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psmitty7373
59 Posts |
 Posted - 21 déc. 2006 : 17:47:28
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| Why does the MIO default to NMEA at 4800bps? It has a SIRF III, and Mio Map supports SIRF protocol... why not 115k using SIRF? I've tested it, it works. Why do you suppose they chose NMEA and only 4800 bps? |
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Space
USA
281 Posts |
Posted - 21 déc. 2006 : 21:58:54
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Why not?
Is there increased functionality/performance from using the faster speed or the different protocol?
Maybe it is more stable at the slower speed.
I just put this in SYS.TXT:
[gps]
com_port_speed=115200
I think that makes it use the higher speed, but I don't know what that will do for me. I think the data is only updated once per second, so does this speed really matter that much?
>UPDATE<
I have been using the spGPS utility to access the GPS, and the only speed that I tried that seems to work is 4800 bps. Are you sure it works at other speeds?
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Edited by - Space on 21 déc. 2006 23:11:42 |
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psmitty7373
59 Posts |
Posted - 23 déc. 2006 : 16:14:23
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| Yeah, you have to change the speed the GPS uses. Using SIRFTech you can enable WAAS and change the protocol/speeds. |
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roscoe
121 Posts |
Posted - 23 déc. 2006 : 17:55:57
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On the GPS chips I've dealt with, there isn't enough data being pumped out to cause any kind of bottleneck at 4800, so upping the baud rate won't give you any better performance, at least with the NMEA and TIP protocols.
I have no idea why they didn't default to SIRF though instead of NMEA, unless they're just waiting to do it for the next round of products. |
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Space
USA
281 Posts |
Posted - 24 déc. 2006 : 05:30:48
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I've changed Mio Map to use SiRF instead of NMEA.
One of the things I noticed is that after running Mio Map and then looking at the parameters in SiRFTech, it changes some of them.
Track Smoothing is turned on, and the "Degraded Mode" is set to "Hold direction, clock".
I've set these to something else, ran Mio Map, and then checked them afterwards, and they are all set back to these values.
I am not sure if this means that Mio Map only sets and uses these parameters when using the SiRF protocol, or if it also sets these when using NMEA protocol, but they just revert back when the GPS connection is closed.
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sprog
83 Posts |
Posted - 24 déc. 2006 : 12:51:12
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Hi Space,
How do you change MioMap to use SiRF instead of NMEA? I read somewhere that NMEA can only update once every 2 seconds, but SiRF can do once every 1 second. By default, MioMap appears to update once every second (look at time sync, position update, speed update, etc).
After I futzed around with SGPS and SiRFTech (I only toggled Static Nav on and off), I noticed that MioMap would only update once every 2 seconds, making it very slow. Thinking it was an NMEA vs. SiRF issue, I left the GPS in SiRF mode in SiRFTech, but MioMap wasn't able to find the GPS when I did that. I resorted to doing a hard reset to get it back to 1 second updates.
Thanks in advance. |
Edited by - sprog on 24 déc. 2006 12:52:07 |
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psmitty7373
59 Posts |
Posted - 24 déc. 2006 : 20:12:46
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Open SYS.TXT
Use the settings below, change them as needed.
[gps]
protocol = "SIRF"
com_port = 4
com_port_speed = 57600
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torowl
Canada
105 Posts |
Posted - 24 déc. 2006 : 20:44:08
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| Why use com_port 4? com_port 4 is an empty port. This setting didn't work for me. Neither com_port 2. How you guys made it work? |
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psmitty7373
59 Posts |
Posted - 24 déc. 2006 : 23:47:30
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| You have to make sure the sys.txt settings match the mode the GPS chip is in. Use SIRFTech to change gps settings, then match them in sys.txt. |
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staljin
27 Posts |
Posted - 25 déc. 2006 : 00:32:38
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Well I managed to switch over to SIRF but satelite screen show that I was moving dog I was sitting on my balkony. Anyone who cares to write small guide for noobies?
Staljin |
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Space
USA
281 Posts |
Posted - 25 déc. 2006 : 03:45:54
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I think both NMEA and SiRF use the same interval (1 second), so I don't think you gain anything by changing in that respect.
But if you want to try it, here is how I did it...
WARNING: I take no responsibility for any damage you may inflict on you C310x by following these instruction! Although I have followed these steps without incident, there is no guarantee that they will not render your unit inoperable. If you do not want to potentially mess up your Mio, then do not follow these instructions.
That being said, I have messed around with this a bit and not had much problem. I did have to hard reset once to get back access to my GPS receiver (I was sweating for a bit), but in retrospect (and with the knowledge of later experiments) I think the real problem there was that I had set the baud rate on the GPS to a certain value and forgot which one it was, so couldn't access it later via SiRFTech (if I had tried all the baud rates, one of then probably would have worked).
So here it goes...
In order to use SiRF protocol with Mio Map, you first have to change the protocol of the GPS receiver to SiRF, then you have to tell Mio Map to use SiRF protocol as well.
I used SiRFTech (a utility that runs on the Mio) to change the GPS receiver to use SiRF protocol by following these steps (NOTE: I also changed the baud rate to 57600):
1) Start SiRFTech, it should start up and show you the time in UTC and some satellite information. If you haven't made any changes previously, it should be using NMEA protocol at 4800 baud.
2) On the bottom of the screen, tap on the "NMEA" menu. If the menu doesn't come up, try tapping in the upper right corner of the menu text (i.e. right above the "A" in "NMEA" or for the "SIRF" menu, right above the "F").
3) Once the "NMEA" menu opens, select "Set Serial Port (Switch to SiRF)". In the "Protocol" field select SiRF (should already be selected), and in the Baudrate field put in what you want, I put in 57600. Then tap the "Set" button. Then tap the "=Baud" button. You should see the "SirfTime" field start incrementing.
4) Select "Exit" from the bottom of the screen to exit SiRFTech.
You have just set your GPS receiver to respond to SiRF protocol commands instead of NMEA protocol commands.
The next step makes Mio Map also use the SiRF protocol at the new baud rate:
5) Edit the file "\My Flash Disk\MioMap\MioMap\SYS.TXT" and add the following lines:
[gps]
com_port=2
com_port_speed=57600
protocol="SIRF"
(If you used a different baud rate than 57600 in step 3, then put that for com_port_speed instead)
Save the file.
6) Now start up Mio Map, and it should now be using SiRF protocol at the new baud rate. If you look at the satellite icon and it has a red exclamation point ("!") in it, then something went wrong and Mio Map can not connect to the GPS, otherwise you can tap on that icon and watch as the new SiRF protocol is used to get updates about the satellites (the green light should be blinking).
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Edited by - Space on 11 janv. 2007 02:52:39 |
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sigi_e
USA
11 Posts |
Posted - 25 déc. 2006 : 07:31:21
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| That doesn't work for me. I can barely get the NMEA screen up (most of the time Mio freezes up and needs soft-reset), when I select SIRF and Baudrate, then hit 'SET' and the '=Baud', I get an error box and nothing changes. Anyone else has the same experience? |
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torowl
Canada
105 Posts |
Posted - 25 déc. 2006 : 07:55:43
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| Thanks for the tips. It works for me. |
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staljin
27 Posts |
Posted - 25 déc. 2006 : 12:46:44
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Thanks for this guide Space. Anyone with an idea why does MIO C710 thinks (when using SIRF) I am moving at 1-6 km/h rate when I was acctually sitting. Only difference I noticed between SIRF and NMEA is that satelite contact was better with SIRF. On my "builed inn" balcony MIO C710 has no contact with satelite when using NMEA, while in SIRF mode it get lock on sitelite(s).
staljin |
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psmitty7373
59 Posts |
Posted - 25 déc. 2006 : 16:14:26
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| The default settings filter the GPS position to limit shifting around when stopped. Also, for some reason the default settings turn WAAS off. I'm also curious why the chip is listed as 20 channels but only ever picks up 12 sats. I realize that you almost never have more than 12 in the sky, but I'm all about using things to their maximum potential. |
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Space
USA
281 Posts |
Posted - 26 déc. 2006 : 09:31:57
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I think it is because of this: while the chipset does support 20 channels (actually 22), there is no available firmware for the chipset that supports more than 12.
I read this in one of the other threads on this site where someone from SiRF tech support was answering a lot of questions about the SiRFstarIII chipset.
The reason for no supporting firmware (yet) is as you said, currently there is rarely ever more then 12 satellites visible in the sky at once from a single location.
Found the thread (page 2 has the info on this subject) note that this answer was from 1 year and 8 months ago:
http://www.gpspassion.com/forumsen/topic.asp?TOPIC_ID=25575&whichpage=2 |
Edited by - Space on 02 janv. 2007 07:48:45 |
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Why NMEA at 4800?
