Programming Arduino with ADXL345 to raise interrupt on inactivity - arduino

Question

I need to use a sparkfun breakout board ADXL345 to detect when my motor system has stopped vibrating. I am also using a Sparkfun RedBoard (Arduino uno).
Things I am doing to configure for this behavior:
enable INACTIVITY event
route INACTIVITY events to INT 1 (pin 2 on the RedBoard)
raise INACTIVITY interrupt without delay
set low threshold for INACTIVITY (rule out too high of a setting)
INACTIVITY considers all axes
clear interrupt data register
Having done all these things I do not receive interrupts after going from shaking the devise to setting it down.
//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
char THRESH_ACT = 0x24; // Activity threshold
char THRESH_INACT = 0x38; // Inactivity threshold to 3g
char TIME_INACT = 0x26; // time before raising interrupt
char INT_ENABLE = 0x2E; // Enabling the interrupt lines
char INT_MAP = 0x2F;
char ACT_INACT_CTL = 0x27; // mask byte for controlling
char INT_SOURCE = 0x30;
//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);
// Create an interrupt that will trigger when inactivity is detected
attachInterrupt(0, interruptHandler, RISING);
//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
// Send the inactivity && activity to PIN 1
// 0xF7 && 0xEF
writeRegister(INT_MAP,0xF7 && 0xEF);
// Set the inactivity threshold to 3g (0x38)
// writeRegister(THRESH_INACT,0x38);
writeRegister(THRESH_INACT,1);
// Raise the inact interrupt immediately after going below threshold
writeRegister(TIME_INACT,0);
// Map INACT event (only) to PIN 1
writeRegister(ACT_INACT_CTL, 0x0F);
// Enab le inactivity to generate interrupts
writeRegister(INT_ENABLE, 0x08);
readRegister(INT_SOURCE, 1, values); // Clear the INT_SOURCE register
Serial.println("Waiting for interrupt!");
}
void interruptHandler(){
// readRegister(INT_SOURCE, 1, values); // Clear the INT_SOURCE register
Serial.println("something raise an interrupt!");
}
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(500);
}
//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 i=0; i<numBytes; i++){
values[i] = SPI.transfer(0x00);
}
//Set the Chips Select pin high to end the SPI packet.
digitalWrite(CS, HIGH);
}

Answer 1

Here is a tutorial, arduino library and example sketch. If you haven't run through something like this, might be worth a try starting with someone else's code that is working (maybe you've already done that).
In the example sketch from above, they are enabling interrupts in the code, they just don't seem to tie them into the Arduino's external interrupt system. Once you verify that the example code is working, you can call attachInterrupt() and abandon the polling approach (as you are doing in your example).