> Hmm, this is 802.3cg which is 10Mbps single-pair, which doesn't seem to be compatible with the 802.3da multidrop iot stuff
802.3cg supports multidrop as part of 10Base-T1S.
802.3da is a draft intended to enhance these capabilities with longer segments, support for more devices in a segment, and support for powered multidrop segments. It's far from final at this point so I wouldn't expect hardware to support .3da any time soon.
That said one of the main objectives of the .3da group is to be backwards compatible with .3cg multidrop networks. Obviously the enhanced features are not guaranteed to work with older devices, but .3da devices should always be able to connect to a .3cg multidrop network.
> Whyyyyyyyyy, IEEE, do we have so many single-pair singletons floating around out there, none of which work with each other?
They all have different use cases that rarely need to interact.
The 10 megabit varieties are primarily focused on being able to operate on existing wiring that was not intended for Ethernet use. They're intended to bring Ethernet in to environments where CAN, Modbus, PROFIBUS, etc. have long dominated with as little external impact as possible.
The faster varieties are mostly for adding high-speed ethernet to wiring harnesses in environments where using one pair over four pairs is advantageous, usually where weight matters like automotive and aerospace applications.
Either way, users are not expected to be mixing and matching single-pair ethernet devices in the same way as you would for "normal" ethernet. They're all still ethernet on top of the physical layer and can be bridged/switched to other varieties in the same way as any other varieties have been for years if someone wants to build a device with both kinds of ports. You just can't physically plug them in to the same cables.
> Either way, users are not expected to be mixing and matching single-pair ethernet devices
Which is precisely what made other Ethernet so powerful and rapidly dominant. I'm not disagreeing with you, just saying it's a shame.
Say I want to make an Ethernet-speaking sensor of some sort, the sort of thing that might be on CAN today. I now have to make multiple versions of it if I want to sell into all those markets, which I'm not likely to do in practice. Which means there will be fewer Ethernet options on the shelf in some of those markets, which means they'll remain CAN for longer. Which ultimately means Ethernet doesn't become as pervasive as it could if all those things worked together.
> Say I want to make an Ethernet-speaking sensor of some sort, the sort of thing that might be on CAN today. I now have to make multiple versions of it if I want to sell into all those markets, which I'm not likely to do in practice.
If it's the sort of thing that might be on CAN today, you'd put it on 10Base-T1S and call it a day
The higher speed varieties aren't even going to be used in the sorts of situations where you'd normally be plugging in random additional hardware. It's a point to point link within a specialized wiring harness, whatever is going on each end is generally going to be specific to that environment.
It's moderately annoying from a tinkerer standpoint to have to use adapters, but I'm really having a hard time coming up with real world scenarios outside of development/testing where it'd be useful to be able to plug a 10Base-T1L device directly in to a 1000Base-T1 link for example, or vice versa.
I guess I could see some utility in a dual mode device for the two 10mbit varieties that could either be on a shorter multidrop network or a long run point to point, but even there I feel like a lot of those use cases would be in building automation type infrastructure where at the end of most of those longer T1L runs you'd have a few devices and a bridge to T1S multidrop would make sense anyways.
802.3cg supports multidrop as part of 10Base-T1S.
802.3da is a draft intended to enhance these capabilities with longer segments, support for more devices in a segment, and support for powered multidrop segments. It's far from final at this point so I wouldn't expect hardware to support .3da any time soon.
That said one of the main objectives of the .3da group is to be backwards compatible with .3cg multidrop networks. Obviously the enhanced features are not guaranteed to work with older devices, but .3da devices should always be able to connect to a .3cg multidrop network.
> Whyyyyyyyyy, IEEE, do we have so many single-pair singletons floating around out there, none of which work with each other?
They all have different use cases that rarely need to interact.
The 10 megabit varieties are primarily focused on being able to operate on existing wiring that was not intended for Ethernet use. They're intended to bring Ethernet in to environments where CAN, Modbus, PROFIBUS, etc. have long dominated with as little external impact as possible.
The faster varieties are mostly for adding high-speed ethernet to wiring harnesses in environments where using one pair over four pairs is advantageous, usually where weight matters like automotive and aerospace applications.
Either way, users are not expected to be mixing and matching single-pair ethernet devices in the same way as you would for "normal" ethernet. They're all still ethernet on top of the physical layer and can be bridged/switched to other varieties in the same way as any other varieties have been for years if someone wants to build a device with both kinds of ports. You just can't physically plug them in to the same cables.