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Comment by addaon | Hacker News Reader

> When was the last time you saw ethernet frame collisions because you used a hub not a switch?

10base-T1S is just beginning to ramp up in the automotive industry, which modifies the super-successful 100base-T1 to be cheaper by (a) allowing cheaper PHYs; (b) allowing cheaper endpoints due to the lower data rate to handle; (c) allowing lower-spec single twisted pair wiring; and ... (d) allowing multi-drop. This is intended to allow Ethernet to push down into the space that CAN-FD is currently occupying, and looks likely to succeed, at least in some niches.

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> 10base-T1S

I think that standard is a huge mistake... 10Mbits isn't enough for a modern vehicle (no cameras, radars, screens etc). Many sensors alone can push megabits, and in the modern world engineers want to send their data json formatted not with bitfields.

Instead they should have used an cdma-like design with the physical being a 2 cent microcontroller for things like bulbs and micro switches. Then, for things like cameras which require more megabits use a 30 cent microcontroller with a higher chip rate, all transmitting in the same bus and using code division to avoid needing to worry about scheduling.

> I think that standard is a huge mistake...

You have to start somewhere. They're going for 25 Gbps:

> In addition to the more computer-oriented two and four-pair variants, the 10BASE-T1,[20] 100BASE-T1[21] and 1000BASE-T1[22] single-pair Ethernet (SPE) physical layers are intended for industrial and automotive applications[23] or as optional data channels in other interconnect applications.[24] The distances that single pair operates at full duplex depends on the speed: 1000m (1km) with 802.3cg-2019 10BASE-T1L; 15 m or 49 ft with 100BASE-T1 (link segment type A); up to 40 m or 130 ft using 1000BASE-T1 link segment type B with up to four in-line connectors. Both physical layers require a balanced twisted pair with an impedance of 100 Ω. The cable must be capable of transmitting 600 MHz for 1000BASE-T1 and 66 MHz for 100BASE-T1. 2.5 Gb/s, 5 Gb/s, and 10 Gb/s over a 15 m single pair is standardized in 802.3ch-2020.[25] In June 2023, 802.3cy added 25 Gb/s speeds at lengths up to 11 m.[26]

* https://en.wikipedia.org/wiki/Ethernet_over_twisted_pair#Sin...

The 100base-T1 and 1000base-T1 standards already exist, and are already widely adopted. 10base-T1S is intended to replace CAN, which is sub-10 Mb/s, and often ~2 Mb/s; this is a niche where cost comes first. For non-multidrop links, intermixing 1000, 100, and 10 Mbit/s ethernet links on the same switch is trivial, so each link can be independently chosen and cost-minimized; and for sensors and high bandwidth items with safety impact, multidrop is generally not the preferred approach anyway. Basically -- 10base-T1S fits a new niche (for Ethernet), where the niches you mention are already well addressed.

So it's like RS-485, but more complicated?

I think this is a terrible idea. Daisy chain multi drop is so last century. Switched point to point networks are so much better!

On paper, yes absolutely.

In reality, the wiring harness is one of the more expensive and complex components in a modern vehicle. The majority of the data being carried is low speed and low risk signalling: climate system controls, entertainment system, lighting control, etc. Obviously braking, steering, throttle controls and things like that are a different class.

Look at a modern luxury vehicle and how many things are in one door alone. Accent lights, window controls and motors, locks and lock controls, speakers (yeah, often plural), side mirrors and controls, side-looking cameras, etc. The wiring harness into a door needs consolidation or else it can become a giant heavy thing, the multi-drop approach makes a lot of sense here.

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