Phase shift issue in pwm generation

[skuma.8]

Hii everyone,

I am working on an inverter application . trying to implement unipolar pwm in the center-aligned mode 2. I am using DMA for the buffer transmission for the sine-wave PWM. Everything seems well without the pwm synchronization. i am initializing DMA one by one

 

 

 

	HAL_TIM_PWM_Start_DMA(&htim1, TIM_CHANNEL_1, (uint32_t*) pwmData0, 20000);
	HAL_TIM_PWM_Start_DMA(&htim1, TIM_CHANNEL_2, (uint32_t*) pwmData1, 20000);

 

 

 

and at the output the second phase is lagging by 5-6 pwm pulses. time period for 1 pwm pulse is 10us. 

Here is the snap of logic analyzer.

According to the post USING MASTER SLAVE CONFIG issue still remains the same.

Any suggestion would be highly appreciable.

ThankYou.

[TDK]

Not sure HAL is going to support starting everything at the same time, you might need to write your own code to do this. Probably if you set up the timer as a slave in gated mode, ran those functions, then started the master timer it would work using HAL functions.

[skuma.8]

Hi TDK ! ,

by "Not sure HAL is going to support starting everything at the same time", do yo mean i'll have to switch over bare-metal?

[TDK]

Potentially. Or use another timer as master and have this one in gated mode.

In any case, it's expected that the code you wrote starts one channel at a time.

[MasterT]

What is uCPU? 

 AFAIK most of ST micro supports DMA Burst Mode, so you don't need two dma channels, (likely two channels have delay in between transactions)

just one channel that updates two consequtive CCR1 & CCR2 registers (could be more than 2 if necessary).  Read Reference Manual for more details. 

Also set Autopreload option to gurantee channels simultanenous updates at timer TRGO event.