CF Plus II / Winfast Navigator NMEA Settings Explaination

soup · Occasional Visitor Joined: Nov 03, 2004 Posts: 8

Hi Folks,
Yet another newbie here looking for a little help.
Just got an ipaq 2210 and Syson CF Plus II. When I first got the two working together, I think I was using NMEA; by using Winfast, I was able to see the SiRF data. I'm still successfully receiving the SiRF data but I can't see the NMEA data (just gobbledy gook on the development screen as per the wonderful tweaks feature).
I wish to be able to have the skill to switch from one to the other. I changed the Baudrate over and over again, com7 seems fine. Could someone enlighten me to what each of the the NMEA settings relate to on the command screen please, maybe I have accidentlt made an adjustment here? As in: GGA GLL GSA GSV RMC VTG and MSS,

lbendlin · Posted: Wed Nov 03, 2004 5:26 pm Post subject:

SiRF is binary code - that's why you see garbage. NMEA, on the other hand, uses ANSI only so you can read the text.

It's your own fault - you played with the fire when you switched to SiRF without reason. You should be able to get the receiver back to NMEA mode with Crux_View or maybe even with WinFast. If not, draining the battery will also reset it to NMEA, but that may take a long time.

There's tons of info on the NMEA sequences on the web. For example here

http://vancouver-webpages.com/peter/nmeafaq.txt
_________________
Lutz

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soup · Occasional Visitor Joined: Nov 03, 2004 Posts: 8

Thanks for the fast response and warm welcome!
I wish to master switching from NMEA to SiRF so I don't considering it playing with fire; draining batteries seems a very amature way of switching between the two. I successfully switched from NMEA to SiRF (albeit by luck) so going the other way with the software I have must also be possible. Once I get a reply (or discover it) I will let you know so you have less fear of the kit you have.
Thanks for the sequences link; maybe I was not clear with my question. I am seeking what the above codes represent on the commands/NMEA screen and how changing them affects the results not what the actual strings themselves are telling me (for example if I change the setting GGA from 1 to 2 what will be difference)?
For your information, the strings I was receiving were not binary but a sequence of squares showing me the settings the wrong (see last picture of this link http://www.pocketgpsworld.com/winfastnavigatorppc.php).
Many Thanks,
soup

lbendlin · Posted: Wed Nov 03, 2004 6:52 pm Post subject:

Soup,

the "squares" you were seeing are a result of a text viewer panicking when it has to display non-text (non ANSI) characters. Basically Byte values above 127.

The numbers in the GPS tool specify how often (every x seconds) a particular NMEA sequence should be sent from the receiver. The values can range frm 0 (this sequence will not be sent) to 20 (or so) .

For example, you may want to receive RMC every second, but GGA only every 5 seconds.

Only in very rare cases you need to change that (for example when a program expects VTG instead of RMC) . Sometimes navigation works but the number of sats is not displayed properly because GSA is switched off etc.

Did this help better?
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Lutz

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soup · Occasional Visitor Joined: Nov 03, 2004 Posts: 8

Thank you. That's what I was after (each setting = time).
That now leads me to another question then (and thank you for your time). If I understand; using the default values (and not changing them as you advise) and therefore gathering data every second or 5 would lead me to believe this is very accurate and up to date information. If I was using the unit for walking guidance (as opposed to driving), would I have any gain slowing down data acquisition? I'm thinking along the lines of battery conservation (if significant) but maybe there could be other benefits?
Regards to the NMEA / SiRF switching; I have now switched back to NMEA using a factory reset on the card using Winfast but I can't recreate how I arrived at SiRF again (yet).
Thanks Again,
soup

lbendlin · Posted: Wed Nov 03, 2004 7:47 pm Post subject:

When you walk you may not need the one second interval. Every 5 seconds should be good, too.

There is one more option - some of the newer SiRF chipsets support "trickle" mode. What this means is that you can influence the time the receiver needs to be on within the 1 second interval.

For example a value of 200 ms means that the receiver is on for 200 ms, gets a fix, sends the NMEA data, and then goes to sleep for 800 ms.

You won't get a five fold increas in battery life, but a good doubling of battery life is possible.

The risk is that 200 ms may not be enough to get the fix and you may see more dropouts.
_________________
Lutz

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soup · Occasional Visitor Joined: Nov 03, 2004 Posts: 8

Many Thanks

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