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How to interface 2 MAX232 on single UC(Rx,Tx,Gnd)

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nscpl

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Hi all,
While designing new hardware for my Weather monitering system. I'm little stucked.
The thing is I my UC(Atmel AT89s8253) is already having interface with PC through
AT89s8253(Rx,Tx)->MAX232->DB9-DB9<-PC
Now as new GPRS card(It works only on RS232) is included, I need to use same Rx, Tx pins with it using other MAX232.
How can I make it possible.
Thanks in advance,
Regards,
Nikhilesh
 

This microcontroller has only one UART, but you can create second "software" UART and connect the second RS-232 device as follows:
RX pin - INT0 or INT1
TX pin - any available general purpose I/O

Goto:
**broken link removed**
and find dupuart.zip ..
It is an example of software UART for reduced-pin, harware UART-less version of 8051 ..

Regards,
IanP
 

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    nscpl

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hi,

if you can use the DPDT Relay for the switching the interface .......... i also did same when i am interfacing the GPS and the GSM modem

coz when i need one device at a time ...... it is nice solution when u wnat to send data to only one device at a time
 

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