Smart Pin Center Aligned PWM for 3 Phase Motor Driver

flxint

I am working my way through the datasheet for the smart pins. I am converting one of my 3 phase motor drivers as an example to determine the feasibility of using the Propeller 2.

I need to generate 3 center aligned PWM signals. It would be extremely helpful if someone more familiar with smart pins could provide some direction?

Thank you for your time.

flxint

I found the information I needed with the Propeller 2 Smart Pin Supplementary Documentation by Jon Titus. Definitely a requirement and hopefully examples like this can be included in the datasheet.

msrobots

remember you can start/stop multiple smartpins at the same time by using addpins to create a pingroup and use the pingroup for dirh/dirl.

Enjoy!

Mike

flxint

@msrobots Thanks Mike, just what I was looking for!

ManAtWork

The PWM triangle mode of the smart pins only supports loading of the Y register once per full up/down counting cycle. I got around this restriction by using sawtooth mode instad and inverted the pin output polarity and negated the Y value at the beginning of each odd/even cycle with an interrupt. This way you can get double the update rate or half the switching frequency which helps reducing switching losses for high power IGBTs or MOSFETs.

flxint

@ManAtWork Thank you, great tip!

mwroberts

I had to look up centered aligned PWM to see what it is...
I think the smart pin triangle mode is center aligned, and the saw tooth mode is left aligned...

https://marcelmg.github.io/pwm_left_vs_centered/

Mike

flxint

@mwroberts Thank you Mike for the reference. Yes, I have confirmed the triangle pwm is center aligned.