How to speed up usart communication?

[Jakub B]

Posted on October 05, 2017 at 13:39

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[Tesla DeLorean]

Posted on October 05, 2017 at 13:59

Wouldn't call HAL_UART_Receive_DMA() blindly in a tight loop

ramka should be a volatile variable, also you don't clear it in the loop after processing the packet

[AvaTar]

Posted on October 05, 2017 at 14:02

I would use a less EMI-prone standard, like RS485 or RS422.

Your communication is package/message based, isn't it ?

Why do you call the CRC2 function on every byte, from an interrupt context ?

I have my problems understanding polish comments, though ...

[Jakub B]

Posted on October 05, 2017 at 14:12

1. ramka is cleared in mail loop after checking packet. so i wait for order, check its crc if i should process it farther, then checking what it wants me to do and then clear.

2. crc is calculated on 15/17 of final answer. last 2/17 are crc. I calculate it before sending answer in 2 parts. i copy part1 and move it to copy part2. Should i make a function for it outside of interrupt?

[Tesla DeLorean]

Posted on October 05, 2017 at 16:44

>>ramka is cleared in mail loop after checking packet

The placement seems to create a race condition, variable should be volatile.

Enabling of DMA also seems problematic, and prone to synchronization issues.

Try implementing with a simple USART IRQ method.

[Jakub B]

Posted on October 06, 2017 at 08:08

>>The placement seems to create a race condition, variable should be volatile

i'll try it

>>Enabling of DMA also seems problematic, and prone to synchronization issues.

with DMA i'm missing less  then without it, but issue is probably something else. I'll try changing it

[Jakub B]

Posted on October 05, 2017 at 14:29

Can you tell me how to clear buffer with this:

void

TM_USART_ClearBuffer

(

USART_TypeDef

*

USARTx

)

;

maybe if i clear it after each recieve it will be enough?

[Jakub B]

Posted on October 06, 2017 at 15:09

After 3 days i found a solution (or walkabout) for future reference.

/* Infinite loop */

  /* USER CODE BEGIN WHILE */

  while (1)

  {

        HAL_UART_Receive_DMA(&huart1, Received, 8); //start of listening

HAL_Delay(1);

   

        if (ramka==1){

            //przekierowanie rozkazu do funkcji

            switch(bufor[1]){

                case 4:{

                stany(); break;

                }

        }

    }

    ramka=0;

  /* USER CODE END WHILE */

i found out that when i send every 1 second order by hand it sometimes miss one or more answers, but if i send it quicker for example 5 times a sec it works perfectly. I figured that maybe there is some problem with time of creating answer so if i put a delay just outside of interrupt it might work..

And it did

[AvaTar]

Posted on October 06, 2017 at 15:38

Polling with delay is possibly a workaround for Cube/HAL code, but still a bad solution.

I would drop the Cube straitjacket alltogether and go for a clear interrupt-based solution, but it's not my project.

I stopped commenting on Cube code a while ago ...