Example on using PWM about phpi HOT 8 CLOSED

Well, I just found the examples/ dir at the root... I'll check out :)

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Nice work. If anything needs clarification, let me know

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Yep, thank you, I'm actually trying this library.

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Well, I'm experiencing some issues.

I have this script:

include __DIR__.'/vendor/autoload.php';

use Calcinai\PHPi\Pin\PinFunction;

$loop = \React\EventLoop\Factory::create();
$board = \Calcinai\PHPi\Factory::create($loop);

$board->getPin(12)->setFunction(PinFunction::PWM0);

$pwm0 = $board->getPWM(\Calcinai\PHPi\Peripheral\PWM::PWM0)
    ->setRange(512)
    ->setEnableMS(true)
    ->start();

$dc = intval($argv[1]);
var_dump($dc);

$pwm0->setDutyCycle($dc);

$loop->run();

Then I run it with sudo php pwm.php 50, where 50 is the duty cycle I set from 0 to 100. The effect is that my robot moves as I want, but I could not vary motor speed.

• First, using sudo php pwm.php 50 seems to set the duty cycle at 100%. So I tried to change range with ->setRange(256), and run it, but it does nothing, 50 is still setting 100% dc.

Btw I can do with wiringPi in command line: gpio pwm 26 350, then it works, and 512 seems to be the 100% duty cycle value.

• Also, I don't find how to use software PWM, for example if I want to run PWM in an other pin, not handled by hardware PWM.

• Finally, I have seen in some forum that I could use MSMODE for PWM, so can I use ->setEnableMS(true) to do the trick ?

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I can't see any reason that what you've got won't work. Out of curiosity, have you tried omitting ->setRange() and -> setEnableMS()?

I had implemented the soft pwm, but it was quite CPU heavy. I'll dig out the example code for that in a sec.

I don't have my test hardware on me at the moment, but I can have a look this afternoon if you can hold on!

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Yes I started my tests without setRange and setEnableMS.

I don't find any difference with setEnableMS, just tried.

And I tried setRange(512) and setRange(256) to try to fix the setDutyCycle(50) case, and because I've seen the default one in the library is 1024. But setDutyCycle(50) always results in a 100% dc.

I don't need a high frequency PWM (100hz is suffisant as I tried it with python), so I guess software PWM could also be suffisant with PHP.

But in fact I don't really need software PWM for now, I can do without.

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@alcalyn - sorry it's taken me so long to get back to you on this one. I've just tested equivalent code:

<?php

include __DIR__.'/vendor/autoload.php';

use Calcinai\PHPi\Peripheral\PWM;
use Calcinai\PHPi\Pin\PinFunction;

$board = \Calcinai\PHPi\Factory::create();

$board->getPin(12)->setFunction(PinFunction::PWM0);

$pwm0 = $board->getPWM(PWM::PWM0)
    ->setRange(512)
    ->setEnableMS(true)
    ->start();

$dc = intval($argv[1]);
var_dump($dc);

$pwm0->setDutyCycle($dc);

And it works as expected. Looking at the range function, it appears to me that that only sets the resolution in the steps - i.e. the setDutyCycle() will still accept 0-100, but will only respect a resolution specified by the range.

The MS function is supported and working in my case too. Are you sure that the motor driver supports the switching speed? What happens if you connect an LED to BCM 12?

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Hi, you're right, I tried your snippet replacing dc motor with a LED, it works as expected !

Also, with your code snippet, setting a duty cycle at 7 or less results as no rotation (but the led is a little on), and setting it from 8 to 100 results as full power (whereas the led light on as expected).

So I thought that my DC motor can't handle PWM, but I think that it's only because the clock has a too high frequency. I think that because I made it work with a software PWM on python (which means low frequency PWM). Then I tried a "software" PWM with:

while (true) {
    $pwm0->setDutyCycle(100);
    usleep($dc - 10);
    $pwm0->setDutyCycle(0);
    usleep((100 - $dc) - 10);
}

And I could get some interesting result. But I'm limited because of this line:

That's why I added - 10 in my usleeps.

Then I also tried to change usleep from this library from 10 to 1, and set a duty cycle at 1, which worked a little better.

So I think that either a software PWM or $pwm->setFrequency could do the trick. (But I couldn't find how to use setFrequency).

By the way, PWM works so I close the issue.

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