Is there a bug in uBlox GPS handing?

I'm not getting a GPS lock with uBlox 5.I wondered if the checksum comparison (below) is correct as UBX_ck_b is not checked but UBX_ck_a is used twice?Code extract from GPS_UBLOX tab:if((ck_a=UBX_ck_a)&&(ck_b=UBX_ck_a)) //Verify the received checksum with the generated checksum..

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  • Developer
    uBlox 5 has locked with this code for me.. but I am having lock problems with ArduIMU, I am getting lat, lon, & alt data though just no blue LED...
  • Have you ever had a GPS lock from your GPS module (presumably it is a uBlox 5)?

    For a first fix try to have a good view of the sky and just be patient.

    There is a utility "u-center" available from uBlox web site which you can run on a PC which I would recommend for setting up the GPS module to your preferred settings. You need to find a way to connect the GPS tx/rx to the PC either via the Ardupilot PCB or by connecting the FTDI cable and the GPS cable somehow. Normally the GPS tx and PC tx are both connected to the ATmega rx. If you keep the ATmega in reset then you can ignore it and just swap the tx and rx wires of either the PC (FTDI) or the GPS module.

    EGNOS was switched from test to operational mode very recently, so yes in Europe I would enable EGNOS (but avoid having the US WAAS enabled, I've found that if your GPS catches sight of a WAAS satellite it can sometimes cause issues as it is not intended for use over here).

    As I don't know what level of experience or knowledge you have of GPS or the electronics sorry if this is all obvious or if it doesn't make any sense - just ask for clarification.
  • Changing the last variable to be UBX_ck_b I can now get a GPS lock indication - hence the line is now:
    if((ck_a=UBX_ck_a)&&(ck_b=UBX_ck_b))

    I hope this is useful - I'm still very new to this so appologies if this turns out to be rubbish.
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