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USB GPS to connect to a NMEA multiplexer not the PC
mi3gto
Folks this is going to be a bit of a long winded question but here goes.

I have a GPS that is connected normally via a USB connection to the laptop running SeaClear. So far so good.

What I want to do is connect the USB cable from the GPS to some sort of device that will power and listen from the GPS without the PC connected/powered up, the GPS still functioning and passing the NMEA sentences to other devices like a DSC radio, just like a multiplexer. The multiplexers I have seen can pass data to the PC, but none seem to have a USB port that would drive the GPS via USB.

I have run GPS Gate on the laptop, and that works great to pass on the GPS data, but requires the PC to be on and working. As the laptop uses power and I am trying to cut power usage to the bone for certain reasons while maintaining a safe feed to the radio and anchor alarm I want a multiplexer type device which uses a fraction of the laptop power.

I hope I have explained this right.

I don't want to change the GPS to a bare wire RS232 type (which would work). Hope someone has an idea, please.

Is there such a thing as a converter that will convert between RS232 (PC) Tx Rx Gnd and USB (device) ** NOT THE COMMON OTHER WAY ROUND of USB (PC) to RS232 (device) ?
tcassidy
Sealevel has them. Whether they work without a computer, you'll have to ask.

USB Serial Adapters - USB to RS-232, USB to RS-422, USB to RS-485 & More

Terry
mi3gto
Will check them out thanks BTW it is multiplexer my spell checker had a wrong word in it...thanks :-)
tcassidy
Except for the Tags section, I wouldn't have noticed. How do you use a spell checker with the forum? I really need one.

Terry
mi3gto
Looks like they do USB out to RS232 etc but NO RS232 TO USB but I have asked them anyhow thanks. RS232 to USB may require separate powering???
mi3gto
My Opera and Firefox do it automatically as I type highlighting words and offering replacements. I think it was a add on or a setting in the browser works on all forms etc.
tcassidy
I am confused now. If the GPS outputs on USB and the equipment needs serial, I thought that was what they offered. USB needs 5v.

Terry
tcassidy
Thanks. I tried ieSpell and it seems faster than offline checking.

Terry
tcassidy
On a closer examination of the devices on the site, you seem to be right. They all appear to be serial in to USB out! My error.

Terry
mi3gto
Not a problem. Yep I have searched the inet but can not find an adapter. I will take a look at the tech specs for RS232 and USB to see why there should be a problem in doing this or providing an adapter. One way is to have the PC on at all times but that is why I am concerned. If the PC locks up or powers down I loose the input to the DSC Radio. Coming from a railway "fail to safe" environment this is not acceptable. Changing the GPS as I said is not really an option at this point plus I am stubborn :-)
Marvin Hlavac
How about using a dual, Bluetooth & USB, GPS receiver? Some of these dual GPS unit can output to two devices simultaneously, one via Bluetooth and one via USB.
mi3gto
sorry you lost me? does bluetooth not need the pc on as well as the usb? can you explain please
Marvin Hlavac
The dual Bluetooth/USB GPS unit could be on at all times.

1. It could be connected to one device via the USB connection (if you have a device that would accept a USB connection, other than your PC).

2. Your PC, when turned on, could automatically connect to the GPS receiver via Bluetooth.

If this works, you would still be limited to using only one device connected to the GPS while the PC is turned off.

Edit: It could also work the other way around. The PC could use the USB connection, while your other external device could accept a Bluetooth connection.
Ken in Regina
Quote:
Originally Posted by mi3gto
Not a problem. Yep I have searched the inet but can not find an adapter. I will take a look at the tech specs for RS232 and USB to see why there should be a problem in doing this or providing an adapter.
You might want to read this to better understand the issues.

USB to RS232 converters

...ken...
mi3gto
Marvin yes thanks for the explanation I see now what your suggesting. But it don't solve my problem. The device I need to feed only has a RS232 input single ended bare wire NMEA multiplexer or direct to the radio GPS input. If the PC/Laptop is off then I have no feed.

I am looking at very small Mini ITX or PlugPC type devices which may provide a way to do this. I connect the GPS to the Mini ITX or PlugPC device via USB and output via a second USB and a USB to RS232 adapter cable to a made up cable and connector to Tx Rx Gnd (single ended RS232 as per NMEA spec). This is a possible low power consumer option. I might just have to get a second GPS to feed say a Actisense multiplexer which does NMEA switching. This would allow switching of the best GPS and would switch in the second GPS when the power to the primary USB GPS is cut or the PC locks /crashes as it would no longer be the best signal. I would have to trap the signal from the primary after the output port from the PC otherwise the USB GPS could be still sending a strong signal keeping the "switch" open. The PC could run GPSgate taking input in on USB 1 and out on USB 2.

I think :-)
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