6 ms·

So that's three separate single-pair standards that I'm aware of, and I can't get _anyone_ to tell me if they interoperate. Perhaps they're different names for

So that's three separate single-pair standards that I'm aware of, and I can't get _anyone_ to tell me if they interoperate. Perhaps they're different names for the same thing? Perhaps the wheel just keeps being reinvented? One is the Single Pair Ethernet industrial partner network mentioned in this post: https://www.single-pair-ethernet.com/en https://www.single-pair-ethernet.com/en which seems to be standardized as 802.3cg and calls itself 10base-T1L. The second is the One-Pair EtherNet (OPEN) Alliance: http://www.opensig.org/ http://www.opensig.org/ which seems to be standardized as 802.3bw and calls itself 100base-T1 and 1000base-T1. I believe this is the one I see deployed in production cars today. The third is HDMI Ethernet, which rides pins 14 and 19 of the HDMI connector. It is absolutely impossible to find information on. Does it have a standard? Does it use a standard MAC? Where can I buy the PHY? What a stinking mess.

bofh23 5y ago
Good luck finding any consumer products that ever supported HDMI Ethernet Channel (HEC). In contrast, HEC capable HDMI cables with pins 14 and 19 in a twisted pair were widely available to the confusion of many. Audio Return Channel (ARC) uses the same pins as HEC. Enhanced ARC (eARC), available on some newer TVs and AV Receivers/preamps/soundbars, takes advantage of the twisted pair to support greater audio bandwidth and surround channels (ARC was limited to 5.1), so it’s a happy ending for folks who bought HEC compatible HDMI cables.
addaon 5y ago
100base-T1 and 1000base-T1 are indeed the old OPEN, and are indeed what's deployed in production cars. 100 Mb PHYs are available from multiple vendors, and are mature and quite pleasant to work with (built in TDM for detecting wiring issues, etc). 1000 Mb PHYs are rarer (I've only seen Broadcom in person), but it's clearly coming. The 100- and 1000- protocols are pretty different; both are really focused on allowing cheap crappy wiring, but this is hard enough for 1000- that things like FEC are added. The equivalent of PoE for -T1 is PoDL (power over data lines), which is much more civilized than PoE (no transformers); and since 1000- runs at a higher lowest frequency than 100-, it's significantly easier to get power over it with smaller inductors. I'm not too familiar with the current state of -T1L, but the little I've seen about it in the past was a focus on taking the advantages of -T1 (low wiring cost, simplicity, robustness, PoDL) and applying it to industrial applications, where MUCH longer cable runs than in automotive are desired. While I was following this was mostly done by adding in a 10base-T1L physical layer, giving up an order of magnitude of speed in exchange for an order of magnitude or two more run length. Don't know if there's any intent to have faster -T1Ls, haven't followed that far. 10base-T1L, 100base-T1, and 1000base-T1 are all pretty different physical layers, although they share some principles. I /think/ the Broadcom 1000base-T1 PHY can run in 100base-T1 mode, and maybe even auto-negotiate (yuck), but they're quite different under the hood.
- tinco 5y ago
  Thanks for sharing your experience! What is the advantage of using single pair ethernet in for example cars? My company owns a largish drone and it has a regular CAT5 network so surely it can't be weight or size.
  - mimentum 5y ago
    Surprised it isn't running a CANBUS system.
    - detaro 5y ago
      CAN is slow compared to Ethernet and really optimized for tiny payload sizes, so for plenty purposes the former isn't that useful. (Which is also why Ethernet is pushing into automotive)
  - zbrozek 5y ago
    I've spent ten years designing electronics for cars. It's very often harness reduction under various motivations. The bundle needs to be small to fit through chassis holes (which are kept small to keep structures strong). Keeping the pin count low increases available connector choices and reduces connector costs (especially where they must be waterproof). Off in the distant corners of minds is weight. Your drone would probably do the same if the manufacturer had more engineers to spend on optimizing the design. But it's probably also sold in lower volume than car parts. Alternatively, maybe it's using CAT5 in a nonstandard way. For example, maybe two links or non-PoE power or even not Ethernet at all.
    - sorenjan 5y ago
      How are car communication done in modern cars? Is there a single cable run from the ECU in the front to the cabin and one to the back, and then some kind of switch connects stuff like gauge cluster, AC, buttons etc in the cabin, and lights, camera etc in the back? How about fiber cable, is there any movement towards that? Some cars have fancy 360 camera systems that I imagine can use a lot of bandwidth.
addaon 5y ago
Putting HDMI ethernet channel thoughts here, since I have no first-hand experience with it. My understanding is that it's basically 100base-TX under the covers, and that's vaguely confirmed by [1] and others. The big difference, as you mentioned, is that it uses a single pair, instead of separate RX/TX pairs like 100base-TX usually does. Rather than doing the 1000base-T trick (share the lines with echo cancellation), it looks like it uses an analog hybrid [2]. Still never seen it in the wild though. [1] https://www.semiconn.com/ep91h1 https://www.semiconn.com/ep91h1 [2] https://en.wikipedia.org/wiki/Telephone_hybrid https://en.wikipedia.org/wiki/Telephone_hybrid
baybal2 5y ago
T1S is a thing, but the only chip on the marked is bugged beyond being usable, and Microchip wanting $4 for it.
bsder 5y ago
One of the key differentiators is that most of these standards are point-to-point--they only connect 2 devices. So, it doesn't work very well for replacing things like CAN. 10Base-T1S is multidrop on single pair--which is basically a CAN replacement. Unfortunately, I haven't seen much movement at all in the T1S space.
- JAlexoid 5y ago
  I have yet to see a reasonable case for CAN replacement, as it's good enough. Maybe we'll get more wireless connectivity from the IoT space, but that's probably not immediate. There's really no goal for these to do anything other than PtP with these solutions.
  - kevin_thibedeau 5y ago
    CAN doesn't scale to high data rates.
    - gumby 5y ago
      But the underlying RS-485 has nice noise rejection and is dead easy to manage.
      - bonzini 5y ago
        Are you confusing CAN with ModBus-RTU perhaps? The wires are similar, but RS485 uses differential encoding for both 0 and 1 while CAN only uses it for 1. In CAN, 0 is represented by lack of difference between the two wires.
        bonzini 5y ago
        Correcting myself, actually CAN is the opposite: 1 (recessive state) is lack of difference, 0 (dominant state) is presence.
        gumby 5y ago
baybal2 5y ago
> One is the Single Pair Ethernet industrial partner network mentioned in this post: > which seems to be standardized as 802.3cg and calls itself 10base-T1L. > The second is the One-Pair EtherNet (OPEN) Alliance: > What a stinking mess. One is high speed point-to-point, to replace expensive proprietary crap like MOST, FLEXRAY, etc. Another to replace slow buses, like CanBus, ModBus.
johnwalkr 5y ago
For what it's worth, I clicked some links on the posted page and the first datasheet I opened was for a 10base-T1 transceiver. So I believe this "single pair ethernet" encompasses both T1 and T1L, with L probably standing for "long distance". It's confusing but it is nice to have a family of standards that hopefully work the same, but have different physical layer for different use cases.
ajb 5y ago
There's also EFM/2BASE-TL which was a sort of IEEE rebadge of the ITU DSL standards with the OAM layer replaced with Ethernet OAM. I never quite figured out if there was any point to it beyond NIH.
NovemberWhiskey 5y ago
The key differentiator here is reach. 10Base-T1L (the subject of the article) is really an industrial/sensing application and supports cables up to 1km in length. The 100Base-T1 and 1000Base-T1 standards are targeting the transportation market with cables <50m in length.
- gertrunde 5y ago
  The article states that the technology being referred to is 1Gbps, plus power, over a distance of up to 40m. (Although it is an 18 month old article, so things may have changed since).

bofh23 5y ago

Good luck finding any consumer products that ever supported HDMI Ethernet Channel (HEC). In contrast, HEC capable HDMI cables with pins 14 and 19 in a twisted pair were widely available to the confusion of many. Audio Return Channel (ARC) uses the same pins as HEC. Enhanced ARC (eARC), available on some newer TVs and AV Receivers/preamps/soundbars, takes advantage of the twisted pair to support greater audio bandwidth and surround channels (ARC was limited to 5.1), so it’s a happy ending for folks who bought HEC compatible HDMI cables.

addaon 5y ago

100base-T1 and 1000base-T1 are indeed the old OPEN, and are indeed what's deployed in production cars. 100 Mb PHYs are available from multiple vendors, and are mature and quite pleasant to work with (built in TDM for detecting wiring issues, etc). 1000 Mb PHYs are rarer (I've only seen Broadcom in person), but it's clearly coming. The 100- and 1000- protocols are pretty different; both are really focused on allowing cheap crappy wiring, but this is hard enough for 1000- that things like FEC are added. The equivalent of PoE for -T1 is PoDL (power over data lines), which is much more civilized than PoE (no transformers); and since 1000- runs at a higher lowest frequency than 100-, it's significantly easier to get power over it with smaller inductors. I'm not too familiar with the current state of -T1L, but the little I've seen about it in the past was a focus on taking the advantages of -T1 (low wiring cost, simplicity, robustness, PoDL) and applying it to industrial applications, where MUCH longer cable runs than in automotive are desired. While I was following this was mostly done by adding in a 10base-T1L physical layer, giving up an order of magnitude of speed in exchange for an order of magnitude or two more run length. Don't know if there's any intent to have faster -T1Ls, haven't followed that far. 10base-T1L, 100base-T1, and 1000base-T1 are all pretty different physical layers, although they share some principles. I /think/ the Broadcom 1000base-T1 PHY can run in 100base-T1 mode, and maybe even auto-negotiate (yuck), but they're quite different under the hood.

tinco 5y ago
Thanks for sharing your experience! What is the advantage of using single pair ethernet in for example cars? My company owns a largish drone and it has a regular CAT5 network so surely it can't be weight or size.
- mimentum 5y ago
  Surprised it isn't running a CANBUS system.
  - detaro 5y ago
    CAN is slow compared to Ethernet and really optimized for tiny payload sizes, so for plenty purposes the former isn't that useful. (Which is also why Ethernet is pushing into automotive)
- zbrozek 5y ago
  I've spent ten years designing electronics for cars. It's very often harness reduction under various motivations. The bundle needs to be small to fit through chassis holes (which are kept small to keep structures strong). Keeping the pin count low increases available connector choices and reduces connector costs (especially where they must be waterproof). Off in the distant corners of minds is weight. Your drone would probably do the same if the manufacturer had more engineers to spend on optimizing the design. But it's probably also sold in lower volume than car parts. Alternatively, maybe it's using CAT5 in a nonstandard way. For example, maybe two links or non-PoE power or even not Ethernet at all.
  - sorenjan 5y ago
    How are car communication done in modern cars? Is there a single cable run from the ECU in the front to the cabin and one to the back, and then some kind of switch connects stuff like gauge cluster, AC, buttons etc in the cabin, and lights, camera etc in the back? How about fiber cable, is there any movement towards that? Some cars have fancy 360 camera systems that I imagine can use a lot of bandwidth.

addaon 5y ago

Putting HDMI ethernet channel thoughts here, since I have no first-hand experience with it. My understanding is that it's basically 100base-TX under the covers, and that's vaguely confirmed by [1] and others. The big difference, as you mentioned, is that it uses a single pair, instead of separate RX/TX pairs like 100base-TX usually does. Rather than doing the 1000base-T trick (share the lines with echo cancellation), it looks like it uses an analog hybrid [2]. Still never seen it in the wild though. [1] https://www.semiconn.com/ep91h1 https://www.semiconn.com/ep91h1 [2] https://en.wikipedia.org/wiki/Telephone_hybrid https://en.wikipedia.org/wiki/Telephone_hybrid

baybal2 5y ago

T1S is a thing, but the only chip on the marked is bugged beyond being usable, and Microchip wanting $4 for it.

bsder 5y ago

One of the key differentiators is that most of these standards are point-to-point--they only connect 2 devices. So, it doesn't work very well for replacing things like CAN. 10Base-T1S is multidrop on single pair--which is basically a CAN replacement. Unfortunately, I haven't seen much movement at all in the T1S space.

JAlexoid 5y ago
I have yet to see a reasonable case for CAN replacement, as it's good enough. Maybe we'll get more wireless connectivity from the IoT space, but that's probably not immediate. There's really no goal for these to do anything other than PtP with these solutions.
- kevin_thibedeau 5y ago
  CAN doesn't scale to high data rates.
  - gumby 5y ago
    But the underlying RS-485 has nice noise rejection and is dead easy to manage.
    - bonzini 5y ago
      Are you confusing CAN with ModBus-RTU perhaps? The wires are similar, but RS485 uses differential encoding for both 0 and 1 while CAN only uses it for 1. In CAN, 0 is represented by lack of difference between the two wires.
      - bonzini 5y ago
        Correcting myself, actually CAN is the opposite: 1 (recessive state) is lack of difference, 0 (dominant state) is presence.
      - gumby 5y ago

baybal2 5y ago

> One is the Single Pair Ethernet industrial partner network mentioned in this post: > which seems to be standardized as 802.3cg and calls itself 10base-T1L. > The second is the One-Pair EtherNet (OPEN) Alliance: > What a stinking mess. One is high speed point-to-point, to replace expensive proprietary crap like MOST, FLEXRAY, etc. Another to replace slow buses, like CanBus, ModBus.

johnwalkr 5y ago

For what it's worth, I clicked some links on the posted page and the first datasheet I opened was for a 10base-T1 transceiver. So I believe this "single pair ethernet" encompasses both T1 and T1L, with L probably standing for "long distance". It's confusing but it is nice to have a family of standards that hopefully work the same, but have different physical layer for different use cases.

ajb 5y ago

There's also EFM/2BASE-TL which was a sort of IEEE rebadge of the ITU DSL standards with the OAM layer replaced with Ethernet OAM. I never quite figured out if there was any point to it beyond NIH.

NovemberWhiskey 5y ago

The key differentiator here is reach. 10Base-T1L (the subject of the article) is really an industrial/sensing application and supports cables up to 1km in length. The 100Base-T1 and 1000Base-T1 standards are targeting the transportation market with cables <50m in length.

gertrunde 5y ago
The article states that the technology being referred to is 1Gbps, plus power, over a distance of up to 40m. (Although it is an 18 month old article, so things may have changed since).