Hi all, I'm using the tone() function at the moment to generate a PWM signal that drives a small speaker directly from my Arduino Nano 33 BLE digital pin. At lower frequencies (c. <8000Hz), the tone comes out fine as a fairly clean sound, but as it goes up in frequency, around 15-20kHz, the sound b…

I'm not sure about the Nano BLE but, for say the uno, the tone library uses digitalWrite(). If the waveform is inconsistent you may have to configure a hardware timer yourself and in such a way that it writes directly to its allocated pin. A 50% duty cycle square wave is ok for this audio applicat…

[image] stef1029: Looking at the signal being generated with a scope, it seems that the noise is being caused by the arduino PWM signal being very inconsistent with the PWM signal. What does this mean? Can you attach an image of your scope traces? I'm using the tone() function at the moment…

[image] stef1029: My guess is that the pulses are inconsistent because of an inability to divide the clock speed accurately at higher frequencies, but I could be wrong. Yes totally wrong. The clock speed is well within the limits as to what you can divide. The problem is the jitter on the ti…

If there are issues with the Tone function the Nano33 it is worth a try to see of the direct generation of pwm on a pin is cleaner. Khoi Hoang who posts on this forum as @khoih-prog has written new library for purely hardware based pwm output on the Nano33 BLE boards. [image] …

Hi, @stef1029 What speaker do you have? What is its impedance/resistance? Can you post a circuit diagram please? A hand drawn schematic would be fine. Thanks.. Tom... :grinning: :+1: :coffee: :australia:

PWM signal very noisy at high frequencies

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6v6gt February 9, 2022, 4:54pm 4

If sounds above 8000Hz are bad, I would guess that would be the limitations of my hearing.
Oh yes, put a capacitor in series with the speaker.

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PWM signal very noisy at high frequencies

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