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Question Regarding U-Blox GPS

I purchased a GS407 U-Blox5 GPS 4Hz as part of order 13206 and I am not confident is behaving according to spec. There are two behaviors which I observe. The first behavior is very consistent, it never varies. The second is new, and I have not yet tested sufficiently to isolate the conditions under which it occurs.

 

I should note that I also have a MediaTek MT3329 GPS 10Hz + Adapter Basic that appears to operate normally, in the same airframe, in the same locations, used at about the same time (immediately before or after the U-Blox5) and does not show either of the two behaviors.

 

I did not assemble the U-Blox5, it came with the DIYdrons UBlox_Basic_V10 adaptor attached and glued to the GPS.

 

-> The first behavior is that the U-Blox5 does not seem to report the number of satellites. I have used four different versions of APM code, including the current and last versions of APM and the current and last versions of ACQ code. When running test->gps, I see #sat as 0. When running the MediaTek, I get good numbers for this value.

 

Is this the normal/expected behavior for this hardware? Should I investigate further with different sketches? Please advise.

 

-> The second behavior, seen in the last three test flights, is that the U-Blox5 will not report consistent locations. I am in the northern virginia area, but it is alternately reporting coordinates in the middle of brazil, in central Alaska, and in the middle of the arctic ocean. This behavior persisted across three power cycles of the APM, and did not settle over an hour of observations (assumed it would sort itself out over time) After that, I finally gave up on the unit and switched over the the MediaTek to continue my test targets, and planned to ask about the # of satellite issue (and, if resolved, I will watch for this second behavior to see if it was an anomaly. 

 

Any suggestions please? Should I investigate the hardware in more detail? Might this be a hardware problem, or do you suspect I am using it wrong in some way (bad electrical connections, bug in the code, configuration setting problem, etc?)

 

U-Blox5 shows the following numbers:

LEA-5H-0-009 29

17403102117 0/31

150000.1307.009

6006211002G

PRT NO 203066[obscured by antenna]

GPS BOARD_ELO_V1_080115 1107

 

The adaptor shows:

v5 soldered

uBlox_Basic_V10

 

Tested with Arducopter 2.0.38 (and prior version, I don't remember the #), APM2.22, APM 2.211, and with APM MissionPlanner 1.0.53 (0 sat issue) and APM Mission Planner 1.0.54 (both issues)

 

I see in the code it looks like it is set for GPS_PROTO_AUTO (from memory) and I did not change any values.

 

Thank you for any suggestions. I will investigate further if you think the problem can be resolved with this hardware, I suppose I am wanting to make sure I should investigate. If, based on the symptoms, you think I have problematic hardware then I don't want to waste 80 hours poking at the software. :)

 

 

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Replies

  • Mike, I looked at the U-blox library code and this number of satellites function is not supported. The U-blox puts out blocks of data and only the necessary ones are enabled. I found a link to the manual here. You want to read the section "UBX protocol". The U-blox library would need have some code added. With U center you can change which blocks of data are sent. Any how I don't think you have a problem with the satellites, you are just not getting that data, or zero.

    I almost forgot,,, here's U-center.

     

  • It can take a very long time for a new or idle GPS to get the proper almanac or some thing like that. I have a U-blox and have seen this behavior before. You just have to be patient and have a good signal. Out doors with a clear sky is the best. You should also download U-Center. You can then see every thing and set everything on the GPS from your PC. It's really cool to play with, but bee careful about changing settings. You need to solder pins on your adapter board and jumper them to an FTDI serial/USB adapter.

    Or just set it outside and wait. It could take a very long time. If you have it connected to a USB it will power it and you don't have to use batteries. Once you start getting the crazy locations it has acquired satellites and is running through solutions until it gets a good lock. If you leave it off for a long time (weeks) it will get lost again and have to start over again. If it's reporting lat/lon readings then it's working, it just needs time to do it's thing.

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