What hasn’t changed much is the architecture of such systems. Most car owners will have a head unit in the central console, wired to individual speakers and microphones around the vehicle. This forces the bulky electronics, along with the heat it generates from its amplifiers, into the center of the dashboard, as well as long lengths of cabling to speakers via the cable harness. Automotive Ethernet - AVB/TSN could change all this, thanks to its topology and features that differentiate it from the classic Ethernet networking technology used in offices and the home.
Ethernet has been the core technology for networking computers for several decade, with continuous development of the standard bringing it up to gigabit speeds. However, the standard has been lacking in features that would enable the reservation of bandwidth or guaranteeing latency. Such capability is critical to ensure that real-time applications, such as audio and video, are delivered without stuttering or breaks to the consumer, regardless of the other data being passed over the network. It will also enable Ethernet to be used in the control-loop of functionally critical applications, something that is currently not possible.
Thanks to the efforts of several working groups, the Audio Video Bridging (AVB) / TSN has resulted in a set of technical standards. Amongst other features these define methods to reserve bandwidth between nodes in a network and how to synchronize audio playback or sampling at different nodes. This delivers the possibility of an architecture change for automotive audio systems. In future, the head unit can concentrate multimedia playback capability and Internet connectivity, while the amplification can be devolved to Audio Ethernet nodes at the ends of the network. The bandwidth reservation ensures that audio data always arrives in due time, while the synchronization feature guarantees that all nodes present the audio simultaneously.
Audio head units have relied upon powerful system-on-chip (SoC) processors for some time, integrating much of the connectivity required. However, automotive Ethernet requires changes in the lower OSI layers to support AVB/TSN, something that is still not yet to be found on many SoCs today. To resolve this challenge, Toshiba has developed the TC9562, a single-chip solution that can be connected to SoCs via its PCIe (PCI express) interface. Audio can be also passed to the device through the SoC’s integrated DSP’s TDM or I2S interface. These Audio streams are then seamlessly integrated into the Ethernet data stream as per the configuration made on the PCIe interface. This TDM audio connectivity into the TC9562 is a new alternative to AVB-stack software-handling by the SoC’s main CPU.
The TC9562 is equally at home at the audio node end thanks to its integrated Cortex-M3 processor. With 320kB of SRAM, the device can be used stand-alone, with the possibility of booting its firmware application optionally from a high-speed QSPI interface. The synchronization capability is transparent to the software developer, being handled automatically in the hardware interface and clock modules.
To find out more about the technology behind Automotive Ethernet and how the TC9562 can be used to implement in-vehicle audio applications, take a look at our white paper available here: