GPSrChive Discussion Forum

Just got an info from garmin, that it is not possible to downgrade the GPS chipset-firmware

Sorry, i dońt know any solution.

But you could share the video on youtube, to get maybe better feedback about people having the same issue, and garmin to enforce a bugfix.


I will us it for hiking maybe in a week.

On my last 66s that I recently RMAed I used to have satellites disappear when resuming from expedition mode. I found rather than rebooting, just going to the satellite page and selecting "Use with GPS off" and then turning back on was enough. I had it with GPS Software ver 2.5 though I think firmware version 3.0 made it much worse.

I don't know if I get it still, I've given up on expedition mode since I find it too buggy. I reported a problem on the forum earlier about the odometer jumping by thousands of kilometers which was the reason for the RMA. The new unit does the same. When at home going into and out of EM will often add 9824.6km. Distance is consistent between the two units (except one day when it was consistently 20km or so). At one location in Yellowstone, the distance was consistently 13301km. When I returned the unit the odometer was over 500000km and I managed to overflow the trip odometer (> 100000km) in one two hour walk. I'm still surprised nobody else has mentioned it.

Garmin should provide a rollback version if they supplied a dud.
It’s a MediaTek MT3333 GPS chipset by the way.

I suspect you will find that large distance that is added to your trip odometer is the distance from your actual position to 'null Island', just off the west coast of Africa...

Although I have experienced similar behavior under different circumstances, I also have reported this phenomenon to Garmin.

Art wrote: Thu Aug 29, 2019 1:06 pm Garmin should provide a rollback version if they supplied a dud.
It’s a MediaTek MT3333 GPS chipset by the way.

Why do they call it 3313 if it should be a 3333
https://www8.garmin.com/support/downloa ... p?id=14457

They call it MT3333 in the GPS firmware version 2.60 and in 2.70.

Is there a way to upload a file here or something?

I’ve created a 2.60 GPS chipset file that identifies itself as version 2.71 inside the gcd file wrapper,
and recalculated the outside gcd checksum, then copied it to the device Garmin/RemoteSW/ folder.
This is enough to fool the GPS into accepting the update. It displays as 2.60 again in the About screen.

It will also keep updating so long as the file is present on the SD card.
You have a few seconds between each update to power the unit off,
and connect it to a PC again in USB mode to delete the update file manually.

The downside is that if the next legitimate version happens to be 2.71, the GPS won’t accept the update.

Use at your own risk, and don’t power the unit off while updating, but immediately after.

Could you also call it 2.701 ?

Nope. That’s actually a later version if it were possible (which it isn’t).

It’s 270, and 260. There is no decimal point.

Art wrote: Thu Aug 29, 2019 3:02 pm Use at your own risk, and don’t power the unit off while updating, but immediately after.

Which GPS Chipset Software version is this? And what have you done to modify it?