Wiring of USB to Serial Adapter

[prroots]

I'm interested in connecting the NMEA gps output of a Garmin 441s to my laptop. I will purchase a USB to serial adapter which terminates with a 9 pin DB-9M connector. Can anyone tell me which leads from the 441s to connect to which pins of the DB-9 connector? So far I have determined that pin 2 of the DB-9 is receive and pin 5 is ground. The blue wire of 441s is labeled NMEA port 1 TX out so I suspect that should be connect to pin 2 of DB-9? I'm not sure where to connect pin 5 of the DB-9; perhaps to the black wire of 441s which is ground. Of course the red wire of 441s goes to +12V and the black wire goes to ship's ground. I'm assuming that the NMEA port 1 RX input wire of 441s should be left unterminated? Thanks
Pete

[donradcliffe]

You have it right. If you want to ever have the PC talk to the GPS, you can hook up the RX input wire to pin 3 while you are at it.

[prroots]

Originally Posted by donradcliffe

You have it right. If you want to ever have the PC talk to the GPS, you can hook up the RX input wire to pin 3 while you are at it.

Thanks for the very prompt reply!
Pete

[svBeBe]

You should buy a Digi brand "Edgeport/4 4 Port USB to Serial converter." This will give you 4 serial ports for one USB. There are other brands, but the Digi brand Edgeport/4 always works. It is powered by the USB connection. You can get these on Ebay for less than $30...originally around $300. The reason you want 4 ports is sooner or later you will add something like AIS, etc.

Best,

Bill
s/v BeBe, Amel 53
Currently Thailand

[prroots]

Originally Posted by svBeBe

You should buy a Digi brand "Edgeport/4 4 Port USB to Serial converter." This will give you 4 serial ports for one USB. There are other brands, but the Digi brand Edgeport/4 always works. It is powered by the USB connection. You can get these on Ebay for less than $30...originally around $300. The reason you want 4 ports is sooner or later you will add something like AIS, etc.

Best,

Bill
s/v BeBe, Amel 53
Currently Thailand

Thanks. Sounds great. I will be wanting to input both gps position and aiso AIS eventually. Also, in years past I controlled a ham HF radio with a serial connection. Why the huge price difference? Do you know if it supports Windows 7?
Pete

[hellosailor]

Pete-
If you want to be reasonably certain that something works with a recent version of Windows, look for the "Logo Certified" designation on the product/box and see if the product is listed in the Hardware Compatibility List (HCL) on the Microsoft web sites. The HCL has some fancy new name...Windows Catalog or something like that for the newer OSes.
In order for a product to be listed, it has to pass extensive real-world tests, so you can be reasonably certain it works. No listing doesn't mean it won't work--it just means either someone couldn't afford the testing, or couldn't pass it, or didn't care about it.

On the serial DB9 ports you are concerned usually with pins 2 and 3, which are the TX and RX pins, and pin 5 is usually a data ground line. A lot of documentation can be confusing because the "TX" from one device connects to the "RX" on another, and vice versa. So as you look at a connection...if one pin is TX on your GPS, the corresponding wire on a cable is the "RX" connection on whatever it goes to. Bottom line is that if something doesn't work, 2/3 are usually reversed, or the data rate and parity aren't set right. The devices are robust enough that reversing 2/3 won't hurt anything, it just won't work till you swap 'em back again.
Price differences often reflect what the market can bear, or the release of new chipsets, or something going from "made by hand in Switzerland" to "banged out in China".