Button Interrupt Usage Instructions

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Introduction

The main function of this routine is to realize the external interrupt through the KEY on the board. When USER_KEY is pressed, the state of LED_G(Green) is changed.

RA8 Series MCU Interrupt System Overview

The RA8 series MCU has the following interrupt features:

  1. NVIC (Nested Vectored Interrupt Controller)

    • Supports nested interrupts: higher-priority interrupts can preempt lower-priority ones.

    • Supports priority grouping (Preemption Priority and Subpriority).

    • IRQn numbers are mapped to the interrupt vector table, and the NVIC calls the corresponding ISR.

  2. GPIO External Interrupt (EXTI)

    • Each GPIO pin can be configured as an external interrupt input.

    • Supports rising edge, falling edge, or both-edge triggers.

    • Interrupt channels are managed by the ICU (Interrupt Controller Unit).

    • Can be configured via Renesas FSP or directly through low-level registers.

    • Provides low-latency response, suitable for buttons, sensors, and other event-driven applications.

  3. RT-Thread PIN Driver Model

    • GPIOs are encapsulated as PIN devices in RT-Thread.

    • Provides a unified interface:

      • rt_pin_mode(pin, mode): configure pin as input or output.

      • rt_pin_read(pin) / rt_pin_write(pin, value): read or write GPIO.

      • rt_pin_attach_irq(pin, mode, callback, args): register an interrupt callback.

      • rt_pin_irq_enable(pin, enable): enable or disable interrupts.

Reference: RT-Thread PIN Device

Using the RT-Thread PIN driver allows interrupt handling without directly accessing the NVIC or MCU registers.

Hardware Description

As shown in the figure below, the USER_KEY pin is connected to the P110 pin of the microcontroller, and the KEY button is pressed for low level and released for high level.

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The position of the KEY in the development board is shown as follows:

image-20250905132707880

FSP Configuration

  • First, download the official FSP code generation tool:

​ https://github.com/renesas/fsp/releases/download/v6.0.0/setup_fsp_v6_0_0_rasc_v2025-04.1.exe

  • Once installed, double-click on the rasc.exe in eclipse and open the configuration file configuration.xml in the Titan_basic_key_irq project directory:

  • Let’s add two stacks: New Stack->Input->External IRQ(r_icu)：

image-20250728115209730

  • Next we need to enable the IRQ feature in the pin config. Select the interrupt pin we want to enable as shown in the following screenshot: USER_KEY(IRQ20) :

image-20250728115408487

  • Back in the Stacks interface, set IRQ20, and configure the interrupt name, channel number, and interrupt callback function:

image-20250728115641528

Example Code Description

The source code for this routine is located at /project/Titan_basic_key_irq.

The microcontroller pin corresponding to USER_KEY is defined as follows:

/* Configure key IRQ pins */
#define KEY_PIN     BSP_IO_PORT_01_PIN_10 /* Onboard KEY pins */

LED灯的单片机引脚定义如下:

/* Configure LED pins */
#define LED_PIN_B   BSP_IO_PORT_00_PIN_12 /* Onboard LED pins */
#define LED_PIN_G   BSP_IO_PORT_06_PIN_13 /* Onboard LED pins */

The source code for the keypress interrupt is located at /project/Titan_basic_key_irq/src/hal_entry.c. When the USER_KEY key is pressed, the green LED is turned on and off.

#define LED_PIN_B   BSP_IO_PORT_00_PIN_12 /* Onboard LED pins */
#define LED_PIN_G   BSP_IO_PORT_06_PIN_13 /* Onboard LED pins */
#define KEY_PIN     BSP_IO_PORT_01_PIN_10 /* Onboard KEY pins */

volatile rt_bool_t flag = 0;

void key_callback(void)
{
    if (flag)
        rt_pin_write(LED_PIN_G, PIN_HIGH);
    else
        rt_pin_write(LED_PIN_G, PIN_LOW);

    flag = flag ? RT_FALSE : RT_TRUE;
}

void hal_entry(void)
{
    rt_kprintf("\nHello RT-Thread!\n");
    rt_kprintf("==================================================\n");
    rt_kprintf("This example project is a key routine!\n");
    rt_kprintf("==================================================\n");

    LOG_I("Tips:");
    LOG_I("You can press the button to run the test case for button interruption.");
    LOG_I("Use the buttons to control the on/off state of the green LED.");

    rt_pin_mode(KEY_PIN, PIN_MODE_INPUT_PULLUP);
    rt_pin_attach_irq(KEY_PIN, PIN_IRQ_MODE_FALLING, key_callback, RT_NULL);
    rt_pin_irq_enable(KEY_PIN, PIN_IRQ_ENABLE);

    while (1)
    {
        rt_pin_write(LED_PIN_B, PIN_HIGH);
        rt_thread_mdelay(1000);
        rt_pin_write(LED_PIN_B, PIN_LOW);
        rt_thread_mdelay(1000);
    }
}

Compilation & Download

  • RT-Thread Studio: In RT-Thread Studio’s package manager, download the Titan Board resource package, create a new project, and compile it.

After compiling, connect the development board’s USB-DBG interface to the PC and download the firmware to the development board.

Run Effect

Press the reset button to restart the development board. LED_G in the initial state is in the light off state. When the USER_KEY is pressed, the light off state of LED_G(Green) will change.

image-20250728114755783