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PWM width measurement in PIC16F877A

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tinto

tinto

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I am a beginner in PIC. I need to measure the width of a pulse coming from an ultrasonic sensor using the capture mode. The duration of the pulse vary from 0 to 30ms. How can I do that? I am using PIC16F877A and microC compiler.
 

You need not really use the CAPTURE mode. Poll the input line for low or high going edge, clear TMR1 and start the TMR1. Next poll for the other edge and stop the timer. If you need more than 16 bits. enable TMR1 overflow interrupt and have another 8 bits register increment in the interrupt. This will give you 24 bits resolution.

Cheers

Ravi
 
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    tinto

    tinto

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Thank you. It works. But which method is the best? Polling or the capture method? Which metod will give better accuracy?
 

tinto said:
Thank you. It works. But which method is the best? Polling or the capture method? Which metod will give better accuracy?
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It all depends on the overhead that you have. If the PICmicro is busy doing other tasks, use capture method. If it has enough free time, use polling methog.

Cheers

Ravi
 

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