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[avr-gcc-list] Re: ATmega16 PWM
From: |
Thomas D. Dean |
Subject: |
[avr-gcc-list] Re: ATmega16 PWM |
Date: |
Mon, 16 Jul 2007 00:09:21 -0700 (PDT) |
I did some measurements on a 600Hz, 50% modulated PWM wave at 32kHz.
Modulate the PWM with 600Hz and 8 samples per cycle. I used a TDS
2014.
I see an interrupt every 202.4usec, 1/(8*600). At every interrupt,
the OCR value is set to value[idx], idx=(idx++)%8
value[8] = { 0x80, 0xad, 0xc0, 0xad, 0x80, 0x52, 0x40, 0x52 };
Looking at the FFT, I see
Freq Level(db)
620 -4.8
1320 -7.6
1880 0 ???
2500 -7.6
3100 -16.0 wide
3760 -6.8
31.00kHz -16.4
31.60kHz -3.79
32.20kHz 0 PWM Frequency
32.80kHz -3.79
33.40kHz -15.2
I was somewhat surprised by the 1880Hz value. Around PWM Freq, I saw
what I expected.
tomdean
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