mikeleslie
Active member
I have an app I've been using for a while which runs on a Mega and I decided that a Teensy would be a great fit. Very few issues in migrating except for the accelerometer. Instead of producing negative values like the Mega (or Uno or Micro I tried it on) it gives me a 65,5xx(ish) The value is an INT, so I'm guessing there's an issue with how the sign is being interpreted...
I thought it was the library I was using and so I went back to the simplest example sketch for the ADXL and it produces the same result.
If I compile the sketch for the Mega, Uno etc, it runs fine. Any help would be much appreciated.
Here's some output:
x: 20 y: 4 z: 115
x: 12 y: 2 z: 119
x: 6 y: 1 z: 116
x: 0 y: 2 z: 117
x: 65525 y: 3 z: 118
x: 65520 y: 3 z: 118
x: 65522 y: 3 z: 112
and here's the code.
I thought it was the library I was using and so I went back to the simplest example sketch for the ADXL and it produces the same result.
If I compile the sketch for the Mega, Uno etc, it runs fine. Any help would be much appreciated.
Here's some output:
x: 20 y: 4 z: 115
x: 12 y: 2 z: 119
x: 6 y: 1 z: 116
x: 0 y: 2 z: 117
x: 65525 y: 3 z: 118
x: 65520 y: 3 z: 118
x: 65522 y: 3 z: 112
and here's the code.
Code:
// Bare bones ADXL345 i2c example for Arduino 1.0
// by Jens C Brynildsen <http://www.flashgamer.com>
// This version is not reliant of any external lib
// Demonstrates use of ADXL345 (using the Sparkfun ADXL345 breakout) with i2c communication
// Datasheet [url]http://www.sparkfun.com/datasheets/Sensors/Accelerometer/ADXL345.pdf[/url]
// If you need more advanced features such as freefall and tap detection, check out
// [url]https://github.com/jenschr/Arduino-libraries[/url]
// (Adapted for Arduino 1.0 from [url]http://code.google.com/p/adxl345driver[/url])
// Cabling for i2c using Sparkfun breakout with an Arduino Uno / Duemilanove:
// Arduino <-> Breakout board
// Gnd - GND
// 3.3v - VCC
// 3.3v - CS
// Analog 4 - SDA
// Analog 5 - SLC
// Cabling for i2c using Sparkfun breakout with an Arduino Mega / Mega ADK:
// Arduino <-> Breakout board
// Gnd - GND
// 3.3v - VCC
// 3.3v - CS
// 20 - SDA
// 21 - SLC
// This example code is in the public domain.
#include <Wire.h>
#define DEVICE (0x53) // Device address as specified in data sheet
byte _buff[6];
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
void setup()
{
Wire.begin(); // join i2c bus (address optional for master)
Serial.begin(57000); // start serial for output. Make sure you set your Serial Monitor to the same!
Serial.print("init");
//Put the ADXL345 into +/- 4G range by writing the value 0x01 to the DATA_FORMAT register.
writeTo(DATA_FORMAT, 0x01);
//Put the ADXL345 into Measurement Mode by writing 0x08 to the POWER_CTL register.
writeTo(POWER_CTL, 0x08);
}
void loop()
{
readAccel(); // read the x/y/z tilt
delay(500); // only read every 0,5 seconds
}
void readAccel() {
uint8_t howManyBytesToRead = 6;
readFrom( DATAX0, howManyBytesToRead, _buff); //read the acceleration data from the ADXL345
// each axis reading comes in 10 bit resolution, ie 2 bytes. Least Significat Byte first!!
// thus we are converting both bytes in to one int
int x = (((int)_buff[1]) << 8) | _buff[0];
int y = (((int)_buff[3]) << 8) | _buff[2];
int z = (((int)_buff[5]) << 8) | _buff[4];
Serial.print("x: ");
Serial.print( x );
Serial.print(" y: ");
Serial.print( y );
Serial.print(" z: ");
Serial.println( z );
}
void writeTo(byte address, byte val) {
Wire.beginTransmission(DEVICE); // start transmission to device
Wire.write(address); // send register address
Wire.write(val); // send value to write
Wire.endTransmission(); // end transmission
}
// Reads num bytes starting from address register on device in to _buff array
void readFrom(byte address, int num, byte _buff[]) {
Wire.beginTransmission(DEVICE); // start transmission to device
Wire.write(address); // sends address to read from
Wire.endTransmission(); // end transmission
Wire.beginTransmission(DEVICE); // start transmission to device
Wire.requestFrom(DEVICE, num); // request 6 bytes from device
int i = 0;
while(Wire.available()) // device may send less than requested (abnormal)
{
_buff[i] = Wire.read(); // receive a byte
i++;
}
Wire.endTransmission(); // end transmission
}
Last edited: