I2C does it work in the automobile if yes then how we can choose wire for the i2c busbar to reduce bus capacitance
I2C has a budget of 400 pF which is dependent on the speed and distance that you which to go. IF the wire is shielded (which typically doubles twisted pair capacitance), then you might be able to go a couple of meters (6 feet).
But quite frankly I2C is meant to be used as Inter-Integrated Circuit that is within a few inches away and typically entirely within the confines the digital domain of a of a single PCB.
As Single Fonts said, CANbus is the typical standard for automotive purposes, which supports a wired topology that you are looking for. Another solution may be a UART approach that is point-to-point, but may be implemented as RS-485 ; similar to CANbus.
The data rate typically dictates the protocol, which dictates the physical layer; not the other way around.
All good points but in automotive especially, budgets dictate performance which dictates protocol and physical layer definitions...
Something else to keep in mind is that because the use of the standards are so prolific in such short amounts of time, the automotive industry likes to plan backward compatibility into new designs many years after planned obsolescence most notably when the public sector is the end customer.
Very rare are the days of complete system replacements in the areas of public transportation. Lots of refurbs and band-aids to squeeze another year out of a system.
Well, one things for certain the automotive industry is unique (as in odd-ball) in almost every regard !! It sets and follows its own standards. It doesn't surprise me that ALL facets of automotive engineering and design is only directed and controlled by one objective - COST !!
The standards that the automotive industry creates is self-serving and is only to reduce liability and planned obsolescence is a BIG part of the auto industry game. The only other industry that is comparable is consumer electronics which lowers the bar even lower since there is virtually no liability and supported by obsolescence within a year !
The standards that I2C is NOT directly for the automotive industry even though it has embraced this technology. Its the same way Intel has created the SMbus which is a derivative of I2C but is morphed into what Intel has defined meets its own terms. The computer industry doesn't have to like it but it does have to accept it (if they need to use it).
I really don't care what happens in the automotive industry since i primarily work in the high reliability industries of Military / Defense / Space / Aerospace / Aviation and Medical Electronics. These are the industries that really care about their end customers and are willing to take (or make) the best standards to ensure that the end products are designed to life critical and mission critical requirements.
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