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Piccolo F28069 - HRPWM - CMPAHR - 0xFF limit

PowerGuy
Intellectual 405 points
Other Parts Discussed in Thread: CONTROLSUITE

Hi,

The issue that I'm seeing is that when the CMPAHR register gets a value of 0xFFxx, the PWM shuts off.
Any value below FF works.

I'm wondering if this is a limitation for the HRPWM or if my configuration is missing something.

This is some info on my system:

I'm switching the PWM at 220Khz with a Sys Clock of 90Mhz. 

Thus my period is 409.

The output of my compensator is a floating point.

I multiply that output  * 409 * 65279 and load it into the EPwm1Regs.CMPA.all register.

  • 0
    TI__Mastermind 24095 points

    Hi,

    I would no expect the PWM to shut off because of writing a certain value into CMPAHR.
    What is the CMPA value? and the AQCTL settings for PWM generation?
    Have you turned on AUTOCONV bit?
    Also, what is the HRMSTEP value? Have you called the SFO calibration routine?

    -Bharathi.

  • 0
    TI__Expert 5940 points
    Hello,

    A good example to refer to for high resolution duty control can be found here:
    controlSUITE\device_support\f2806x\v151\F2806x_examples_ccsv5\hrpwm_duty_sfo_v6
    You can also review other HRPWM examples in controlSUITE and compare with your configuration.

    If you haven't already, the SFO Library can be used to calculate an appropriate MEP scale factor. You can check the HRPWM chapter in the TRM for more information on the SFO calibration.

    Elizabeth
  • 0 in reply to Subrahmanya
    Intellectual 405 points
    -Bharathi

    I followed the high resolution example from control suite "Example_2806xHRPWM"

    and even on that code, if you make the variable "DutyFine = 255" the PWMS shut off.

    As for my code, I'm finding out that enabling AUTOCONV stops the high resolution from working.
    The CMPAHR is still being loaded but when AUTOCONV is on, it does not take effect on the duty cycle.

    When I have it off, I can see the high resolution working but get those glitches when CMPAHR = 0x255.


    Right now I'm not using the SFO calibration routine. It should work without it. right ?
    Also, in the example program I dont see where the call the SFO(); function.

    This is my config for PWM1
    EPwm1Regs.TBPRD = period; // 220Khz
    EPwm1Regs.TBPHS.half.TBPHS = 0; // Set Phase register to zero
    EPwm1Regs.CMPA.half.CMPAHR = (1 << 8); // initialize HRPWM extension
    EPwm1Regs.TBCTR = 0;

    EPwm1Regs.TBCTL.bit.PRDLD = TB_SHADOW;
    EPwm1Regs.TBCTL.bit.SYNCOSEL = TB_SYNC_IN;
    EPwm1Regs.TBCTL.bit.CTRMODE = TB_COUNT_UP;
    EPwm1Regs.TBCTL.bit.PHSEN = TB_ENABLE;
    EPwm1Regs.TBCTL.bit.PHSDIR = TB_SHADOW;
    EPwm1Regs.TBCTL.bit.HSPCLKDIV = TB_DIV1;
    EPwm1Regs.TBCTL.bit.CLKDIV = TB_DIV1;


    // Counter compare submodule registers
    EPwm1Regs.CMPCTL.bit.LOADAMODE = CC_CTR_PRD;
    EPwm1Regs.CMPCTL.bit.SHDWAMODE = CC_SHADOW;
    EPwm1Regs.CMPCTL.bit.LOADBMODE = CC_CTR_ZERO;
    EPwm1Regs.CMPCTL.bit.SHDWBMODE = CC_SHADOW;
    EPwm1Regs.CMPA.half.CMPA = 0;
    EPwm1Regs.CMPB = 0;

    // high resolution config
    EPwm1Regs.HRCNFG.all = 0x0;
    EPwm1Regs.HRCNFG.bit.EDGMODE = 3; //MEP control on Rising edge
    EPwm1Regs.HRCNFG.bit.CTLMODE = HR_CMP;
    EPwm1Regs.HRCNFG.bit.HRLOAD = HR_CTR_ZERO;
    // EPwm1Regs.HRCNFG.bit.AUTOCONV = 1 ; // ENABLE AUTOCONVERSION
    // EPwm1Regs.HRMSTEP = 83*256;

    // Action Qualifier SubModule Registers
    EPwm1Regs.AQCTLA.bit.ZRO = AQ_SET;
    EPwm1Regs.AQCTLA.bit.PRD = AQ_CLEAR;

    // DeadBand Control Register
    EPwm1Regs.DBCTL.bit.OUT_MODE = DB_FULL_ENABLE;
    EPwm1Regs.DBCTL.bit.POLSEL = DB_ACTV_HIC; // Active Hi Complimentary
    EPwm1Regs.DBRED = 0; // Initial value
    EPwm1Regs.DBFED = 0; // Initial value


    EPwm1Regs.AQCTLA.bit.ZRO = 2;
    EPwm1Regs.AQCTLA.bit.CAU = 1;
    EPwm1Regs.AQCTLB.bit.ZRO = AQ_NO_ACTION; //
    EPwm1Regs.AQCTLB.bit.CAU = AQ_NO_ACTION;
    EPwm1Regs.AQCTLB.bit.PRD = AQ_NO_ACTION;


    EDIS;
  • 0 in reply to PowerGuy
    TI__Expert 5940 points
    Hello,

    You’re right, Example_2806xHRPWM doesn’t use SFO(). It is a more general example showing sample writes to HRPWM registers. I recommend reviewing 'Example_2806xHRPWM_Duty_SFO_V6.c' found at controlSUITE\device_support\f2806x\v151\F2806x_examples_ccsv5\hrpwm_duty_sfo_v6
    The above example shows usage of the SFO library and updating CMPAHR.

    The SFO calibration is needed to update HRMSTEP with the calculated MEP scale factor. Auto-conversion is used along with the SFO calibration. Setting AUTOCONV bit allows SFO to automatically scale CMPAHR.

    Elizabeth