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477 cascade 1
/****************************************************************************
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 *   Copyright (C) 2009-2013 by Claas Anders "CaScAdE" Rathje               *
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 *   admiralcascade@gmail.com                                               *
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 *   Project-URL: http://www.mylifesucks.de/oss/c-osd/                      *
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 *                                                                          *
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 *   This program is free software; you can redistribute it and/or modify   *
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 *   it under the terms of the GNU General Public License as published by   *
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 *   the Free Software Foundation; either version 2 of the License.         *
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 *                                                                          *
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 *   This program 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 General Public License for more details.                           *
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 *                                                                          *
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 *   You should have received a copy of the GNU General Public License      *
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 *   along with this program; if not, write to the                          *
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 *   Free Software Foundation, Inc.,                                        *
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 *   59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.              *
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 ****************************************************************************/
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#include "main.h"
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#include <avr/io.h>
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#include <avr/interrupt.h>
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#include "ppm.h"
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#include "max7456_software_spi.h" // clearing
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#if !(ALLCHARSDEBUG|(WRITECHARS != -1))
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volatile uint16_t old_timer1 = 0, ppm = 0;
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/**
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 * init ppm, including timer1 for measurement
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 */
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void ppm_init() {
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    PORTE |= (1 << PORTE0); // enable pullup on INT0 pin
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    GICR |= (1 << INT2); // External Interrupt Request 2 Enable
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    EMCUCR |= (1 << ISC2); // a rising edge on INT2 activates the interrupt
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    TCCR1B |= (0 << CS12) | (1 << CS10) | (1 << CS11); // timer1 up with prescaler 64
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}
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/**
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 * Handle INT2 interrupts that occur on changing edges of ppm signal
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 */
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ISR(INT2_vect) {
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    // since the pin might get bogus reads we wait for 123 signals
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    static uint8_t valid_ppm_to_go = 123;
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    if (EMCUCR & (1 << ISC2)) { // rising
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        old_timer1 = TCNT1;
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        EMCUCR &= ~(1 << ISC2); // next one is falling
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    } else {
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        if (valid_ppm_to_go) {
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            valid_ppm_to_go--;
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        } else {
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                        if (TCNT1 > old_timer1 + 256) {
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                ppm = TCNT1 - old_timer1;
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                ppm -= 256;
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                        } else {
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                                ppm = 0;
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                        }
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            if (ppm < 128) { // we want HUD
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                if (!(COSD_FLAGS_MODES & COSD_FLAG_HUD)) {
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                    COSD_FLAGS_RUNTIME &= ~COSD_ICONS_WRITTEN;
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                }
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                COSD_FLAGS_MODES |= COSD_FLAG_HUD;
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            } else { // we do not want hud
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                COSD_FLAGS_MODES &= ~COSD_FLAG_HUD;
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            }
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        }
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        EMCUCR |= (1 << ISC2); // next one is rising
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    }
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    //write_ndigit_number_u(2, 6, valid_ppm_to_go, 100, 0); // debug
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    //write_ndigit_number_u(2, 7, COSD_FLAGS_CONFIG, 100, 0); // debug
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    //PORTC ^= (1 << PC3); // LED4_TOGGLE // debug
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    //uptime = ppm;
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}
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#endif