UART printing gibbersh to TeraTerm

[NicRoberts]

NUCLEO F767ZI, CubeIDE 2.1.1, CubeMX 6.17.0

I'm trying to set up UART with printf()

#include <stdio.h>

UART_HandleTypeDef huart3;
static void MX_USART3_UART_Init(void);

int __io_putchar(int ch)
{
 HAL_UART_Transmit(&huart3, (uint8_t *)ch, 1, 10);
 return ch;
}

....
// in main
// in while
prinf("UART test\r\n");

// MX generated USART3 init
static void MX_USART3_UART_Init(void)
{

 /* USER CODE BEGIN USART3_Init 0 */

 /* USER CODE END USART3_Init 0 */

 /* USER CODE BEGIN USART3_Init 1 */

 /* USER CODE END USART3_Init 1 */
 huart3.Instance = USART3;
 huart3.Init.BaudRate = 115200;
 huart3.Init.WordLength = UART_WORDLENGTH_8B;
 huart3.Init.StopBits = UART_STOPBITS_1;
 huart3.Init.Parity = UART_PARITY_NONE;
 huart3.Init.Mode = UART_MODE_TX_RX;
 huart3.Init.HwFlowCtl = UART_HWCONTROL_NONE;
 huart3.Init.OverSampling = UART_OVERSAMPLING_16;
 huart3.Init.OneBitSampling = UART_ONE_BIT_SAMPLE_DISABLE;
 huart3.AdvancedInit.AdvFeatureInit = UART_ADVFEATURE_NO_INIT;
 if (HAL_UART_Init(&huart3) != HAL_OK)
 {
 Error_Handler();
 }
 /* USER CODE BEGIN USART3_Init 2 */

 /* USER CODE END USART3_Init 2 */

}

 

Clock tree from MX

 

Output in Tera Term window

 

TT is set up exactly the same as the UART init in the code.

Anyone know whats going on here?

[mƎALLEm]

Hello,

You have set a wrong HSE clock value to 25MHz:

You need to set it to 8MHz as the ST-LINK-V2 MCO output on that Nucleo board is 8MHz

[NicRoberts]

Still gibberish

[mƎALLEm]

Did you regenerate the code, compile it with that config and upload the application to the MCU?

[Andrew Neil]

Gibberish on a terminal is almost always due to wrong baud rate.

As @mƎALLEm said, if you enter the wrong value for the HSE clock frequency, then your baud rate will be wrong - as will any other frequencies derived from HSE.

[mƎALLEm]

And what if you select HSI as clock source instead of HSE?:

If it's working, that means definetly you have an issue with HSE, a missing solder bridge on STLINK MCO output path or something similar. If not, you have an issue with TeraTerm UART configuration.

[NicRoberts]

No not working with HSI either

 

Settings in TT are the same as in the USART3 init. (I've also tried RealTerm & get the same gibberish there too)

[mƎALLEm]

Configure the data lenght in Tera term to 7 bit instead of 8 bit.

This is the example from CubeF7 https://github.com/STMicroelectronics/STM32CubeF7/blob/master/Projects/STM32F767ZI-Nucleo/Examples/UART/UART_Printf/

that suggests in its readme file that you need to set the datalenght to 7 bit:

This is what was said in a comment the example code: Word Length = 8 Bits (7 data bit + 1 parity bit)

 /* UART configured as follows:
 - Word Length = 8 Bits (7 data bit + 1 parity bit) : 
	 BE CAREFUL : Program 7 data bits + 1 parity bit in PC HyperTerminal
 - Stop Bit = One Stop bit
 - Parity = ODD parity
 - BaudRate = 9600 baud
 - Hardware flow control disabled (RTS and CTS signals) */
 UartHandle.Instance = USARTx;

 UartHandle.Init.BaudRate = 9600;
 UartHandle.Init.WordLength = UART_WORDLENGTH_8B;
 UartHandle.Init.StopBits = UART_STOPBITS_1;
 UartHandle.Init.Parity = UART_PARITY_ODD;
 UartHandle.Init.HwFlowCtl = UART_HWCONTROL_NONE;
 UartHandle.Init.Mode = UART_MODE_TX_RX;
 UartHandle.Init.OverSampling = UART_OVERSAMPLING_16;
 if (HAL_UART_Init(&UartHandle) != HAL_OK)
 {
 /* Initialization Error */
 Error_Handler();
 }

 This is apart of the wrong HSE frequency value you set in CubeMx: 25MHz instead of 8MHz (the issue I raised in a previous post).

Hope that helps

[NicRoberts]

@mƎALLEm 
OK found it after comparison with the reference code linked above. user error (when isn't it) it turns out I wasn't retargeting the printf function correctly. A missing ampersand in the data passed to the UART_transmit function,

 

int __io_putchar(int ch)
{
 HAL_UART_Transmit(&huart3, (uint8_t *)&ch, 1, 10);
 return ch;
}

 

[mƎALLEm]

---

@NicRoberts wrote:

int __io_putchar(int ch)
{
 HAL_UART_Transmit(&huart3, (uint8_t *)&ch, 1, 10);
 return ch;
}

 

---

Sorry I didn't understand your feedback. What is the difference between the retargeting printf you have shared now and what you have shared in your original post? I don't see any difference!: 

int __io_putchar(int ch)
{
 HAL_UART_Transmit(&huart3, (uint8_t *)ch, 1, 10);
 return ch;
}

 

[Andrew Neil]

---

@mƎALLEm wrote:

What is the difference

Before After:

HAL_UART_Transmit(&huart3, (uint8_t *)&ch, 1, 10);
 ^-- Here!

 

After Before:

HAL_UART_Transmit(&huart3, (uint8_t *)ch, 1, 10);
 ^-- Here!

 

@NicRoberts so the problem was that you were actually sending gibberish to the terminal!

 

This is exactly why I always recommend to get direct comms working first - before adding the extra complications of printf redirection!

---

Edited to correct 'Before' & 'After'

[CTapp.1]

One of those mistakes that we've probably all made that take forever to spot as you read what you thought you had typed when looking at the code ;)

Something that static analysis can help with on a good day.

[Andrew Neil]

Unfortunately, the mistake was masked by the (uint8_t*) cast - without that, you'd have got a compiler warning...

[CTapp.1]

---

@Andrew Neil wrote:

Unfortunately, the mistake was masked by the (uint8_t*) cast - without that, you'd have got a compiler warning...

---

GCC does generate a warning for it: