SAM4E MCU Tour - 6. LED Flashing Button Control-EEWORLD

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Now try controlling an LED with a button... make the LED light up when a button is pressed and turn off when it is released.

The main purpose is to learn GPIO input and interrupt.

1. Circuit

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J39-n in the picture are several jumper sockets, located near the LCD of the development board. Make sure the jumpers are connected before proceeding.

It can be seen that when the button is pressed, the pin is grounded. That is, if the pin is connected to a pull-up resistor, the pin is in a high level state when the button is popped up, and in a low level state when the button is pressed.

The button used this time is BP3, which is the PA20 pin; the LED is a blue LED, which is PA0.

When the additional interrupt control is not enabled, the interrupt will be triggered on both edges.

7. Interrupt Service Function

There are several registers:

PIO_ELSR——Used to indicate whether the interrupt is triggered by level or edge
PIO_FRLHSR——Used to indicate whether the interrupt is triggered by a falling edge or a low level, or a rising edge or a high level

Unfortunately, these registers have no effect when no additional interrupt control modes are used.

However, you can directly determine the pin level by reading the PIO_PDSR register. Note that when using this register, you need to turn on the clock of the PIO controller first.

The code logic is relatively simple:

#define LED_PIO PIO_PA0

void PIOA_Handler()

{

/* Get the interrupt status and pull the interrupt low*/

uint32_t status = PIOA->PIO_ISR;

/* First determine whether the interrupt is triggered by the button pin*/

if ((status & BUTTON_PIO) != 0)

{

if (PIOA->PIO_PDSR & BUTTON_PIO)

{

/* High level, button pops up*/

PIOA->PIO_SODR = LED_PIO;

}

else

{

/* Low level, button pressed*/

PIOA->PIO_CODR = LED_PIO;

}

Keywords：SAM4E Reference address：SAM4E MCU Tour - 6. LED Flashing Button Control

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