7.Interrupt Concept and Usage

Interrupt Concept and Usage

Interrupts are special functions that interrupt the flow of a microcontroller and perform a specific action when a particular event occurs. This is an important concept that interrupts the normal flow of the microcontroller and allows the execution of a prioritized task.

Why are Interrupts Used?

Interrupts can be used in a variety of useful scenarios. For example:

1. Temporal Operations: Interrupts can be used when a specific operation needs to be performed within a defined time frame. This is commonly used to organize scheduled tasks and improve timing accuracy.

2. Monitoring External Events: External hardware events can trigger interrupt functions. For example, pressing a button or exceeding a certain threshold for sensor signals.

3. Data Transmission: Interrupts can be used in asynchronous data transmissions such as serial communications. This allows processing of incoming data without interrupting the main flow.
   

Examples of Interrupt Usage

For example, let's consider a simple application where an LED should illuminate when a button is pressed:

1. Hardware Connection: Connect a button and an LED. The button is connected as an input and the LED as an output to the microcontroller.

2. Software Configuration: The GPIO pin connected to the button is configured for interrupt function. This allows the microcontroller to perform a specific action when the state of the button changes.

3. Definition of Interrupt Function: An interrupt function is defined. This function toggles the state of the LED when the state of the button changes.

4. Main Program: The main program typically runs in an endless loop. This loop can perform other tasks alongside the interrupt function.

5. Waiting for Interrupt Trigger: The main program does not continuously monitor the interrupt function. Instead, the microcontroller responds to events (such as pressing a button) via interrupts and waits for a specific event to occur.
   

Points to Consider When Using Interrupts

1. Priority and Continuity: The priority and continuity of interrupts must be managed properly. Care should be taken if critical tasks can be interrupted by interrupt functions.

2. Simplicity of Interrupt Function: Interrupt functions should be as simple and fast as possible. Complex operations within interrupts can negatively impact the overall performance of the microcontroller.

3. Efficiency of Interrupt Functions: Interrupt functions should be used efficiently. Unnecessary or frequently triggered interrupts can waste the resources of the microcontroller.
   

Interrupts are an important concept in microcontrollers and are used in a variety of applications. When properly configured, interrupts can improve system performance, reduce power consumption, and overall enhance the efficiency of microcontroller-based applications.

Interrupt functions in the HAL (Hardware Abstraction Layer) used in STM32 microcontrollers are employed to respond to external factors (hardware or software events) and typically play a significant role in the usage of various peripherals. Here are the commonly used interrupt functions and their explanations in the STM32 HAL library:

1.GPIO Interrupt Functions (External Interrupts):

HAL_GPIO_EXTI_IRQHandler(): This function is called when an interrupt occurs on GPIO interrupt lines. It is used by software to determine which pin was triggered.

2.USART Interrupt Functions:

HAL_UART_TxCpltCallback(): This function is called when transmission over USART (serial communication) is completed. It is particularly used in asynchronous data transmission (UART).

HAL_UART_RxCpltCallback(): This function is called when reception over USART is completed. It is used to process the received data.

3.SPI Interrupt Functions:

HAL_SPI_TxRxCpltCallback(): This function is called when SPI transmission and reception are completed. It is used to process the transmitted and received data.

I2C Interrupt Functions:

HAL_I2C_MasterTxCpltCallback(): This function is called when transmission of the master device over I2C is completed. It is used by applications that send data from the master device.

HAL_I2C_MasterRxCpltCallback(): This function is called when reception of the master device over I2C is completed. It is used by applications that receive data from the master device.

4.Timer Interrupt Functions:

HAL_TIM_PeriodElapsedCallback(): This function is called when the timer period elapses. It is used for periodic operations in timer-based applications.

These functions inform the microcontroller about interrupts through the HAL library and are called when certain events occur. This enables the application to dynamically respond to specific events and interact with peripherals. These interrupt functions can be customized to meet application requirements and typically serve as the basic building blocks for handling interrupts.

5.ADC Interrupt Functions:

HAL_ADC_ConvCpltCallback(): This function is called when ADC conversion is completed. It is used to convert analog signals to digital values.

DAC Interrupt Functions:

HAL_DAC_ConvCpltCallback(): This function is called when DAC conversion is completed. It is used to convert digital data to analog signals.

RTC Interrupt Functions:

HAL_RTC_AlarmAEventCallback(): This function is called when the RTC (Real-Time Clock) alarm event occurs. It is triggered when a specified time is reached.

HAL_RTCEx_WakeUpTimerEventCallback(): This function is called when the RTC wake-up timer event occurs. It is used to wake up from sleep mode.

DMA Interrupt Functions:

HAL_DMA_XferCpltCallback(): This function is called when DMA (Direct Memory Access) transfer is completed. It is used to transfer data between memories or between peripherals and memories.

These interrupt functions are used to control the operation of various peripherals and handle interrupt events. Each of them performs a specific function when a particular event occurs. These functions enable the microcontroller to interact with various components and support a wide range of applications.