hi,
am new to microcontroller.i have been assigned a project of calculator.i am stuck on one thing that when i have to give input through keyboard to microcontroller my pc voltages and 8051 microcontroller voltages are not same.so what device i must use in between them to make my pc and microntroller voltages same.do i have to use voltage converter.please elaborate.thank u.

 

First, how are you to communicate with the PC? Through the Serial (RS-232) port, through the printer port, or through the USB bus? The answer to this question will indicate the answer.

ASSuming the serial port, the easiest way is to use a level-shifter chip, such as the MAX 232.

--Rich

 

yup i have to use serial parallel port between pc and microcontroller.thanks 2 u.

 

and i dont know which port to use?printer port or usb port?what do u suggest to use?

 

Try using these handy parts. They work in both directions by virtue of using "TTL" levels.
http://www.onsemi.com/pub_link/Collateral/MC74VHC1GT50-D.PDF

 

buy one of these and you can use your USB port:
http://www.smileymicros.com/index.php?module=pagemaster&PAGE_user_op=view_page&PAGE_id=31