added incomplete RTC module

Makefile

@@ -1,5 +1,5 @@
 PRG            = rgbyteclock
-OBJ            = rgbyteclock.o timer.o lcd.o main.o
+OBJ            = rgbyteclock.o timer.o lcd.o main.o rtc.o
 MCU_TARGET     = atmega16
 OPTIMIZE       = -Os
 
@@ -25,10 +25,11 @@ $(PRG).elf: $(OBJ)
 	@echo
 
 # dependency:
-rgbyteclock.o: timer.o lcd.o rgbyteclock.h
+rgbyteclock.o: timer.o lcd.o rgbyteclock.h rtc.o
 main.o: rgbyteclock.o
 timer.o:timer.h
 lcd.o: lcd.h
+rtc.o: rtc.h
 
 clean:
 	rm -rf *.o $(PRG).elf *.eps *.png *.pdf *.bak 

rtc.c

@@ -0,0 +1,132 @@
+/*
+ * ----------------------------------------------------------------------------
+ * "THE BEER-WARE LICENSE" (Revision 42):
+ * <struppi@struppi.name> wrote this file. As long as you retain this notice you
+ * can do whatever you want with this stuff. If we meet some day, and you think
+ * this stuff is worth it, you can buy me a beer in return.
+ * (c) 2014 Stefan Rupp
+ * ----------------------------------------------------------------------------
+ */
+ 
+#include <avr/io.h>
+#include "rtc.h"
+#include <stdlib.h>
+#include <avr/interrupt.h>
+
+
+static volatile uint32_t rtc_time;
+
+ISR(TIMER2_COMP_vect) {
+  ++rtc_time;
+  return;
+}
+
+void rtc_init(void)
+{
+  // Stop all interrupts
+  cli();
+  // Reset timer to zero
+  rtc_time = 0;
+
+  // ...
+  // ...
+  // ...
+  
+  sei();
+}
+
+
+/**
+ * Get the current time
+ * \return the current time (in s)
+ */
+inline uint32_t rtc_get(void)
+{
+  uint32_t t;
+  uint8_t sreg;
+
+  sreg = SREG;
+  cli();
+  t = rtc_time;
+  SREG = sreg;
+  return t;
+}
+
+#if 0
+
+/**
+ * Decode a integer timestamp (in seconds)
+ * into days, hours, minutes, seconds
+ * \param time the time in seconds
+ * \param days will be filled in to contain the days after return
+ * \param hours will be filled in to contain the hours after return
+ * \param minutes will be filled in to contain the minutes after return
+ * \param seconds will be filled in to contain the seconds after return
+ * \param ms be filled in to contain the microseconds after return
+ */
+void rtc_decode(uint32_t time, uint16_t days, uint8_t *hours, uint8_t *minutes, uint8_t *seconds)
+{
+  if (seconds != NULL) {
+    *seconds = time % 60;
+  }
+  time /= 60;
+  if (minutes != NULL) {
+    *minutes = time % 60;
+  }
+  time /= 60;
+  if (hours != NULL) {
+    *hours = time;
+  }
+  return;
+}
+
+/**
+ * Encode a time given as hours, minutes, seconds and microsecods into a integer storing micorseconds
+ * \param time the variable to store the time into
+ * \param hour the hours to store
+ * \param hour the minutes to store
+ * \param hour the seconds to store
+ * \param hour the microseconds to store
+ */
+void timer_encode(uint32_t *time, uint8_t hours, uint8_t minutes, uint8_t seconds, uint16_t ms)
+{
+
+  *time = hours;
+  *time *= 60;
+
+  *time += minutes;
+  *time *= 60;
+
+  *time += seconds;
+  *time *= 1000U;
+
+  *time += ms;
+
+  return;
+}
+
+/*
+void timer_validate(uint8_t *hours, uint8_t *minutes, uint8_t *seconds, uint16_t *ms)
+{ 
+
+  while (*ms >= 1000) {
+    *ms -= 1000;
+    (*seconds)++;
+  }
+
+  while (*seconds >= 60) {
+    *ms -= 60;
+    (*minutes)++;
+  }
+
+  while (*minutes >= 60) {
+    *minutes -= 60;
+    (*hours)++;
+  }
+
+  return;
+}
+*/
+
+#endif
+

rtc.h

@@ -0,0 +1,10 @@
+#if !defined RTC_H
+#define RTC_H
+
+#include <inttypes.h>
+
+
+uint32_t rtc_get(void);
+void rtc_init(void);
+
+#endif // RTC_H