Usart4 no TX

[stenasc]

Posted on May 15, 2017 at 10:40

Hi Forum,

I'm using the stm32f091RCt6, (LQFP64) to set up USART4

Kind Regards

Bob

  USART_InitTypeDef USART_InitStructure;

  GPIO_InitTypeDef GPIO_InitStructure;  NVIC_InitTypeDef NVIC_InitStructure;  // Enable GPIOC clock   RCC_AHBPeriphClockCmd(RCC_AHBPeriph_GPIOC, ENABLE);   // Enable USART3 APB clock   RCC_APB1PeriphClockCmd(RCC_APB1Periph_USART4, ENABLE);        // Connect pin to Periph  GPIO_PinAFConfig(GPIOC, GPIO_PinSource10, GPIO_AF_0);   //  USART4 TX  GPIO_PinAFConfig(GPIOC, GPIO_PinSource11, GPIO_AF_0);   //  USART4 RX   // Configure pins as AF pushpull   GPIO_InitStructure.GPIO_Pin = GPIO_Pin_10 | GPIO_Pin_11;  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;  GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;  GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;  GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_DOWN;  GPIO_Init(GPIOC, &GPIO_InitStructure);        USART_InitStructure.USART_BaudRate = 9600;  USART_InitStructure.USART_WordLength = USART_WordLength_8b;  USART_InitStructure.USART_StopBits = USART_StopBits_1;  USART_InitStructure.USART_Parity = USART_Parity_No;  USART_InitStructure.USART_HardwareFlowControl = USART_HardwareFlowControl_None;  USART_InitStructure.USART_Mode = USART_Mode_Rx | USART_Mode_Tx;  USART_Init(USART4, &USART_InitStructure);      USART_Cmd(USART4, ENABLE);       //  Enable the COM4 Receive interrupt: this interrupt is generated when the//  COM4 receive data register is not empty   USART_ITConfig(USART4, USART_IT_RXNE, ENABLE);

  // USART4 IRQ Channel configuration

  NVIC_InitStructure.NVIC_IRQChannel = USART3_8_IRQn;   

  NVIC_InitStructure.NVIC_IRQChannelPriority = 1;

  NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;  NVIC_Init(&NVIC_InitStructure);

Although I can receive data I cannot get any TX at all.  I have usart1 and usart2 working fine. not sure what is is. I've buzzed out all the board connections and they are fine. Looking at the clock tree on page16 of the datasheet, I notice PCLK only goes to usart1, usart2 and usart3. Does usart4 need some aqlternative form of clocking? The datasheet really doesnt say to much about usarts4 to 8 and there are no app notes out there to refer to so i'm stuck at this point.

Thanks for any help.

Regards Bob

[Tesla DeLorean]

Posted on May 15, 2017 at 16:20

Check VDDIO2 pin

[Imen.D]

Posted on May 15, 2017 at 16:45

Check also your reference manual, it may help you on your USART configuration.

[Tesla DeLorean]

Posted on May 15, 2017 at 17:38

Not sure that's terribly helpful, on the surface of things the code doesn't appear unreasonable, is there some specific insight you can share?

[Tesla DeLorean]

Posted on May 15, 2017 at 17:39

Don't enable the IRQ, write a simple demo that tightly loops outputting a 'U' character. Double check the board, pin connectivity, etc. Not familiar with the board in question.

[stenasc]

Posted on May 15, 2017 at 23:25

VDDIO is at 3.3V. The following is my test code. I scope PC10 but see absolutely no activity at all. Changed boards but made no difference.

   send_test_string('aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa');

int send_test_string(unsigned char * byte)

{      for (;*byte;++byte)     {                   send_char (*byte);     }             return 1; }

void   send_char (uint8_t ch)

{

  USART_SendData(USART4, (uint8_t) ch);

  /* Loop until the end of transmission */

  while (USART_GetFlagStatus(USART4, USART_FLAG_TC) == RESET)      {}        }

[Tesla DeLorean]

Posted on May 16, 2017 at 00:27

Perhaps there is a design issue, I have neither the board nor the chip.

[Tesla DeLorean]

Posted on May 16, 2017 at 02:38

I would front check TXE rather than back check TC

[stenasc]

Posted on May 16, 2017 at 09:20

Hi Clive,

Yeah, I did try checking TXE before sending characters. it made no difference. Also disabled the RX IRQ, but again no difference. Will talk to H/W designer today to get a second opinion. This code was ported from a STM32f051 so possibly a conflict there.However, it compiles fine and everything else runs fine.

[stenasc]

Posted on May 16, 2017 at 10:18

Hi Clive,

Also tried driving PC10 High and Low. That works fine...I can see pulses on the scope.