How it works
APIX2 continuously transmits data in frames - micro data packages - and supports video, audio, and bus protocol formats in what are called data containers. (Figure 3) The necessary high-speed clock is synthesized by the transmitting device, not derived from the pixel clock of the graphics processor or camera; this makes the link highly immune to pixel-clock jitter, and leads to stable and reliable transmission over relatively long cables.
Figure 3: The APIX2 frame accomodates two independent video streams plus audio and Ethernet data.
The architecture allows easy and inexpensive "daisy-chaining" of displays, with splitters to interface with individual displays. Using interface ICs such as the ADV7680 from Analog Devices, the system can provide the connection between the bus and a HDMI enabled GPU or CPU.
The net data rate for APIX2 is 2.8 Gbps (downlink) and 187.5 Mbps (uplink); this allows two independent video streams, multichannel digital audio, and control data; further, using a standard-compliant media independent interface (MII), even Ethernet data can be transmitted. The approach supports a cable distance up to 12 meters (more than sufficient for automotive) because its internal algorithm continuously adjusts the digital filters to maximum throughout and minimize bit error rate.
The other issue which automotive applications can't ignore is the stringent EMC (electromagnetic compatibility) emission limits. The constant serial stream of the APIX2 approach provides an even spread of the energy spectrum, with overall emission levels well below permitted maximums.
The car of the future: different than what was envisioned
There have been countless predictions about the automobile of the future: silent, flying, and even self-driving (autonomous). And while there is good progress in that last category - Google, for example, is doing some interesting work - most of these futurists did not envision a vehicle that would be so intensely networked, connected to the "cloud", and loaded with both driver displays and passenger infotainment. The auto is becoming a combination of a sophisticated, data- and display-heavy aircraft cockpit, plus an infotainment center for the passenger (and perhaps even the driver).
Nonetheless, that's where the market is going, due to the expectations of today's buyers, especially the newer ones for whom digital access and connectivity have always been their reality. For auto vendors and especially the IC vendors who supply them, it's both a challenge and an opportunity: the challenge of meeting expectations of features, functions, and performance at acceptable prices, but with the opportunity to add valuable content to the vehicle with resultant profit and return on investment in a growth market.
About the author:
This article originally appeared on EE Times Europe.
Peter Hall is Automotive Connectivity Marketing Manager for Analog Devices, Inc.