[rwedinburgh]

On this question of what kinds of USB sticks and sizes a Volvo audio head unit can communicate with, I'm a computer scientist, so did a little digging and testing.

All of the different eras of Volvo cars that have a USB port and an audio head unit that can communicate with it, will have different standards according to the era. Speaking only of the first generation of Volvo XC60s, roughly 2009 - 2016, (I have a 2009) this is what I found out about the USB and compatibility.

The audio unit will only read a USB stick smaller than 32GB, because it can only read a stick or drive formatted as FAT32. FAT32 as a format only allows a drive up to 32GB; above that, it has to be formated to exFAT, which the car's head unit cannot read. For example, if you take a (working, FAT32) USB stick and format it to exFAT or NTFS, it cannot read it and the head unit says "Unreadable USB". This means for this era, 32GB is the absolute maximum size of drive it can read technically. If someone on the forum says they are using a USB stick larger than 32GB, then they have a newer Volvo XC, and not the first generation without a modern entertainment unit. In my car's year, 2009, there were three different levels for the audio system installed at the factory, and they might also have been slightly different in their handling of USBs (I doubt it though - I think they all shared the same head unit).

According to the manual, it can read up to 64,000 files and up to 500 folders. It can only read WAV and MP3 files (and some few WMV where such exist), and nothing else. If MP3 files are at non-standard bit rates, etc., or encoded using a very modern method, they may not read and will just be skipped when you try to play them. Broadly, to function, the head unit has to create an index of what's on the USB stick, so the more files on it, the longer it takes to start the music, because it is reading the file table on the stick and creating a big index. For this reason, if you insert a USB stick with 10 MP3s on it, it starts playing immediately, but the same stick with 10,000 MP3s, and it will take maybe three minutes to load the table and make an index and start playing. If you insert a stick with more than 500 folders, or more than 64,000 songs, it will truncate (cut short) the files it can play, because it fills its internal memory index until it is full, and then stops reading. For this reason, if you have too much on a stick, it may only allow you to play songs starting with the letters A through S, for example. The letter S is where it ran out of memory and stopped reading the USB stick's file table. I would guess that if you have very long folder names, and folders in folders, this also reduces the number of files it can read, but it would depend on how the unit is doing the indexing. Strangely, the audio head unit does not remember the stick's index when you turn the car's ignition off, so every time you get in the car, it reads the index again.

Connecting a device like an iPod or iPhone or Android phone is a different thing, as the car has custom code for communicating with and controlling an iPod or iPhone, but for the first generation, not an Android phone. If you plug in an Android or similar phone, you have to put it into "USB storage mode" and then it will depend on how your phone is configured whether the car's head unit is able to see anything on the phone (likely it will not).

As an aside, most owners of these cars have noticed that in this era you can connect your car through Bluetooth and use it as a phone, and on Android it will even communicate using Skype, etc., anything telling Android that it is a phone call. However, you can't play music through the Bluetooth, only voice. It seems possible to simply have your phone mark audio out of any type, including music, as a voice call, to allow playing it in the car over Bluetooth, but I would guess the car's Bluetooth is locked to very low bitrates and standards specific to voice calls, so the quality would end up being pretty poor.

Hope this helps - Richard