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Pls help me..........this is secondtime i am posting this...

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vibeesh

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I am going to interface..keypad with 89c51...my problem is my port pins are alredy uesd for diffrent purpose icant change the configuration...i need a key pad that produce serial output or RS232 compatible output....Is there any dedicated keypad encoder IC available in market that produce rs 232 compatible output...
 

Re: Pls help me..........this is secondtime i am posting thi

One option is to "create" such an IC by yourself ..
Take, for example, PICAXE microcontroller .. It has several general purpose I/O pins and RS-232 TX and RX pins ..
Here is an example of a KEYPAD lock based on PICAXE microcontroller ..
https://smendes.com/el31p/KeypadLock.pdf
With just slight modifications it can read keypad and transmit data through serial port, and it can perform this task THE WAY YOU WANT ..

Regards,
IanP
 

Re: Pls help me..........this is secondtime i am posting thi

IanP said:
One option is to "create" such an IC by yourself ..
Take, for example, PICAXE microcontroller .. It has several general purpose I/O pins and RS-232 TX and RX pins ..
Here is an example of a KEYPAD lock based on PICAXE microcontroller ..
https://smendes.com/el31p/KeypadLock.pdf
With just slight modifications it can read keypad and transmit data through serial port, and it can perform this task THE WAY YOU WANT ..

Regards,
IanP

otherthan microcontroller is there any dedicated IC to do this...
 
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Re: Pls help me..........this is secondtime i am posting thi

Not that I am aware of ..
There is Keypad IC, namely the 74C922, but it doesn't have serial port and has to be read by a microcontroller through 4-bit data + control signals port ..
https://www.elexp.com/tips/74C922.pdf
So, from that point of view option with PICAXE microcontroller can be very tempting ..

Regards,
IanP
 

Re: Pls help me..........this is secondtime i am posting thi

Hel0
vibeesh
There is way to do with SINGLE port line try this one,
But u have to dedicate one interrupt line.
This techniqu is basically pulse width modulation.

All the best
--babesh
 

for your purposs you can program other microcontroller for keyboard application with serial interface
 

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