more or less.


I am sure that I have no loose wires (it was hard to solder so I covered those areas with silicone).

I hesitate to mention that, unlike solder, silicone is non-conductive.
The art of getting good answers lies in asking good questions.


Dec 10, 2012, 12:37 am Last Edit: Dec 10, 2012, 12:41 am by retrolefty Reason: 1

I am sure that I have no loose wires (it was hard to solder so I covered those areas with silicone).

I hesitate to mention that, unlike solder, silicone is non-conductive.

Paul, pretty ballsy of you to venture outside the software realm with that observation, even if made with hesitation.  :D

So to OP. So it was hard to solder, so did you then not solder the wires and just use silicone glue instead? Or did you solder it first, even though hard, and then covered it with silicone glue?
If the code worked on your Uno then if will work on the Dueimanove, problem is elsewhere, and I suspect the electrical integrity of your wiring is suspect #1.



Thanks for the response! It appears that my code was flawed. I went to
Code: [Select]
http://bildr.org/2011/03/adxl345-arduino/ and used their sample code. It works great!

I soldered first, and then I used silicone to help hold the wires in place.  XD I would have used a breadboard, but I am extremely limited on space.

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