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Technical Question About Computer Interfaces


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I have a Garmin Legend. I have a cable that connects from the GPSr to a serial port on my desktop computer.

 

When I go to wander around, I use my laptop. My laptop does NOT have a serial interface, but it does have several USB 2.0 ports.

 

Is there anyway to connect to my laptop? Do I need a new cable, or is there an adapter to convert a serial interface to USB?

 

thanks,

carl

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Almost any quality USB/SERIAL adapter will work.... Generally ones manufactured using PROLIFIC chip set work well with any GPS unit. Adapters come anywhere from $0.49 on ebay to $60 in retail stores... Personally I have a $14.95 unit with PROLIFIC chip set (don't even remember brand name) and works excellent with my Magellan GPS...

 

One thing many people fail to do is to load USB drivers for USB/SERIAL before plugging in adapter for first time. Failing to load driver first is a great recipe for failure.

 

Here is also a work up to determine how to configure parameters on USB/Serial COM port numbers...

 

Finding Com Port

 

It’s quite possible your lap top or desk top machine can not "find" correct COM port!...

 

Or your computer does not have traditional serial port. (they are slowly going away in favor of USB). A USB/Serial adapter may be the answer for you.

 

If you have Serial/USB adapter and are not getting it to work, suggest you delve into what COM ports or USB/adapter ports your "systems" have available or are configured for....

 

Major problem is usually identifying what COM port number the USB/RS-232 (serial) adapter was assigned by WINDOWS system. This is also valid for locating available hardwired serial ports. Port numbers can be verified in the "control panel" under "system" under "hardware" under "device manager". Scroll down to “ports” and it will tell you the port number and at what speed (baud) port is configured at. You can actually plug in and unplug adapter and see the "port" appear and disappear. Right clicking on "port" and selecting "properties" will tell you everything you need to know about port. This info is necessary to get EasyGPS and GSAK and “other” programs to communicate with GPS unit. Yes you do need to set baud rate on GPS to match computer COM port which may be set with whatever software computer is running.

 

Most software applications and hardware (modems) like to work with COM 1 ... Also if you have any "synchronize” software running for a Palm or other hand held, it grabs COM 1 and will not let any other applications use it. You may need to disable any synchronization software it you have it as a running application to release COM 1 if you have to use that specific COM port.

 

Also just plugging in a USB/Serial adapter to USB port may not trigger system to assign COM port number. In some cases you must have a valid device (GPS) on end of data cable from USB/Serial adapter and the device must be turned on for system to respond and assign a COM port number. Also having a loop back plug in USB/Serial adapter will trigger adapter/system to assign com port number if serial adapter requires a "valid" device on end of cable.

 

 

Hyper Link Test

 

Here is procedure to test COM/SERIAL/USB port. It will work with both hardwired serial port (COM) on older computers or with USB/SERIAL adapters if proper drivers are loaded. This test will require a “loop back” plug for serial connector that has pins 2 and 3 connected (shorted) back to each other.

 

1. Determine COM port number using the process above to find the port number (Finding Com Port).

 

2. Open HYPER-TERM the communications terminal program that is standard part of Windows supplied utilities. If installed it may be found under “Communications” on main menus. (or any other terminal program you are familiar with)

 

3. Establish a “new connection” file name something like “serialtest” or “loopbacktest”. Specifying the specific COM port number (found in above procedure). Set ASCII options to NOT echo characters locally (Uncheck – Echo Characters Locally).

 

4. Plug in USB/SERIAL adapter and install “loop back” plug on serial connector plug ( if using hardwired port on computer that is where loop back plug goes also) . IF you can now type characters on key board and see them appear on screen the com port and path (and USB adapter) are good. If you unplug loop back plug and then type and characters do not appear on screen this further verifies port is working properly and adapter is working. If you type and get double characters (aa-bb-cc) for each key stroke with loop back plug in place it means “local echo” is turned on. If you only get single characters when loop back plug is removed then it still proves serial path is good.

 

Hyper Terminal setup.

 

Start Hyper Terminal and when “New Connection” window box is presented enter your file name (“looptest” or whatever) Click ok.

 

Next box should say “Connect To:”

In this box, at bottom it should say “Connect Using“and there should be a com port number ( mine comes up COM 4 – Yours may be different). Click OK.

Note: Hyper Terminal should only show you any valid COM ports available by system. IF you don’t see and COM ports your adapter is not configured ( drivers?). Your computers MODEM should also be listed if computer is so equipped and modem is “active”.

 

With loop back plug in place try typing. Do you get characters? Answer should be yes.

Remove loop back plug, do you get characters? Answer should be no.

 

If you need to change “echo” settings. Go to File drop down menu and click on Properties. In properties box, click on Settings Tab. In setting box select ASCII Setup. Either check or uncheck “ Echo typed characters locally” (what ever you prefer).

 

 

USB-PARAMETERS

 

I think if you will fine that if you set up port parameters in GPS and Software (GSAK-EasyGPS) to same as "default" parameters found in "properties" for USB/Serial adapter you will not have any connection problems.

 

Did you even know that there is a properties setting for COM port on control panel. Try right clicking 'Port" once you have hot swap - plugged in USB/Serial adapter.

 

By default mine are:

 

Baud =9600

DataBits = 8

Parity = None

Stop Bits = 1

Flow Control = None

 

The driver "defaults" set in port parameters (Properties) in "hardware" can be adjusted and saved so every time you plug in adapter it will default to desired setting... You have to have software and GPS unit set to match.

 

I still believe most of the "problems" is not having "port defaults" at (initialization- plug-in time), software, GPS all set to same parameters.... And boot up has nothing or very little to do with it.

 

Though RS-232 Serial Ports are on way out, it would probably be a little beneficial for one to look up how they function and what parameters do..

 

http://www.arcelect.com/rs232.htm

 

FINDING – PORT

 

Here is how I find my USB/SERAIL adapter...

 

Easiest solution to find COM port is to go into "Control Panel" >> Select "System " icon >> Select "Hardware" >> Select "Device Manager" >> Scroll down to "PORTS" (COM & LPT) and see what new "port" pops up when you plug in USB/SERIAL adapter cable

 

Mine comes up as "Prolific USB to Serial Comm Port (COM5) "

 

What ever Comm port number USB port is assigned by "system" (COM5 in my case) is Comm port number you need to use when setting up parameters/properties in your software used to communicate with GPS unit through USB/SERIAL adapter cable.

 

Be sure USB drivers for adapter cable are loaded from CD FIRST (or off I-net) before trying to plug in USB/Serial adapter cable.

 

Pretty much like other user described in previous responses..

 

In this cases you probably need to clean out drivers and reinstall them BEFORE you attempt to plug in adapter cable.... Even though BELKIN is brand name, Prolific makes about 90% of USB/serial adapters on market today.

 

Dale

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