Connecting a Trimble GEO XT

[newace]

I have a Trimble GEO XT handheld unit. The only connection that it has is a USB cable. Is there an emulator or an adapter that I can use to connect it to TS/PP?

john.newton@ci.greensboro.nc.us

Thanks

[bullock]

Hi, John.

Let me give a couple of suggestions, as haven't tried these particular Trimble GPS receivers to know exactly what will work.

From the Trimble web site, it seems that the GeoXT receiver has a Bluetooth connection in addtion to the USB cable. If your computer has a Bluetooth port, that will probably be the best option rather than USB. Even if your computer doesn't have a Bluetooth interface, you could add one with a USB stick, so that would provide at least a fallback, if not a preferable, option.

Some GPS manufacturers that offer USB connections also include a serial port driver which, when installed, software-emulates a serial port. If the GeoXT offers this (you'll have to check Trimble's documentation), then it should work fine with TS/PP-Draft. Once installed, the serial port emulator should list a new serial port as being available in the Device Manager, and that will tell you the port number as well (often COM5).

Note that if both options are available, USB and Bluetooth, then the USB connection would probably provide power to the receiver, but on the other hand, Bluetooth is wireless, so those might be considerations.

I hope this helps. Please let me know what else you learn, especially if none of this works.

Regards.
Greg

[bullock]

Hi, John.

Here are some comments from a user in Colorado who's working with the GeoXT:

I wanted to take a minute to explain to you my experiences using a laptop and GPS unit to record travel runs. The GPS unit I'm using is a Trimble GeoXT. My laptop has a usb-to-serial adapter as there is no serial port on the laptop. For my initial attempt, I connected the GPS to my laptop and set its output to NMEA/4800 baud. I set the appropriate port settings in TSPPD and started GPS tracking. Under this setup, TSPPD would only track for a few seconds, then start "searching for fix" and would not recover. For my next attempt, I set the GPS output to "Custom" and with 9600 baud. I left TSPPD at NMEA but increased baud to 9600. This time TSPPD was able to track for about 15-20 seconds, then start "searching for fix" and never recover. For my third attempt, I set the GPS output to "Custom" with 19200 baud. I left TSPPD at NMEA but increased baud to 19200. This time TSPPD was able to immediately start tracking and did not lose its fix for the duration of the afternoon and into the evening. Data from the travel runs I did under this setting seems appropriate.

I tried to incease the NMEA baud rate in the GPS unit, but the GeoXT does not allow the user to adjust the baud rate for NMEA output. I'm not sure what the "Custom" output of the GeoXT is comprised of, but it seems to work well for me. I just thought I'd pass this information on to you. I'm kind of puzzled as to why TSPPD would not be able to track using NMEA/4800 output from the GeoXT. Do you think there is an issue with using a usb-to-serial adapter at lower comm speeds, or possibly and issue with the GeoXT NMEA output?

We're still not sure right now why the NMEA mode didn't work, but he might look into it further and give us more information, which we'll post here.

Regards.
Greg

[newace]

I will try these ideas. I have just gotten in the serial/usb adapter, and will try it today.

John

[dalston]

John,

When using the Trimble GeoXT as a GPS unit, the output does not run through USB on the unit. GPS output is only allowed through the GeoXT's serial port. You will have to purchase a serial clip (part # TRM46509-00) that attaches to the GeoXT. Check your user's manual for a picture reference of the serial clip. Then run a serial cable to your laptop. If you already have a serial port on your laptop, then you can plug right in. If you only have USB ports on your laptop (like myself), then that's where the serial-to-usb adapter comes in. Once all cabling is connected, you will have to change the GeoXT's communication settings to output the GPS information to the specified port (I can't remember what it is off-hand).

Darrell