Timer 2 PWM and DMA not working

[yoma1993]

Posted on May 27, 2015 at 01:16The original post was too long to process during our migration. Please click on the attachment to read the original post.

[Tesla DeLorean]

Posted on May 27, 2015 at 01:33

Ok, you can't make random associations between TIM and DMA

TIM2_UP is DMA1 Channel 2 per RM0008 You could associate TIM2_CH3 (CC3) with DMA1 Channel 1, but I wouldn't advise that.

[Tesla DeLorean]

Posted on May 27, 2015 at 01:41

Specifically, not

TIM_DMACmd(TIM2, TIM_DMA_CC1, ENABLE); // CC3 ? 

Pulse = 0; // Something >=1

[yoma1993]

Posted on May 27, 2015 at 02:07

Thanks clive1, I knew it was something stupid! Is there a reason why you would not recommend the TIM2CH3 and DMA1CH1 combo? is there another combo you would recommend? 

Edit: Just for clarification for other users, the issue was resolved by changing the following.DMA_InitStruct.DMA_PeripheralBaseAddr = (uint32_t)&TIM2->CCR1; toDMA_InitStruct.DMA_PeripheralBaseAddr = (uint32_t)&TIM2->CCR3; and TIM_DMACmd(TIM2, TIM_DMA_CC1, ENABLE); toTIM_DMACmd(TIM2, TIM_DMA_CC3, ENABLE);

[Tesla DeLorean]

Posted on May 27, 2015 at 02:20

I prefer the Update trigger. With CCx you're going to have to be careful about the preload mode, and if you just advance the current count vs the next iteration of the timer period.

At the end of the day it might come down to the TIM/DMA resources you have available.

[yoma1993]

Posted on May 27, 2015 at 02:38

I see. This is my first time using DMA so i'll have to read up on that later. In the mean time i need to figure out how to get the PWM wave working properly for these LEDs. Thanks so much for your help!

[yoma1993]

Posted on May 27, 2015 at 05:37

Can someone explain why im getting impulses instead of a PWM signal?

Here is a picture: 

http://i.imgur.com/QNntfWf.png

[Tesla DeLorean]

Posted on June 01, 2015 at 07:16

I'm pretty sure 50 K sample per second is not going to do well with a signal at 800 KHz, try 2 MSps