CCS/TMS320F28377D: INPUTXBAR & OUTPTXBAR how to set up equation

Mohammed Alharbi

Intellectual 380 points

Part Number: TMS320F28377D

Tool/software: Code Composer Studio

Hi,

I am trying to do almost the same task as this previous forum:

I want to XOR three PWM signals. (PWM1A, PWM2A, PWM3A). and output the signal on GPIO6.

I understood it would be much easier to do it with CLB but unfortunately, I am using the F28377D MCU which is not compatible with the CLB feature. So I am left with the INPUTXBAR & OUTPTXBAR option.

I figure out that I have to use Input XBAR to take the signal from the GPIO's back into the device. So I used the source for INPUTXBAR INPUT1/2/3 to be the GPIO number and then I have to do the equation for the XOR of the signals and place the output on GPIO.

I am only confused about how to set up the equation and assign the output to OutputXbarRegs and which MUX I should use. So please help me out?

EALLOW; 
  GpioCtrlRegs.GPAPUD.bit.GPIO0 = 1; // Disable pull-up
  GpioCtrlRegs.GPAMUX1.bit.GPIO0 = 1;  /* Configure GPIOGPIO0 as EPWM1A*/
  GpioCtrlRegs.GPAGMUX1.bit.GPIO0 = 0; 

  GpioCtrlRegs.GPAPUD.bit.GPIO2 = 1; // Disable pull-up
  GpioCtrlRegs.GPAMUX1.bit.GPIO2 = 1;  /* Configure GPIOGPIO0 as EPWM2A*/
  GpioCtrlRegs.GPAGMUX1.bit.GPIO2 = 0; 
  //GpioCtrlRegs.GPADIR.bit.GPIO2 = 0; 

  GpioCtrlRegs.GPAPUD.bit.GPIO4 = 1; // Disable pull-up
  GpioCtrlRegs.GPAMUX1.bit.GPIO4 = 1;  /* Configure GPIOGPIO0 as EPWM3A*/
  GpioCtrlRegs.GPAGMUX1.bit.GPIO4 = 0; 
  //GpioCtrlRegs.GPADIR.bit.GPIO4 = 0; 
                                                                                                 
  GpioCtrlRegs.GPAPUD.bit.GPIO6 = 1; // Disable pull-up                                                                                                                   
  GpioCtrlRegs.GPAMUX1.bit.GPIO6 = 1; // Configure GPIO6 as EPWM4A 
  //GpioCtrlRegs.GPADIR.bit.GPIO6 = 1; 
                                      
  InputXbarRegs.INPUT1SELECT = 0;  //Selecting GPIO0 to go to INPUT1 of InputXbar PWM1A
  InputXbarRegs.INPUT2SELECT = 2;  //Selecting GPIO2 to go to INPUT2 of InputXbar PWM2A
  InputXbarRegs.INPUT3SELECT = 4;  //Selecting GPIO4 to go to INPUT3 of InputXbar PWM3A

  /* I believe I should set up the XOR equation somewhere here and which MUX I should use*/

// Select INPUTXBAR2 from InputXbar to be the OUTPUT4MUX0TO15CFG=GPIO6  (MUX1=INPUTXBAR1)
  OutputXbarRegs.OUTPUT4MUX0TO15CFG.bit.MUX1 = 1;  
  OutputXbarRegs.OUTPUT4MUXENABLE.bit.MUX1 = 1;  // Enable Mux

// Select INPUTXBAR2 from InputXbar to be the OUTPUT4MUX0TO15CFG=GPIO6  (MUX3=INPUTXBAR2)
  OutputXbarRegs.OUTPUT4MUX0TO15CFG.bit.MUX3 = 1; 
  OutputXbarRegs.OUTPUT4MUXENABLE.bit.MUX3 = 1; // Enable Mux

// Select INPUTXBAR3 from InputXbar to be the OUTPUT4MUX0TO15CFG=GPIO6  (MUX5=INPUTXBAR3)
  OutputXbarRegs.OUTPUT4MUX0TO15CFG.bit.MUX5 = 1; 
  OutputXbarRegs.OUTPUT4MUXENABLE.bit.MUX5 = 1; // Enable Mux

  EDIS;

over 4 years ago

0 Subrahmanya over 4 years ago

TI__Mastermind 24095 points

Hi,

Yes - your part selection doesn't have CLB enabled.

In the Output X-Bar you cannot do XOR operation. But you can combine the signals and OR them.
You can refer to "Figure 9-4. GPIO Output X-BAR Architecture" of the TRM.

0 Mohammed Alharbi over 4 years ago in reply to Subrahmanya

Intellectual 380 points

Hi Subrahmanya,

Thanks for your reply. Yes I understood that all muxes which are enabled will be logically OR’d before being passed on to the respective OUTPUTx signal on the GPIO module. as follows:

XBAR_enableOutputMux(XBAR_OUTPUT4, XBAR_MUX01 | XBAR_MUX03 | XBAR_MUX05);

But I was wondering if I replace the OR ( | ) symbol with an XOR (^), will that be enough to replace the internal OR logic with an XOR, or that is not possible?

So I am just trying to replace the default OR logic by an XOR, then I would get the signal I am looking for. So please advice?

Thanks

Mohammed

0 Subrahmanya over 4 years ago in reply to Mohammed Alharbi

TI__Mastermind 24095 points

Hi,

No. It doesn't work like that. The OR you've above is for the s/w driverlib configuration function.
You can not change that to an XOR. Hardware only has OR capability as you've shown in the diagram.

0 Mohammed Alharbi over 4 years ago in reply to Subrahmanya

Intellectual 380 points

Hi,

Thanks for your prompt response!

Can you or someone else suggest a way to achieve my task of XORing three PWM signals internally in the device and tapping the output on a GPIO pin, other than using the CLB tool or using an external logic circuit?

Best regards,

Mohammed

0 Mohammed Alharbi over 4 years ago in reply to Mohammed Alharbi

Intellectual 380 points

Any suggestions, please?

0 Subrahmanya over 4 years ago in reply to Mohammed Alharbi

TI__Mastermind 24095 points

Hi, CLB is the peripheral capable of such logical operations. It was intended for such use cases. No other peripheral has such logical operations.

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CCS/TMS320F28377D: INPUTXBAR & OUTPTXBAR how to set up equation