PwmOut resets settings after suspend.

[lefebvresam]

Description of defect

When using PwmOut and putting the settings to 4kHz/25% it starts to output the right PWM-signal, but as soon as you do a suspend and resume, the frequency will be reset to 50Hz and you need to redo the settings again. Maybe it's a suggestion to use a start/stop functionality which is separate from the configuration settings.

Target(s) affected by this defect ?

NUCLEO_G474RE

Toolchain(s) (name and version) displaying this defect ?

GCC_ARM

What version of Mbed-os are you using (tag or sha) ?

mbed-os-6.2.0
#a2ada74770f043aff3e61e29d164a8e78274fcd4

What version(s) of tools are you using. List all that apply (E.g. mbed-cli)

mbed-cli 1.10.4

How is this defect reproduced ?

Create a small project to test:

PwmOut buzzer(PC_0);

void stopBuzzer() {
    buzzer.suspend();
}

void startBuzzer() {
    buzzer.resume();
}

void initBuzzer() {
    buzzer.period_us(250);
    buzzer.write(0.25f);
    buzzer.suspend();
}

int main()
{
    Timeout t;
    initBuzzer();

    ThisThread::sleep_for(5s);

    startBuzzer();
    t.attach(&stopBuzzer, 2s);

    while(true) ThisThread::sleep_for(1s);
}

[ciarmcom]

Thank you for raising this detailed GitHub issue. I am now notifying our internal issue triagers.
Internal Jira reference: https://jira.arm.com/browse/MBOTRIAGE-2797

[LMESTM]

From a quick look at pwmout.cpp and #11641 it seems that only duty cycle is saved and restored, not the period / frequency. I guess also the period needs to be saved and restored.

[lefebvresam]

Indeed. I see on the scope that my duty cycle stays on 25% but the frequency changes from 4kHz to 50Hz. In my opinion it should be better to do the setup first without being started automatically and later on start and stop the waveform with commands.

[jeromecoutant]

@lefebvresam Do you think you could propose some update and complete #11641 ?

@hugueskamba @kjbracey-arm

[lefebvresam]

@jeromecoutant I'm not actively working on the mbed project.

[jeromecoutant]

@lefebvresam could you check #13492