noise after tone remains

[ChrisVeigl]

i found that the connected buzzer emits a barely noticable noise after a call to

void tone(uint8_t pin, unsigned int frequency, unsigned long duration)

i think it could fix it by adding noTone(tone->pin);
after line

arduino-pico/cores/rp2040/Tone.cpp

Line 45 in 4cc6c36

pio_sm_set_enabled(tone->pio, tone->sm, false);

PS: if you prefer i can fork/pull request

[earlephilhower]

Thanks for the description and debug, but I think your problem is analog noise, not the PIO.

The line you have shown calls pio_sm_set_enabled(false) which per https://raspberrypi.github.io/pico-sdk-doxygen/group__hardware__pio.html#gaa47ec4090dcdc251e44bf4e4cb89a7bc stops the SM (the actual thing making the tone). So, the pin at that point will no longer toggle under the PIO's countrol.

[earlephilhower]

Maybe the pinMode; digitalWrite might make sense, though. Potentially the I/O goes tri-state when under the control of a PIO device which is not running. So, how about doing a PR that includes the pinMode(OUTPUT); digitalWrite(low)?

[ChrisVeigl]

hi!
i added pinMode(tone->pin, OUTPUT); digitalWrite(tone->pin, LOW); instead of noTone(tone->pin);

but this seems to compromise the function: now only the first call to 'tone ()' produces an audible result ..

[earlephilhower]

Did it remove the noise, though? It may be a little complicated (because we can't call noTone from an IRQ because it uses functions that aren't in RAM) but I can hack in something appropriate to make it work, if that was the underlying problem.

Thx again for the debug!

[ChrisVeigl]

yes - it seems to remove the noise.
no problem! - thanks for the great work - the RP2040 core is epic :)

[earlephilhower]

@ChrisVeigl can you try out #887 ? I don't have a speaker handy (used it on my last PC build!) but it's basically doing the hard-LOW-set on tone timeout followed by re-initting the I/O direction/control on a new tone() call.

[ChrisVeigl]

that does the trick, indeed! nice, thank you :)

[earlephilhower]

Great, thanks for the follow-up!