Rt1021 timer DMA mode PWM output problem feedback

[StarMao159376]

MCU: RT1021CAG4A;  Timer:  QTMR2; PWM: 50KHz

During the test, the duty cycle of 10% to 90% is sent. When setting the value of updateddutycycle to change the PWM output duty cycle, it is found that the PWM waveform transmitted one value at a time is normal, that is, the positive duty cycle increases and the negative duty cycle decreases. However, when transmitting an array containing 9 duty cycle values, the positive duty cycle changes normally while the negative duty cycle remains unchanged

[StarMao159376]

[diego_charles · Accepted solution]

Hi @StarMao159376 

I am very sorry for the delayed response   , I have not been able to reproduce the behavior that you are showing ,  using latest SDK v 2.11 and my RT1020 Rev A0. In  my side,  duty cycle remains unchanged. I also prepared an array with respective duty  cycles and increased the transfer size to 18 bytes. 

However in your code I noted that you are using the same DMA channel for updating the low and high duty cycles and also , that one transfer is made after the other.

I can see that you are able to  increase the high duty cycle, so I recommend you using 2 DMA channels per each compare loader register (CMPLD1 and CMPLD2) and trigger DMA transfers for both at the same time , see RT1050_DMA_example.c attached. This one was made by one of my colleagues in this thread for the RT1050

If you are still facing issues , I want  to get to the bottom of this, could you share me your complete main.c file for review, and specify me your SDK version?

Best regards, 

Diego.

[StarMao159376]

Thanks,  Solved my problem

[diego_charles]

Hi @StarMao159376 

Thanks for the detailed reply!  I will try to replicate on my side and get back to you as soon as I can. 

Diego.

[diego_charles]

Hi @StarMao159376 

I want to replicate the behavior you are  reporting. It seems that the PWM frequency increases , correct? As negative duty cycle does not decrease while positive duty cycle does.

Could you share with me  your project?  or  a representative  code snippet that you used ? This to check your settings.

Also, are you using the qtmr_inputcapture_outputpwm_dma SDK example as a reference? 

Many thanks for your patience,

Diego.