Interfacing of GSM modem with 8051 microcontroller

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So, instead of talking about multiplexing a serial port, you throw in the word NAND, and expect the rest of the world to understand what you where thinking?

Then you specifically write that you don't know how to use a NAND IC. Why suggest a specific solution you don't know how it works, instead of describing the problem you have and ask for tips on how to solve it?

NAND gates are very general and can solve quite a lot of things, but multiplexing a number of signals (RX, TX and an unknown number of handshake lines) while making sure that the signals are non-inverted might not be the best situation to learn about the use of NAND gates.

I really recommend that you look at normal MUX chips, containing a number of two-to-one MUXes. They are trivial to use and very cheap. You could almost say that they where specifically made for solving this kind of problem...

i?

u?

thru?

ur?

So, instead of talking about multiplexing a serial port, you throw in the word NAND, and expect the rest of the world to understand what you where thinking?

Then you specifically write that you don't know how to use a NAND IC. Why suggest a specific solution you don't know how it works, instead of describing the problem you have and ask for tips on how to solve it?

NAND gates are very general and can solve quite a lot of things, but multiplexing a number of signals (RX, TX and an unknown number of handshake lines) while making sure that the signals are non-inverted might not be the best situation to learn about the use of NAND gates.

I really recommend that you look at normal MUX chips, containing a number of two-to-one MUXes. They are trivial to use and very cheap. You could almost say that they where specifically made for solving this kind of problem...

There are plenty of 8051 derivatives available with two UARTs - why not just use one of them?

http://www.keil.com/dd/search_parm.asp

Get your system working like this first, then think about adding the complication of multiplexing if you still think it's worth it...

Remember that GSM modems can send unsolicited messages - you will miss them if they happen while the multiplexer is switched to the GPS...
The converse may also be true of your GPS...

If you people are uncomfortable with the writing then I will try to improve it now. I am new to the field of microcontrollers and I am reading it from the book of Scott Mcknzie. So,I will not be needing NAND operation.Instead I can use the two UART of 8051. Can anybody suggest me the algorithm of the program.What I have thought is that first of all microcontroller will take a string from gps reciever and pick the string of lattitude and longitude.After that the microcontroller will send the AT commands to the GSM modem to send the lattitude and longitude as a sms.

It seems like you already have the algorithm.

The only think that remains is the startup - to initialize the processor (I/O pins, serial ports, baudrate, interrupt handlers, time keeping...).

Yes,This is the idea which I have in my mind.But as I have told you that I am new to programming so I am facing alot of difficulty.If anybody can provide me a good keil tutorial other than available on this website or a good guideline so that I can continue my work.

HI Abbas,

Instead of trying to learn the architeture of 8051 mc. I would suggest you to try http://www.oopic.com. They have their own compiler and it is very easy to interface,

Best of Luck

Venu

"Instead of trying to learn the architeture of 8051 mc. I would suggest you to try ">http://www.oopic.com."

So then you'd just have to learn the architecture of the PIC, and all about this proprietary OO framework that they've built upon it!

And you'd still need exactly the same understanding of GSM modems!

Whatever you take, you need to understand it before you can use it!