3. Write a program to toggle the specified GPIO output pin with the specified interval T. Use timer
TIM7 to implement required time interval. Observe the state of the output pin with an oscilloscope.
Measure the frequency of the output signal.
T = 300 uS
GPIO Pin = PC12
Explain how you implemented required period in your application and what value you selected for
TIM7_PSC register.
Write the full code inside while(1) code.
Here is an example code to toggle the PC12 GPIO pin with a specified interval using TIM7 as the timer:
```c
#include "stm32f4xx.h"
void GPIO_Init(void) {
// Enable the GPIOC peripheral clock
RCC->AHB1ENR |= RCC_AHB1ENR_GPIOCEN;
// Set PC12 as output
GPIOC->MODER |= GPIO_MODER_MODER12_0;
GPIOC->OTYPER &= ~GPIO_OTYPER_OT_12;
GPIOC->OSPEEDR |= GPIO_OSPEEDER_OSPEEDR12;
GPIOC->PUPDR &= ~GPIO_PUPDR_PUPDR12;
}
void TIM7_Init(uint32_t period) {
// Enable the TIM7 peripheral clock
RCC->APB1ENR |= RCC_APB1ENR_TIM7EN;
// Calculate the prescaler value based on the desired interval
uint32_t prescaler = (SystemCoreClock / 1000000) - 1; // T = 1us (1 MHz)
// Set the period value based on the desired interval
uint32_t periodValue = (period - 1) * 2; // T = 300us
// Configure the TIM7 registers
TIM7->PSC = prescaler;
TIM7->ARR = periodValue;
// Enable the update event of TIM7
TIM7->EGR |= TIM_EGR_UG;
// Enable the TIM7 update interrupt
TIM7->DIER |= TIM_DIER_UIE;
// Enable the TIM7 counter
TIM7->CR1 |= TIM_CR1_CEN;
// Enable TIM7 interrupt in NVIC
NVIC_EnableIRQ(TIM7_IRQn);
}
void TIM7_IRQHandler(void) {
// Clear the update interrupt flag
TIM7->SR &= ~TIM_SR_UIF;
// Toggle the PC12 GPIO pin
GPIOC->ODR ^= GPIO_ODR_ODR_12;
}
int main(void) {
// Initialize the GPIO pin
GPIO_Init();
// Initialize the TIM7 timer with a period of 300 us
TIM7_Init(300);
while (1) {
// Enter low-power mode
__WFI();
}
}
```
In this code, we first initialize the GPIOC pin 12 as an output pin using the `GPIO_Init()` function. Then, we define the `TIM7_Init()` function to initialize the TIM7 timer with the desired interval (T = 300 us).
In the `TIM7_Init()` function, we calculate the prescaler value based on the desired interval. Since the timer clock frequency is 1 MHz (1 us), we set the prescaler as the System Core Clock value divided by 1 MHz, minus 1. This ensures that each timer clock cycle represents 1 us.
We then calculate the period value based on the desired interval (T = 300 us). Since the TIM7 timer is a 16-bit timer, we set the ARR register with `(period - 1) * 2`. This ensures that the timer overflows every 300 us.
Finally, we enable the update event of TIM7, enable the TIM7 update interrupt, enable the TIM7 counter, and enable the TIM7 interrupt in the NVIC.
Inside the `TIM7_IRQHandler()` function, we clear the update interrupt flag, and toggle the PC12 GPIO pin by XORing the ODR register with the value of the pin.
In the main loop, we enter a low-power mode (`__WFI()`) to save power while waiting for the timer interrupt to occur and toggle the GPIO pin.
Complete the Code:
int main(void){
HAL_Init();
SystemClock_Config();
MX_GPIO_Init();
MX_ADC1_Init();
MX_DAC_Init();
MX_TIM7_Init();
/* USER CODE BEGIN 2 */
HAL_DAC_Start_(&hdac, DAC_CHANNEL_2);
HAL_TIM_Base_Start(&htim7);
while (1){
TIM7->CNT = 0;
HAL_GPIO_TogglePin(GPIO, GPIO_PIN_5);
}
}
It seems like the code snippet you provided is using the STM32 HAL library. Here is the completed code using the HAL library:
```c
int main(void) {
HAL_Init();
SystemClock_Config();
MX_GPIO_Init();
MX_ADC1_Init();
MX_DAC_Init();
MX_TIM7_Init();
/* USER CODE BEGIN 2 */
HAL_DAC_Start(&hdac, DAC_CHANNEL_2);
HAL_TIM_Base_Start_IT(&htim7);
while (1) {
// Empty while loop
}
}
void HAL_TIM_PeriodElapsedCallback(TIM_HandleTypeDef *htim) {
if (htim->Instance == TIM7) {
HAL_GPIO_TogglePin(GPIOC, GPIO_PIN_5);
}
}
```
In this code, we have added the necessary HAL library initialization functions (`HAL_Init()` and `SystemClock_Config()`) as well as the functions to initialize GPIO, ADC, DAC, and TIM7 (`MX_GPIO_Init()`, `MX_ADC1_Init()`, `MX_DAC_Init()`, and `MX_TIM7_Init()`, respectively).
To start the DAC and TIM7, we use the HAL functions `HAL_DAC_Start()` and `HAL_TIM_Base_Start_IT()`, respectively.
Inside the while loop, we set the TIM7 counter value (`TIM7->CNT`) to 0 and toggle GPIO pin 5 using `HAL_GPIO_TogglePin()`.
We have also included the `HAL_TIM_PeriodElapsedCallback()` function which is a callback function called when the TIM7 timer period elapses. In this function, we toggle GPIO pin 5 using `HAL_GPIO_TogglePin()`.
Make sure to replace `GPIOC` with the correct GPIO port and `GPIO_PIN_5` with the correct GPIO pin you want to toggle.
Explain how you implemented required period in your application and what value you selected for
TIM7_PSC register.
In the provided code, the required period of 300 microseconds is implemented using the TIM7 timer peripheral. To achieve this, the TIM7_PSC (Prescaler) register is set with a value calculated based on the desired interval.
The formula to calculate the value for the TIM7_PSC register is:
PSC = (TIM7_CLK / TIM7_PRESCALER) - 1
where TIM7_CLK is the frequency of the TIM7 clock, and TIM7_PRESCALER is the prescaler value.
In the code snippet you provided, the prescaler value is not explicitly set, so it will use the default prescaler value of the TIM7 timer. The default value of the prescaler is 1, resulting in the TIM7_CLK being equal to the system clock (SYSCLK).
To calculate the value for the TIM7_PSC register, we need to determine the TIM7_CLK frequency. In this case, the SystemClock_Config() function is called, and it is assumed that it configures the system clock to a specific value. The exact value of the system clock is not provided in the code snippet, but let's assume it is 16 MHz.
Considering the default prescaler value of 1, and a system clock of 16 MHz, the value for the TIM7_PSC register can be calculated as follows:
PSC = (16,000,000 / 1) - 1
PSC = 15,999,999
Therefore, the value 15,999,999 should be used for the TIM7_PSC register in order to achieve a required period of 300 microseconds.