Solved Robustness of USB backward compatibility 3.1 to 2.0

Buddy · Mar 23, 2023

Not exactly a Win 11 question, but maybe someone here can help.

I have a 2022 Subaru Outback. There's a well-known bug in the infotainment system where it forgets where it was playing music from a USB flash drive when you switch the car off and then restart it later. The bug is inconsistent - sometimes it remembers, sometimes it doesn't.

My understanding is that the system reads the file structure and contents of a USB device when it's first inserted to construct an index, a database if you will. That index is then used for its user interface and playback. Speculation on the Subaru forums is that it loses its index on the restart and defaults to the first song it finds when it reconstructs the index.

Recently, a guy posted that he started using an old USB flash drive that only supports USB 2.0 and that his car no longer fails to restart play where it left off. The owner manual says the system supports USB 2.0 communication, not 3.0 or 3.1. My flash drive, of course, is 3.1. But it should be backward compatible, you'd think.

Finally getting to my question - Is backward compatibility in 3.1 devices robust, or can it be spotty? And if it was spotty, wouldn't that preclude it reading the device in the first place? For the record, I've been using a Samsung Fit USB flash drive - I'd figure a proper brand like Samsung would be more likely to work correctly than a cheap clone, but is that really true?

bob3d · Mar 23, 2023

Purchase a cheap USB 2.0 stick (they are still out there - https://www.amazon.com/PNY-128GB-At...id=1679588309&sprefix=USB+2.0+,aps,603&sr=8-5 ) and try it out since you have some assurance that this will work from some guy posting that it'll work.

Winuser · Mar 23, 2023

Buddy said:
Not exactly a Win 11 question, but maybe someone here can help.

I have a 2022 Subaru Outback. There's a well-known bug in the infotainment system where it forgets where it was playing music from a USB flash drive when you switch the car off and then restart it later. The bug is inconsistent - sometimes it remembers, sometimes it doesn't.

My understanding is that the system reads the file structure and contents of a USB device when it's first inserted to construct an index, a database if you will. That index is then used for its user interface and playback. Speculation on the Subaru forums is that it loses its index on the restart and defaults to the first song it finds when it reconstructs the index.

Recently, a guy posted that he started using an old USB flash drive that only supports USB 2.0 and that his car no longer fails to restart play where it left off. The owner manual says the system supports USB 2.0 communication, not 3.0 or 3.1. My flash drive, of course, is 3.1. But it should be backward compatible, you'd think.

Finally getting to my question - Is backward compatibility in 3.1 devices robust, or can it be spotty? And if it was spotty, wouldn't that preclude it reading the device in the first place? For the record, I've been using a Samsung Fit USB flash drive - I'd figure a proper brand like Samsung would be more likely to work correctly than a cheap clone, but is that really true?

The answer to your question lies with the unit in your car. Have you checked to see if the unit can do firmware updates. If it can, check to see if there is a newer firmware version available. My aftermarket JVC units' firmware can be updated.

Catnip · Mar 23, 2023

In my Mazda 3, if I use a USB3 drive, all hell breaks loose with the entertainment system. I have to use USB2 drives to get the audio player to work properly. In my case, newer Mazdas do not have this issue. But there is no upgrade for me as my car is a 2017.

In your case, @Buddy there may be an upgrade from Subaru if the car isn't too old, but you may wind up like me and have to scrounge for USB2 drives somewhere.

A pro tip for those of you with a recent Mazda. Don't plug in or unplug the USB drive when the car is running. It borks the USB stick permanently.

Buddy · Mar 23, 2023

All, thanks for the replies. Still interested if anyone has informed general comments on backward compatibility, either in the USB device itself or in the host.

@Catnip Very interesting, indeed. Any chance the Mazda head unit is Denso? That's what's in the Subaru.

@Winuser My car is a 2022, delivered in late 2021. For the longest time, it was on the delivery software version, which was from November 2021. It worked fine. My dealer upgraded it two weeks ago to October 2022 and that borked it. A week after they did that, a new March 2023 dropped. A lot of Outback owners have moved to it (you can install it yourself) and, sadly, they all report that the USB playback bug is still there after the update.

@bob3d I have done exactly that. "The guy" was using a Sandisk Cruzer Blade", so I bought one. Copying my music to it today. We'll see.

Winuser · Mar 23, 2023

Buddy said:
All, thanks for the replies. Still interested if anyone has informed general comments on backward compatibility, either in the USB device itself or in the host.

If I'm not mistaken, Your radio is probably running Linux.

Buddy · Mar 23, 2023

Winuser said:
If I'm not mistaken, Your radio is probably running Linux.

I know 0.000 about Linux. If the radio is on it, how does that relate to USB backward compatibility?

Winuser · Mar 23, 2023

Buddy said:
I know 0.000 about Linux. If the radio is on it, how does that relate to USB backward compatibility?

Windows might be more backwards compatible then linux. If the radio is using Linux it's not goin to work the same as if it was using Windows or even Android.

Winuser · Mar 23, 2023

Did you get a chance to try the Sandisk Cruzer Blade with the radio. I'm curious to see if it does solve your problem.

Buddy · Mar 23, 2023

Winuser said:
Did you get a chance to try the Sandisk Cruzer Blade with the radio. I'm curious to see if it does solve your problem.

It worked after several restarts. Let's see if that holds up overnight and through tomorrow. The bug had been inconsistent, not necessarily losing its place on every restart.

And folks on the Outback forum confirmed that the HU is on Automotive Grade Linux.

Catnip · Mar 24, 2023

@Buddy I'm not sure what the head unit is, unfortunately.

Winuser · Mar 24, 2023

Winuser said:
Did you get a chance to try the Sandisk Cruzer Blade with the radio. I'm curious to see if it does solve your problem.

The unit in my Ram pickup always defaults to SiriusXM. I tried to find a way change it to default to my phone but found it's not possible.

barman58 · Mar 24, 2023

Usb is a badly abused set of standards, unfortunately, some of the hardware manufacturers have been known to "bend" the rules that should apply, In addition to using only those usb devices that were current when the head unit was originally fitted [this can easily be several years earlier that the date of the Vehicle release] it's also best to try not to use devices with a capacity higher then those in use when the car was built.

I have run "modern classics" for my daily driver for a number of years and have no issue playing from the latest 128GB and 256 GB sticks, or cards of course the first thing I did when I purchased the car was to replace the head unit

Buddy · Mar 24, 2023

The Owners Manual calls for USB 2.0 media devices. Yes, in a 2022 car.

@barman58, it's not even that simple. The folder structure has to be no more than 3 levels below the root. Root-folder-folder-songs. And the system will only play the first 5000 songs it finds on the device.

One oddity is that a new and much-anticipated firmware update dropped on 3/13/23. Lots of owners have upgraded. Even though the infotainment system calls for FAT32, the upgrade has to be NTFS to accommodate a 5GB file. And the punch line - a lot of those who have upgraded did the upgrade from a USB 3.1 stick. Go figure...

And the bug persists on the new release. Ain't it grand?

Winuser · Mar 24, 2023

barman58 said:
In addition to using only those usb devices that were current when the head unit was originally fitted [this can easily be several years earlier that the date of the Vehicle release

On average it takes an automobile 3-5 years to go from being a concept to production. The head unit may be even older than that.

Buddy · Mar 27, 2023

Update - I bought the EXACT SAME 2.0 flash drive that one of the Subaru forum members says has always played correctly for him. Put my songs on it. It worked, for 2 or 3 days. Then, the whole infotainment/driver recognition system got its shorts momentarily in a wad over me getting in and out, starting and switching off, to deal with the liftgate not closing because of an obstruction. And, bada-bing, it forgot where it was.

Played OK for another couple of days, then forgot again. Started up on the first alphabetic song title in the first alphabetic folder. That's it's favorite place.

Then today, without any menu press from me, it decided to turn on song repeat.

I doesn't seem a stretch to say that whatever this issue is, what it's not is a choice of 2.0 vs 3.1 flash drive.

Buddy · Apr 16, 2023

I'll put a bow on this and wrap it up, as far as this forum is concerned. Whatever it is, it's not the choice of 3.1 vs. 2.0 USB drives. Plenty of people on the Outback forum have now tried 2.0 drives without success. And not that it matters to Win 11 folks, but the hope was that the new head unit firmware would fix it - one item in the "fixed bug" list sounded similar. I installed it two days ago and it didn't help. Oh well...

Solved Robustness of USB backward compatibility 3.1 to 2.0

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