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40inD
Joined: 30 Jul 2007
Posts: 112
Location: Moscow, Russia
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| How to generate 457 kHz carrier using PIC? |
 Posted: Tue Mar 21, 2017 11:44 am |
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Is it possible to generate 457 kHz (+/-100Hz) carrier using PIC?
It is better to toggle some pin or to use CCP? But I can't choose right CCP and crystal settings for PIC10 or 12 series. |
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asmboy
Joined: 20 Nov 2007
Posts: 2128
Location: albany ny
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| Posted: Tue Mar 21, 2017 1:36 pm |
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what waveform and amplitude are needed?
is modulation part of the picture? |
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Ttelmah
Joined: 11 Mar 2010
Posts: 19218
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| Posted: Tue Mar 21, 2017 1:41 pm |
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To get to this sort of frequency, you would have to use a hardware PWM (or something more complex like a COG, but these don't exist on the smallest PIC's).
So you need a chip with a PWM module.
Your crystal frequency would need to be an integer multiple of the frequency you want to generate (/4). So if you used (say) a 7.314272MHz crystal, you could use /16 (4*4) and get an exact frequency.
So a PIC with a PWM (smallest/cheapest say the PIC12F752 or the PIC12F1822).
| Code: |
SETUP_TIMER_2(T2_DIV_BY_1,3,1);
SETUP_CCP1(CCP_PWM);
SET_PWM1_DUTY(8L);
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Once started, the hardware generates this, and the PIC can do anything else you want, but only a very few pins left (2 for power, 2 for crystal, 1 for PWM - only three pins left).
This is for a simple square wave. |
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