GPS Location -> PC RF Link

[Neil Stainton]

A am wondering how hard it would be to hook a 5 sample per sec GPS receiver to a RF modem type device, so I can view a model's location on a PC in realtime. The range would need to be about 400m.

I can do the PC program, but I don't have the expertise to locate, select, and interface the bit in the model. To be legal in the UK it would probably have to be on 433 MHz.

Any help from you electronics gurus would be much appreciated.

Thanks in advance,

Neil.

[Peter Seddon]

Hello Neil,

I have recently built and tested exactly what you are after using a 5Hz GPS (EB85A) connected to an ATMega168 to extract the bits of the GPS sentences I am interested in, combie them with air pressure and current/volatge data and send all data via an LPRS (www.lprs.co.uk) 433Mhz Module. Not sure of the range but could be about 200m - but that is dependant on the RF module. On the ground I receive the data, calculate distance from home, bearing to home and various other bits and pieces and display them as well as interfacing with Google Earth to show a live plot as to where the aircraft is.

I would not class the system as bullet proof or finished - I will shortly be building version 2 using a bigger processos to allow onboard data logging as well as an RF link to ground. Timescales - well despite being retired I am very slow so possibly first flight around August!

If I can help then let me know, but I must add I don't have many years of experience in this field - hence the speed I work at.

regards Peter
ps One thing I would like to add is voiced data output for certain parameters on the ground.

[Neil Stainton]

Thank you for your reply Peter. What an amazing cooincidence that your project is so similar and you are so close. We must get together at some point.

As I don't want to add air pressure etc data could I feed the GPS output straight into the LPRS module, or will I need a processor too? What language & dev tool do you use to program the AVR?

Regards,

Neil.

[Peter Seddon]

You might be able to feed the GPS straight to the LPRS module but a couple of things to watch - the default baud rate of the GPS data and whether any setup is required on the GPS. I have to turn the baud rate down to 19200. Also the LPRS module cannot accept a continuous data stream due to its internal buffer.

I use BASCOM (www.mcselec.com) to compile from basic which has quite good support and a good help forum. AVR's have a built in In Circuit Programmer using the SPI port so I just bring that port out and use the live system as a development system. Active Robots have a number of simple AVR boards that are great for development and come with all i/o ports brought out, a crystal and RS232 level shifter.

If I can help you in any way let me know.
regards Peter