stm32CubeMX stm32f407 discovery printf doesn't work

[nikola1010]

Posted on December 15, 2015 at 10:46

Hi all,

trying to retarget printf on stm32f407 discovery with cubemx generated code isn't working. Inside main.c i've put:

/**

  * @brief  Retargets the C library printf function to the USART.   * @param  None   * @retval None   */ int fputc(int ch, FILE *f){   /* Place your implementation of fputc here */   /* e.g. write a character to the USART */   HAL_UART_Transmit(&huart6,(uint8_t*)&ch,1,1);// 1 tick waiting (1ms) enough for 87us/byte at 115200   return ch; }

HAL_UART_Transmit

works without problem on it's own, printf doesn't output. Could anyone help  please?

[markb]

Posted on December 15, 2015 at 11:03 Hi, Perhaps printf() doesn't use fputc() for its output? I am providing an implementation of _write(fd, buf, count) which sends the output to USB CDC and printf works fine. Cheers, Mark

[nikola1010]

Posted on December 15, 2015 at 13:56

Thanks for hint!

I did the same and it works. Here is the code for others: int _write( int file, char *ptr, int len ){     int i;     for(i = 0 ; i < len ; i++){         HAL_UART_Transmit(&huart6,(uint8_t*)&ptr[i],1,10);     }     char ch='\r';     HAL_UART_Transmit(&huart6,(uint8_t*)&ch,1,10); }

[gaurav2]

Posted on June 08, 2016 at 19:07

Hello all,

I am trying to get the UART output (send some character strings over UART via USB CDC class). My code is based upon CubeF0 codebase and HAL and USB_Device CDC class.USBD_HandleTypeDef USBD_Device;extern UART_HandleTypeDef UartHandle;void main(void){   uint8_t ch = 'a';    HAL_Init();    SystemClock_Config();      /* Init Device Library */    USBD_Init(&USBD_Device, &VCP_Desc, 0);      /* Add Supported Class */    USBD_RegisterClass(&USBD_Device, &USBD_CDC);      /* Add CDC Interface Class */    USBD_CDC_RegisterInterface(&USBD_Device, &USBD_CDC_fops);      /* Start Device Process */    USBD_Start(&USBD_Device);        while (1) {        status = HAL_UART_Transmit(&UartHandle, (uint8_t *)&ch, 1, 10);    }}However, nothing comes out on the Hyper-terminal connected on Windows. The HAL_Transmit_UART is going through but I fear that somehow the UART transmit data struct is not connected to the USB CDC class buffer and/or some DMA issue. I don't want to use DMA but not sure how to just be in polling mode and if the UART (huart->Instance->TDR) in stmf0xx_hal_uart.c is really giving the character to the CDC.I think that USB CDC class transmits a packet in the USBD_CDC_TransmitPacket() function where it calls      USBD_LL_Transmit(pdev, CDC_IN_EP, hcdc->TxBuffer, hcdc->TxLength);Do I instead need to use HAL_UART_Transmit_IT() to transmit in interrupt mode for USB to recognize that data is pending? Otherwise I don't see how the HAL_UART_Transmit() connects to USB CDC. The _IT() version seems to connect via the UserTxBuffer[].Any pointers in making progress will help me. Thanks.