16 bit pwm

[alanwms]

Hello.
I notice the "note" in the pwm property macro that states "16 bit pics have a 16 bit period available"

The selections for changing the period are "set duty cycle" and "set duty cycle 10 bit"

How do I set a duty cycle 16 bit?
Ref PIC24FJ64GB002-I/SP

As an extra feedback - The notes only stay on long enough to read a few words. The note goes away after a fixed time period. Might be better to keep the note in play while the mouse is hovering over the subject?

[medelec35]

Hi.
If you right-click on the PWM that's on the panel, then select help, you should see all the information within the Wiki.

How do I set a duty cycle 16 bit?

You use SetDutyCycle10Bit.
It will allow 16bit as the period goes up to 65535, which is higher than the standard 10bit.

[alanwms]

Thank you for the explanation - The help thing didn't run for me.

I'm attempting to get higher resolution from the PWM and notice that the rollover point value changes based on frequency. I thought that the input clock to this was derived from the system osc. But I change the clock speed and the roll over numbers don't change in the PWM.

Im fighting with:

I want higher frequency due to noise
I want higher resolution
I'm running RC osc at 8mhz.

Don't know if you have input for me?

[medelec35]

The higher the clock frequency the higher you can have the PWM frequency with a greater resolution.
Is there a reason for such a low clock frequency?
As you increase the PWM frequency the maximum period decreases, which in turn decreases the resolution.
You will need to look at PWM Calculated period and that value is 100% duty.
As for the help, it should open a new Help and resources window within Flowcode.

Help Wiki for PWM.png (140.32 KiB) Viewed 2183 times

[alanwms]

Great Marin. Thanks.

Lower frequency is due to having no clock input. The help button for that doesn't work for me. But I can always go to the wiki and search.

I did think that the higher clock gives higher pwm freq with better resolution, but in the pwm properties box, things don't seem to change

[alanwms]

I tested with a 20mhz clock input (crystal) got some good results. Thanks for your input Martin.

[medelec35]

Hi
Your welcome.
The key thing to remember is the PWM duty can go from 0 = 0% to the maximum period register value = 100%
The exception being SetDuty10bit for non-16bit pics and the max will be 4 x period register.
For 16bit pic, if the period value is 65535 them 100% duty = 65535, 50% duty is 32767 etc.
As you increase the frequency the period register value decreases hence the lower resolution.