tip/components/u8g2/csrc/u8x8_debounce.c

/*

  u8x8_debounce.c
  
  Key/button simple debounce algorithm (Addon for u8x8)
  
  Universal 8bit Graphics Library (https://github.com/olikraus/u8g2/)

  Copyright (c) 2016, olikraus@gmail.com
  All rights reserved.

  Redistribution and use in source and binary forms, with or without modification, 
  are permitted provided that the following conditions are met:

  * Redistributions of source code must retain the above copyright notice, this list 
    of conditions and the following disclaimer.
    
  * Redistributions in binary form must reproduce the above copyright notice, this 
    list of conditions and the following disclaimer in the documentation and/or other 
    materials provided with the distribution.

  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND 
  CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, 
  INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF 
  MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE 
  DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR 
  CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 
  SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 
  NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 
  LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER 
  CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, 
  STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 
  ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF 
  ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.  
  
*/

#include "u8x8.h"

static uint8_t u8x8_read_pin_state(u8x8_t *u8x8)
{
  uint8_t i;
  uint8_t pin_state;
  
  pin_state = 255;	/* be compatible with the setup of the default pin setup, which is 255 */
  for( i = 0; i < U8X8_PIN_INPUT_CNT; i++ )
  {
    pin_state <<= 1;
    
    /* the callback function should put the return value into this variable */
    u8x8->gpio_result = 1;
    u8x8_gpio_call(u8x8, U8X8_MSG_GPIO(i+U8X8_PIN_OUTPUT_CNT), 0);
    pin_state |= u8x8->gpio_result & 1;
  }
  
  return pin_state;
}

/*
  return 0 to U8X8_PIN_INPUT_CNT-1 if there is a difference
  return U8X8_PIN_INPUT_CNT if there is no difference
*/
static uint8_t u8x8_find_first_diff(uint8_t a, uint8_t b)
{
  uint8_t mask;
  uint8_t i;
  mask = 1;
  i = U8X8_PIN_INPUT_CNT;
  do
  {
    i--;
    if ( (a & mask) != (b & mask) )
      return i;
    mask <<= 1;
  } while( i > 0 );
  return U8X8_PIN_INPUT_CNT;
}

/*
  State A:
    u8x8->debounce_last_pin_state == current_state 
      --> State A
    u8x8->debounce_last_pin_state != current_state 
      --> u8x8->debounce_last_pin_state = current_state 
      --> State B + cnt

  State B + cnt
    --> state--

  State B
    u8x8->debounce_last_pin_state == current_state 
      --> keypress detected
      --> State C
    u8x8->debounce_last_pin_state != current_state 
      --> State A

  State C
    u8x8->debounce_last_pin_state == current_state 
      --> State C
    u8x8->debounce_last_pin_state != current_state 
      --> State A

*/

#ifdef __unix__xxxxxx_THIS_IS_DISABLED

#include <stdio.h>
#include <stdlib.h>
uint8_t u8x8_GetMenuEvent(u8x8_t *u8x8)
{
    int c;
    c = getc(stdin);
    switch(c)
    {
        case 'n':
            return  U8X8_MSG_GPIO_MENU_NEXT;
        case 'p':
            return  U8X8_MSG_GPIO_MENU_PREV;
        case 's':
            return  U8X8_MSG_GPIO_MENU_SELECT;
        case 'h':
            return  U8X8_MSG_GPIO_MENU_HOME;
        case 'x':
            exit(0);
        default:
            puts("press n, p, s, h or x");
            break;
    }
    return 0;
}


#else  /* __unix__ */


#define U8X8_DEBOUNCE_WAIT 2
/* do debounce and return a GPIO msg which indicates the event */
/* returns 0, if there is no event */
#if defined(__GNUC__) && !defined(__CYGWIN__)
# pragma weak  u8x8_GetMenuEvent
#endif
uint8_t u8x8_GetMenuEvent(u8x8_t *u8x8)
{
  uint8_t pin_state;
  uint8_t result_msg = 0;	/* invalid message, no event */
  
  pin_state = u8x8_read_pin_state(u8x8);
  
  /* States A, B, C & D are encoded in the upper 4 bit*/
  switch(u8x8->debounce_state)
  {
    case 0x00:	/* State A, default state */
      if ( u8x8->debounce_default_pin_state != pin_state )
      {
	//u8x8->debounce_last_pin_state = pin_state;
	u8x8->debounce_state = 0x010 + U8X8_DEBOUNCE_WAIT;
      }
      break;
    case 0x10:	/* State B */
      //if ( u8x8->debounce_last_pin_state != pin_state )
      if ( u8x8->debounce_default_pin_state == pin_state )
      {
	u8x8->debounce_state = 0x00;	/* back to state A */
      }
      else
      {
	/* keypress detected */
	u8x8->debounce_last_pin_state = pin_state;
	//result_msg = U8X8_MSG_GPIO_MENU_NEXT;
	u8x8->debounce_state = 0x020 + U8X8_DEBOUNCE_WAIT;	/* got to state C */	
      }
      break;
      
    case 0x20:	/* State C */
      if ( u8x8->debounce_last_pin_state != pin_state )
      {
	u8x8->debounce_state = 0x00;	/* back to state A */
      }
      else
      {
	u8x8->debounce_state = 0x030;	/* got to state D */	
      }
      break;
      
    case 0x30:	/* State D */
      /* wait until key release */
      if ( u8x8->debounce_default_pin_state == pin_state )
      {
	u8x8->debounce_state = 0x00;	/* back to state A */
	result_msg = U8X8_MSG_GPIO(u8x8_find_first_diff(u8x8->debounce_default_pin_state, u8x8->debounce_last_pin_state)+U8X8_PIN_OUTPUT_CNT);
      }
      else
      {
	//result_msg = U8X8_MSG_GPIO_MENU_NEXT;
	// maybe implement autorepeat here 
      }
      break;
    default:
      u8x8->debounce_state--;	/* count down, until there is a valid state */
      break;
  }
  return result_msg;
}

#endif /* __unix__ */