I ran printf over UART but the results were not displayed in Tera Term

[t-oka]

Hello everyone

I'm using stm32f207ztg6 and want to do printf using UART, but it doesn't show up in Tera Term.
How can I solve this problem?

■ Program used

// *-*-*↓main()-*-*-*-*-*-*-*-*-*-*-*-*
setbuf(stdout, NULL);
while (1)
{
/* USER CODE END WHILE */
printf("Hello World\r\n");
HAL_Delay(1000);
/* USER CODE BEGIN 3 */
}
// *-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*

int _write(int file, char *ptr, int len)
{
HAL_UART_Transmit(&huart2,(uint8_t *)ptr,len,10);
return len;
}

static void MX_USART2_UART_Init(void)
{

/* USER CODE BEGIN USART2_Init 0 */ /* USER CODE END USART2_Init 0 */ /* USER CODE BEGIN USART2_Init 1 */ /* USER CODE END USART2_Init 1 */ huart2.Instance = USART2; huart2.Init.BaudRate = 115200; huart2.Init.WordLength = UART_W ORDLENGTH_8B; huart2.Init.StopBits = UART_STOPBITS_1; huart2.Init.Parity = UART_PARITY_NONE; huart2.Init.Mode = UART_MODE_TX_RX; huart2.Init.HwFlowCtl = UART_HWCONTROL_NONE; huart2.Init.OverSampling = UART_OVERSAMPLING_16;
if (HAL_UART_Init(&huart2) != HAL_OK)
{
Error_Handler();
}
/* USER CODE BEGIN USART2_Init 2 */

/* USER CODE END USART2_Init 2 */

}

■STLink: STLink Virtual COM Port

■Situation
When HAL_UART_Transmit is executed, HAL_OK is returned, but nothing is displayed in "Tera Term".

[SofLit]

Hello,

You didn’t tell which board you are using?

[t-oka]

Hello!
I am using a Nucleo board.

[Andrew Neil]

Which Nucleo board?

Please see the posting tips - including how to properly post source code:

https://community.st.com/t5/community-guidelines/how-to-write-your-question-to-maximize-your-chances-to-find-a/ta-p/575228

Before adding the complications of printf, have you got this working by just doing the HAL_UART_Transmit direct?

If that doesn't work then, clearly, printf is never going to work!

Also note that stdout is line-buffered - ie, the output won't appear until you send a newline...

PS:

https://community.st.com/t5/stm32cubeide-mcus/retarget-printf-on-stm32g070rbxx-cortex-m0/m-p/721066/highlight/true#M30729

[SofLit · Accepted solution]

Hello @t-oka ,

First, before starting the printf usage over UART, you need to validate the UART transmission by for example just sending a couple of characters using HAL_UART_Transmit().

Second, you need always to check the schematics or board's user manual before suspecting an issue in the FW.

According to the schematics of MB1137 the UART instance connected to STLink-VCP on NUCLEO-F207ZG (MB1137) is USART3 and not USART2:

So you need to select USART3 instead of USART2

Refer to this printf example. on NUCLEO-F207

Hope it helps.

[t-oka]

I was able to solve the problem with the help of your schematic and example.
Thanks.

>You should always check the schematic or the board's user manual before suspecting a FW problem.
→You're right...
Also, see the tips in your posting - how to properly post source code, etc:
I'll be careful about that too.

[Andrew Neil]

---

@t-oka wrote:

>You should always check the schematic or the board's user manual before suspecting a FW problem.

---

That's probably the key difference between embedded C (particularly on small microcontrollers), and C on "big" systems (Linux, Windows, et al) - you need to understand the hardware context.

See also:

https://community.st.com/t5/stm32-mcus-embedded-software/ds18b20-sensor-detection-via-one-wire-1-wire-protocol/m-p/729960/highlight/true#M55863

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