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Re-Triggerable One Shot Needed

Question asked by ByronS on Jun 26, 2013
Latest reply on Jul 25, 2013 by ByronS

My application involves the 1701. Thanks to other posts, I have a configuration that detects the audio level with an envelope detector and as long as the audio stays below a threshold, I output a logic 1. As soon as the audio goes beyond the threshold the logic output goes to 0 after the 'IsRMSthreshold' block. So far this works perfectly and I use this logic output to start a timer for 15 seconds. I need a tone brief tone burst to get added to my audio signal every 15 seconds that no source audio occurs. I have the timer circuit working to handle the 15 seconds detection and output a logic 1 after the 15 seconds transpires. The part I'm having problems with is turning this logic 1 from my timer output into a one shot enable signal for a brief 100-200 ms duration. The idea of the one shot is to control the duration of the tone burst added back to the audio stream.

 

Since this application requires continuous operation, so I also need a feedback loop to reset the 15 second timer and get it to start over. For this I'm thinking I could use the output of whatever one shot pulse generator, invert it to a logic zero and feed this back to one of the inputs of my AND gate. The main issue is coming up with the equivalent to a hardware 'retriggerable one shot timer'.

 

Any insight would be appreciated!

 

Threshold detect with Timer.JPG

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