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gtjoseph / mt3339-utils

MIT License
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MTK models #1

Open fouadchamoun opened 9 years ago

fouadchamoun commented 9 years ago

Hello,

I was wondering if the library works with other MediaTek chipsets like the MTK3336 ?

Thank you,

Fouad

gtjoseph commented 9 years ago

I don't have a MTK3336 to test with but I think it'll work.

fouadchamoun commented 9 years ago

hello again :)

I ended up buying the Adafruit ultimate GPS with the MT3339 chipset.

But i'm having a problem actually getting the AGPS to work. Even when I send EPO, position and time to the chipset, I can't get a fix with the built in antenna and indoors.

When I use an external antenna and put it outside I get a fix almost instantly even without sending the EPO,position,time data.

Do you have any idea why this would happen ?

Also, when the module loses power (i.e. when I restart the BeaglBone), does it restart in factory reset mode or cold/warm/hot start ?

Thank you very much

marpy commented 9 years ago

Hi there,

To answer your question regarding why it didn't work indoors without an antenna: EPO data/AGPS is not a magic bullet. It still requires that you have a good signal from at least 3 satellites for 2D location and 4 satellites for 3D location. The fact that you didn't use an external antenna indoors means that the signal received (if any) is not strong enough to determine a location.

Why your GPS unit found a fix almost immediately outdoors: EPO data persists between power cycles, so if you sent the EPO data to test the unit indoors before outdoors, it makes sense that the GPS picked up a location almost immediately. If you didn't upload EPO data beforehand, then this just further strengthens my argument above. Using an external antenna increases the gain of your unit, which allows it to better pick up weaker signals, thus providing more information to the MTK3339.

Answer to your power loss question: According to the manual and adafruit's product page: The unit will factory reset upon power loss. This does not include EPO data, which is stored on non-volatile memory. Exception to this is if you have the backup battery installed, in which case it will preserve settings until backup battery dies.

gtjoseph commented 9 years ago

The other factor to consider is time. The EPO data is completely useless if the unit doesn't have the correct time. Outside, it can get the time well before it gets a fix. In fact, it has to have the time BEFORE it can get a fix. It sounds like inside it's not even getting the time so a fix will be impossible. BTW, not only does the battery preserve settings, it also keeps the internal RTC working so even if you disconnect power, the unit will have accurate time immediately on main power up.

Use the gpsstatus tool while indoors to see if the unit has good time and what kind of signal you're seeing.

fouadchamoun commented 9 years ago

Thank you very much for this information !! :) the gpsstatus tool was really helpful in comparing TTFF between different conditions. I love the work you've done on this library. Have a good day, Fouad