GPS Module selection

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Hey i wanted to buy a GPS module online to interface with my atmega8 for a couple of projects I had in mind. I am uploading two that I came across ,one is on spark fun and other is from some chinese vendor cheaper but less extensively used in projects that i came across. If someone could guide me as to what to look for in a good GPS module in terms of ease of interfacing ,protocols(level converters might be needed).

Also has anyone used the GM-301 gps module,EM-406 i know has been pretty extensively used.

Any tips for other cheap and easy to use modules

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abhishekbhardwaj007 wrote:
Hey i wanted to buy a GPS module online to interface with my atmega8 for a couple of projects I had in mind. I am uploading two that I came across ,one is on spark fun and other is from some chinese vendor cheaper but less extensively used in projects that i came across. If someone could guide me as to what to look for in a good GPS module in terms of ease of interfacing ,protocols(level converters might be needed).

Also has anyone used the GM-301 gps module,EM-406 i know has been pretty extensively used.

Any tips for other cheap and easy to use modules

Is cheap and easy interfacing your only criterion? Do you have accuracy or tracking constraints?

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These are both very similar modules with the SiRF III chip set, and patch antennas. They both put out serial NMEA at 0/3V level.

They both support WAAS, and the 406 adds GLL to its output sentence capabilities.

Both have -159 dBm sensitivities.

The newer 301 has a bit better, (lower) power consumption, at 31mA vs the 406's 44 mA at 5V input.

The 301 supports EGNOS, the 406 doesn't. Google Wiki EGNOS to learn more about this European satellite network, and decide if it is important to you or not.

Both will provide essentially the same sensitivity, core NMEA data output, hardware interfacing requirements, and the same accuracy.

I've used the 406 on several projects, but the 301 is a very similar unit.

You have narrowed your selection down to two good choices!

JC

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Dear abhishekbhardwaj:

Consider a SiRF III based GPS.
Here's one I'm using.
http://www.globalsat.com.tw/eng/...
it's RS232 internally, out to a PS2 connector. Cut it off, or buy their PS2 to DB9 or USB adapters. Runs on 5V.

With all these, the commands to configure baud rate, what sentences you want, are not in NMEA 0183, so they're proprietary. Some chip makers hold that as proprietary. For SiRF, it is thus, but their documents on this have leaked out.

That same website has open modules too. I wanted a weatherproof packaged one for $50. Garmin's OEM equivalet is nicer but $150 or so as I recall.

Vincotech is another
http://www.vincotech.com/Positio...
Mouser or Digikey sells them.

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Thanks for the responses guys.I am assuming a lot of you have worked on GPS. Regarding my criterion I expect both these modules to be fairly accurate (from reviews),I just dont want to get stuck in a situation where I order a part from abroad and I dont know how to interface it in my project.

@stevech

I have pretty much narrowed my selection to the first two.But your first link looks interesting.Once I get a PS/2 to DB9 converter I can use it like normal UART with a MAX232?

Regarding GM-301 and EM-406A,i have a vendor willing to sell me GM-301 for about 46$ with shipping.

Any ideas where I can get these cheaper, I live in India and will be ordering a single unit only.

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I have used the EM406A with a Mega 32 and also interfaced it with a max232 to computers and marine sounders. Futurlec have them for 39.90 USD.

http://www.futurlec.com/GPS.shtml

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I was thinking about buying a GPS module too, to make a GPS logger for photo geotagging purposes, but I found out you can buy them ready made for little money completely ready-made :)

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With the exception of special features you will probably never use, all GPS units are basically the same.

1) Connect the RS-232 Data-out and GND
2) Insert antenna (or not if built-in)
3) Apply power.

Now you will get 4800 baud NMEA formatted sentences, which you decode in your software.

Some units can switch to a higher baudrate, have extra sentences or more updates per second, but everything can fall back to the default.

Good luck!

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Though quality of the chipsets seem to differ. The SiRFstar III seems to be best in regards to being able to retain a signal lock in urban areas and short time to first fix. So I've heard...

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u-blox GPS modules are used in military and police equipment because they work best in "urban canyons". They use standard chips with clever software.

Leon Heller G1HSM

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thanks I think I'll go for EM-406A. My dad is going to China and I have given him the datasheet ,if he can scour the module for a cheaper price that would be awesome otherwise ill go for the futurlec link.

Thanks a lot.

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abhishekbhardwaj007 wrote:
@stevech
I have pretty much narrowed my selection to the first two.But your first link looks interesting.Once I get a PS/2 to DB9 converter I can use it like normal UART with a MAX232?.

That link I gave is to a $55 weatherproof packaged GPS with an internal RS232 voltage level chip. So the TX, RX on the cable, regardless of the connector, is RS232, not CMOS/TTL. That's what I wanted, weatherproof, RS232. That vendor sells adapter cables to go to USB and DB9, from the PS2. That same vendor's website also shows bare modules, no package, no RS232. So it depends on what you want to do.

I chose SiRF because their proprietary commands to turn sentences on/off, set baud rate, etc., are easily had on the 'net. Not so some others. NMEA 0183 does not standardize such.

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One more query, has anyone used EM-406A GPS module to somehow act as a GPS receiver with one's phone? (i have a nokia e51 without any internal GPS)...is it possible to send data to your phone via somehow making a rs-232 to bluetooth connection on your gps receiver?..

I have a usb to serial converter if i connect my rs232 gps on the serial side and a usb bluetooth dongle on the usb side ,would i be able to relay data to my phone?

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abhishekbhardwaj007 wrote:
One more query, has anyone used EM-406A GPS module to somehow act as a GPS receiver with one's phone? (i have a nokia e51 without any internal GPS)...is it possible to send data to your phone via somehow making a rs-232 to bluetooth connection on your gps receiver?..

I have a usb to serial converter if i connect my rs232 gps on the serial side and a usb bluetooth dongle on the usb side ,would i be able to relay data to my phone?


No.
The app on the phone needs to be involved.

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any other ideas to use the GPS module with a mobile?...

E51 does support external GPS receivers