here is my experiment with i2c bus for interfacing serial EEPROM (24C256) and RTC (DS1307) using AVR microcontroller ATmega128. The circuit is also provided with an RS232 port for connecting with PC to send commands for reading/writing EEPROM or setting date/time in RTC (Click on images to enlarge them).
Communication with PC is done through Hyper Terminal. A screen shot of the message sent to PC by microcontroller immediately after power ON is shown in the figure at the left, where the user is asked to enter choice from the menu options related to EEPROM and RTC. User can store data in EEPROM, or set RTC date and time by entering them using PC keyboard.
Hyper Terminal is used with 19200 Baud, No parity, No hardware flow control settings.
When the circuit is powered on, a welcome message is displayed on the Hyper Terminal window and a menu with 9 options (0-8) is displayed (refer to the figure). The options are explained here:
0: Erase EEPROM (fills eeprom with 0xff bytes)
1: Write EEPROM (starts writing eeprom starting with 0x0000 address)
2: Read EEPROM (reads eeprom starting with 0x0000 address)
3: Write eeprom page (writes one page of eeprom at specified page number)
4: Read eeprom page (Reads one page of eeprom at specified page number)
5: Display RTC Date (Displays current date from RTC)
6: Display RTC time (Displays current time from RTC)
7: Update RTC Date (Setting new date in RTC)
8: Update RTC time (Setting new time in RTC)
The option is selected from PC keyboard. While writing to eeprom or RTC the data is entered using PC keyboard as specified by the program.
The software routines include DS1307 library, 24C256 library & I2C library along with the main function.
The code is written in C using winAVR (inside AVRStudio). The complete project folder can be downloaded here in zip format (updated on 25-April-2009, earlier it was in ICCAVR format):
Here is running simulation on Proteus ISIS (click on image to enlarge it):
Complete Source code (winAVR, AVRStudio-4 format)
Proteus Simulation Model
(last updated on 25-April-2009)