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DCCTimerMEGAAVR.cpp
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DCCTimerMEGAAVR.cpp
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/*
* © 2021 Mike S
* © 2021 Harald Barth
* © 2021 Fred Decker
* © 2021 Chris Harlow
* © 2021 David Cutting
* All rights reserved.
*
* This file is part of Asbelos DCC API
*
* This is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* It is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with CommandStation. If not, see <https://www.gnu.org/licenses/>.
*/
/* This timer class is used to manage the single timer required to handle the DCC waveform.
* All timer access comes through this class so that it can be compiled for
* various hardware CPU types.
*
* DCCEX works on a single timer interrupt at a regular 58uS interval.
* The DCCWaveform class generates the signals to the motor shield
* based on this timer.
*
* If the motor drivers are BOTH configured to use the correct 2 pins for the architecture,
* (see isPWMPin() function. )
* then this allows us to use a hardware driven pin switching arrangement which is
* achieved by setting the duty cycle of the NEXT clock interrupt to 0% or 100% depending on
* the required pin state. (see setPWM())
* This is more accurate than the software interrupt but at the expense of
* limiting the choice of available pins.
* Fortunately, a standard motor shield on a Mega uses pins that qualify for PWM...
* Other shields may be jumpered to PWM pins or run directly using the software interrupt.
*
* Because the PWM-based waveform is effectively set half a cycle after the software version,
* it is not acceptable to drive the two tracks on different methiods or it would cause
* problems for <1 JOIN> etc.
*
*/
// ATTENTION: this file only compiles on a UnoWifiRev3 or NanoEvery
// Please refer to DCCTimer.h for general comments about how this class works
// This is to avoid repetition and duplication.
#ifdef ARDUINO_ARCH_MEGAAVR
#include "DCCTimer.h"
INTERRUPT_CALLBACK interruptHandler=0;
extern char *__brkval;
extern char *__malloc_heap_start;
void DCCTimer::begin(INTERRUPT_CALLBACK callback) {
interruptHandler=callback;
noInterrupts();
ADC0.CTRLC = (ADC0.CTRLC & 0b00110000) | 0b01000011; // speed up analogRead sample time
TCB0.CTRLB = TCB_CNTMODE_INT_gc & ~TCB_CCMPEN_bm; // timer compare mode with output disabled
TCB0.CTRLA = TCB_CLKSEL_CLKDIV2_gc; // 8 MHz ~ 0.125 us
TCB0.CCMP = CLOCK_CYCLES -1; // 1 tick less for timer reset
TCB0.INTFLAGS = TCB_CAPT_bm; // clear interrupt request flag
TCB0.INTCTRL = TCB_CAPT_bm; // Enable the interrupt
TCB0.CNT = 0;
TCB0.CTRLA |= TCB_ENABLE_bm; // start
interrupts();
}
// ISR called by timer interrupt every 58uS
ISR(TCB0_INT_vect){
TCB0.INTFLAGS = TCB_CAPT_bm;
interruptHandler();
}
bool DCCTimer::isPWMPin(byte pin) {
(void) pin;
return false; // TODO what are the relevant pins?
}
void DCCTimer::setPWM(byte pin, bool high) {
(void) pin;
(void) high;
// TODO what are the relevant pins?
}
void DCCTimer::clearPWM() {
// Do nothing unless we implent HA
}
void DCCTimer::getSimulatedMacAddress(byte mac[6]) {
memcpy(mac,(void *) &SIGROW.SERNUM0,6); // serial number
mac[0] &= 0xFE;
mac[0] |= 0x02;
}
volatile int DCCTimer::minimum_free_memory=__INT_MAX__;
// Return low memory value...
int DCCTimer::getMinimumFreeMemory() {
noInterrupts(); // Disable interrupts to get volatile value
int retval = minimum_free_memory;
interrupts();
return retval;
}
extern char *__brkval;
extern char *__malloc_heap_start;
int DCCTimer::freeMemory() {
char top;
return __brkval ? &top - __brkval : &top - __malloc_heap_start;
}
#endif