Added timing library

include/timer.h

+/*
+ * Time-Keeping helper
+ */
+
+#ifndef _TIMER_H
+#define _TIMER_H
+
+typedef uint64_t time_t;
+
+void timerInit(void);
+time_t timerGet(void);
+
+#endif
+

makefile

 MCU = attiny85
 F_CPU = 16000000
 RM = rm -rf
+MKDIR = mkdir -p
 EXTRAINCDIR = include
 CSTANDARD = gnu99
+BUILDDIR = build
 
 GCC = avr-gcc
 SIZE = avr-size
 OBJDUMP = avr-objdump
 AVRDUDE = avrdude
 
-SRC = src/spi.c
+SRC = src/main.c
+SRC += src/timer.c
+SRC += src/spi.c
 SRC += src/cc2500.c
-SRC += src/frsky_arduino_rx_complete.c
+SRC += src/rx.c
 
-OBJ = $(SRC:.c=.o)
+OBJ = $(addprefix $(BUILDDIR)/, $(SRC:.c=.o))
 
 CARGS = -mmcu=$(MCU)
 CARGS += -I$(EXTRAINCDIR)
 CARGS += -fshort-enums
 CARGS += -Wall -pedantic -Wstrict-prototypes -Wshadow
 CARGS += -Wpointer-arith -Wcast-qual -Wextra
-CARGS += -Wno-write-strings -Wno-unused-parameter
+CARGS += -Wno-main -Wno-write-strings -Wno-unused-parameter
 CARGS += -std=$(CSTANDARD)
 CARGS += -DF_CPU=$(F_CPU)
-#CARGS += -lm -lprintf_flt
 CARGS += -ffunction-sections
 
 LINKER = -Wl,--relax
-#LINKER = -Wl,--relax,-u,vfprintf,-lm,-lprintf_flt,-u,vfscanf,-lscanf_flt
-#LINKER += -Wl,--defsym=__heap_start=0x802200,--defsym=__heap_end=0x80ffff
-#LINKER += -Wl,-gc-sections
 
 PROGRAMMER = avrisp2
 ISPPORT = usb
 
 TARGET = rx
 
-all: $(TARGET).hex
+all: $(BUILDDIR)/$(TARGET).hex
 
-%.o: %.c
+$(BUILDDIR)/%.o: %.c
+	@$(MKDIR) $(BUILDDIR)/$(dir $<)
 	$(GCC) -c $< -o $@ $(CARGS)
 
-$(TARGET).elf: $(OBJ)
+$(BUILDDIR)/$(TARGET).elf: $(OBJ)
 	$(GCC) $(CARGS) $(OBJ) --output $@ $(LINKER) -Wl,-Map -Wl,$(@:.elf=.map)
-	$(SIZE) --mcu=$(MCU) -C $@
+	$(SIZE) $@
 
-$(TARGET).hex: $(TARGET).elf
+$(BUILDDIR)/$(TARGET).hex: $(BUILDDIR)/$(TARGET).elf
 	$(OBJCOPY) -O ihex $< $@
 	$(OBJDUMP) -h -S $< > $(@:.hex=.lss)
 
-program: $(TARGET).hex
+program: $(BUILDDIR)/$(TARGET).hex
 	$(AVRDUDE) -p $(MCU) -c $(PROGRAMMER) -P $(ISPPORT) -e -U $(TARGET).hex
 
 clean:
-	$(RM) $(OBJ)
-	$(RM) *.o
-	$(RM) *.elf
-	$(RM) *.hex
-	$(RM) *.lss
-	$(RM) *.map
+	$(RM) $(BUILDDIR)
+

src/timer.c

+/*
+ * Time-Keeping helper
+ */
+
+#include <avr/io.h>
+#include <avr/interrupt.h>
+
+#include "timer.h"
+
+volatile time_t systemTime = 0;
+
+void timerInit(void) {
+    TCCR1 |= (1 << CTC1); // CTC Mode
+    TCCR1 |= (1 << CS12) | (1 << CS11) | (1 << CS10); // Prescaler: 64
+    OCR1A = 250; // Count to 250
+    TIMSK |= (1 << OCIE1A); // Enable compare match interrupt
+}
+
+ISR(TIMER1_COMPA_vect) {
+    systemTime++; // one millisecond has passed
+}
+
+time_t timerGet(void) {
+    return systemTime;
+}
+