Using GMSL Technology for Transmitting Stream of High-Quality Video Data
Authors: Ponomarenko Bohdan Andriiovych 
Published: December 2021

The article is devoted to the description and research of technologies for data flow transmission from video cameras designed for use in modern cars. The paper provides a theoretical analysis of the most popular wired and wireless data streaming technologies, such as Gigabit Ethernet and Wi-Fi. Analysis of the most important characteristics showed, that the mentioned technologies are not effective due to their significant shortcomings, which are critical in the production of cars, and will not allow their usage. The main disadvantages of Gigabit Ethernet technology are the lack of guarantees of full delivery of transmitted data. Given that the data obtained can be used for self-driving control systems, the technology cannot be used for transmitting the data stream to the camera, as there will be a possibility of endangering the safety of the passenger and accidents to the vehicle. Disadvantages of Wi-Fi technology include low data rates and lack of reliable protection against electromagnetic interference. Given the advantages and disadvantages of the above technologies, it was decided to abandon the possibility of their usage and consider suitable options. It is shown, that in the considered conditions, the most expedient solution for data transmission from the video camera is GMSL technology, which makes it possible to significantly increase the resistance to electromagnetic interference, the overall transmission rate, and the quality of the transmitted data. The technical features of GMSL technology, in particular SerDes technology, which is one of the main components of the above technology, are considered. For SerDes technology, the process and features of converting a parallel data stream into a serial, data transmission, and inverse data conversion into a parallel form are described. The usage of this technology makes it possible to transmit data over a distance of up to 15 meters (without significant loss of quality). Described is a method of encoding input data in the format 8b/10b. This encoding makes it possible to ensure the stability of data transmission and their overall resistance to electromagnetic interference. This is achieved by noise of the useful carrier signal. Describes the possibility of restoring the clock signal using the CDR block after receiving data on the differential pair, as it does not contain a separate line for this signal. At the same time the problem of current and voltage balance is solved. The methods of controlling the video camera module and SerDes components using I2C and UART interfaces are shown. The peculiarity of the control signals is that they can be directed in different directions due to the duplex transmission channel. The expediency of using GMSL technology in a device that implements data transmission from the camera module is considered. The advantages of using the described technology and their compliance with the established requirements are given. It is proposed to implement the ability to control the mode of operation of the camera from the control device using GMSL technology.