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CCS/TMS320F28379D: XOR of 3 PWM signals

HQ
Intellectual 360 points

Part Number: TMS320F28379D

Tool/software: Code Composer Studio

Hi, 

I have two questions to ask.
Q1.

I am using F28379D controller to generate PWM signals for my three phase inverter. But the PWM method I am using requires to XOR three PWM signals to generate 1 PWM that can be used for 1 phase of inverter (say Phase A). What is the feasible way to XOR three PWM signals to generate 1 PWM signal?

Q2.

I have been reading some questions on the TI forum about tapping the PWM signals at GPIO using Input X bar but I could not really find any example for that? For example, I am using GPIO-16 (PWM 9A) as one of the PWM signals. How do I tap this PWM as INPUT1 using Input X bar? Can you provide me one example of it?

  • 0
    TI__Guru 52080 points

    Q1. If you know what the logic function for 3 Input XOR is, you can do multiple things:

    1. Use Input XBAR to take the signal from your GPIO's back into the device (All you have to do is the source for INPUT XBAR INPUT1/2/3 to be the GPIO number of your PWM outputs) and the do the equation in SW and place the output on a GPIO.

    2. You can use the CLB, directly use the ePWM outputs and have the equation of a three-way XOR in a LUT submodule of the CLB. You have to pick the correct EPWMs that the CLB has access to.

    You have a lot of reading I am assigning you, 

    1. Read the INPUT XBAR chapter and take a look at the XBAR.h file in the driverlib folder.

    2. Figure out the equation for a 3-way XOR

    3. Read the CLB chapter in the TRM and the CLB User Guide (maybe even take a look at this application report http://www.ti.com/lit/an/spracl3/spracl3.pdf on how the CLB design process works )

    Nima

  • 0 in reply to Nima Eskandari
    Intellectual 360 points

    Hi, thank you so much for your response. 

    Am I getting it right that these are two independent methods to achieve XOR of three PWM signals that you suggested, one is using Input Xbar and figuring the equation of XOR and then place the output on GPIO and second is using CLB? 

    I am planning to target approach one for now if it works for me.

  • 0 in reply to HQ
    TI__Guru 52080 points

    Correct they are two different methods as you mentioned!