Rewrite on libavr

Same driver surface as the yazoalfa version — clock and alarm get/set,
alarm interrupts, flag check/clear — plus oscillator-stop detection and
die temperature. One source for tiny85 (software I2C) and mega328P (TWI),
built against libavr in both generated and reflect mode, byte-identical
.text across modes. Errors surface as std::expected instead of being
dropped; weekday-rate alarms now really set the DY bit (legacy cleared
it); multi-register access is one coherent bus transaction. Legacy stays
on master.

Co-Authored-By: Claude <noreply@anthropic.com>

.gitignore

@@ -1,11 +1,2 @@
-.vs
-Release
-Debug
-*.componentinfo.xml
-*.elf
-*.o
-*.hex
-*.srec
-*.eeprom
-*.lss
-*.map
+build/
+.cache/

CMakeLists.txt

@@ -0,0 +1,25 @@
+cmake_minimum_required(VERSION 3.28)
+
+project(ds3231 LANGUAGES CXX)
+
+# libavr comes from a local checkout (LIBAVR_ROOT cache/env variable) or,
+# failing that, straight from the forge. The toolchain file also lives in
+# that checkout — see CMakePresets.json.
+include(FetchContent)
+if(NOT LIBAVR_ROOT AND DEFINED ENV{LIBAVR_ROOT})
+	set(LIBAVR_ROOT $ENV{LIBAVR_ROOT})
+endif()
+if(LIBAVR_ROOT)
+	FetchContent_Declare(libavr SOURCE_DIR ${LIBAVR_ROOT})
+else()
+	FetchContent_Declare(libavr GIT_REPOSITORY git@git.blackmark.me:avr/libavr.git GIT_TAG main)
+endif()
+FetchContent_MakeAvailable(libavr)
+
+add_library(ds3231 INTERFACE)
+target_include_directories(ds3231 INTERFACE ${CMAKE_CURRENT_SOURCE_DIR}/include)
+target_link_libraries(ds3231 INTERFACE libavr)
+
+if(PROJECT_IS_TOP_LEVEL)
+	add_subdirectory(example)
+endif()

CMakePresets.json

@@ -0,0 +1,43 @@
+{
+	"version": 8,
+	"configurePresets": [
+		{
+			"name": "base",
+			"hidden": true,
+			"generator": "Ninja",
+			"binaryDir": "${sourceDir}/build/${presetName}",
+			"toolchainFile": "$env{LIBAVR_ROOT}/cmake/avr-toolchain.cmake",
+			"cacheVariables": {
+				"CMAKE_BUILD_TYPE": "Release",
+				"CMAKE_EXPORT_COMPILE_COMMANDS": "ON",
+				"CMAKE_COLOR_DIAGNOSTICS": "ON"
+			}
+		},
+		{
+			"name": "attiny85-generated",
+			"inherits": "base",
+			"cacheVariables": { "LIBAVR_MCU": "attiny85", "LIBAVR_REFLECT": "OFF" }
+		},
+		{
+			"name": "attiny85-reflect",
+			"inherits": "base",
+			"cacheVariables": { "LIBAVR_MCU": "attiny85", "LIBAVR_REFLECT": "ON" }
+		},
+		{
+			"name": "atmega328p-generated",
+			"inherits": "base",
+			"cacheVariables": { "LIBAVR_MCU": "atmega328p", "LIBAVR_REFLECT": "OFF" }
+		},
+		{
+			"name": "atmega328p-reflect",
+			"inherits": "base",
+			"cacheVariables": { "LIBAVR_MCU": "atmega328p", "LIBAVR_REFLECT": "ON" }
+		}
+	],
+	"buildPresets": [
+		{ "name": "attiny85-generated", "configurePreset": "attiny85-generated" },
+		{ "name": "attiny85-reflect", "configurePreset": "attiny85-reflect" },
+		{ "name": "atmega328p-generated", "configurePreset": "atmega328p-generated" },
+		{ "name": "atmega328p-reflect", "configurePreset": "atmega328p-reflect" }
+	]
+}

README.md

@@ -0,0 +1,29 @@
+# ds3231
+
+Maxim DS3231 RTC driver on [libavr](https://git.blackmark.me/avr/libavr):
+clock and alarm read/write, alarm interrupts, oscillator-stop detection,
+die temperature. One source runs on every libavr chip — TWI hardware on
+the mega328P, open-drain software I2C on the tinies. All bus errors
+surface as `std::expected`.
+
+```cpp
+using bus = dev::i2c<{.frequency = 100_kHz}>;
+using rtc = ds3231::device<bus>;
+
+auto now = rtc::read_clock();       // result<date_time>
+(void)rtc::set_alarm1({}, ds3231::alarm1_rate::once_per_second);
+```
+
+`example/main.cpp` is the full tour. Build with a libavr checkout:
+
+```sh
+LIBAVR_ROOT=/path/to/libavr cmake --preset attiny85-generated
+cmake --build --preset attiny85-generated
+```
+
+Presets cover attiny85/atmega328p in both libavr modes (generated and
+reflect). The legacy yazoalfa-based driver lives on the `master` branch.
+
+Differences from legacy: weekday-rate alarms now actually set the DY bit
+(the old `setAlarmHelper` always cleared it), reads/writes are single
+coherent bus transactions, and errors are reported instead of ignored.

example/CMakeLists.txt

@@ -0,0 +1,3 @@
+add_executable(clock main.cpp)
+target_link_libraries(clock PRIVATE ds3231)
+add_custom_command(TARGET clock POST_BUILD COMMAND ${CMAKE_SIZE} $<TARGET_FILE:clock>)

example/main.cpp

@@ -0,0 +1,32 @@
+#include <ds3231/ds3231.hpp>
+#include <libavr/libavr.hpp>
+
+using namespace avr::literals;
+
+// One source for the tiny85 (open-drain software I2C on the USI pins) and
+// the mega328P (TWI hardware). On first power-up the clock is seeded and
+// alarm 1 armed; then the LED mirrors the seconds parity — a stuck LED
+// means bus errors.
+using dev = avr::device<{.clock = 8_MHz}>;
+using bus = dev::i2c<{.frequency = 100_kHz}>;
+using rtc = ds3231::device<bus>;
+using led = dev::output<avr::pb3>;
+
+int main()
+{
+	avr::init<bus, led>();
+
+	if (auto stopped = rtc::oscillator_stopped(); stopped.value_or(false)) {
+		(void)rtc::write_clock({{2026, 1, 1}, {12, 0, 0}});
+		(void)rtc::set_alarm1({}, ds3231::alarm1_rate::once_per_second);
+		(void)rtc::clear_oscillator_stopped();
+	}
+
+	while (true) {
+		if (auto now = rtc::read_clock(); now.has_value())
+			led::write(now->second % 2 == 0);
+		if (auto fired = rtc::alarm1_fired(); fired.value_or(false))
+			(void)rtc::clear_alarm1();
+		dev::delay<100_ms>();
+	}
+}

include/ds3231/ds3231.hpp

@@ -0,0 +1,304 @@
+#pragma once
+
+#include <array>
+#include <cstdint>
+#include <expected>
+
+#include <libavr/i2c.hpp>
+
+namespace ds3231 {
+
+using avr::i2c::error;
+using avr::i2c::status;
+template <typename T>
+using result = std::expected<T, error>;
+
+struct date {
+	std::uint16_t year; // 2000..2099
+	std::uint8_t month; // 1..12
+	std::uint8_t day;   // 1..31 (weekday 1..7 in weekday-alarm reads)
+	friend constexpr bool operator==(const date &, const date &) = default;
+};
+
+struct time_of_day {
+	std::uint8_t hour; // 0..23
+	std::uint8_t minute;
+	std::uint8_t second;
+	friend constexpr bool operator==(const time_of_day &, const time_of_day &) = default;
+};
+
+struct date_time : date, time_of_day {
+	friend constexpr bool operator==(const date_time &, const date_time &) = default;
+};
+
+// Alarm match rates (datasheet Table 2). Alarm 2 has no seconds register
+// and fires at :00 of the matching minute.
+enum class alarm1_rate : std::uint8_t {
+	once_per_second = 0b01111,
+	seconds_match = 0b01110,
+	minutes_seconds_match = 0b01100,
+	time_match = 0b01000,
+	date_time_match = 0b00000,
+	weekday_time_match = 0b10000,
+};
+
+enum class alarm2_rate : std::uint8_t {
+	once_per_minute = 0b0111,
+	minutes_match = 0b0110,
+	time_match = 0b0100,
+	date_time_match = 0b0000,
+	weekday_time_match = 0b1000,
+};
+
+namespace detail {
+
+constexpr std::uint8_t to_bcd(std::uint8_t value)
+{
+	return static_cast<std::uint8_t>(((value / 10) << 4) | (value % 10));
+}
+
+constexpr std::uint8_t from_bcd(std::uint8_t value)
+{
+	return static_cast<std::uint8_t>((value >> 4) * 10 + (value & 0x0f));
+}
+
+// Hours register: bit 6 selects 12-hour mode, bit 5 is then PM. Writes
+// always use 24-hour form; reads accept either.
+constexpr std::uint8_t hours_from_reg(std::uint8_t reg)
+{
+	if (reg & 0x40) {
+		auto hour = from_bcd(reg & 0x1f);
+		bool pm = reg & 0x20;
+		if (hour == 12)
+			return pm ? 12 : 0;
+		return static_cast<std::uint8_t>(pm ? hour + 12 : hour);
+	}
+	return from_bcd(reg & 0x3f);
+}
+
+// Sakamoto's method; the device counts weekdays 1..7 with a free epoch,
+// this maps Sunday to 1.
+constexpr std::uint8_t weekday(std::uint16_t year, std::uint8_t month, std::uint8_t day)
+{
+	constexpr std::uint8_t offsets[]{0, 3, 2, 5, 0, 3, 5, 1, 4, 6, 2, 4};
+	if (month < 3)
+		--year;
+	return static_cast<std::uint8_t>((year + year / 4 - year / 100 + year / 400 + offsets[month - 1] + day) % 7 + 1);
+}
+
+} // namespace detail
+
+// Maxim DS3231 RTC on any libavr i2c master (register map: datasheet
+// 19-5170 Table 1). Every call is one bus transaction; errors surface as
+// std::expected. Weekday registers maintain themselves from the date when
+// SetWeekday is on.
+template <typename Bus, bool SetWeekday = true>
+class device {
+	using dev = avr::i2c::device<Bus, 0x68>;
+
+	static constexpr std::uint8_t reg_clock = 0x00;
+	static constexpr std::uint8_t reg_alarm1 = 0x07;
+	static constexpr std::uint8_t reg_alarm2 = 0x0b;
+	static constexpr std::uint8_t reg_control = 0x0e;
+	static constexpr std::uint8_t reg_status = 0x0f;
+	static constexpr std::uint8_t reg_temp = 0x11;
+
+	static constexpr std::uint8_t a1ie = 0x01, a2ie = 0x02, intcn = 0x04, bbsqw = 0x40;
+	static constexpr std::uint8_t a1f = 0x01, a2f = 0x02, osf = 0x80;
+
+  public:
+	[[nodiscard]] static result<date_time> read_clock()
+	{
+		std::array<std::uint8_t, 7> raw;
+		if (auto s = dev::read_regs(reg_clock, raw); !s)
+			return std::unexpected(s.error());
+		date_time now;
+		now.second = detail::from_bcd(raw[0] & 0x7f);
+		now.minute = detail::from_bcd(raw[1] & 0x7f);
+		now.hour = detail::hours_from_reg(raw[2]);
+		now.day = detail::from_bcd(raw[4] & 0x3f);
+		now.month = detail::from_bcd(raw[5] & 0x1f);
+		now.year = static_cast<std::uint16_t>(2000 + detail::from_bcd(raw[6]));
+		return now;
+	}
+
+	[[nodiscard]] static result<date> read_date()
+	{
+		auto now = read_clock();
+		if (!now)
+			return std::unexpected(now.error());
+		return static_cast<date>(*now);
+	}
+
+	[[nodiscard]] static result<time_of_day> read_time()
+	{
+		std::array<std::uint8_t, 3> raw;
+		if (auto s = dev::read_regs(reg_clock, raw); !s)
+			return std::unexpected(s.error());
+		return time_of_day{detail::hours_from_reg(raw[2]), detail::from_bcd(raw[1] & 0x7f),
+		                   detail::from_bcd(raw[0] & 0x7f)};
+	}
+
+	[[nodiscard]] static status write_clock(const date_time &now)
+	{
+		std::array<std::uint8_t, 7> raw{detail::to_bcd(now.second),
+		                                detail::to_bcd(now.minute),
+		                                detail::to_bcd(now.hour),
+		                                SetWeekday ? detail::weekday(now.year, now.month, now.day) : std::uint8_t{1},
+		                                detail::to_bcd(now.day),
+		                                detail::to_bcd(now.month),
+		                                detail::to_bcd(static_cast<std::uint8_t>(now.year % 100))};
+		return dev::write_regs(reg_clock, raw);
+	}
+
+	[[nodiscard]] static status write_date(const date &value)
+	{
+		if constexpr (SetWeekday) {
+			std::array<std::uint8_t, 4> raw{detail::weekday(value.year, value.month, value.day),
+			                                detail::to_bcd(value.day), detail::to_bcd(value.month),
+			                                detail::to_bcd(static_cast<std::uint8_t>(value.year % 100))};
+			return dev::write_regs(reg_clock + 3, raw);
+		} else {
+			std::array<std::uint8_t, 3> raw{detail::to_bcd(value.day), detail::to_bcd(value.month),
+			                                detail::to_bcd(static_cast<std::uint8_t>(value.year % 100))};
+			return dev::write_regs(reg_clock + 4, raw);
+		}
+	}
+
+	[[nodiscard]] static status write_time(const time_of_day &value)
+	{
+		std::array<std::uint8_t, 3> raw{detail::to_bcd(value.second), detail::to_bcd(value.minute),
+		                                detail::to_bcd(value.hour)};
+		return dev::write_regs(reg_clock, raw);
+	}
+
+	// Alarm times use .day as the date of month, or as weekday 1..7 with
+	// the weekday_time_match rates.
+	[[nodiscard]] static status set_alarm1(const date_time &at, alarm1_rate rate, bool enable_interrupt = true)
+	{
+		auto m = static_cast<std::uint8_t>(rate);
+		std::array<std::uint8_t, 4> raw{
+		    static_cast<std::uint8_t>(detail::to_bcd(at.second) | ((m & 1) << 7)),
+		    static_cast<std::uint8_t>(detail::to_bcd(at.minute) | (((m >> 1) & 1) << 7)),
+		    static_cast<std::uint8_t>(detail::to_bcd(at.hour) | (((m >> 2) & 1) << 7)),
+		    static_cast<std::uint8_t>(day_date(at.day, rate == alarm1_rate::weekday_time_match) |
+		                              (((m >> 3) & 1) << 7))};
+		if (auto s = dev::write_regs(reg_alarm1, raw); !s)
+			return s;
+		return enable_interrupt ? enable_alarm_interrupt(a1ie) : status{};
+	}
+
+	[[nodiscard]] static status set_alarm2(const date_time &at, alarm2_rate rate, bool enable_interrupt = true)
+	{
+		auto m = static_cast<std::uint8_t>(rate);
+		std::array<std::uint8_t, 3> raw{
+		    static_cast<std::uint8_t>(detail::to_bcd(at.minute) | ((m & 1) << 7)),
+		    static_cast<std::uint8_t>(detail::to_bcd(at.hour) | (((m >> 1) & 1) << 7)),
+		    static_cast<std::uint8_t>(day_date(at.day, rate == alarm2_rate::weekday_time_match) |
+		                              (((m >> 2) & 1) << 7))};
+		if (auto s = dev::write_regs(reg_alarm2, raw); !s)
+			return s;
+		return enable_interrupt ? enable_alarm_interrupt(a2ie) : status{};
+	}
+
+	[[nodiscard]] static result<date_time> read_alarm1()
+	{
+		std::array<std::uint8_t, 4> raw;
+		if (auto s = dev::read_regs(reg_alarm1, raw); !s)
+			return std::unexpected(s.error());
+		date_time at{};
+		at.second = detail::from_bcd(raw[0] & 0x7f);
+		at.minute = detail::from_bcd(raw[1] & 0x7f);
+		at.hour = detail::hours_from_reg(raw[2] & 0x7f);
+		at.day = (raw[3] & 0x40) ? (raw[3] & 0x0f) : detail::from_bcd(raw[3] & 0x3f);
+		return at;
+	}
+
+	[[nodiscard]] static result<date_time> read_alarm2()
+	{
+		std::array<std::uint8_t, 3> raw;
+		if (auto s = dev::read_regs(reg_alarm2, raw); !s)
+			return std::unexpected(s.error());
+		date_time at{};
+		at.minute = detail::from_bcd(raw[0] & 0x7f);
+		at.hour = detail::hours_from_reg(raw[1] & 0x7f);
+		at.day = (raw[2] & 0x40) ? (raw[2] & 0x0f) : detail::from_bcd(raw[2] & 0x3f);
+		return at;
+	}
+
+	[[nodiscard]] static result<bool> alarm1_fired()
+	{
+		return flag_set(a1f);
+	}
+
+	[[nodiscard]] static result<bool> alarm2_fired()
+	{
+		return flag_set(a2f);
+	}
+
+	[[nodiscard]] static status clear_alarm1()
+	{
+		return clear_flag(a1f);
+	}
+
+	[[nodiscard]] static status clear_alarm2()
+	{
+		return clear_flag(a2f);
+	}
+
+	// True after the oscillator was ever stopped (first power-up, battery
+	// ran out): the clock needs to be set.
+	[[nodiscard]] static result<bool> oscillator_stopped()
+	{
+		return flag_set(osf);
+	}
+
+	[[nodiscard]] static status clear_oscillator_stopped()
+	{
+		return clear_flag(osf);
+	}
+
+	// Die temperature in quarter °C (updated every 64 s by the device).
+	[[nodiscard]] static result<std::int16_t> temperature_quarters()
+	{
+		std::array<std::uint8_t, 2> raw;
+		if (auto s = dev::read_regs(reg_temp, raw); !s)
+			return std::unexpected(s.error());
+		return static_cast<std::int16_t>((static_cast<std::int16_t>(static_cast<std::int8_t>(raw[0])) << 2) |
+		                                 (raw[1] >> 6));
+	}
+
+  private:
+	static constexpr std::uint8_t day_date(std::uint8_t day, bool weekday_mode)
+	{
+		if (weekday_mode)
+			return static_cast<std::uint8_t>(0x40 | (day & 0x0f));
+		return detail::to_bcd(day) & std::uint8_t{0x3f};
+	}
+
+	static status enable_alarm_interrupt(std::uint8_t enable_bit)
+	{
+		auto control = dev::read_reg(reg_control);
+		if (!control)
+			return std::unexpected(control.error());
+		return dev::write_reg(reg_control, static_cast<std::uint8_t>((*control & ~bbsqw) | intcn | enable_bit));
+	}
+
+	static result<bool> flag_set(std::uint8_t bit)
+	{
+		auto flags = dev::read_reg(reg_status);
+		if (!flags)
+			return std::unexpected(flags.error());
+		return (*flags & bit) != 0;
+	}
+
+	static status clear_flag(std::uint8_t bit)
+	{
+		auto flags = dev::read_reg(reg_status);
+		if (!flags)
+			return std::unexpected(flags.error());
+		return dev::write_reg(reg_status, static_cast<std::uint8_t>(*flags & ~bit));
+	}
+};
+
+} // namespace ds3231

rtc.cpp

@@ -1,617 +0,0 @@
-/*
- * DS RTC Library: DS1307 and DS3231 driver library
- * (C) 2011 Akafugu Corporation
- *
- * This program 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 2 of the License, or (at your option) any later
- * version.
- *
- * This program 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.
- *
- */
-
-/*
- * DS1307 register map
- *
- *  00h-06h: seconds, minutes, hours, day-of-week, date, month, year (all in BCD)
- *     bit 7 of seconds enables/disables clock
- *     bit 6 of hours toggles 12/24h mode (1 for 12h, 0 for 24h)
- *       when 12h mode is selected bit 5 is high for PM, low for AM
- *  07h: control
- *      bit7: OUT
- *      bit6: 0
- *      bit5: 0
- *      bit4: SQWE
- *      bit3: 0
- *      bit2: 0
- *      bit1: RS0
- *      bit0: RS1
- *  08h-3fh: 56 bytes of SRAM
- *
- * DS3231 register map
- *
- *  00h-06h: seconds, minutes, hours, day-of-week, date, month, year (all in BCD)
- *       bit 7 should be set to zero: The DS3231 clock is always running
- *  07h: A1M1  Alarm 1 seconds
- *  08h: A1M2  Alarm 1 minutes
- *  09h: A1M3  Alarm 1 hour (bit6 is am/pm flag in 12h mode)
- *  0ah: A1M4  Alarm 1 day/date (bit6: 1 for day, 0 for date)
- *  0bh: A2M2  Alarm 2 minutes
- *  0ch: A2M3  Alarm 2 hour (bit6 is am/pm flag in 12h mode)
- *  0dh: A2M4  Alarm 2 day/data (bit6: 1 for day, 0 for date)
- *       <see data sheet page12 for Alarm register mask bit tables:
- *        for alarm when hours, minutes and seconds match set 1000 for alarm 1>
- *  0eh: control
- *      bit7: !EOSC
- *      bit6: BBSQW
- *      bit5: CONV
- *      bit4: RS2
- *      bit3: RS1
- *      bit2: INTCN
- *      bit1: A2IE
- *      bit0: A1IE
- *  0fh: control/status
- *      bit7: OSF
- *      bit6: 0
- *      bit5: 0
- *      bit4: 0
- *      bit3: EN32kHz
- *      bit2: BSY
- *      bit1: A2F alarm 2 flag
- *      bit0: A1F alarm 1 flag
- * 10h: aging offset (signed)
- * 11h: MSB of temp (signed)
- * 12h: LSB of temp in bits 7 and 6 (0.25 degrees for each 00, 01, 10, 11)
- *
- */
-
-#include <avr/io.h>
-
-#define TRUE 1
-#define FALSE 0
-
-#include "../clock.hpp"
-
-#include "../i2c/i2c.hpp"
-using i2c_t = i2c::I2c<i2c::Hardware<100'000>>;
-
-#include "rtc.h"
-
-#define RTC_ADDR 0x68 // I2C address
-#define CH_BIT 7 // clock halt bit
-
-// statically allocated structure for time value
-struct rtc_tm _rtc_tm;
-
-uint8_t dec2bcd(uint8_t d)
-{
-  return ((d/10 * 16) + (d % 10));
-}
-
-uint8_t bcd2dec(uint8_t b)
-{
-  return ((b/16 * 10) + (b % 16));
-}
-
-uint8_t rtc_read_byte(uint8_t offset)
-{
-	i2c_t::start<RTC_ADDR>(false);
-	i2c_t::write(offset);
-	i2c_t::stop();
-
-	i2c_t::start<RTC_ADDR>(true);
-	const auto received = i2c_t::read<true>();
-	i2c_t::stop();
-
-	return received;
-}
-
-void rtc_write_byte(uint8_t b, uint8_t offset)
-{
-	i2c_t::start<RTC_ADDR>(false);
-	i2c_t::write(offset);
-	i2c_t::write(b);
-	i2c_t::stop();
-}
-
-static bool s_is_ds1307 = false;
-static bool s_is_ds3231 = false;
-
-void rtc_init(void)
-{
-	i2c_t::init();
-
-	// Attempt autodetection:
-	// 1) Read and save temperature register
-	// 2) Write a value to temperature register
-	// 3) Read back the value
-	//   equal to the one written: DS1307, write back saved value and return
-	//   different from written:   DS3231
-
-	uint8_t temp1 = rtc_read_byte(0x11);
-	uint8_t temp2 = rtc_read_byte(0x12);
-
-	rtc_write_byte(0xee, 0x11);
-	rtc_write_byte(0xdd, 0x12);
-
-	if (rtc_read_byte(0x11) == 0xee && rtc_read_byte(0x12) == 0xdd) {
-		s_is_ds1307 = true;
-		// restore values
-		rtc_write_byte(temp1, 0x11);
-		rtc_write_byte(temp2, 0x12);
-	}
-	else {
-		s_is_ds3231 = true;
-	}
-}
-
-// Autodetection
-bool rtc_is_ds1307(void) { return s_is_ds1307; }
-bool rtc_is_ds3231(void) { return s_is_ds3231; }
-
-// Autodetection override
-void rtc_set_ds1307(void) { s_is_ds1307 = true;   s_is_ds3231 = false; }
-void rtc_set_ds3231(void) { s_is_ds1307 = false;  s_is_ds3231 = true;  }
-
-struct rtc_tm* rtc_get_time(void)
-{
-	uint8_t rtc[9];
-	uint8_t century = 0;
-
-	// read 7 bytes starting from register 0
-	// sec, min, hour, day-of-week, date, month, year
-	i2c_t::start<RTC_ADDR>(false);
-	i2c_t::write(0x0);
-	i2c_t::stop();
-
-	i2c_t::start<RTC_ADDR>(true);
-	i2c_t::readBytes<7>(rtc);
-	i2c_t::stop();
-
-	// Clear clock halt bit from read data
-	// This starts the clock for a DS1307, and has no effect for a DS3231
-	rtc[0] &= ~(_BV(CH_BIT)); // clear bit
-
-	_rtc_tm.sec = bcd2dec(rtc[0]);
-	_rtc_tm.min = bcd2dec(rtc[1]);
-	_rtc_tm.hour = bcd2dec(rtc[2]);
-	_rtc_tm.mday = bcd2dec(rtc[4]);
-	_rtc_tm.mon = bcd2dec(rtc[5] & 0x1F); // returns 1-12
-	century = (rtc[5] & 0x80) >> 7;
-	_rtc_tm.year = century == 1 ? 2000 + bcd2dec(rtc[6]) : 1900 + bcd2dec(rtc[6]); // year 0-99
-	_rtc_tm.wday = bcd2dec(rtc[3]); // returns 1-7
-
-	if (_rtc_tm.hour == 0) {
-		_rtc_tm.twelveHour = 0;
-		_rtc_tm.am = 1;
-	} else if (_rtc_tm.hour < 12) {
-		_rtc_tm.twelveHour = _rtc_tm.hour;
-		_rtc_tm.am = 1;
-	} else {
-		_rtc_tm.twelveHour = _rtc_tm.hour - 12;
-		_rtc_tm.am = 0;
-	}
-
-	return &_rtc_tm;
-}
-
-void rtc_get_time_s(uint8_t* hour, uint8_t* min, uint8_t* sec)
-{
-	uint8_t rtc[9];
-
-	// read 7 bytes starting from register 0
-	// sec, min, hour, day-of-week, date, month, year
-	i2c_t::start<RTC_ADDR>(false);
-	i2c_t::write(0x0);
-	i2c_t::stop();
-
-	i2c_t::start<RTC_ADDR>(true);
-	i2c_t::readBytes<7>(rtc);
-	i2c_t::stop();
-
-	if (sec)  *sec =  bcd2dec(rtc[0]);
-	if (min)  *min =  bcd2dec(rtc[1]);
-	if (hour) *hour = bcd2dec(rtc[2]);
-}
-
-// fixme: support 12-hour mode for setting time
-void rtc_set_time(struct rtc_tm* tm_)
-{
-	i2c_t::start<RTC_ADDR>(false);
-	i2c_t::write(0x0);
-
-	uint8_t century;
-	if (tm_->year > 2000) {
-		century = 0x80;
-		tm_->year = tm_->year - 2000;
-	} else {
-		century = 0;
-		tm_->year = tm_->year - 1900;
-	}
-
-	// clock halt bit is 7th bit of seconds: this is always cleared to start the clock
-	i2c_t::write(dec2bcd(tm_->sec)); // seconds
-	i2c_t::write(dec2bcd(tm_->min)); // minutes
-	i2c_t::write(dec2bcd(tm_->hour)); // hours
-	i2c_t::write(dec2bcd(tm_->wday)); // day of week
-	i2c_t::write(dec2bcd(tm_->mday)); // day
-	i2c_t::write(dec2bcd(tm_->mon) + century); // month
-	i2c_t::write(dec2bcd(tm_->year)); // year
-
-	i2c_t::stop();
-}
-
-void rtc_set_time_s(uint8_t hour, uint8_t min, uint8_t sec)
-{
-	i2c_t::start<RTC_ADDR>(false);
-	i2c_t::write(0x0);
-
-	// clock halt bit is 7th bit of seconds: this is always cleared to start the clock
-	i2c_t::write(dec2bcd(sec)); // seconds
-	i2c_t::write(dec2bcd(min)); // minutes
-	i2c_t::write(dec2bcd(hour)); // hours
-
-	i2c_t::stop();
-}
-
-// DS1307 only (has no effect when run on DS3231)
-// halt/start the clock
-// 7th bit of register 0 (second register)
-// 0 = clock is running
-// 1 = clock is not running
-void rtc_run_clock(bool run)
-{
-  if (s_is_ds3231) return;
-
-  uint8_t b = rtc_read_byte(0x0);
-
-  if (run)
-    b &= ~(_BV(CH_BIT)); // clear bit
-  else
-    b |= _BV(CH_BIT); // set bit
-
-  rtc_write_byte(b, 0x0);
-}
-
-// DS1307 only
-// Returns true if the clock is running, false otherwise
-// For DS3231, it always returns true
-bool rtc_is_clock_running(void)
-{
-  if (s_is_ds3231) return true;
-
-  uint8_t b = rtc_read_byte(0x0);
-
-  if (b & _BV(CH_BIT)) return false;
-  return true;
-}
-
-void ds3231_get_temp_int(int8_t* i, uint8_t* f)
-{
-	uint8_t msb, lsb;
-
-	*i = 0;
-	*f = 0;
-
-	if (s_is_ds1307) return; // only valid on DS3231
-
-	i2c_t::start<RTC_ADDR>(false);
-	// temp registers 0x11 and 0x12
-	i2c_t::write(0x11);
-	i2c_t::stop();
-
-	i2c_t::start<RTC_ADDR>(true);
-	msb = i2c_t::read(); // integer part (in twos complement)
-	lsb = i2c_t::read<true>(); // fraction part
-
-	// integer part in entire byte
-	*i = msb;
-	// fractional part in top two bits (increments of 0.25)
-	*f = (lsb >> 6) * 25;
-
-	// float value can be read like so:
-	// float temp = ((((short)msb << 8) | (short)lsb) >> 6) / 4.0f;
-}
-
-void rtc_force_temp_conversion(uint8_t block)
-{
-	if (s_is_ds1307) return; // only valid on DS3231
-
-	// read control register (0x0E)
-	i2c_t::start<RTC_ADDR>(false);
-	i2c_t::write(0x0E);
-	i2c_t::stop();
-
-	i2c_t::start<RTC_ADDR>(true);
-	uint8_t ctrl = i2c_t::read<true>();
-	i2c_t::stop();
-
-	ctrl |= 0b00100000; // Set CONV bit
-
-	// write new control register value
-	i2c_t::start<RTC_ADDR>(false);
-	i2c_t::write(0x0E);
-	i2c_t::write(ctrl);
-	i2c_t::stop();
-
-	if (!block) return;
-
-	// Temp conversion is ready when control register becomes 0
-	do {
-		// Block until CONV is 0
-		i2c_t::start<RTC_ADDR>(false);
-		i2c_t::write(0x0E);
-		i2c_t::stop();
-
-		i2c_t::start<RTC_ADDR>(true);
-		// HACK: Missing stop after read, might still work though
-	} while ((i2c_t::read<true>() & 0b00100000) != 0);
-}
-
-
-#define DS1307_SRAM_ADDR 0x08
-
-// SRAM: 56 bytes from address 0x08 to 0x3f (DS1307-only)
-void rtc_get_sram(uint8_t* data)
-{
-	// cannot receive 56 bytes in one go, because of the TWI library buffer limit
-	// so just receive one at a time for simplicity
-  	for(int i=0;i<56;i++)
-		data[i] = rtc_get_sram_byte(i);
-}
-
-void rtc_set_sram(uint8_t *data)
-{
-	// cannot send 56 bytes in one go, because of the TWI library buffer limit
-	// so just send one at a time for simplicity
-  	for(int i=0;i<56;i++)
-		rtc_set_sram_byte(data[i], i);
-}
-
-uint8_t rtc_get_sram_byte(uint8_t offset)
-{
-	i2c_t::start<RTC_ADDR>(false);
-	i2c_t::write(DS1307_SRAM_ADDR + offset);
-	i2c_t::stop();
-
-	i2c_t::start<RTC_ADDR>(true);
-	const auto received = i2c_t::read<true>();
-	i2c_t::stop();
-	return received;
-}
-
-void rtc_set_sram_byte(uint8_t b, uint8_t offset)
-{
-	i2c_t::start<RTC_ADDR>(false);
-	i2c_t::write(DS1307_SRAM_ADDR + offset);
-	i2c_t::write(b);
-	i2c_t::stop();
-}
-
-void rtc_SQW_enable(bool enable)
-{
-	if (s_is_ds1307) {
-		i2c_t::start<RTC_ADDR>(false);
-		i2c_t::write(0x07);
-		i2c_t::stop();
-
-		// read control
-		i2c_t::start<RTC_ADDR>(true);
-		uint8_t control = i2c_t::read<true>();
-		i2c_t::stop();
-
-		if (enable)
-			control |=  0b00010000; // set SQWE to 1
-		else
-			control &= ~0b00010000; // set SQWE to 0
-
-		// write control back
-		i2c_t::start<RTC_ADDR>(false);
-		i2c_t::write(0x07);
-		i2c_t::write(control);
-		i2c_t::stop();
-
-	}
-	else { // DS3231
-		i2c_t::start<RTC_ADDR>(false);
-		i2c_t::write(0x0E);
-		i2c_t::stop();
-
-		// read control
-		i2c_t::start<RTC_ADDR>(true);
-		uint8_t control = i2c_t::read<true>();
-		i2c_t::stop();
-
-		if (enable) {
-			control |=  0b01000000; // set BBSQW to 1
-			control &= ~0b00000100; // set INTCN to 0
-		}
-		else {
-			control &= ~0b01000000; // set BBSQW to 0
-		}
-
-		// write control back
-		i2c_t::start<RTC_ADDR>(false);
-		i2c_t::write(0x0E);
-		i2c_t::write(control);
-		i2c_t::stop();
-	}
-}
-
-void rtc_SQW_set_freq(enum RTC_SQW_FREQ freq)
-{
-	if (s_is_ds1307) {
-		i2c_t::start<RTC_ADDR>(false);
-		i2c_t::write(0x07);
-		i2c_t::stop();
-
-		// read control (uses bits 0 and 1)
-		i2c_t::start<RTC_ADDR>(true);
-		uint8_t control = i2c_t::read<true>();
-		i2c_t::stop();
-
-		control &= ~0b00000011; // Set to 0
-		control |= freq; // Set freq bitmask
-
-		// write control back
-		i2c_t::start<RTC_ADDR>(false);
-		i2c_t::write(0x07);
-		i2c_t::write(control);
-		i2c_t::stop();
-
-	}
-	else { // DS3231
-		i2c_t::start<RTC_ADDR>(false);
-		i2c_t::write(0x0E);
-		i2c_t::stop();
-
-		// read control (uses bits 3 and 4)
-		i2c_t::start<RTC_ADDR>(true);
-		uint8_t control = i2c_t::read<true>();
-		i2c_t::stop();
-
-		control &= ~0b00011000; // Set to 0
-		control |= (freq << 4); // Set freq bitmask
-
-		// write control back
-		i2c_t::start<RTC_ADDR>(false);
-		i2c_t::write(0x0E);
-		i2c_t::write(control);
-		i2c_t::stop();
-	}
-}
-
-void rtc_osc32kHz_enable(bool enable)
-{
-	if (!s_is_ds3231) return;
-
-	i2c_t::start<RTC_ADDR>(false);
-	i2c_t::write(0x0F);
-	i2c_t::stop();
-
-	// read status
-	i2c_t::start<RTC_ADDR>(true);
-	uint8_t status = i2c_t::read<true>();
-	i2c_t::stop();
-
-	if (enable)
-		status |= 0b00001000; // set to 1
-	else
-		status &= ~0b00001000; // Set to 0
-
-	// write status back
-	i2c_t::start<RTC_ADDR>(false);
-	i2c_t::write(0x0F);
-	i2c_t::write(status);
-	i2c_t::stop();
-}
-
-// Alarm functionality
-// fixme: should decide if "alarm disabled" mode should be available, or if alarm should always be enabled
-// at 00:00:00. Currently, "alarm disabled" only works for ds3231
-void rtc_reset_alarm(void)
-{
-	if (s_is_ds1307) {
-		rtc_set_sram_byte(0, 0); // hour
-		rtc_set_sram_byte(0, 1); // minute
-		rtc_set_sram_byte(0, 2); // second
-	}
-	else {
-		// writing 0 to bit 7 of all four alarm 1 registers disables alarm
-		rtc_write_byte(0, 0x07); // second
-		rtc_write_byte(0, 0x08); // minute
-		rtc_write_byte(0, 0x09); // hour
-		rtc_write_byte(0, 0x0a); // day
-	}
-}
-
-// fixme: add an option to set whether or not the INTCN and Interrupt Enable flag is set when setting the alarm
-void rtc_set_alarm_s(uint8_t hour, uint8_t min, uint8_t sec)
-{
-	if (hour > 23) return;
-	if (min > 59) return;
-	if (sec > 59) return;
-
-	if (s_is_ds1307) {
-		rtc_set_sram_byte(hour, 0); // hour
-		rtc_set_sram_byte(min,  1); // minute
-		rtc_set_sram_byte(sec,  2); // second
-	}
-	else {
-		/*
-		 *  07h: A1M1:0  Alarm 1 seconds
-		 *  08h: A1M2:0  Alarm 1 minutes
-		 *  09h: A1M3:0  Alarm 1 hour (bit6 is am/pm flag in 12h mode)
-		 *  0ah: A1M4:1  Alarm 1 day/date (bit6: 1 for day, 0 for date)
-		 *  Sets alarm to fire when hour, minute and second matches
-		 */
-		rtc_write_byte(dec2bcd(sec),  0x07); // second
-		rtc_write_byte(dec2bcd(min),  0x08); // minute
-		rtc_write_byte(dec2bcd(hour), 0x09); // hour
-		rtc_write_byte(0b10000001,         0x0a); // day (upper bit must be set)
-
-		// clear alarm flag
-		uint8_t val = rtc_read_byte(0x0f);
-		rtc_write_byte(val & ~0b00000001, 0x0f);
-	}
-}
-
-void rtc_set_alarm(struct rtc_tm* tm_)
-{
-	if (!tm_) return;
-	rtc_set_alarm_s(tm_->hour, tm_->min, tm_->sec);
-}
-
-void rtc_get_alarm_s(uint8_t* hour, uint8_t* min, uint8_t* sec)
-{
-	if (s_is_ds1307) {
-		if (hour) *hour = rtc_get_sram_byte(0);
-		if (min)  *min  = rtc_get_sram_byte(1);
-		if (sec)  *sec  = rtc_get_sram_byte(2);
-	}
-	else {
-		*sec  = bcd2dec(rtc_read_byte(0x07) & ~0b10000000);
-		*min  = bcd2dec(rtc_read_byte(0x08) & ~0b10000000);
-		*hour = bcd2dec(rtc_read_byte(0x09) & ~0b10000000);
-	}
-}
-
-struct rtc_tm* rtc_get_alarm(void)
-{
-	uint8_t hour, min, sec;
-
-	rtc_get_alarm_s(&hour, &min, &sec);
-	_rtc_tm.hour = hour;
-	_rtc_tm.min = min;
-	_rtc_tm.sec = sec;
-	return &_rtc_tm;
-}
-
-bool rtc_check_alarm(void)
-{
-	if (s_is_ds1307) {
-		uint8_t hour = rtc_get_sram_byte(0);
-		uint8_t min  = rtc_get_sram_byte(1);
-		uint8_t sec  = rtc_get_sram_byte(2);
-
-		uint8_t cur_hour, cur_min, cur_sec;
-		rtc_get_time_s(&cur_hour, &cur_min, &cur_sec);
-
-		if (cur_hour == hour && cur_min == min && cur_sec == sec)
-			return true;
-		return false;
-	}
-	else {
-		// Alarm 1 flag (A1F) in bit 0
-		uint8_t val = rtc_read_byte(0x0f);
-
-		// clear flag when set
-		if (val & 1)
-			rtc_write_byte(val & ~0b00000001, 0x0f);
-
-		return val & 1 ? 1 : 0;
-	}
-}

rtc.h

@@ -1,106 +0,0 @@
-/*
- * DS RTC Library: DS1307 and DS3231 driver library
- * (C) 2011 Akafugu Corporation
- *
- * This program 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 2 of the License, or (at your option) any later
- * version.
- *
- * This program 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.
- *
- */
-
-#ifndef DS1307_H
-#define DS1307_H
-
-#include <stdbool.h>
-#include <avr/io.h>
-
-#define DS1307_SLAVE_ADDR 0b11010000
-
-/** Time structure
- *
- * Both 24-hour and 12-hour time is stored, and is always updated when rtc_get_time is called.
- *
- * When setting time and alarm, 24-hour mode is always used.
- *
- * If you run your clock in 12-hour mode:
- * - set time hour to store in twelveHour and set am to true or false.
- * - call rtc_12h_translate (this will put the correct value in hour, so you don't have to
- *   calculate it yourself.
- * - call rtc_set_alarm or rtc_set_clock
- *
- * Note that rtc_set_clock_s, rtc_set_alarm_s, rtc_get_time_s, rtc_set_alarm_s always operate in 24-hour mode
- * and translation has to be done manually (you can call rtc_24h_to_12h to perform the calculation)
- *
- */
-struct rtc_tm {
-	int sec;      // 0 to 59
-	int min;      // 0 to 59
-	int hour;     // 0 to 23
-	int mday;     // 1 to 31
-	int mon;      // 1 to 12
-	int year;     // year-99
-	int wday;     // 1-7
-
-    // 12-hour clock data
-    bool am; // true for AM, false for PM
-    int twelveHour; // 12 hour clock time
-};
-
-// statically allocated
-extern struct rtc_tm _rtc_tm;
-
-// Initialize the RTC and autodetect type (DS1307 or DS3231)
-void rtc_init(void);
-
-// Autodetection
-bool rtc_is_ds1307(void);
-bool rtc_is_ds3231(void);
-
-void rtc_set_ds1307(void);
-void rtc_set_ds3231(void);
-
-// Get/set time
-// Gets the time: Supports both 24-hour and 12-hour mode
-struct rtc_tm* rtc_get_time(void);
-// Gets the time: 24-hour mode only
-void rtc_get_time_s(uint8_t* hour, uint8_t* min, uint8_t* sec);
-// Sets the time: Supports both 24-hour and 12-hour mode
-void rtc_set_time(struct rtc_tm* tm_);
-// Sets the time: Supports 12-hour mode only
-void rtc_set_time_s(uint8_t hour, uint8_t min, uint8_t sec);
-
-// start/stop clock running (DS1307 only)
-void rtc_run_clock(bool run);
-bool rtc_is_clock_running(void);
-
-// Read Temperature (DS3231 only)
-void  ds3231_get_temp_int(int8_t* i, uint8_t* f);
-void rtc_force_temp_conversion(uint8_t block);
-
-// SRAM read/write DS1307 only
-void rtc_get_sram(uint8_t* data);
-void rtc_set_sram(uint8_t *data);
-uint8_t rtc_get_sram_byte(uint8_t offset);
-void rtc_set_sram_byte(uint8_t b, uint8_t offset);
-
-  // Auxillary functions
-enum RTC_SQW_FREQ { FREQ_1 = 0, FREQ_1024, FREQ_4096, FREQ_8192 };
-
-void rtc_SQW_enable(bool enable);
-void rtc_SQW_set_freq(enum RTC_SQW_FREQ freq);
-void rtc_osc32kHz_enable(bool enable);
-
-// Alarm functionality
-void rtc_reset_alarm(void);
-void rtc_set_alarm(struct rtc_tm* tm_);
-void rtc_set_alarm_s(uint8_t hour, uint8_t min, uint8_t sec);
-struct rtc_tm* rtc_get_alarm(void);
-void rtc_get_alarm_s(uint8_t* hour, uint8_t* min, uint8_t* sec);
-bool rtc_check_alarm(void);
-
-#endif