HSI clock and baudrate ?

[antonius]

Dear Members,

I changed my clock from MSI to HSI but my SPI and UART baudrate becoming wrong,

What do I miss here ?

thanks

[S.Ma]

Only you can answer a question with so little details, except Sherlock maybe?

[antonius]

Is the answer here ?

https://www.st.com/content/ccc/resource/technical/document/application_note/group0/66/fa/62/a2/5c/75/48/a8/DM00327191/files/DM00327191.pdf/jcr:content/translations/en.DM00327191.pdf

[antonius]

Not good for me, it's not supported for STM32LX series :(

[Tesla DeLorean]

If you change clocks on ​the fly, you'll have to change dividers dependent on them also.

[antonius]

yes what value for divider ?

the setting for UART3

:

void MX_USART3_UART_Init(void)

{

 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;

 if (HAL_UART_Init(&huart3) != HAL_OK)

 {

   Error_Handler();

 }

}

[antonius]

clock

[S.Ma]

What do you want to do? Use HSI through PLL and generate the same SYSCLK 2.097 MHz default MSI frequency?

[antonius]

I want to use 16MHz HSI, but SPI2 and UART3 are misconfigured , working on 2.097MHz but not on HSI 16MHz, by the time I have 16MHz

any clues or same experiences ? thanks

[antonius]

I put on 32MHz, only USART3 can not work properly

I make :

   USART3->BRR = 32000000/115200;

Correct me ?

///

void MX_USART3_UART_Init(void)

{

 // Configure BRR by deviding the bus clock with the baud rate

 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;

   USART3->BRR = 32000000/115200;

 if (HAL_UART_Init(&huart3) != HAL_OK)

 {

   Error_Handler();

 }

}

[antonius]

Please correct my configuration ?

====

void MX_USART3_UART_Init(void)

{

 huart3.Instance = USART3;

   huart3.Instance->BRR=34;

 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_8;

 if (HAL_UART_Init(&huart3) != HAL_OK)

 {

   Error_Handler();

 }

}

=====

I read from :

[Tesla DeLorean]

I would decompose the clocks as seen of the AHB/APB. Print them out a USART that is working. Use the SWV channel if available.

HAL_UART_Init() is going to overwrite the value you put in BBR, and BBR might well be locked when the USART is enabled.

What bit rate do you see if you send 0x55 data patterns? You see anything at the pins?

Assuming the L152, any board we might be familiar with?

Drops into Error_Handler() ?

[antonius]

Assuming the L152, any board we might be familiar with?

Nucleo STM32L152RE

Drops into Error_Handler() ?

printf on my Error_Handler ? It's working with uart2, which is talking with GPS, but uart3 not working on a proper speed ??

0x55 pattern to uart3 ? and ping back ?

thanks

[antonius]

decomposing ? sounds advance for me, trying to figure it out on implementing it ...

Thanks

[Tesla DeLorean]

Starts by doing simple stuff

Like

 printf("Core=%d, %d MHz\n", SystemCoreClock, SystemCoreClock / 1000000);

 printf("HCLK=%d\n", HAL_RCC_GetHCLKFreq());

 printf("APB1=%d\n", HAL_RCC_GetPCLK1Freq());

 printf("APB2=%d\n", HAL_RCC_GetPCLK2Freq());

Outputting internal clocks via PA8 MCO and scoping them.

And then looking at RCC and peripheral settings in debugger, finding settings in the chain that look/are wrong.

[antonius]

On 2.097MHz :

[antonius]

On STM32CubeMX, it said, UART3 has a conflict, does it matter ?

[Tesla DeLorean]

Sorry I don't use CubeMX, what does the Reference Manual suggest are the connectivity modes here, and what pin conflicts are there. As presented you're showing with work with clock source X and failing with clock source Y

So I'd focus on the clock trees and sources, and determine is the clock routing is broken, for example you've selected a source that isn't present, or is at a different frequency.

Outputting a stream of 'U' characters (0x55) gives you something to measure on a scope. ie does something come out of the pin? is it the right frequency?

Try doubling or halving the baud rate you program whilst leaving the terminal at 115200. See data then?

[antonius]

the stable setting only :

/**
 * @brief System Clock Configuration
 * @retval None
 */
void SystemClock_Config(void)
{
 RCC_OscInitTypeDef RCC_OscInitStruct = {0};
 RCC_ClkInitTypeDef RCC_ClkInitStruct = {0};
 
 /**Configure the main internal regulator output voltage 
 */
 __HAL_PWR_VOLTAGESCALING_CONFIG(PWR_REGULATOR_VOLTAGE_SCALE1);
 /**Initializes the CPU, AHB and APB busses clocks 
 */
 RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_MSI;
 RCC_OscInitStruct.MSIState = RCC_MSI_ON;
 RCC_OscInitStruct.MSICalibrationValue = 0;
 RCC_OscInitStruct.MSIClockRange = RCC_MSIRANGE_5;
 RCC_OscInitStruct.PLL.PLLState = RCC_PLL_NONE;
 if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK)
 {
 Error_Handler();
 }
 /**Initializes the CPU, AHB and APB busses clocks 
 */
 RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_HCLK|RCC_CLOCKTYPE_SYSCLK
 |RCC_CLOCKTYPE_PCLK1|RCC_CLOCKTYPE_PCLK2;
 RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_MSI;
 RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1;
 RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV1;
 RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV1;
 
 if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_0) != HAL_OK)
 {
 Error_Handler();
 }
}