Finalize C <=> C++ interface

src/avclan/target/avr-attiny3216/cd_timer_avr.c

@@ -0,0 +1,72 @@
+// copyright (C) 2006 Marcin Slonicki <marcin@softservice.com.pl>
+// copyright (C) 2007 Louis Frigon
+// Copyright (C) 2015 Allen Hill <allenofthehills@gmail.com>
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+#include <avr/interrupt.h>
+#include <avr/io.h>
+#include <stdint.h>
+#include <util/atomic.h>
+
+#include "hal/cd_timer.h"
+
+// Measured wall-clock duration (in ms) of one nominal 32768-tick RTC period,
+// used to calibrate out the internal OSCULP32K's error. The RTC runs from
+// OSCULP32K, which is only spec'd to +/-3% and has no user calibration
+// register, so a nominal 32768-count period does not land on exactly 1 s.
+// Override per-board via the CMake cache (see CMakeUserPresets.json).
+#ifndef RTC_STATUS_PERIOD_MS
+  #define RTC_STATUS_PERIOD_MS 1000
+#endif
+
+// RTC overflow period (in 32.768 kHz ticks) for the ~1 Hz status-update tick.
+// ticks = round(32768 * 1000 / RTC_STATUS_PERIOD_MS); the RTC overflows after
+// PER+1 ticks, so PER = ticks - 1.
+static constexpr uint16_t rtc_status_per =
+    (uint16_t)(32768UL * 1000UL / RTC_STATUS_PERIOD_MS) - 1U;
+
+static void* changer = nullptr;
+static void (*increment)(void *) = nullptr;
+static bool (*isplaying)(void *) = nullptr;
+
+void cdtimer_init(void *ptr, void (inc)(void *), bool (isplay)(void *)) {
+  // Setup RTC as a ~1 sec periodic timer via the normal counter's overflow.
+  // Use the RTC directly (not PIT) to tune the status report interval closer to
+  // 1 sec (internal osc may be slightly off)
+  loop_until_bit_is_clear(RTC_STATUS, RTC_CTRLABUSY_bp);
+  RTC.CLKSEL = RTC_CLKSEL_INT32K_gc;
+  loop_until_bit_is_clear(RTC_STATUS, RTC_PERBUSY_bp);
+  RTC.PER = rtc_status_per;
+  RTC.INTCTRL = 0;
+  loop_until_bit_is_clear(RTC_STATUS, RTC_CTRLABUSY_bp);
+  RTC.CTRLA = RTC_PRESCALER_DIV1_gc | RTC_RTCEN_bm;
+
+  changer = ptr;
+  increment = inc;
+  isplaying = isplay;
+}
+
+void cdtimer_reset() {
+  ATOMIC_BLOCK(ATOMIC_RESTORESTATE) {
+    loop_until_bit_is_clear(RTC_STATUS, RTC_CNTBUSY_bp);
+    RTC.CNT = 0;
+    RTC.INTFLAGS = RTC_OVF_bm; // Clear interrupt flag just in case
+    RTC.INTCTRL |= RTC_OVF_bm;
+  }
+}
+
+void cdtimer_restore() { 
+  if (isplaying(changer))
+    RTC.INTCTRL |= RTC_OVF_bm; 
+}
+void cdtimer_disable() { RTC.INTCTRL &= ~RTC_OVF_bm; }
+
+// Set once per overflow; consumed by the app via cdtimer_pending().
+volatile bool cdtimer_pending_flag = false;
+
+// Periodic interrupt with a ~1 sec period; only enabled while playing.
+ISR(RTC_CNT_vect) {
+  increment(changer);
+  cdtimer_pending_flag = true;
+  RTC.INTFLAGS = RTC_OVF_bm;
+}