Speedisp

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Speedisp
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A very simple program that demonstrates how to communicate to GPS (Global Positioning System) receiver. This program receives GPS feedback via serial interface and displays your position and speed.

To make Speedisp work, select the correct serial port (usually COM1 or COM2) and the correct port speed. The port speed must be equal to the baud rate in the setup of GPS receiver. Or just try the most commonly used COM port speeds that are 2400, 4800 and 9600.

Do not forget that the receiver only works if no obstacles are blocking the sky view. It is really curious that virtually nobody mentions that.

When I started to program the GPS receiver communications, I quickly found some pretty good manuals. All commands were listed and all options were explained. But when I tried, everything failed. I spent several weeks on and off but it didn't help. Until I accidentally tried this program from my laptop outdoors...

Usually, when you program and run your GPS tests, you and your computer are located at your home or office, under roof that is nontransparent to satellite signal. And the GPS. Sounds very stupid but my search across the Internet showed that nobody explains this trick explicitly. Hope I filled this gap.

When the receiver sees the satellites, it starts to feed text file into COM port without request. The format of common GPS phrases is explained in this excerption.

The program consists of a dialog window and of the separate thread that reads serial port and decode GPS feedback. (Files thread.cpp and wtalker-com.cpp.) It is intended to read from Magellan 315 receiver, but of course can be modified to accept the feed from any receiver.