LAUNCHXL-F28379D: ePWM phaseshift(or phasedelay) between ePWM1 & ePWMx not predicatble in the ""Up-Down" Counting mode

Pradeep Braun

Prodigy 30 points

Part Number: LAUNCHXL-F28379D
Other Parts Discussed in Thread: C2000WARE

Hello,

I am trying to syncronize 2 ePWM blocks for a specific phaseshift.

I am using the ePWM blocks from the C2000 blockset.

I have modified the following example to suit my case:

Using Time-Base Counter Synchronization to Synchronize ePWMs and eCAPS - MATLAB & Simulink - MathWorks Switzerland

I have attached the modified model *.slx and the *.m files for your reference.

“modi_f2837x_TimeBaseSync.slx”

“modi_c28xgetPhaseOffsetValue_modi.m”

My objective is to vary the phase between 2 ePWM blocks, in my case ePWM1 & ePWM4 in the "Up-Down" counting mode.

The examples provided seem to work fine for “Up” or “Down” Counting mode, i,e I see the correct phaseshift between ePWM1 and ePWM4 for different values for phaseDelay = 90, 120,180 etc.,

But in the case of “Up-Down” Counting mode, the phase-shift between ePWM1 and ePWM4. Is indeterministic/unpredictable.

Testcase:

TimePeriod = 2.5e-6;

duty_cycle = 50%;

cpuFrequency = 200MHz;

epwmFrequency = 200MHz;

phaseDelay = 180;

The screen shot shows the measurement done on PWM1A & PWM4A @ 100MS/sec with a logic analyzer, also cross checked with at CRO.

over 2 years ago

0 Pradeep Braun over 2 years ago

Prodigy 30 points

A wrong model was attached previously. Please use this model for test etc..

0 Ryan Ma over 2 years ago

TI__Mastermind 21046 points

Hi Pradeep,

It is not recommended to have your PWM frequency to be 200Mhz for F2837xD but should be instead set to 100Mhz.

For up-down counting mode, are your action qualifiers the same as in up count mode or down count mode?

Best,

Ryan Ma

0 Pradeep Braun over 2 years ago in reply to Ryan Ma

Prodigy 30 points

Hi Ryan,

100Mhz ? Okay I have set the EPWM clock divider to SYSCLK/2 now.

No, the action qualifiers is modified according to up-down mode. i,e. its set when counter = CMPA on up-count and cleared when counter = CMPA on down-count..for all other cases do-nothing.

0 Ryan Ma over 2 years ago in reply to Pradeep Braun

TI__Mastermind 21046 points

When are you sending out a synchronization pulse? What are your TBPRD and TBPHS values?

Best,

Ryan Ma

0 Pradeep Braun over 2 years ago in reply to Ryan Ma

Prodigy 30 points

For ePWM1 : TBPHS = 0; and TBPRD = 250;

and for ePWM4 : TBPHS = 125(expect a 180deg phaseshift between ePWM1 & ePWM4); and TBPRD = 250;

0 Ryan Ma over 2 years ago in reply to Pradeep Braun

TI__Mastermind 21046 points

Hi Pradeep,

Have you tried importing our C2000WARE example 3 synchronization? You can change the counter mode to be up-down count and should observe a phase shift of 180 degrees.

Best,

Ryan Ma

0 Pradeep Braun over 2 years ago in reply to Ryan Ma

Prodigy 30 points

Hi Ryan,

sorry, I am not sure which 3rd example you are referering to. By the way I have figured out to achieve 0-180 degrees(or the positive angles)...And then 181-360 degrees now can only be achieved by manually changing the ‘Counting direction after phase synchronization’ to 'countUpaftersyc'. But is there a better way to achieve the negative angles(181 to 360 degrees) Or complete 0-360 at one go.

regards,

Pradeep

+1 Ryan Ma over 2 years ago in reply to Pradeep Braun

TI__Mastermind 21046 points

Hi Pradeep,

Great to hear, and for your second question that is how you will need to achieve the negative angles (181-360).

Best,

Ryan Ma

0 Ryan Ma over 2 years ago in reply to Ryan Ma

TI__Mastermind 21046 points

Hi Pradeep,

I am going to close this thread.

Best,

Ryan Ma

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LAUNCHXL-F28379D: ePWM phaseshift(or phasedelay) between ePWM1 & ePWMx not predicatble in the ""Up-Down" Counting mode