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The range of GPIO PWM is 0-100, not 0-1024. #192

Closed abee2 closed 8 years ago

abee2 commented 8 years ago

The document says as following.

gpio + pin number + pwm + [ 0..1024 ] (we can use the software-driven PWM output facility)

However, the pin that is set more than 100 always outputs 3.3 V. It seems the correct range is 0-100. Is it a bug or an error of the document?

timrowledge commented 8 years ago

You are right; it's a bug in both the code and the document, making it even worse.

abee2 commented 8 years ago

Thanks. But, what is the correct range? I'm writing a book about the GPIO server now. So I'd like to know that. I'm sorry about my private reasons.

timrowledge commented 8 years ago

Ouch, sorry about that.

OK, right now in the jan 2016 release I can see a bug in my use of the wiringPi softPWM mode - I didn't notice that the default value range is set to 100 and not the 1024 that the hardware pwm assumes. Such is the joy of peering at other people's C code libraries.

The version about to be released uses pigpio instead (to provide ultrasonic and serve support etc) and I think I have found a problem in that the default pwm range is 256, not 1024. This is also going to be a problem for the assorted motor driver boards that work off the pwm system. I can see how to fix it but I think it is too late to get those fixes into the next release.

For your book, unless it is just about to be published, I think we can make sure the real system matches the book by the time it reaches the printer. I would suggest documenting the pwm as having 0-1024 range (actually, shouldn't that be 0-1023? Well, that's something to change the doc a little for) and the motor command as using -100...+100. In fact, since writing a book is very like writing a specification, please, please tell me everything you find that is difficult to understand, not consistent, could be better, is missing, or in any other way not good. Wherever possible I will make use of any such comments to clean up the gpioserver. As I think you might know, my email is simply tim at rowledge dot org

timrowledge commented 8 years ago

Fixed ready for next release; motors are set to have 0..100 rang and general pwm 0..1023