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I have a LS20031 GPS connected to a Pololu USB-Serial adapter. I’ve written a simple interface in VB10 Express and it works OK. When I send packets that are listed in the MTK NMEA Packet User Manual, I get more responses than I expect from reading the manual. There usually is a PMTK response, but if I send the same command packet again, I get a different response–usually with G codes. After sending the same packet and receiving a number of different each time, I usually get a PMTK result that’s in the manual. I have the MC-1513 GPS module datasheet too and am trying to use the manual and datasheet to make sense out of the commands. All I want to do is send a packet and receive a useful response. Where can I find more info?

Have you tried using the MiniGPS application? You can use the utility to control which NMEA formats are output. Could you post what you are sending and receiving to and from the GPS module? Also, what are you using to send and receive that information?

- Jeremy

Thansk Jeremy. I’m using a Dell tower (T5500) with Win7Pro. The MiniGPS and the Locosys GPS Fox both work OK today (didn’t yesterday for some reason). I’m clearly having start-up problems and need to dig into everything deeper before I send code. I can send and receive packets OK using my VB10 program.

Question: Are the packets contained in the MTK user manual sufficient to make the LS20031 work as it does with the MiniGPS and Fox apps? If so, then I know what I have to do.

I am not sure, but I think that is likely to be the case.

Problem solved.

Two things:

  1. Your suggestion of using the Mini GPS app to configure the GPS is excellent and it works. While I was using it, I noticed item #2 below while I was changing the setup values.

  2. When you query the GPS or issue a command to it, the result isn’t immediate. For example, when I issue a Test Packet request while the unit is sending location info, the $PMTK result happens later–sometimes right away, sometimes after several location info packets have been sent.

Another example: When I send a baud rate change, the GPS output will continue for a while at the old baud rate. The commands are probably queued in the device.

It’s easy to parse the return string to get the desired result.

This is a great product. It’s especially useful for learning to use GPS. It would be a perfect world if the GPS would work INDOORS like my iPhone and iPad do. If you ever sell an active antenna with sufficient gain, I’ll want one.