ADuC841 PWM: random full duty cycle periode

Hi Federico,

I haven't encountered anything similar to your problem, but you can zip your code and send it to me. I'll try to look at it if anything in the code is causing the issue.

What is the blue signal you are measuring?

Regards,
Karl

Hi Karl, How are you?

Thanks for your immediate response! 

Unfortunately software can't be shared because of proprietaries limitations.

What i can assure is that PWM0L and PWM0H are loaded by a PI controller with an anti blow up limit, so those values are never greater than PWM1 which isn't modified once it is configured. 

What you are seeing in blue is the Base - Emitter signal from the IGBT controlled with the PWM. It represents perfectly how PWM should be working until the spurious full duty cycle periode. 

Regards.

Federico D. Ceccarelli

Hi Karl, How are you?

Thanks for your immediate response! 

Unfortunately software can't be shared because of proprietaries limitations.

What i can assure is that PWM0L and PWM0H are loaded by a PI controller with an anti blow up limit, so those values are never greater than PWM1 which isn't modified once it is configured. 

What you are seeing in blue is the Base - Emitter signal from the IGBT controlled with the PWM. It represents perfectly how PWM should be working until the spurious full duty cycle periode. 

Regards.

Federico D. Ceccarelli

Hi Federico,

Can you share the register configurations for the PWM?

Can you check if the part is resetting or if any pins are being reconfigured?

Regards,

Karl

Hi Karl, 

My PWM registers configurations are

CFG841 = 0x50;          // Set PWM on pins P3.3/P3.4
PWMCON = 0x93           // Enable PWM on Mode 1

// FOSC = 14.7456 MHz, RATED_FREQ = 12000 Hz        
// PWM1H = FOSC [Hz] / RATED_FREQ [Hz];
PWM1H = 0x04;
PWM1L = 0xCD;

PWM0H = 0x00;
PWM1L = 0x28; 

The part definitely isn't resetting, this would be a massive disaster for hardware because it is handling power. 

We reconfigure P3.3 as a GPIO to set PWM duty cycle to 100% 0 when disabled but that is something I have double and triple checked to be sure the system weren't reconfiguring pin when we don't want it. What is also strange to me is that the fail occurs only on one PWM period.

Do you think that any other pin reconfiguration could cause a PWM fail like that? 

Regards

Federico D. Ceccarelli

You mentioned that the failure occurs only in one PWM period. Does this mean that it only happens once during the entire testing?

Is there anything else configured aside from the PWM registers during your testing? Are you using any other functionality of the device?

Other pin reconfiguration should not have any effect on the PWM.

Hello Mark, sorry for the delay. 

You mentioned that the failure occurs only in one PWM period. Does this mean that it only happens once during the entire testing?

The malfunctioning occurs periodically during the test. It doesn't happen only once. It is something that keeps happening all the time but I found it happens on a stochastic way. 

What I'm trying to say is that calls my attention that the full duty cycle error appears only on one pwm period and in the immediate next periode pwm duty cycle counts correctly. I imagine that pwm's counter register is resetting or overflowing or something like that. 

Is there anything else configured aside from the PWM registers during your testing? Are you using any other functionality of the device?

Yes, I'm using ADC by pulling, SPI, GPIOs, UART.

Regards, 

Federico D. Ceccarelli

Hi Federico, can you try testing the PWM alone without the other functionality to see if the PWM flip occurs? You can try adding the other functionality later, one by one, to test which may trigger the issue.

Are you also using an ADuC841 evaluation board, or are you already using your design in your current setup?

Regards,
Karl

Hello Karl, 

Sorry for the delay. I ran out of time to continue testing and moved on to a new project. Hopes to have some new updates about topic in future time.

Are you also using an ADuC841 evaluation board, or are you already using your design in your current setup?

The testing was done over a proprietary board on the current setup.

Regards.

Federico D. Ceccarelli