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I am trying to use 2x UARTs with ChibiOS on the STM32F072RB Nucleo Board.

I initialized UART2 but I am still getting output on UART1 pins, which is totally weird.

#include "ch.h"
#include "hal.h"


/*
 * UART driver configuration structure.
 */
static UARTConfig uart_cfg_1 = {
    NULL,   //txend1,
    NULL,   //txend2,
    NULL,   //rxend,
    NULL,   //rxchar,
    NULL,   //rxerr,
    800000,
    0,
    0,      //USART_CR2_LINEN,
    0
};

static UARTConfig uart_cfg_2 = {
    NULL,   //txend1,
    NULL,   //txend2,
    NULL,   //rxend,
    NULL,   //rxchar,
    NULL,   //rxerr,
    800000,
    0,
    0,
    0
};

/*
 * Application entry point.
 */
int main(void) {

  /*
   * System initializations.
   * - HAL initialization, this also initializes the configured device      drivers
   *   and performs the board-specific initializations.
   * - Kernel initialization, the main() function becomes a thread and the
   *   RTOS is active.
   */
  halInit();
  chSysInit();

  /*
   * Activates the serial driver 1, PA9 and PA10 are routed to USART1.
   */
  //uartStart(&UARTD1, &uart_cfg_1);
  uartStart(&UARTD2, &uart_cfg_2);

  palSetPadMode(GPIOA, 9, PAL_MODE_ALTERNATE(1));  // USART1 TX.
  palSetPadMode(GPIOA, 10, PAL_MODE_ALTERNATE(1)); // USART1 RX.
  palSetPadMode(GPIOA, 2, PAL_MODE_ALTERNATE(1));  // USART2 TX.
  palSetPadMode(GPIOA, 3, PAL_MODE_ALTERNATE(1));  // USART2 RX.

  /*
   * Starts the transmission, it will be handled entirely in background.
   */
  //uartStartSend(&UARTD1, 13, "Starting...\r\n");
  uartStartSend(&UARTD2, 13, "Starting...\r\n");

  /*
   * Normal main() thread activity, in this demo it does nothing.
   */
  while (true) {
    chThdSleepMilliseconds(500);
    uartStartSend(&UARTD2, 7, "Soom!\r\n");
    //uartStartSend(&UARTD1, 7, "Boom!\r\n");
  }
}

The line uartStartSend(&UARTD2, 7, "Soom!\r\n"); gives output on UART1.

Is there anything else I need to do?

mcuconfig.h reads

#define STM32_UART_USE_USART1               TRUE
#define STM32_UART_USE_USART2               TRUE
#define STM32_UART_USART1_IRQ_PRIORITY      3
#define STM32_UART_USART2_IRQ_PRIORITY      3
#define STM32_UART_USART1_DMA_PRIORITY      0
#define STM32_UART_USART2_DMA_PRIORITY      0
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  • $\begingroup$ So if you uncomment both uartStartSend(&UARTD2, 7, "Soom!\r\n"); and uartStartSend(&UARTD1, 7, "Boom!\r\n");, you get both outputs on UART1? $\endgroup$
    – Ian
    Jan 4, 2016 at 21:48
  • $\begingroup$ USART2 also available on PA14 and PA15 pins, you should try those too. $\endgroup$
    – Bence Kaulics
    May 4, 2016 at 8:44
  • $\begingroup$ The best option was to use a custom proto board to avoid all those conflicts. Thanks for the suggestion. CHeers $\endgroup$
    – user2967920
    May 10, 2016 at 9:39
  • 1
    $\begingroup$ @user2967920, you can add a new answer with more details, and later accept it! That would help others with similar problem in the future. $\endgroup$
    – Shahbaz
    Jun 3, 2016 at 20:37
  • $\begingroup$ @user2967920 - Did you ever resolve this? $\endgroup$
    – Chuck ♦
    Dec 21, 2018 at 19:19

1 Answer 1

Reset to default
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Perhaps try UART3? UART2 might be in use for something else as the manual says,

"By default the USART2 communication between the target MCU and ST-LINK MCU is enabled..." on page 23, section 5.8.

Manual for reference

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  • $\begingroup$ UART2 Is shared with the STLnk BUS, so i am trying to get UART3 to work. I am stuck in a unhandled exception phase now need to sort out the vector tables and isr numbers. $\endgroup$
    – user2967920
    Jul 3, 2015 at 13:31

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