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Re: [Paparazzi-devel] UBX vs NMEA Protocol Inquiry

From: Andre Devitt
Subject: Re: [Paparazzi-devel] UBX vs NMEA Protocol Inquiry
Date: Thu, 1 Mar 2012 17:43:46 -0500

Additionally, NMEA support is currently broken in pprz 4_0 beta branch
(think head as well) as indicated my my 19-D GPS fix the other day. I
was only going for 2-D or 3-D. Not sure if it was just flavor of NMEA
my MTK 3329 was spitting out or in general. I have a working driver
will try to submit a pull in the next week.


On Thu, Mar 1, 2012 at 3:25 PM, Stephen Dwyer <address@hidden> wrote:
> Hello,
> Another nice thing about binary is you are guaranteed messages of a
> specific length. With NMEA if all fields are 0 or something like that,
> you might get a message of only 20 or 30 bytes in length, but with all
> values populated to near maximums, you will get closer to the limit,
> up to perhaps 70 or 80 bytes in length. This is much less predictable
> than being able to specify the same number of bytes and the same value
> in the same offset location in a binary message, and varies the
> timing. This in addition to the fact it takes more effort to convert
> numbers from text representation to binary representation, which takes
> more time than either using the value raw or doing a simple operation
> like scaling the value.
> And NMEA sucks, as mentioned several times before. :)
> Thanks,
> -Stephen Dwyer
> On Thu, Mar 1, 2012 at 12:48 PM, Roman Krashanitsa
> <address@hidden> wrote:
>> Chris, you still sort of have to match the binary frames to the message
>> types but you dont have to convert textual representation of numbers into
>> binary form. Some may argue, but I think this is not the main reason why
>> NMEA is not good compared to proprietary ublox binary protocol. NMEA is just
>> a poor standard, it is not robust and the minimum spanning set of commands
>> is too small. I think wiki will do a better job than me explaining this.
>> Roman
>> 2012/3/1 Chris Wozny <address@hidden>
>>> All,
>>> I was wondering if someone had a technical explanation as to why the
>>> UBX protocol is faster than NMEA parsing. I know in the past people
>>> have said NMEA sucks and binary protocol's are faster, but I just want
>>> to make sure I understand the technical reason. I know parsing ASCII
>>> strings requires more CPU cycles, but don't you still have to parse
>>> the UBX output as well?
>>> Best,
>>> Chris
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