mirror of
https://github.com/halleysfifthinc/AVCLAN-Mockingboard.git
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Allen Hill
73 lines
2.5 KiB
C
73 lines
2.5 KiB
C
// copyright (C) 2006 Marcin Slonicki <marcin@softservice.com.pl>
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// copyright (C) 2007 Louis Frigon
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// Copyright (C) 2015 Allen Hill <allenofthehills@gmail.com>
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// SPDX-License-Identifier: GPL-3.0-or-later
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#include <avr/interrupt.h>
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#include <avr/io.h>
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#include <stdint.h>
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#include <util/atomic.h>
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#include "hal/cd_timer.h"
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// Measured wall-clock duration (in ms) of one nominal 32768-tick RTC period,
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// used to calibrate out the internal OSCULP32K's error. The RTC runs from
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// OSCULP32K, which is only spec'd to +/-3% and has no user calibration
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// register, so a nominal 32768-count period does not land on exactly 1 s.
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// Override per-board via the CMake cache (see CMakeUserPresets.json).
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#ifndef RTC_STATUS_PERIOD_MS
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#define RTC_STATUS_PERIOD_MS 1000
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#endif
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// RTC overflow period (in 32.768 kHz ticks) for the ~1 Hz status-update tick.
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// ticks = round(32768 * 1000 / RTC_STATUS_PERIOD_MS); the RTC overflows after
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// PER+1 ticks, so PER = ticks - 1.
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static constexpr uint16_t rtc_status_per =
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(uint16_t)(32768UL * 1000UL / RTC_STATUS_PERIOD_MS) - 1U;
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static void* changer = nullptr;
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static void (*increment)(void *) = nullptr;
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static bool (*isplaying)(void *) = nullptr;
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void cdtimer_init(void *ptr, void (inc)(void *), bool (isplay)(void *)) {
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// Setup RTC as a ~1 sec periodic timer via the normal counter's overflow.
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// Use the RTC directly (not PIT) to tune the status report interval closer to
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// 1 sec (internal osc may be slightly off)
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loop_until_bit_is_clear(RTC_STATUS, RTC_CTRLABUSY_bp);
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RTC.CLKSEL = RTC_CLKSEL_INT32K_gc;
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loop_until_bit_is_clear(RTC_STATUS, RTC_PERBUSY_bp);
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RTC.PER = rtc_status_per;
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RTC.INTCTRL = 0;
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loop_until_bit_is_clear(RTC_STATUS, RTC_CTRLABUSY_bp);
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RTC.CTRLA = RTC_PRESCALER_DIV1_gc | RTC_RTCEN_bm;
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changer = ptr;
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increment = inc;
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isplaying = isplay;
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}
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void cdtimer_reset() {
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ATOMIC_BLOCK(ATOMIC_RESTORESTATE) {
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loop_until_bit_is_clear(RTC_STATUS, RTC_CNTBUSY_bp);
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RTC.CNT = 0;
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RTC.INTFLAGS = RTC_OVF_bm; // Clear interrupt flag just in case
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RTC.INTCTRL |= RTC_OVF_bm;
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}
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}
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void cdtimer_restore() {
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if (isplaying(changer))
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RTC.INTCTRL |= RTC_OVF_bm;
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}
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void cdtimer_disable() { RTC.INTCTRL &= ~RTC_OVF_bm; }
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// Set once per overflow; consumed by the app via cdtimer_pending().
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volatile bool cdtimer_pending_flag = false;
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// Periodic interrupt with a ~1 sec period; only enabled while playing.
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ISR(RTC_CNT_vect) {
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increment(changer);
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cdtimer_pending_flag = true;
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RTC.INTFLAGS = RTC_OVF_bm;
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}
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