Jitter in PWM HWI due to TI/BIOS timer interrupt.

Christian Fuchs1

Other Parts Discussed in Thread: TMS320F28377S

Hi.

I'm using TI/BIOS 2.16.1.14, XDCtools v3.32.0.06_core on a TMS320F28377S.

I see a PWM HWI jitter of ~5us like described in this thread: https://e2e.ti.com/support/embedded/tirtos/f/355/p/493492/2023327#2023327

Now I know that the TI/BIOS timer interrupt causes this jitter, and it disappears if I disable the interrupt with "BIOS.clockEnabled = false;. But this is no option for my project. So, how else can I reduce the jitter?

Can I configure the TI/BIOS timer HWI that way it can be preemted by the PWM HWI?

Thank you

Christian

over 8 years ago

0 Alan DeMars over 8 years ago

TI__Mastermind 30830 points

Have you configured your PWM interrupt to be a "Zero Latency" interrupt as described here:

If your PWM ISR has no interaction with BIOS (ie does not post a Semaphore or Swi), you can configure it to never (almost never) be disabled by BIOS.

Alan

0 Christian Fuchs1 over 8 years ago in reply to Alan DeMars

Expert 1250 points

Hi Alan.

No I didn't. If I do, is it still interuptable by other interrupts (like SDFM). Because this is the reason why I made a PWM interrupt as HWI and not directly plugged as ISR.

Thank you

Christian

0 Alan DeMars over 8 years ago in reply to Christian Fuchs1

TI__Mastermind 30830 points

It is only interruptible if you re-enable interrupts within your ISR. The C28x hardware automatically disables interrupts during the fetch and jump to the interrupt vector. The Zero Latency interrupt is not managed by BIOS, which means that your ISR is vectored to directly.

Alan

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Jitter in PWM HWI due to TI/BIOS timer interrupt.