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vvvv
75 posts
Frequent Visitor
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17-05-2010 01:19
I am getting fed up of tripping over all my USB cables so I thought I'd use bluetooth instead, considering the fact that the ARF32 bluetooth RS232 module is only 20 quid.
First thing to do is convert my GPS to notebook project which uses a FTDI USB/RS232 cable.Simple enough -4800 NMEA ASCII goes from a GPS module to Microsofts autoroute or Google earth via the USB cable.Works a treat.
Should be simple feeding the ascii from the GPS module to the ARF32 bluetooth (power from a 3.6 lithium battery) whereas previously powered taken from the USB cable.My notebook is bluetooth equipped so it should be a doddle.Wish it was as simple as that.
Bets are that the ascii logic needs to be inverted before feeding to bluetooth,and since the bluetooth defaults to 9600 baud and autoroute and google earth defaults to 4800 baud and no way of changing,there is baud incompatability.
However 'simply blue command' software is available to configure the bluetooth module for 4800 baud,hopefully.
So what appears at first to be a simple task turns out to be quite complicatated!
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vvvv
75 posts
Frequent Visitor
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19-05-2010 21:49
Yep,problems.Blew up rx side of bluetooth module by connecting USB/RS232 cable (9 volts on tx pin) but tx side works ok.i.e bluetooth enabled notebook sees the module.(pin code 0000)Run terminal emulator and transmit 9600 baud data wirelessly.Connected tx line of bluetooth module to a 2nd computer via usb/rs232 lead with logic invertor,ran terminal emulator and received data @ 9600.
Note changing the baud rate on notebook terminal emulator has no effect.Data is still transmitted @9600.
So next step is to change the bluetooth module to 4800 baud as anticipated.The pdf file for module is as clear as mud but it appears that the module needs to be connected (txd and rxd lines) to pc serial port via a max232 powered by 3.6 volts.Won't make same mistake again.Then run bluetooth software.
Just as well I have a ME laptop with serial port.Connected a max232- powered with 3.6 volts.Otherwise would have to use usb/rs232 convertor.If a max232 is connected to it would it provide logic conversion?
Recieved 2nd bluetooth module from Farnell today but was proved duff.Replacement to be sent tomorrow.
Firefly bluetooth/RS232 has AT commands to change baud rate but costs 50 quid and has a lmuch larger footprint.spec sheet says voltage from 4 volts.ANy chance of it operating from 3.6 volts?????
Post edited by vvvv
on 19-05-2010 21:52 Post edited by vvvv
on 21-05-2010 02:09
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vvvv
75 posts
Frequent Visitor
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20-05-2010 21:53
progress.
unable to change baud rate to 4800 on BT module.So using SIRFTECH software to change SIRFIII gps module to 9600.
Connected ARF32 module rxd line to GPS tx line (no invertor required).
My bluetooth enable notebook found BT module and hey presto. GPS simple software receiving NMEA data @ 9600.
Of course Autoroute only 4800 baud so incompatable.'
BUT:
Directions.ltd have PC NAvigator 9 gps software which is baud rate selectable!! so will order.
Now for the bad new.
Total cost =£25 bluetooth module
£15 1300 mA LiPo battery
£39 SirfIII gps module
£? pcb design and build
Looked @ internet and found BT/GPS for £29.99!
+of course GPS mapping software and BT enabled notebook.
Still, can use the bluetooth module for mi own projects.Haven't dreamt of anything yet.Possible heart rate monitor....
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vvvv
75 posts
Frequent Visitor
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20-05-2010 23:02
Careful when using sirftech software when changing baud rate.Ensure NMEA selected.IF sirf mode selected took me 1 hour to reconfigure the GPS to NMea TO 9600
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vvvv
75 posts
Frequent Visitor
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05-06-2010 22:54
BT range was < 20 meters,but since I have not 1 but 2 mobile phone masts within 100 feet of my front door this is not suprising.
My bluetooth mice work perfectly since they incorporate active antenae.
Oh well,might have a look at zigbee whatever that is.
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