Set up two clock sources with an STM32F103?

Question

As above really. I'd like to set up two clock signals on my STM32F103 for external circuits, one at 4 MHz and the other at 2 MHz.

Here's what I've tried so far, but I'm not measuring any signal at all at the appropriate pins (PA0 and PA6.) What am I doing wrong?

#include "main.h"
#include "stm32f1xx_hal.h"

TIM_HandleTypeDef htim2;
TIM_HandleTypeDef htim3;

UART_HandleTypeDef huart2;

void SystemClock_Config(void);
static void MX_GPIO_Init(void);
static void MX_TIM3_Init(void);
static void MX_USART2_UART_Init(void);
static void MX_TIM2_Init(void);
static void MX_NVIC_Init(void);                                    
void HAL_TIM_MspPostInit(TIM_HandleTypeDef *htim);

int main(void)
{
  HAL_Init();

  /* Configure the system clock */
  SystemClock_Config();

  /* Initialize all configured peripherals */
  MX_GPIO_Init();
  MX_TIM3_Init();
  MX_USART2_UART_Init();
  MX_TIM2_Init();

  /* Initialize interrupts */
  MX_NVIC_Init();

  /* Infinite loop */
  while (1)
  {
        // Flash the LED twice a second to show we're alive
        HAL_Delay(800);

        /* Turn on LED for 50 ms */
        HAL_GPIO_WritePin(GPIOC, GPIO_PIN_13, GPIO_PIN_RESET);
        HAL_Delay(50);
        HAL_GPIO_WritePin(GPIOC, GPIO_PIN_13, GPIO_PIN_SET);

        HAL_Delay(100);

        /* Turn on LED for 50 ms */
        HAL_GPIO_WritePin(GPIOC, GPIO_PIN_13, GPIO_PIN_RESET);
        HAL_Delay(50);
        HAL_GPIO_WritePin(GPIOC, GPIO_PIN_13, GPIO_PIN_SET);
  }

}

/*
* System Clock Configuration
*/
void SystemClock_Config(void)
{

  RCC_OscInitTypeDef RCC_OscInitStruct;
  RCC_ClkInitTypeDef RCC_ClkInitStruct;

    /*
        *Initialise the CPU, AHB and APB bus clocks 
    */
  RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSE;
  RCC_OscInitStruct.HSEState = RCC_HSE_ON;
  RCC_OscInitStruct.HSEPredivValue = RCC_HSE_PREDIV_DIV1;
  RCC_OscInitStruct.HSIState = RCC_HSI_ON;
  RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
  RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSE;
  RCC_OscInitStruct.PLL.PLLMUL = RCC_PLL_MUL2;
  if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK)
  {
    _Error_Handler(__FILE__, __LINE__);
  }

    /*
        *Initialise the CPU, AHB and APB bus 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_DIV1;
  RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV1;

  if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_0) != HAL_OK)
  {
    _Error_Handler(__FILE__, __LINE__);
  }

    /*
        *Configure the Systick interrupt time 
    */
  HAL_SYSTICK_Config(HAL_RCC_GetHCLKFreq()/1000);

    /*
        *Configure the Systick 
    */
  HAL_SYSTICK_CLKSourceConfig(SYSTICK_CLKSOURCE_HCLK);

  /* SysTick_IRQn interrupt configuration */
  HAL_NVIC_SetPriority(SysTick_IRQn, 0, 0);
}

/*
* NVIC Configuration
*/
static void MX_NVIC_Init(void)
{
  /* USART2_IRQn interrupt configuration */
  HAL_NVIC_SetPriority(USART2_IRQn, 0, 0);
  HAL_NVIC_EnableIRQ(USART2_IRQn);
}

/* TIM2 init function */
/* 4 MHz clock output */
static void MX_TIM2_Init(void)
{

  TIM_ClockConfigTypeDef sClockSourceConfig;
  TIM_MasterConfigTypeDef sMasterConfig;
  TIM_OC_InitTypeDef sConfigOC;

  htim2.Instance = TIM2;
  htim2.Init.Prescaler = 1;
  htim2.Init.CounterMode = TIM_COUNTERMODE_UP;
  htim2.Init.Period = 0;
  htim2.Init.ClockDivision = TIM_CLOCKDIVISION_DIV1;
  htim2.Init.AutoReloadPreload = TIM_AUTORELOAD_PRELOAD_DISABLE;
  if (HAL_TIM_Base_Init(&htim2) != HAL_OK)
  {
    _Error_Handler(__FILE__, __LINE__);
  }

  sClockSourceConfig.ClockSource = TIM_CLOCKSOURCE_INTERNAL;
  if (HAL_TIM_ConfigClockSource(&htim2, &sClockSourceConfig) != HAL_OK)
  {
    _Error_Handler(__FILE__, __LINE__);
  }

  if (HAL_TIM_OC_Init(&htim2) != HAL_OK)
  {
    _Error_Handler(__FILE__, __LINE__);
  }

  sMasterConfig.MasterOutputTrigger = TIM_TRGO_RESET;
  sMasterConfig.MasterSlaveMode = TIM_MASTERSLAVEMODE_DISABLE;
  if (HAL_TIMEx_MasterConfigSynchronization(&htim2, &sMasterConfig) != HAL_OK)
  {
    _Error_Handler(__FILE__, __LINE__);
  }

  sConfigOC.OCMode = TIM_OCMODE_FORCED_ACTIVE;
  sConfigOC.Pulse = 0;
  sConfigOC.OCPolarity = TIM_OCPOLARITY_HIGH;
  sConfigOC.OCFastMode = TIM_OCFAST_DISABLE;
  if (HAL_TIM_OC_ConfigChannel(&htim2, &sConfigOC, TIM_CHANNEL_1) != HAL_OK)
  {
    _Error_Handler(__FILE__, __LINE__);
  }

  HAL_TIM_MspPostInit(&htim2);

}

/* TIM3 init function */
/* 2 MHz clock output */
static void MX_TIM3_Init(void)
{

  TIM_ClockConfigTypeDef sClockSourceConfig;
  TIM_MasterConfigTypeDef sMasterConfig;
  TIM_OC_InitTypeDef sConfigOC;

  htim3.Instance = TIM3;
  htim3.Init.Prescaler = 7;
  htim3.Init.CounterMode = TIM_COUNTERMODE_UP;
  htim3.Init.Period = 0;
  htim3.Init.ClockDivision = TIM_CLOCKDIVISION_DIV1;
  htim3.Init.AutoReloadPreload = TIM_AUTORELOAD_PRELOAD_DISABLE;
  if (HAL_TIM_Base_Init(&htim3) != HAL_OK)
  {
    _Error_Handler(__FILE__, __LINE__);
  }

  sClockSourceConfig.ClockSource = TIM_CLOCKSOURCE_INTERNAL;
  if (HAL_TIM_ConfigClockSource(&htim3, &sClockSourceConfig) != HAL_OK)
  {
    _Error_Handler(__FILE__, __LINE__);
  }

  if (HAL_TIM_OC_Init(&htim3) != HAL_OK)
  {
    _Error_Handler(__FILE__, __LINE__);
  }

  sMasterConfig.MasterOutputTrigger = TIM_TRGO_RESET;
  sMasterConfig.MasterSlaveMode = TIM_MASTERSLAVEMODE_DISABLE;
  if (HAL_TIMEx_MasterConfigSynchronization(&htim3, &sMasterConfig) != HAL_OK)
  {
    _Error_Handler(__FILE__, __LINE__);
  }

  sConfigOC.OCMode = TIM_OCMODE_FORCED_ACTIVE;
  sConfigOC.Pulse = 0;
  sConfigOC.OCPolarity = TIM_OCPOLARITY_HIGH;
  sConfigOC.OCFastMode = TIM_OCFAST_DISABLE;
  if (HAL_TIM_OC_ConfigChannel(&htim3, &sConfigOC, TIM_CHANNEL_1) != HAL_OK)
  {
    _Error_Handler(__FILE__, __LINE__);
  }

  HAL_TIM_MspPostInit(&htim3);

}

/* USART2 init function */
/* For serial communication */
static void MX_USART2_UART_Init(void)
{

  huart2.Instance = USART2;
  huart2.Init.BaudRate = 62500;
  huart2.Init.WordLength = UART_WORDLENGTH_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(__FILE__, __LINE__);
  }

}

static void MX_GPIO_Init(void)
{

  GPIO_InitTypeDef GPIO_InitStruct;

  /* GPIO Ports Clock Enable */
  __HAL_RCC_GPIOC_CLK_ENABLE();
  __HAL_RCC_GPIOD_CLK_ENABLE();
  __HAL_RCC_GPIOA_CLK_ENABLE();
  __HAL_RCC_GPIOB_CLK_ENABLE();

  /*Configure GPIO pin Output Level */
  HAL_GPIO_WritePin(LED_GPIO_Port, LED_Pin, GPIO_PIN_RESET);

  /*Configure GPIO pin : LED_Pin */
  GPIO_InitStruct.Pin = LED_Pin;
  GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
  GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
  HAL_GPIO_Init(LED_GPIO_Port, &GPIO_InitStruct);

  /*Configure GPIO pins : PC14 PC15 */
  GPIO_InitStruct.Pin = GPIO_PIN_14|GPIO_PIN_15;
  GPIO_InitStruct.Mode = GPIO_MODE_ANALOG;
  HAL_GPIO_Init(GPIOC, &GPIO_InitStruct);

  /*Configure GPIO pins : PA1 PA4 PA5 PA7 
                           PA8 PA9 PA10 PA11 
                           PA12 PA13 PA14 PA15 */
  GPIO_InitStruct.Pin = GPIO_PIN_1|GPIO_PIN_4|GPIO_PIN_5|GPIO_PIN_7 
                          |GPIO_PIN_8|GPIO_PIN_9|GPIO_PIN_10|GPIO_PIN_11 
                          |GPIO_PIN_12|GPIO_PIN_13|GPIO_PIN_14|GPIO_PIN_15;
  GPIO_InitStruct.Mode = GPIO_MODE_ANALOG;
  HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);

  /*Configure GPIO pins : PB0 PB1 PB2 PB10 
                           PB11 PB12 PB13 PB14 
                           PB15 PB3 PB4 PB5 
                           PB6 PB7 PB8 PB9 */
  GPIO_InitStruct.Pin = GPIO_PIN_0|GPIO_PIN_1|GPIO_PIN_2|GPIO_PIN_10 
                          |GPIO_PIN_11|GPIO_PIN_12|GPIO_PIN_13|GPIO_PIN_14 
                          |GPIO_PIN_15|GPIO_PIN_3|GPIO_PIN_4|GPIO_PIN_5 
                          |GPIO_PIN_6|GPIO_PIN_7|GPIO_PIN_8|GPIO_PIN_9;
  GPIO_InitStruct.Mode = GPIO_MODE_ANALOG;
  HAL_GPIO_Init(GPIOB, &GPIO_InitStruct);

}

void _Error_Handler(char * file, int line)
{
  while(1) 
  {
  }
}

#ifdef USE_FULL_ASSERT

void assert_failed(uint8_t* file, uint32_t line)
{

}

#endif

EDIT: Some more info on my current setup

nockieboy · Accepted Answer · 2018-01-19 11:52:52Z

Okay, timing considerations aside (thanks for the help @charansai), I've found out what the issue was with the lack of PWM output by trawling tutorials and examples.

I was missing the code to actually start the PWM output in the first place. The code below, added into the USER CODE BEGIN 2 section just before entering the 'infinite while loop', fixes the issue and gives me an output I can measure and subsequently adjust the timings:

HAL_TIM_Base_Start(&htim4);
HAL_TIM_PWM_Start(&htim4,TIM_CHANNEL_1);  // Start PWM signal on Pin PB6

Obviously the code above refers to Timer4 which I was using to debug the issue. I've now got a nice visual output via an LED, so I know it's working and can move on to working out exact settings for the 2 and 4 MHz outputs.

charansai · Accepted Answer · 2018-01-18 15:05:22Z

0

A quick look at your code, tells me that you have not configured the timers correctly! I am not sure what's your system clock, but if it's 8MHz according to your TIM2 configuration(4MHz*(Prescaler+1)), then you will not get 2MHz with TIM3 configuration as it will be 8MHz/(7+1) i.e 1Mhz.

Again your both Timer period configurations are 0 and AutoReloadPreload configurations are disabled! That means, the Timers will count from 0 to 1(timer_period_value+1) and stop counting!! In general, it is needed to use a proper period value rather than just 0!

If you would like to make the timer clock 4MHz for a system clock of 64MHz, you can use Prescaler value as 0, Period value as 15 i.e 64/4 = 16 = (0-15) and enable auto-reload attribute!

Finally, go through this and read how to configure the Timers!

answered Jan 18, 2018 at 15:05

charansai

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1

\$\begingroup\$ Is that the only issue with the set up though? I've set AutoReloadPreload to ENABLE and Counter Period to 65535 and there's still no signal at the appropriate pin.. :/ \$\endgroup\$
– nockieboy
Commented Jan 18, 2018 at 16:00
\$\begingroup\$ What's your Timer clock frequency and System clock frequency? \$\endgroup\$
– charansai
Commented Jan 18, 2018 at 16:02
\$\begingroup\$ and have you understood how the timer frequency is adjusted? If you randomly put period value 65535, you should accordingly check for the very low-frequency signal and how are you checking the clock signal?? \$\endgroup\$
– charansai
Commented Jan 18, 2018 at 16:35
\$\begingroup\$ I've added some more pictures in the original question to answer your questions (and hopefully provide some more information.) I've been reading up on the Timers and have adjusted the parameters accordingly - i.e. I'm now trying to use PWM output, with a clock of 48 MHz, prescaler of 0 and counter period of 11, should give me: 48/1/12 = 4 MHz? Still got nothing on the output pins... Checking for signal using an oscilloscope. \$\endgroup\$
– nockieboy
Commented Jan 18, 2018 at 17:14
\$\begingroup\$ So, your pwm pulse value is 6. I hope you have considered that in the calculations! But if you are not at all getting any signal output on the pin, then try checking time_base generation using interrupts. Simply try blinking a LED by scaling down the timer frequency to an appropriate value so that blinking can be perceived. Refer this post for further details. I will also provide PWM controlled LED program that I have written for STM32f407 soon, cross check all the configurations with it! It should work! \$\endgroup\$
– charansai
Commented Jan 18, 2018 at 17:47

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