Gps and AVR microcontroller

avr gps

Hi,
I have some questions about connecting a GPS to an
AVR MCU.
We have a GPS pack that send serial data with NMEA
format(GM-R500). It has a femail PS2 connector and we have to
use another cable to connect the GPS to the PC which
has got 3 head. A mail ps2 for connecting to the GPS
femail ps2 and 2 other head, one mail ps2 and a rs232
connector . We have to connect both of them to the PC .
One head (ps2) is for power and another head (
RS232) is for data. I checked the output of GPS by
hyper terminal and there is nothing wrong with it.
The baud rate of the GPS is 4800. It has no parity , 8
data bits and 1 stop bit.
After that we conncted the femail ps2 of the GPS to an
AVR MCU , but when I read data from the GPS I got
wrong information .
I changed the baud rate , and crystal but I could'nt
get correct information.
Is this problem related to the MCU or baud rate or
clock frequency?
What is the relashionship between Baud Rate and frequency?
What frequency is needed to use?
Is it possible that female ps2 generates inverted
information?
Can anybody help me?
Please tell me what should I do?
I am in a hurry.please answer me soon.

Regards.

gps avr

from bewehthcraes ) :

**broken link removed**

and give us chance to see your schematics

nmea avr

In order to have a complete picture of ur setup it will be better if u kindly provide the schematics of ur setup.

avr nmea

Hi,
Thankyou for replying.
I have a gps(GM-R500).It has a ps/2(femail) port that has 6 pins:
1:VCC
2:GND
3:RX (RS232 level)
4:RXD (TTL level)
5:TXD(TTL level)
6:TX(RS232 level)
I use the pins with number 4 (RXD) and 5 (TXD) for connecting Gps to AVR to pins RXD and Txd.
RXD pin(GPS)-------->TXD pin(AVR)
TXD pin(GPS)-------->RXD pin(AVR)
I programed AVR to show "NMEA" sentences in LCD.but the data taht i see in LCD isn't correct.
I set the Buad Rate in AVR to 4800.
Should i use invertor between AVR and Gps?
What clock frequency should i set in AVR?
There is nothing else in my circuit.

gps microcontroller

i dont know much about this gps model , but you can compare txd an tx pins polarity by osc. If they are same - you will need invertor .

AVR cloc and baud setting relation is precisely described in data sheet for concerned microcontroller under uart/usart clause . If you are beginner - connect avr to com port (through rs232 driver of course) and write simple program to receive packet from pc and send them back. That will ensure you dont have a problem in communication . The rest is described in link to the library i have posted