Button library
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Button Library

The Button Library provides routines for detecting button presses and debouncing (eliminating the influence of contact flickering upon pressing a button)

Library Routines

Button

Prototype

function Button(var port: word; pin: word; time: word; ActiveState: word) : word;
Description

The function eliminates the influence of contact flickering upon pressing a button (debouncing). The Button pin is tested just after the function call and then again after the debouncing period has expired. If the pin was in the active state in both cases then the function returns 255 (true).
Parameters
  • port: button port address
  • pin: button pin
  • time: debouncing period in milliseconds
  • active_state: determines what is considered as active state. Valid values: 0 (logical zero) and 1 (logical one)
Returns
  • 255 if the pin was in the active state for given period.
  • 0 otherwise
Requires

Nothing.
Example

Stellaris

program Button_Test;
  var oldstate : byte;
begin
  GPIO_Digital_Input(@GPIO_PORTE_DATA_BITS, _GPIO_PINMASK_1);    // Set GPIO_PORTE.1 as digital input
  GPIO_Digital_Output(@GPIO_PORTF_DATA_BITS, _GPIO_PINMASK_ALL); // Set GPIO_PORTF as digital output
  oldstate := 0;

   while TRUE do
     begin
       if (Button(GPIO_PORTE_DATA, 1, 1, 1)) then                // detect logical one on PE1 pin
         oldstate := 1;
       if (oldstate and Button(GPIO_PORTE_DATA, 1, 1, 0)) then
         begin                                                   // detect one-to-zero transition on PE1 pin
           GPIO_PORTF_DATA := not GPIO_PORTF_DATA;              // invert GPIO_PORTF value
           oldstate := 0;
         end;
     end;                                                         // endless loop
end.

STM32

program Button_Test;
  var oldstate : byte;
begin
  GPIO_Digital_Input(@GPIOA_BASE, _GPIO_PINMASK_0);      // Set PA0 as digital input
  GPIO_Digital_Output(@GPIOD_BASE, _GPIO_PINMASK_ALL);   // Set PORTD as digital output
  oldstate := 0;

   while TRUE do
     begin
       if (Button(GPIOA_IDR, 0, 1, 1)) then               // detect logical one on PA0 pin
         oldstate := 1;
       if (oldstate and Button(GPIOA_IDR, 0, 1, 0)) then
         begin                                            // detect one-to-zero transition on PA0 pin
           GPIOD_ODR := not GPIOD_ODR;                    // invert PORTD value
           oldstate := 0;
         end;
     end;                                                 // endless loop
end.
Notes

None.
Copyright (c) 2002-2012 mikroElektronika. All rights reserved.
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