Here's a (quickly) start: Don't know either end of where you need to 
get, but if the Garmin is true RS-232 (+ and _ 12 VDC signals) you will 
need a MAX232 see: http://www.maxim-ic.com/quick_view2.cfm/qv_pk/1798. 
The MAX232 schematic will have buffers look  like diode arrows. Point 
one to the RX PIC pin, and from the TX pin the arrow should face away 
from the PIC. The other ends of the buffers is where you hook the 
Garmin. The common is your PIC ground. There may be other Garmin pins 
needing connecting, and then again if the Garmin doesn't need talking 
to, all you need is the PIC RX pin and the common. The MAX232 will need 
some capacitors, refer to it's schematic for those. Since I'm not 
familiar with the particular PIC, I haven't addressed other issues like 
MCLR.

anthonysakr wrote:
> hey everyone i need help with connecting my garmin gps via a rs232 to a
> 18f4620 using usart. plz could someone tell me how to connect them and what
> other pins should i use on the 18f and what should i leave not connected?
> i've already figured out the oscillator connection (I have to use a crystal
> oscillator) i saw the diagram in the 18f datasheet.
>
> And further more i've been searching everywhere to find the program that i
> should use so that the pic receives the input correctly, i have MPLAB IDE
> and i can't find how to program my pic on it, if someone has such a program
> or the generale guidlines that i should use to configure my pic to receive
> from the gps via the rs232 please help me.
>
> Anthony
>
>
>
>   
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