stm32f411 spi4 low clock speed

[mcufan]

Hello!

I have problem with spi4 clock speed. I want to drive a lcd tft display but spi clock is max 500Khz, baudrate prescaler set to SPI_BAUDRATEPRESCALER_2. Is very weird. Initial setup was made with CubeMX to 48Mbit/s. APB2 clock is set to 96Mhz. I tried with dma, and without hal but the speed remains the same

What is the cause of this very low spi clock output speed?

[Tesla DeLorean]

Your clocks are wrong?

printf("%d\n", SystemCoreClock);

Output internal clock via MCO/PA8 and scope that against SPI Clock, and attach.

[mcufan]

Is not wrong. HSE_VALUE = 8000000

i check with assert in early main. The SystemCoreClock is 16000000 but not think is a problem, if i set to 8000000 the spi working the same

[Tesla DeLorean]

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

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

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

Make sure to clear the initialization structures for the SPI4

[mcufan]

with printf:

HCLK=16000000

APB1=1000000

APB2=1000000

what do you mean clear the initialization structures for the SPI4?

[Tesla DeLorean]

So SPI4 clock half of APB clock. Not sure why we are at 1 MHz for those.

​

= {0​}; // clears auto variables on stack

[mcufan]

here my clock config:

void SystemClock_Config(void)

{

 RCC_OscInitTypeDef RCC_OscInitStruct = {0};

 RCC_ClkInitTypeDef RCC_ClkInitStruct = {0};

 RCC_PeriphCLKInitTypeDef PeriphClkInitStruct = {0};

 /**Configure the main internal regulator output voltage 

 */

 __HAL_RCC_PWR_CLK_ENABLE();

 __HAL_PWR_VOLTAGESCALING_CONFIG(PWR_REGULATOR_VOLTAGE_SCALE1);

 /**Initializes the CPU, AHB and APB busses clocks 

 */

 RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSE;

 RCC_OscInitStruct.HSEState = RCC_HSE_BYPASS;

 RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;

 RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSE;

 RCC_OscInitStruct.PLL.PLLM = 4;

 RCC_OscInitStruct.PLL.PLLN = 192;

 RCC_OscInitStruct.PLL.PLLP = RCC_PLLP_DIV4;

 RCC_OscInitStruct.PLL.PLLQ = 8;

 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_PLLCLK;

 RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1;

 RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV4;

 RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV1;

 if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_3) != HAL_OK)

 {

  Error_Handler();

 }

 PeriphClkInitStruct.PeriphClockSelection = RCC_PERIPHCLK_I2S;

 PeriphClkInitStruct.PLLI2S.PLLI2SN = 200;

 PeriphClkInitStruct.PLLI2S.PLLI2SM = 5;

 PeriphClkInitStruct.PLLI2S.PLLI2SR = 2;

 if (HAL_RCCEx_PeriphCLKConfig(&PeriphClkInitStruct) != HAL_OK)

 {

  Error_Handler();

 }

}

[waclawek.jan]

> spi clock is max 500Khz,

And you know that how?

JW

[mcufan]

no idea..

the HAL_RCC_GetPCLK2Freq() give me 1000000Hz

very strange..

[waclawek.jan]

And what's the actual SPI clock, as measured on the SCK pin?

JW

[waclawek.jan]

Read out and check/post the relevant RCC register's content.

Do you use any bootloader?

JW

[mcufan]

I use stm32f411 disco board, the actual spi clk frequency measured with logic analyzer is exactly 500Khz

[mcufan]

I use stm32f411 disco board. The spi sck pin freq. is 500khz measured with logic analyzer