GSM and GPS Serial Communication Problem

Hello Rickey,
Iam Done with my GPS programming by getting my Required string from GPS " $GPRMC...." Now i have to send it through GSM am also done with GSM at commands but the problem iam Facing is that at a same time in 89c52 GPS or GSM will work so i take a sbit P1^5 as a Mux activation bit.if its 1 then GPS data will be recieved if its 0 then GSM will transmitt and Recieve...So tell me how will i interface two RS232 with a one sbit which i have...

Thanks

well you might need little more pins for mux purpose. take a look at CD4052 Analog MUX/DEMUX you use it for uart muxing.

Try some of the posts around this post
http://www.8051projects.net/forum-t28099-120.html#post_32582

hey Rickey i have been through this program which is some how similar to mine..here u can c he used a single pin name mux....


void main()
{
int ddd=0
lcd_delay();
int_lcd();
clear_lcd();

while(1)
{
qq=1;
mux=1;
r4=0;
Set_Baud_Rate_For_GPS();
Receive_gps_data();
mux=0;
Set_Baud_Rate_For_Mob();
Transmit_First(); //at
delay();
Transmit_Second(); //at+cmgf=1
delay();
Send_sms_gps_data();
for(ddd=0;<26;ddd++)
{
recv[ddd]=0;
}
r4=0
if(c1==0)
{
ACC=0x4f;
lcd_write_txt();
lcd_delay();
ACC=0x4b;
lcd_write_txt();
lcd_delay();
hex_lcd();
r4=1;
}
delay();
//delay();
//delay();

Transmit_First(); //at
delay();
Transmit_Second(); //at+cmgf=1
delay();
Read_command();
qq=0
if(read[0]=='!')
car_engine=0;

if(read[1]=='!')
car_engine=0;


if(read[2]=='!')
car_engine=0;


if(read[0]=='%')
car_engine=1;


if(read[1]=='%')
car_engine=1;


if(read[2]=='%')
car_engine=1;
delay();
}
}

hi shezo i am really not sure what component he is using for mux-ing uarts. so if you can come up with the circuit it would be easy to help.

well he is using max232...my friends said that to use buffer..i dont have enuf knowledge about buffer so prefer me some...i thought about nand or xor logic implementation

Hey Rickey wot u think about this??

this 1

yes that will work for sure

and using only one pin.. clever i never thought that way

Dear Ajay and Shezo

I am doing almost the same project. I am using 89v51rd2, garming gps 15h and sim300

Please do advise me which option should i choose for connecting 2 serial devices (gps and gsm) to 89v51

1. Emulating a software UART like mentioned on the tutorials on the site
2. Using a 2:1 Mux - Quadraple
3. Do something like Shezo has done by using nand gates.

Regards

Abhishek