GPS Unit works under 3.1.5, not under 3.2.1

Well, sort of. This is a strange problem. I recently had a bad flyaway which I couldn’t understand but was clearly GPS related. Finally located the copter and looked at the logs, and basically the GPS just disappeared mid-flight, satellites went from nine to zero. This was running AC 3.2.1.

Fired it up again, and this is the situation:

– GPS unit (Ublox Neo 6m) working fine when connected to u-config. Showing correct lights etc.

– Arducopter 3.2.1 does not recognize that it is connected to the GPS (gpsstatus = 0)

– Arducopter 3.1.5 recognizes the GPS but refuses to arm, but does not give a bad G
PS message (or any other message). If I try to arm from Misson Planner I get a ‘Mavlink Command rejected’ dialog.

– Status messages on Misson Planner show it is receiving good GPS info (gpsstatus = 3 and the plot is good on the map).

This is totally repeatable… if I flash to 3.2.1 without touching the quad it will not see the GPS, then if I reflash to 3.1.5 it will see it fine (but will not arm).

The hardware is the FC and GPS unit you see here:…dProduct=74652

When I connect to the GPS unit using the Ublox software and the APM pass-through firmware, it appears to be functioning completely normally, which seems to negate any hardware issues.

Any suggestions?

Is there any place where can i download older firmwares, im also having hard time with gps 3.2.1 firmware

i cant get any of those working with my ublox-7m gps…

baudrate has been changed from gps to 38k and other settings too

What the F is the problem

In Mission Planner you can choose ‘browse previous firmwares’ and choose 3.1.5 from the menu.

I still don’t understand why it won’t work in 3.2.1. Is it because 3.2.1 tries to write its own config file to the Ublox and 3.1.5 doesn’t?

Okay, it is definitely an issue with the APM board not being able to write the config file to the GPS unit.

For some reason the GPS unit simply ignores commands, although otherwise functions fine.

I have continuity from the TX and RX pins on the APM to the RX and TX pins on the GPS respectively and both are showing voltage. The GPS baud rate is fine since I can see the output and the APM recognizes it under 3.1.5.