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What is the maximum frequency of a pulse width modulation signal for the raspberry pi 3? Also, how fast is the software PWM, as well as the hardware PWM?

When looking at the pulse width modulation signals, what is the number of signals of the software and hardware PWM?

deltontrosky
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2 Answers2

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  • Hardware minimum: 1.14 Hz

  • Hardware maximum: 19.2 MHz

  • Software minimum and maximum: depends on the software.

Sources: Can I use the GPIO for pulse width modulation (PWM)? | Control Hardware PWM frequency

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Aloha
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  • Addendum: Technically, there is no minimum. You could set it high/low manually. – Aloha Nov 06 '18 at 18:14
  • Are you sure it's 19.2 MHz ? The ChatGPT says it's 19.2 KHz ! I don't know what to believe... – Marus Gradinaru Oct 27 '23 at 21:59
  • @MarusGradinaru I have a modest electronics lab now. I'll try actual tests later and check with an oscilloscope. This answer was from 7 years ago. I just started college back then. – Aloha Oct 28 '23 at 02:42
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Nobody knows the effective limits for software or hardware.

For software PWM you would have to define the number of steps between off and fully on you need for the dutycycle. Generally I'd expect a practical limit for software PWM of about 10kHz. Software PWM will suffer from jitter so it's probably okay for DC motor speed control, but little use for servos or LEDs unless you can ignore glitches.

The hardware PWM limit is down to how well your Pi was manufactured and the quality of the silicon.

The hardware pads are designed to work up to say 25MHz.

pigpio will let you set frequencies in the range 1 to 125MHz. I don't expect anything above 30MHz will actually work.

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joan
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