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help me:how to interface between keyboard and computer

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baby-in-elec

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I want to design a circuit which has fuctions like computer's keyboard. With it, i can put numbers to microprocessor that it can understand what that number is so that i can process it as i want. I dont know exactly how computer can understand which number it receive?
Thanks for helping me!
 

Strange, normally people interface a standard keyboard to a microcontroller. You are doing the opposite.
Anyway, the simplest way is to simply implement a matrix keypad to the parallel port. If you want to interface to the PS/2 port, the protocol can be found at . The kbd clk and data lines are open collector. Just do a direct connection with a pull-up resistor.
Sincerely speaking, it'll be easier to just use a mini keyboard for your application. If you really need something really compact, I've seen keyboards that only contain the numeric keypad, though they are often a couple times the price of a full PS/2 keyboard.
 

Keyboards use RS232 to communicate with the microprocessor. The speed of the data is slow so the microprocessor can do other things while it waits on the RS232 communication.
 

Kevin Weddle said:
Keyboards use RS232 to communicate with the microprocessor. The speed of the data is slow so the microprocessor can do other things while it waits on the RS232 communication.
Click to expand...
Keyboards use a serial protocol, but not the RS232 one. They typically have 2 biodirectional lines, one for clk and one for data, with an additional common ground line. I don't know what is your definition of slow, but I've personally seen clock rates of up to 30kHz output from PCs, and they seem to vary from PC to PC. There is no specified frequency with which the clock should be. But 30kHz is sufficient to load a standard 10MIPs PIC quite heavily, especially if it has other tasks to fulfill.
 

**broken link removed**

This project it is a good starting point, because the author offers the source code.
 

Checkmate, that is a good point. I did not realize your knowledge of the subject. I was being general in my statements.
 

i was also looking for same thing actually not using today's microprocessor but using 8085 mircoprocessor.......... if any one has done as project please let me know....
 

in a 4x4 keyboard we have 4x4 matrix line where each key connect to a row & a coloumn line. microprocessor sweep vertical & horizontal lines in specific intervals to find changes.
 

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