Free GPS for the Weekend, Sir?

Well, not QUITE – the Navspark Mini + UART to USB adaptor is free – but with a caveat of postal shipping charges.

http://navspark.mybigcommerce.com/navspark-mini-uart-to-usb-adapter/

Already the more savvy of you will have noticed a treat here.  Let’s say you have no interest whatsoever in GPS – the second half of this equation is a little board with USB-serial conversion – chucking out 3v3. That alone has to be worth the postage if you’re into device programming!!!

So – cheap? Yes but… the GPS unit is not quite complete – as you need an aerial. There is an “active antenna which I think is around $9. So depending on postage, the whole lot might cost you $18 which is, what, £12.33 in UK money.

So, the antenna comes with lead that plugs straight into the “free” Navspark unit – and the USB unit provides power and serial I/O to whatever is is you want to use this with – if attaching to a microprocessor then obviously you don’t need the usb adaptor and so you get to use that for something else. The unit as you will see also has two other interfaces – handy if you don’t have serial.

I should state right at the start that I know very little about sat-nav other than it works in my phone and car and I know that the units put out a serial stream with all sorts of textual info including the time. I also have an idea of how the actual system works but I’m not at all a whiz on the data formats.

Did I say time? I did – and the reason I sent off for one of these was the realisation that sat-nav time is just about the most accurate source of time on the planet. It occurred to me that my Raspberry Pi has a spare serial input and would it not be nice to pull the time in – for the odd occasion I don’t have an internet signal after a power cut.

Attempt 1:

So – I sat here armed with all three units above. The Navspark has all sorts of signals but the easy one to use is simple serial.

There are lots of tutorials on their site…

http://www.navspark.com.tw/tutorials/

But here in a nutshell for testing on a PC:

I connected the board as per above, connected the aerial to the board… plugged in the USB to my PC and pulled up my Arduino serial monitor – just as it was handy.

And… a red light and….  nothing. For some reason I kind of thought it would just fire out serial information.

Then I realised I’d plugged the serial adaptor into my power supply – not my PC – duhhhh.

Attempt 2:

Sure enough – a steady stream of strange data coming out of the serial port. I change baud rate and voila…

$GPRMC,120255.000,V,0000.0000,N,00000.0000,E,000.0,000.0,280606,,,N*7D
$GPVTG,000.0,T,,M,000.0,N,000.0,K,N*02
$GPZDA,120255.000,28,06,2006,00,00*5F
$GPGGA,120256.000,0000.0000,N,00000.0000,E,0,00,0.0,0.0,M,0.0,M,,0000*6F
$GPGLL,0000.0000,N,00000.0000,E,120256.000,V,N*43
$GPGSA,A,1,,,,,,,,,,,,,0.0,0.0,0.0*30
$BDGSA,A,1,,,,,,,,,,,,,0.0,0.0,0.0*21
$GPRMC,120256.000,V,0000.0000,N,00000.0000,E,000.0,000.0,280606,,,N*7E
$GPVTG,000.0,T,,M,000.0,N,000.0,K,N*02
$GPZDA,120256.000,28,06,2006,00,00*5C

WELL that was easy enough – of course I’ve no idea what most of that means – and i realised the time was wrong. I very quickly remembered these things don’t like working indoors.

I happened to have a USB extender and put the aerial in the Dormer roof, held with packaging tape.. 30 seconds late.

$GPGGA,122557.000,0000.0000,N,00000.0000,E,0,00,0.0,0.0,M,0.0,M,,0000*6B
$GPGLL,0000.0000,N,00000.0000,E,122557.000,V,N*47
$GPGSA,A,1,,,,,,,,,,,,,0.0,0.0,0.0*30
$BDGSA,A,1,,,,,,,,,,,,,0.0,0.0,0.0*21
$GPRMC,122557.000,V,0000.0000,N,00000.0000,E,000.0,000.0,080116,,,N*7E
$GPVTG,000.0,T,,M,000.0,N,000.0,K,N*02
$GPZDA,122557.000,08,01,2016,00,00*5C

I’ve highlighted the time and date above. As I’m doing this in the UK there was no need for any hour offset.

There is a LOT of information online – I mean a LOT – and it’s in English…

http://navspark.mybigcommerce.com/content/NavSpark-User-Guide_rev0.8.pdf

They have a download for Windows – an EXE program that just runs. I shut down my Arduino IDE, punched the UART and speed details into their program and…about my only gripe is that even with the unit stuck in the centre of the dormer window – it would pick up on the right time – but not the location. After 15 minute still no location.  I downloaded an AGPS file and a whole boatload of satellites appeared – but still no location.

There are SO many settings and queries available in this little program – and Arduino code available for embedded applications. Looks like a good gadget for the winter months..

I sat looking at the system for around half an hour just hoping that somehow it would realise it was looking at entirely the wrong part of the planet.. and sure enough, just as I was about to give up…

Can’t be bad – a nice GPS unit AND an FTDI or sorts for a tenner or so….