wanna create frequency

hayee · Joined: 05 Sep 2007 Posts: 252

Hi everyone,
i want to create a frequency that starts from 100hz and ends at 5hz when i press a pushbutton.the duration between start and end is 30 sec.i am using pic16f84a and want to use timer0 for this purpose.i am using ccs compiler version 4.020
i have no idea about using timers and interrupts.
can anyone give me a proper guidence from where i start.
have anyone any example.

kender · Joined: 09 Aug 2004 Posts: 768 Location: Silicon Valley

A lot of example code come with CCS compiler. The files are installed into C:\Program Files\PICC\Examples directory. The descriptions of the examples are here – http://www.ccsinfo.com/devices.php?page=exlist

To start using timer, you should, probably look at the EX_STWT.C example.
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hayee · Joined: 05 Sep 2007 Posts: 252

Thanks kender.
i have already saw the examples but i am still confused

how to use timer and interupts.can anyone have easy way/method from which i can understand.

SherpaDoug · Joined: 07 Sep 2003 Posts: 1640 Location: Cape Cod Mass USA

I would create a "numerically controlled oscillator" for this. Since you just want a square wave output you don't need any waveform lookup table. You just need to add another register for the delta frequency per computation cycle.

A few years ago I wrote one for a 16C58 running at 20MHz that synthesized a sonar burst between 24kHz and 32kHz, so working below 100Hz should be easy.
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