Why Do Car Radios Have USB Ports?

The main reason that so many car audio systems now come equipped with a USB port is simply to add another input type. USB has become or less ubiquitous in all sorts of different electronics, including cell phones and MP3 players, so it only makes sense that OEMs and aftermarket manufacturers would both adopt the standard.

What that means is that you can use the USB port in your head unit to play music from a phone, MP3 player, or even a USB stick, provided there aren’t any compatibility issues. You may also be able to charge your phone or power up an accessory device like a portable GPS navigation unit if your head unit supports that.

The Primary Reason Car Radios Use USB

USB, in its many incarnations, has more or less become the de facto way to connect electronic devices to other electronic devices and computers, which is probably why so many automakers and aftermarket car audio manufacturers decided to adopt it over proprietary connections. Some car audio systems still use proprietary connectors, but you’re much more likely to find a USB port in your new car stereo.

Although USB connections can be used for firmware updates, to charge and power devices, and for other less common scenarios, the main reason that car audio systems use USB is an alternate way to play music and other audio content.

In some cases, especially in older head units, a USB connection will act simply as an alternate auxiliary input. This type of head unit allows you to play music from a phone or dedicated MP3 player, but the car radio itself contains no DAC or software capable of playing your music files.

Most car radios that include USB connectors also include the necessary software or firmware to decode and play music files. If you have this type of head unit, then you can plug in a cell phone, MP3 player, USB thumbstick, or even a USB hard drive — provided that it has a power source available — and play music straight from that device.

Listening to Music via Car Audio USB

Every head unit is different, so you may have to fiddle with the options or even read the manual if you want to listen to music via the USB connection. In a perfect world, you would be able to simply plug in an MP3 player, or storage media with music files on it, the head unit would recognize it, and your music would play. However, that isn’t always the case.

If you’re using a phone or MP3 player plugged into the USB connection, then it’s often a simple matter of selecting the auxiliary or USB input. Some head units, in conjunction with specific phones, will also include additional functionality and may require you to open a corresponding app on the head unit.

Listening to music that’s stored on a USB thumbstick is often more complicated. You may get lucky and have everything work fine the first time you plug in the thumbstick, or it may take a little more work. For instance, you may find that your head unit can only read data from the thumbstick if it is formatted a certain way, such as FAT32 or NTFS. You may also have to dive into the head unit options to specify a location to find music on the thumbstick, or there may be a ‘sync’ option that will prompt the head unit to automatically locate music on any attached media.

Using Other Car Audio USB Functions

USB is an interesting type of connection because it is capable of simultaneously transmitting both data and power. However, not all USB ports are wired the same way. In addition to USB ports that can do both, some are data only, and others are power only.

When a car stereo comes with a built-in USB port, it will typically be wired to provide power in addition to a data connection. While data connectivity is the primary purpose of the port, this type of car audio USB connection can also be used to charge your phone or power up other USB devices.

Since USB is increasingly used in place of proprietary power ports in all sorts of different portable electronics, a powered USB port in your head unit can be used to charge or power anything from your phone, to a portable GPS navigation device, and everything in between.

If your head unit doesn’t have a powered USB connector, then you’ll only be able to use it to play music. There are also a few situations, particularly with Apple devices, where a device won’t charge properly. This is primarily due to the way that different devices recognize that a USB port is a charging port instead of a simple data port.

Adding USB for Music or Charging

In situations where a head unit came with a port that isn’t capable of providing power or simply has no USB port at all, it’s also possible to add different types of USB ports to a car. Although a USB to aux cable won’t allow a car stereo to play music from a USB thumbstick, there are workarounds that can mimic that functionality with a little extra work.

Since car radios that come with USB lack the ability to play the music files contained on storage media like a USB thumbstick, the basic idea is to wire in a small, inexpensive MP3 decoder board that includes a USB input and can be wired to an auxiliary input.

It’s also fairly easy to add a USB charging port, or even replace your cigarette lighter with USB, although some soldering and other work will typically be required.

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