Here is a list of all files with brief descriptions:

[detail level 1234]

core_types
format
time.h	Time and date format structures for embedded applications
return
status.h	Enumeration for return status options
drivers
rtc
mcp7940
mcp7940.c	Implementation of the MCP7940 driver functions
mcp7940.h	Header file with declarations and macros for driving an mcp7940
hal
avr0
twi
twi.c	Source file with implementation of hardware TWI/I2C functions and macros
twi.h	Header file with declarations and macros for hardware TWI/I2C
common
defines
TWI_defines.h	Macro definitions for TWI/I2C communication flags and operations
enums
TWI_enums.h	Enumerations for TWI/I2C interface modes, operations, acknowledgment, and error codes
utils
macros
stringify.h	Helper macros for stringification in C preprocessor
systick
systick.c	Implements the SysTick utility functions
systick.h	Header file with declarations and macros for systick utility
time
validate.c
validate.h