Vehicle Audio Moves on as Number of USB Ports Grows
The increase in USB Type C interface technology is being adopted by automotive manufacturers who see it as a gateway to the complete entertainment experience.
The lure of simultaneous transfer of data and video along with fast charging through a universal port is proving popular, with IHS Markit Consumer Electronics Intelligence Service expecting increases in the use of USB-C ports from 300 million in 2016 to nearly five billion in 2021.
Although the majority of USB-C interfaces are used in wireless devices, mobile phones, and tablets, for example, they are increasingly used in vehicles as well as consumer and computing products.
One of the advantages that appeal to the automotive market is the size and weight savings afforded by the USB Type-C connector format.
One of the advantages that appeal to the automotive market is the size and weight savings afforded by the USB Type-C connector format. The connector is larger than the USB Type-A version, measuring 2.5 x 8.3mm compared to 2.5 x 7.5mm for the micro USB-A connector. It is, however, double-sided and reversible, making it possible to design slimmer, lighter designs with a high data transfer rate.
The USB-IF is currently looking into how USB Power Delivery and data over USB 3.2 can be used for in-vehicle systems that are either lighter in traffic, for convenience, or to track people and goods to enhance security.
The Connected Car
In-vehicle infotainment systems are a prime recipient for the energy-saving USB Type-C connectivity. The industry organization that helps develop standards and supports its members to deliver products to market, the USB Implementers Forum (USB-IF), is examining new opportunities for USB in embedded systems. It believes that the open standard, used in billions of devices worldwide, can improve in-vehicle connectivity when used in embedded systems.
The USB-IF is currently looking into how USB Power Delivery and data over USB 3.2 can be used for in-vehicle systems to deliver media sharing, image capture, and aggregate sensor data for vehicles that either operate autonomous or Advance Driver Assistance Systems (ADAS), which rely on sensor data.
One step has been for the USB-IF to announce the USB Audio Device Class 3.0 specification for USB Audio over USB Type-C. It allows a single cable to deliver data, power and video over a single connector, saving wiring costs, as well as weight and space in the constraints of automotive design. It can be used in headsets, mobile devices, gaming, and Virtual Reality (VR) as well as docking stations.
The specification allows for support of digital audio over USB and the addition of capabilities to reduce power consumption. This is particularly pertinent in automotive design. There are concerns that USB charging ports in vehicle can adversely impact efficiency by drawing on the vehicle’s electrical network and reducing range by 0.03 miles per gallon of gasoline (Bloomberg).
Standardizing the approach to audio is expected to encourage device interoperability across digital applications, especially in the automotive space. The USB Audio Device Class 3.0 specification defines minimum interoperability requirements across analog and digital solutions—all devices support audio consistently. Original Equipment Manufacturers (OEMs) can design systems without the conventional 3.5mm analog audio jack and reduce the number of connectors in a device to save space and costs. It should also be easier, proposes the USB-IF, to design waterproof and water-resistant devices with less areas for ingress.
Audio for Embedded Design
German embedded tool supplier Segger Microcontroller has added audio support for its emUSB-Device USB device software stack designed for embedded systems. The software is written in ANSI C and can run on any platform, says the company, including Linux, Mac, and Windows. It adds that support for new platforms can usually be added at no extra charge.
The emUSB-Device Audio allows an embedded device to be used as a recorder or speaker, without requiring an audio jack or audio hardware to handle audio data. For example, says the company, audio data from a Linux, Windows or Mac PC can be saved directly onto a Secure Digital (SD) card. It can be used in embedded designs for speaker phones or headsets, voice recorders, music players or wearable devices.
If the target device incorporates or attaches to microphones, speakers, headsets, and/or musical instruments, the USB interface can stream the audio data to or from the host.
The Audio class V1.0 is designed for embedded devices and supports the use of a speaker Input/Output (I/O) terminal and a microphone (I/O audio terminal). The embedded developer writes the driver to interface with audio hardware.
Audio data is transferred in the Pulse-code Modulation (PCM) encoding in multiple audio samples per packet.
Segger’s emUSB-Device stack runs on any microcontroller and can be used in embedded systems to create different USB interfaces, for storage, file communication, and to connect standalone devices on a local network.
The company offers evaluation boards, such as the empower (Figure 2) for use with trial packages to allow developers to innovate with audio and other USB capabilities. With the universality and proven track record of USB and a worldwide ecosystem and support, the possibilities for integrating USB and audio functions should be exciting developers everywhere.
Caroline Hayes has been a journalist covering the electronics sector for more than 20 years. She has worked on several European titles, reporting on a variety of industries, including communications, broadcast and automotive.