Quadature Generation

Hello Andrew,

A quick glance at the code brought out an interesting observation: The code is not correct

        PWMOutputState(GPIO_PORTF_BASE, PWM_OUT_1_BIT | PWM_OUT_0_BIT, true);

Why do the PWM Functiosn call GPIO_PORTF_BASE?

I think code correction first, then we can get the phase issue sorted.

Regards

Amit

Amit,

Oh, thank you! I replaced GPIO_PORTF_BASE with PWM0_BASE and now I can vary the duty cycle and frequency. However, my phase is still not correct. In the picture below, I am sending a 50% duty cycle at 10 kHz with a phase of 90 degrees. It seems that duty cycle of the blue signal is be cut in half.

Hello Andrew,

I reckon you would need to use two PWM Generators to do the same with synchronization enabled between them. Reason being that you need to vary the DC independently for each of the signal. The Frequency and phase relation of 90 degree can be maintained with a single generator but not the DC.

Regards

Amit

Amit,

It looks like the TM4C1294 only has one PWM generator. Is there any other way to implement what I am trying to do?

Hello Andrew,

Each PWM Module has 4 generators. I was referring to the generators as they can be sync-ed

Regards

Amit

Amit,

Thank you for all of your help! However, I am having trouble syncing gen 0 and  gen 1 of pwm module 0. i have attached my code below.

 1067.Quadature_Generation.zip

Hello Andrew

OK. Let me check the code and see what the issue is. Will need a day or two.

Regards

Amit

Hello Andrew,

It was tough using PWM alone so I had to insert a General Purpose Timer to be able to phase offset the two PWM generators. Also I had to forgo the Sync Mode Update on PWM. Attached is the project and a snapshot of what I get on the scope (There is an issue with the scope measruing the phase on the wrong edge: I need to correct that but if I do the maths for the edge it works out to be as per the code)

http://e2e.ti.com/cfs-file.ashx/__key/communityserver-discussions-components-files/908/6886.TM4C129_5F00_Quadrature_5F00_Generation.7z

Regards

Amit

Amit,

This is awesome! Thank you so much. I am probably doing something wrong but when I try to send 50% / 50% duty cycles at 10 kHz with a 90 degree phase, I get the following waveforms. I am reading pins PF0 and PF1. Should I be reading different pins?

Hello Andrew,

PF0 and PF3 or PF0 and PF2 (can't clearly remember where the scope probe was)

Regards

Amit

Amit,

Nevermind. I figured out that I was indeed reading the wrong pins. Thank you again. You're the man!

Amit,

I do have one last question though. How do I flip the phase so that gen 0 is lagging gen 1 instead of what it is doing now which is gen 0 is leading gen 1?