Comparing data input with itself?

Using Arduino Sensors
1

Hi I have a sensor input with a continuous random stream until it receives a good signal, which it then spits out a short burst of the same value. I need to somehow use that burst to trigger an output.

For example, if I wanted to check for 3 or 4 values in the input stream that were the same, that could trigger my output, to turn on an LED or whatever. I'm stuck on this one.

Thanks,
Brian

2

Hmmm....neat problem. Thinking out loud:

#define NUM_VALUES 4   // How many values should be the same
#define VALTYPE uint8_t         // Replace with whatever type your values are

VALTYPE values[NUM_VALUES];
uint8_t valIndex = 0;

void addValue(VALTYPE value) {
  values[valIndex++] = value;
  if (valIndex == NUM_VALUES) valIndex = 0;
}

uint8_t checkValues(void)
{
  uint8_t i;

  for (i=0; i < NUM_VALUES-1; i++) {
    if (values[i] != values[i+1]) return 0;
  }

  return 1;
}

In your main loop you would call addValue() whenever you got a new sensor reading, and checkValues() when you wanted to see if the last NUM_VALUES values were all the same.

--
The Gadget Shield: accelerometer, RGB LED, IR transmit/receive, speaker, microphone, light sensor, potentiometer, pushbuttons

3

Use "timer = millis()" to note when the signal last changed. Look for (millis() - timer) > 100 to see if the signal has been steady for more then 0.1 seconds. Adjust the threshold to whatever time interval distinguishes 'random' from 'a short burst'.

4

Another way is to subtract the current value from the last value. When this spits out say three zeros on the run you have your reading.