mirror of
https://github.com/DCC-EX/CommandStation-EX.git
synced 2024-12-23 21:01:25 +01:00
90 lines
3.4 KiB
C++
90 lines
3.4 KiB
C++
/*
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* © 2021 Mike S
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* © 2021 Harald Barth
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* © 2021 Fred Decker
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* All rights reserved.
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*
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* This file is part of CommandStation-EX
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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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/* There are several different implementations of this class which the compiler will select
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according to the hardware.
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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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* If the motor drivers are BOTH configured to use the correct 2 pins for the architecture,
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* (see isPWMPin() function. )
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* then this allows us to use a hardware driven pin switching arrangement which is
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* achieved by setting the duty cycle of the NEXT clock interrupt to 0% or 100% depending on
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* the required pin state. (see setPWM())
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* This is more accurate than the software interrupt but at the expense of
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* limiting the choice of available pins.
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* Fortunately, a standard motor shield on a Mega uses pins that qualify for PWM...
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* Other shields may be jumpered to PWM pins or run directly using the software interrupt.
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*
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* Because the PWM-based waveform is effectively set half a cycle after the software version,
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* it is not acceptable to drive the two tracks on different methiods or it would cause
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* problems for <1 JOIN> etc.
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*
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*/
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#ifndef DCCTimer_h
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#define DCCTimer_h
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#include "Arduino.h"
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typedef void (*INTERRUPT_CALLBACK)();
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class DCCTimer {
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public:
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static void begin(INTERRUPT_CALLBACK interrupt);
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static void getSimulatedMacAddress(byte mac[6]);
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static bool isPWMPin(byte pin);
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static void setPWM(byte pin, bool high);
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static void clearPWM();
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// Update low ram level. Allow for extra bytes to be specified
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// by estimation or inspection, that may be used by other
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// called subroutines. Must be called with interrupts disabled.
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//
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// Although __brkval may go up and down as heap memory is allocated
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// and freed, this function records only the worst case encountered.
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// So even if all of the heap is freed, the reported minimum free
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// memory will not increase.
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//
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static void inline updateMinimumFreeMemoryISR(unsigned char extraBytes=0) {
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int spare = freeMemory()-extraBytes;
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if (spare < 0) spare = 0;
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if (spare < minimum_free_memory) minimum_free_memory = spare;
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}
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static int getMinimumFreeMemory();
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private:
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static int freeMemory();
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static volatile int minimum_free_memory;
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static const int DCC_SIGNAL_TIME=58; // this is the 58uS DCC 1-bit waveform half-cycle
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static const long CLOCK_CYCLES=(F_CPU / 1000000 * DCC_SIGNAL_TIME) >>1;
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};
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#endif
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