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ddr4s / fw / wiringPi / devLib / piNes.c @ 32:cadb9025f1e0

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/*
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 * piNes.c:
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 *        Driver for the NES Joystick controller on the Raspberry Pi
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 *        Copyright (c) 2012 Gordon Henderson
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 ***********************************************************************
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 * This file is part of wiringPi:
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 *        https://projects.drogon.net/raspberry-pi/wiringpi/
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 *
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 *    wiringPi is free software: you can redistribute it and/or modify
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 *    it under the terms of the GNU Lesser General Public License as
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 *    published by the Free Software Foundation, either version 3 of the
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 *    License, or (at your option) any later version.
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 *
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 *    wiringPi is distributed in the hope that it will be useful,
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 *    but WITHOUT ANY WARRANTY; without even the implied warranty of
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 *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
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 *    GNU Lesser General Public License for more details.
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 *
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 *    You should have received a copy of the GNU Lesser General Public
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 *    License along with wiringPi.
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 *    If not, see <http://www.gnu.org/licenses/>.
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 ***********************************************************************
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 */
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#include <wiringPi.h>
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#include "piNes.h"
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#define        MAX_NES_JOYSTICKS        8
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#define        NES_RIGHT        0x01
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#define        NES_LEFT        0x02
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#define        NES_DOWN        0x04
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#define        NES_UP                0x08
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#define        NES_START        0x10
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#define        NES_SELECT        0x20
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#define        NES_B                0x40
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#define        NES_A                0x80
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#define        PULSE_TIME        25
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// Data to store the pins for each controller
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struct nesPinsStruct
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{
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  unsigned int cPin, dPin, lPin ;
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} ;
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static struct nesPinsStruct nesPins [MAX_NES_JOYSTICKS] ;
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static int joysticks = 0 ;
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/*
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 * setupNesJoystick:
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 *        Create a new NES joystick interface, program the pins, etc.
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 *********************************************************************************
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 */
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int setupNesJoystick (int dPin, int cPin, int lPin)
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{
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  if (joysticks == MAX_NES_JOYSTICKS)
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    return -1 ;
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  nesPins [joysticks].dPin = dPin ;
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  nesPins [joysticks].cPin = cPin ;
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  nesPins [joysticks].lPin = lPin ;
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  digitalWrite (lPin, LOW) ;
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  digitalWrite (cPin, LOW) ;
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  pinMode (lPin, OUTPUT) ;
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  pinMode (cPin, OUTPUT) ;
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  pinMode (dPin, INPUT) ;
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  return joysticks++ ;
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}
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/*
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 * readNesJoystick:
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 *        Do a single scan of the NES Joystick.
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 *********************************************************************************
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 */
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unsigned int readNesJoystick (int joystick)
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{
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  unsigned int value = 0 ;
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  int  i ;
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  struct nesPinsStruct *pins = &nesPins [joystick] ;
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// Toggle Latch - which presents the first bit
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  digitalWrite (pins->lPin, HIGH) ; delayMicroseconds (PULSE_TIME) ;
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  digitalWrite (pins->lPin, LOW)  ; delayMicroseconds (PULSE_TIME) ;
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// Read first bit
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  value = digitalRead (pins->dPin) ;
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// Now get the next 7 bits with the clock
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  for (i = 0 ; i < 7 ; ++i)
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  {
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    digitalWrite (pins->cPin, HIGH) ; delayMicroseconds (PULSE_TIME) ;
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    digitalWrite (pins->cPin, LOW)  ; delayMicroseconds (PULSE_TIME) ;
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    value = (value << 1) | digitalRead (pins->dPin) ;
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  }
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  return value ^ 0xFF ;
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}