Mobile phone as GPS data source?

Boreades said:
Given that Globalsat offer the BU-353-S4 SiRF Star IV with either USB or PS2 connections, does it matter which one I choose? As in, the plan is to chop the end off and connect the bare wires to a 5V source and the NMEA input of something else?
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Yes, it matters a great deal!

The "PS2" connection is not really PS/2, it just uses the same circular DIN plug as the old PS/2 stuff. Connected to those pins are a positive and negative wire, and an NMEA output wire (also a programming input, but you can ignore that). These are what you want to connect to. The USB version, oddly enough, has data wires expecting to be plugged into something that speaks USB. Fine for a laptop, but not for a radio.

Pete
 
prv said:
The "PS2" connection is not really PS/2 ... The USB version, oddly enough, has data wires expecting to be plugged into something that speaks USB...
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Actually for many devices the data are exactly the same. If you don't talk to a USB device, it just behaves like a serial one. In fact you can get converters that are straight-through, I've got loads from early mice.
 
nigelmercier said:
Actually for many devices the data are exactly the same. If you don't talk to a USB device, it just behaves like a serial one. In fact you can get converters that are straight-through, I've got loads from early mice.
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Sure, for devices which actually are PS/2 or USB. But this one does not talk PS/2 under any circumstances, even though it has a DIN plug that happens to look like it. The wires inside the plug are 2x power and 2x NMEA, one out, one in. Presumably TTL level, but seems to work ok with my radio and AIS display. They were originally intended for old PDAs that didn't have built-in GPS, the idea being that you would also buy an adaptor from the circular DIN plug to whatever non-standard connector your Psion, Newton, or iPaq happened to have.

Pete
 
So are the USB ones actually any different to the PS/2 ones, other than the plug - the USB ones appear readily available and I could do with replacing my Raymarine GPS that is only used as a lat/lon display and a NMEA 0183 feed to my chartplotter and DSC radio. If I cut the plug off a USB one, will I have the same 4 wires - power and NMEA in/out?

Thanks

Neil
 
neil1967 said:
So are the USB ones actually any different to the PS/2 ones, other than the plug - the USB ones appear readily available and I could do with replacing my Raymarine GPS that is only used as a lat/lon display and a NMEA 0183 feed to my chartplotter and DSC radio. If I cut the plug off a USB one, will I have the same 4 wires - power and NMEA in/out?
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No. The cheapest way is to get a Globalsat BR-355 for £25 and arrange to get it 5V power supply, either using a regulator or the YAPP box which does just that. I'm not sure what Nigel means in his last post by saying a USB one will behave like a serial one.
 
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neil1967 said:
If I cut the plug off a USB one, will I have the same 4 wires - power and NMEA in/out?
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Um, no. You will have power (that's the same), and USB data - and USB data +. How could it be anything different? Your computer's USB port doesn't speak TTL-level NMEA, does it?

Pete
 
AngusMcDoon said:
I'm not sure what Nigel means in his last post by saying a USB one will behave like a serial one.
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He's talking about the PS/2 / USB mice that you used to get when USB was still a novelty. They had a USB plug, but came with a converter that adapted the physical form factor to PS/2. Clever circuitry in the mouse would notice when it was connected via this converter to a PS/2 socket, and speak PS/2 down the cable instead of USB.

The clever part of that system was that the mouse was bilingual; it doesn't mean that you can in general convert USB to PS/2 using a dumb adaptor. And the "PS/2" in reference to the BR-355 is a red herring anyway, as it doesn't speak PS/2, it just happens to use the same DIN plug. But people know what a "PS/2 plug" looks like, so they use the term that will be recognised.

Pete
 
Thanks for all the clarification everybody, I've ordered the "PS/2" version.

I have made sure I got the SIRF IV chipset, from here. it's £32 instead of £25 for the older III chipset, but a group test I've seen shows it is more sensitive (necessary if the GPS mouse is below deck), and it acquires satellites quicker.

Now eagerly waiting for that and Angus' YAPP to arrive. :)
 
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