Master thesis : DisplayPort - Auxiliary channel monitoring and main link optimization for ProAV applications

Abstract

Upon the establishment of a DisplayPort connection between a source and a sink device, the two entities perform a link training. Link training is a communication that occurs on an auxiliary channel which aims at determining the configuration of the main link.

Indeed, the main link is composed of four differential lanes for which the voltage swing and pre-emphasis levels are adapted depending on the channel quality and the source and sink capabilities, for optimizing the data transmission.

High-bandwidth digital signal such as those carried by DisplayPort main link lanes suffer from degradation due to PCB traces or due to the signal attenuation in long cables. However, a redriver can be put on the path of the main link lanes to equalize the digital signals and apply a gain to counteract these losses. The gains applied in the redriver channels should take the outcome of the link training into account.

For a video playout module equipped with a DisplayPort interface developed by Deltacast.TV for the ProAV market, the settings of the redriver mounted on its PCB are not adapted depending on the link training results.

This thesis proposes an FPGA-based embedded system that combines: an hardware level capable of decoding and interpreting the data exchanged on the DisplayPort auxiliary channel during the link training, and a software level including a softcore processor responsible to dynamically configure a redriver placed on the path of the DisplayPort main link.