STM32L476RG SPI gap between transmission

[anonymous.020721_1050]

Posted on April 27, 2017 at 09:20

Hello all,

I'm trying to setup the STM32L476RG via SPI with an external DAC (SPI clock speed: 40MHz). I used the HAL_SPI_Transmit() function to transmit a 24Bit word.After one transmission there is a gap of 2.5�s befour the new transmission starts. For my application I need a fast transmission. Is there a posibility to purge the gap?

Thank you in advance,

Fabian

#stm32l4 #spi #spi-bus #gap

[AvaTar]

Posted on April 27, 2017 at 13:48

You might need to show relevant part of your code, this is definitely not a hardware/peripheral issue.

Profiling and measuring your application would be even better.

[Tesla DeLorean]

Posted on April 27, 2017 at 17:37

Tell HAL_SPI_Transmit() to send multiple words, better still look at the code behind-the-curtain, the HAL permits/enables a whole circus of stupidity. Avoid.

[DOSS FOF]

Posted on May 19, 2017 at 17:26

Hello Clive ,

Do you manage to resolve this issue ?

[Tesla DeLorean]

Posted on May 19, 2017 at 20:05

Not my issue, no time invested in it here.

[S.Ma]

Posted on May 21, 2017 at 11:13

When high baud rate is needed, use dma with its interrupts on the rx dma side only. Then the isr will define the pause time between packets transmission.

[DOSS FOF]

Posted on May 21, 2017 at 13:16 The original post was too long to process during our migration. Please click on the provided URL to read the original post. https://st--c.eu10.content.force.com/sfc/dist/version/download/?oid=00Db0000000YtG6&ids=0680X000006I6sJ&d=%2Fa%2F0X0000000bx5%2FSoZzDulIWYalRUkJ_kbRaezKGcaixocsT0EVyg1sWCo&asPdf=false

[S.Ma]

Posted on May 22, 2017 at 01:07

Spi requires 2 dma streams, one for tx and one for rx. It seems only one declared here.

[DOSS FOF]

Posted on May 22, 2017 at 01:23

Even though I don't receive any message (transmission only). 

[waclawek.jan]

Posted on May 22, 2017 at 12:13

         DMA1_init_struct.Instance->CMAR = Txdata;    // Specify memory address that contains data to transmit.

            DMA1_init_struct.Instance->CPAR  = SPI1->DR;    // Data register of the SPI peripheral to read received data.            DMA1_init_struct.Instance->CNDTR = 16;            // Number of elements to receive (our buffers consist of 8 byte elements)            DMA1_init_struct.Instance->CCR   |= DMA_CCR_EN|DMA_CCR_TCIE|DMA_CCR_HTIE  ; // Enable the DMA stream

I don't use Cube but I'd say you are supposed to use some prescribed incantation rather directly manipulate the DMA registers. In other words, I wouldn't mix the two approaches.

            DMA1_init_struct.Instance->CPAR  = SPI1->DR;    // Data register of the SPI peripheral to read received data.

You want to take the address of data register, not its content.

JW