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[on:]

I have interfaced an ADXL335 3-axis accelerometer with an atmega8 microcontroller.. what i would like to know is how can i use the analog output of the accelerometer to interrupt the microcontroller whenever the outputs deviate from their mean value? any kind of help will be greatly appreciated.... thanks

[Reply #1 on:]

(no electrical guru)

If you want an interrupt you must add some hardware as analog ports cannot generate an IRQ on some threshold value.

Do you have a real time constraint in your application?
Maybe it is a good Idea to post your code so we can have a look at it how it can be done.

Do you use delay() in your code? Code can be more reactive if it is written without delays'...

[Reply #2 on:]

yea... there is a real time constraint.... basically we are building a window washer.... and using the accelerometer as an anemometer so that whenever the bot which is suspended from the top starts swaying, it needs to be interrupted...

[Reply #3 on:]

here is the code for the accelerometer alone, i have been polling the status of the outputs of accelerometer to get the desired result...

int x, y, z;

void setup()
{
Serial.begin(9600);           // sets the serial port to 9600
}
void loop()
{
x = analogRead(0);       // read analog input pin 0
y = analogRead(1);       // read analog input pin 1
z = analogRead(2);       // read analog input pin 2
Serial.print("accelerations are x, y, z: ");
Serial.print(x, DEC);    // print the acceleration in the X axis
Serial.print(" ");       // prints a space between the numbers
Serial.print(y, DEC);    // print the acceleration in the Y axis
Serial.print(" ");       // prints a space between the numbers
Serial.println(z, DEC);  // print the acceleration in the Z axis
delay(1000);// wait 100ms for next reading
if (x<375||x>390 && y<375||y>390 && z<310||z>325)
{
  digitalWrite(13,HIGH);
}
else
{
  digitalWrite(13,LOW);
}



}

[Reply #4 on:]

PLease use the # button to get code tags , makes at least the look better.

some observations:
- why not use higher baudrate 115200 is 12 times faster
- if code and comments differ the code wins ==> check the delay(1000) in your code

- you need to add extra ()'s in the boolean statement to enforce what you really want (I guess)
  see my change in the code below.
  => google for short circuit boolean evaluation why you should do that. (operator precedence is also a good reader)

Code:

int x, y, z;

void setup()
{
Serial.begin(115200);    <<<<<<<<<<<<<<<<<<<<
}
void loop()
{
x = analogRead(0);       // read analog input pin 0
y = analogRead(1);       // read analog input pin 1
z = analogRead(2);       // read analog input pin 2

Serial.print("accelerations are x, y, z: ");
Serial.print(x, DEC);    // print the acceleration in the X axis
Serial.print(" ");       // prints a space between the numbers
Serial.print(y, DEC);    // print the acceleration in the Y axis
Serial.print(" ");       // prints a space between the numbers
Serial.println(z, DEC);  // print the acceleration in the Z axis

delay(1000);// wait 100ms for next reading <<<<<<<<<<<<<<<<<<


if ((x<375||x>390) && (y<375||y>390) && (z<310||z>325))  <<<<<<<<<<<<<<<<
{
digitalWrite(13,HIGH);
}
else
{
digitalWrite(13,LOW);
}
}

[Reply #5 on:]

well actually  the code was originally written by a friend... i just tweaked it a little and forgot to change the comments and as far as using the brackets... the code works perfectly fine without using them also