[FOSS-GPS] Raw Data from NEO-6M

Scott Harrison scott at sharrison.net
Wed Apr 30 14:39:17 PDT 2014


The problem with the NEO-6M is that raw messages are disabled by
default so there is no explicit way to activate the RXM RAW & RXM SFRB
messages in the normal manner in U-Center.   This is why you have to
send a custom message to modify the firmware that resides in volatile
memory.  I don't think a battery backup will help the because the
firmware will be reloaded from ROM when the chip reboots and the raw
messages will be turned back off.  I am not 100% sure though, and this
should be tested.

Scott

On Wed, Apr 30, 2014 at 1:59 PM, Josh Leighton <leighton.josh at gmail.com> wrote:
> You should also be able to provide a startup message for RTKLIB to send to
> the receiver.  I use it with str2str and if I recall rtkrcv / RKNAVI support
> it as well.  For ublox it looks like:
>
> !UBX CFG-RATE 1000 1 1      # set update period in milliseconds
> !UBX CFG-MSG 2 17 0 0 0 1   # RXM RAW - required for rtklib
> !UBX CFG-MSG 2 16 0 0 0 1   # RXM SFRB - recommended for rtklib
> !UBX CFG-MSG 240 0 0 0 0 1  # NMEA GGA
> !UBX CFG-MSG 240 1 0 0 0 0  # NMEA GLL
> !UBX CFG-MSG 240 2 0 0 0 0  # NMEA GSA
> !UBX CFG-MSG 240 3 0 0 0 0  # NMEA GSV
> !UBX CFG-MSG 240 4 0 0 0 1  # NMEA RMC
> !UBX CFG-MSG 240 5 0 0 0 0  # NMEA VTG
> !UBX CFG-MSG 240 8 0 0 0 0  # NMEA ZDA
>
> The first two numbers of each CFG-MSG line define the message, and the
> following 4 0s and 1s turn that message on and off for different interfaces
> (usb, serial, etc)
>
> -Josh
>
>
> On Wed, Apr 30, 2014 at 1:46 PM, Danny Miller <dannym at austin.rr.com> wrote:
>>
>> Be sure to increase your serial port baud rate.
>>
>> There's MUCH longer packets, and more of them, than data than NMEA fixes.
>> In my experience if there's too much data it just overruns the buffer and
>> data gets lost.  The link is full of errors and the fix disappears.
>>
>> It may appear fine early on after power-up.  But as more satellites get
>> added, the data gets longer and longer, and you may oddly lose the fix as it
>> becomes "good".
>>
>> You can also disable data you don't need to keep the link bandwidth down.
>>
>> The graphical interface of U-Center allows you to turn on/off msg types
>> for each port.  It'll be saved if you have a battery on the GPS, which you
>> should to maintain the RTC.
>>
>> Danny
>>
>>
>> On 4/30/2014 12:16 PM, Scott Harrison wrote:
>>>
>>> Leor,
>>>
>>> You have to go into U-Center and enter the following custom message:
>>>
>>> to enable RXM-RAW
>>>
>>> b5 62 09 01 10 00 c8 16 00 00 00 00 00 00 97 69 21 00 00 00 02 10 2b 22
>>>
>>> to enable RXM-SFRB
>>>
>>> b5 62 09 01 10 00 0c 19 00 00 00 00 00 00 83 69 21 00 00 00 02 11 5f f0
>>>
>>> This will turn on the raw data you need, but it is stored in RAM so
>>> you will need to resend the codes every time you power up.
>>>
>>> Also, set your type to PPP and then you should start to see sub-meter
>>> accuracy with RTKLib.
>>>
>>> see http://wiki.openstreetmap.org/wiki/RTKLIB
>>>
>>>
>>> Scott
>>>
>>> On Wed, Apr 30, 2014 at 7:56 AM, vbenso <vbenso at gmail.com> wrote:
>>>>
>>>> Leor,
>>>>
>>>> It's been a long time since I don't touch my GPS hardware, so I could be
>>>> wrong. That being said.
>>>> As far as I remember, rtklib needs more information than just
>>>> UBX-RXM-RAW in
>>>> order to obtain an accurate fix. The neo6m should send another message
>>>> (maybe RXM-SFRB?) that I wasn't able to get from the receiver.
>>>> I could get ordinary gps precision in static and single modes of rtklib.
>>>> Good luck, and in case of any development let me know.
>>>>
>>>>
>>>> Victor A. P. Benso
>>>> Sementes Benso
>>>> Major Vieira - SC
>>>> (47) 9922-9599
>>>> (47) 3655-1192
>>>>
>>>>
>>>> On Mon, Apr 28, 2014 at 4:49 PM, leor [via Open Source GPS-related
>>>> discussion and support] <[hidden email]> wrote:
>>>>>
>>>>> I got 2 CN-06 (neo6m) recievers to output into RTKlib both over serial
>>>>> COM. Problem is that I have not been able to get a fix and always get a
>>>>> single status. Also whenever I choose static it seems to change
>>>>> everytime I
>>>>> start it. Using dgps and kinematic gives me an accuraccy of around 50m.
>>>>> I
>>>>> have tested this indoors and managed to get RAW data. Any idea how it
>>>>> would
>>>>> perform outdoors? I am trying to collect data to creat GCP for use in
>>>>> ortho
>>>>> correction
>>>>> [IMG]http://i.imgur.com/kj3Z5IV.jpg[/IMG]
>>>>>
>>>>>
>>>>> Great info you guys have. I got it to work but I am not sure what kind
>>>>> of
>>>>> accuracy I will be getting
>>>>>
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>>>>
>>>>
>>>>
>>>> ________________________________
>>>> View this message in context: Re: Raw Data from NEO-6M
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>>>> list
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>>>>
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