Debouncing code

abhishek Sabnis

Hi,

I am getting a noise on Edge triggered interupt. Below is the code for that. I make a decesion SwitchedACCycleDetected = 1; on every edge detected.

But some times noise getting edge triggered making my variable SwtichedACCycleDeteced = 1.

Can somebody  send me debouncing code for edge triggered interrupt.

#pragma vector=PORT1_VECTOR
__interrupt void Port_1(void)
{
		INT++;
		P1IFG &= ~BIT2;
		SwitchedACCycleDetected = 1;
		SwACDetection = 0;
}  
	
Thanks,

over 13 years ago

0 kazola over 13 years ago

Guru 18545 points

Hey,

I'm new to MSP430, but I think for software debouncing you need to check, delay, and check again ;)

http://e2e.ti.com/support/microcontrollers/msp43016-bit_ultra-low_power_mcus/f/166/t/28266.aspx

I think the function is more or less:

__delay_cycles(count);

or something like

for(i = 0xFFF; i> 0; i--) {}

Good luck!

0 Roberto Romano over 13 years ago in reply to kazola

Guru 27285 points

kazola said:

I think the function is more or less:

__delay_cycles(count);

or something like

for(i = 0xFFF; i> 0; i--) {}

Hi Kazola, first is ok, second one cannot work if variable is not declared as volatile, if optimization is enabled all the for code can be flushed away.

To be sure key get debounced you need a decision on time of pressure, if time after bouncing elapse and key is still stable and pressed then decide key is down. Again when key released short change can be ignored and start timing after it is stable for a while.

regards

0 blb over 13 years ago

Genius 3020 points

HI, in a different thread Jan Kesten provided the following link.

There is some general reading about bounces here:

http://www.ganssle.com/debouncing.htm

HTH,

Barry

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Debouncing code