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This commit is contained in:
Asbelos 2024-02-07 19:50:08 +00:00
parent cd47782052
commit 1443ea8df9
1 changed files with 19 additions and 6 deletions
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25
DCCTimerAVR.cpp
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@ -75,22 +75,22 @@ void DCCTimer::startRailcomTimer(byte brakePin) {
(there will be 7 DCC timer1 ticks in which to do this.)
*/
const int cutoutDuration = 436; // Desired interval in microseconds
const int cutoutDuration = 430; // Desired interval in microseconds
// Set up Timer2 for CTC mode (Clear Timer on Compare Match)
TCCR2A = 0; // Clear Timer2 control register A
TCCR2B = 0; // Clear Timer2 control register B
TCNT2 = 0; // Initialize Timer2 counter value to 0
// Configure Phase and Frequency Correct PWM mode
//TCCR2A = (1 << COM2B1) | (1 << WGM20) | (1 << WGM21);
TCCR2A = (1 << COM2B1); // enable pwm on pin 9
TCCR2A |= (1 << WGM20);
// Set Fast PWM mode with non-inverted output on OC2B (pin 9)
TCCR2A = (1 << WGM21) | (1 << WGM20) | (1 << COM2B1);
// Set Timer 2 prescaler to 32
TCCR2B = (1 << CS21) | (1 << CS20); // 32 prescaler
// Set the compare match value for desired interval
OCR2A = (F_CPU / 1000000) * cutoutDuration / 32 - 1;
OCR2A = (F_CPU / 1000000) * cutoutDuration / 64 - 1;
// Calculate the compare match value for desired duty cycle
OCR2B = OCR2A+1; // set duty cycle to 100%= OCR2A)
@ -98,10 +98,23 @@ void DCCTimer::startRailcomTimer(byte brakePin) {
// Enable Timer2 output on pin 9 (OC2B)
DDRB |= (1 << DDB1);
// TODO Fudge TCNT2 to sync with last tcnt1 tick + 28uS
// Previous TIMER1 Tick was at rising end-of-packet bit
// Cutout starts half way through first preamble
// that is 2.5 * 58uS later.
// TCNT1 ticks 8 times / microsecond
// auto microsendsToFirstRailcomTick=(58+58+29)-(TCNT1/8);
// set the railcom timer counter allowing for phase-correct
// CHris's NOTE:
// I dont kniow quite how this calculation works out but
// it does seems to get a good answer.
TCNT2=193 + (ICR1 - TCNT1)/8;
}
void DCCTimer::ackRailcomTimer() {
OCR2B= 0x00; // brfake pin pwm duty cycle 0 at next tick
OCR2B= 0x00; // brake pin pwm duty cycle 0 at next tick
}