DMA multi-using problem

[weiwei liu]

Posted on October 24, 2017 at 11:30

I use STM32F103, DMA1->CH6

USART2 RX and TIM3 TIM3_CH1 both can use this channel.

If only 

USART2 RX or TIM3 

TIM3_CH1 to use this channel,it is ok!

but how to multi use for two request?

thank you very much.

[waclawek.jan]

Posted on October 29, 2017 at 16:03

You can't.

Couldn't you use a different channel of TIM3, mapping to different DMA channel?

JW

[weiwei liu]

Posted on October 30, 2017 at 09:45

TIM3_CH1

 request only map to DMA channel 6.

[S.Ma]

Posted on October 30, 2017 at 09:58

Before I design a board schematic, I print the alternate function table and the DMA channel tables to make sure there is no conflicts. Now this is done by CubeMX to avoid challenges ahead.

Use a different timer channel or different time or a different usart, if the pinout is compatible.

[weiwei liu]

Posted on October 30, 2017 at 10:13

Thank you, I will re-design

board schematic.

[waclawek.jan]

Posted on October 30, 2017 at 10:36

Based on that picture I assume you have already occupied channel2 to channel 7.

Can't you use TIM4_CH1 or TIM2_CH3 for the DMA, maybe without redesign of the board, for example employing timer chaining in some way?

JW

[weiwei liu]

Posted on November 04, 2017 at 11:00

hehe, you are right. Actually, from ch1 to ch7, all be used!

Instead, use interrupt to handle request.

[bernieserver]

Hello, we are currently having the same problem on an STM32F427. We want use 5 UARTS, ADC1 and one SPI interfaces togehter with DMA and now we have a stream collision.

Is it possible to share a stream by examining the channel (reading CHSEL bits) on the ISR of corresponding stream to get the hardware instance relating to the channel? We are using the STM32F4 HAL

[waclawek.jan]

> Is it possible to share a stream

Not simultaneously, i.e. in the same time.

USARTs are usually slow enough so that they can be comfortably handled by interrupts.

JW