mirror of
https://github.com/DCC-EX/CommandStation-EX.git
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55 lines
1.8 KiB
C++
55 lines
1.8 KiB
C++
/*
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* © 2021, Chris Harlow & David Cutting. All rights reserved.
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*
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* This file is part of Asbelos DCC API
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*
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* This 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 3 of the License, or
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* (at your option) any later version.
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*
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* It 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 CommandStation. If not, see <https://www.gnu.org/licenses/>.
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*/
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/* This timer class is used to manage the single timer required to handle the DCC waveform.
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* All timer access comes through this class so that it can be compiled for
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* various hardware CPU types.
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*
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* DCCEX works on a single timer interrupt at a regular 58uS interval.
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* The DCCWaveform class generates the signals to the motor shield
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* based on this timer.
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*/
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#include "DCCTimer.h"
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const int DCC_SIGNAL_TIME=58; // this is the 58uS DCC 1-bit waveform half-cycle
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const int DCC_SLOW_TIME=58*512; // for <D DCC SLOW> command diagnostics
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INTERRUPT_CALLBACK interruptHandler=0;
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void DCCTimer::begin(INTERRUPT_CALLBACK callback, bool slow) {
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interruptHandler=callback;
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// Initialise timer1 to trigger every 58us (DCC_SIGNAL_TIME)
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noInterrupts();
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TCCR1A = 0;
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ICR1 = ((F_CPU / 1000000) * (slow? DCC_SLOW_TIME : DCC_SIGNAL_TIME)) >>1;
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TCNT1 = 0;
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TCCR1B = _BV(WGM13) | _BV(CS10); // Mode 8, clock select 1
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TIMSK1 = _BV(TOIE1); // Enable Software interrupt
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interrupts();
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}
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// Timer interrupt every 58uS
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ISR(TIMER1_OVF_vect)
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{
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if (interruptHandler) interruptHandler();
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}
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