Two things I've learned working with SPE in its 100 Mb and 1 Gb configurations for a few years:<p>1) PoDL is substantially lighter, smaller, and simpler (though not necessarily cheaper) at 1 Gb than at 100 Mb, due to the increased frequency separation. Just like with other Ethernet protocols, the lowest frequency of comms is basically DC; it's only statistically brought above that by the scrambler, but there's no useful true lower bound. Having an order of magnitude more separation, such as it is, allows a more reasonably sized filter to stomp over less (ideally, approximately none) of the data.<p>2) Only the 1 Gb protocol includes FEC, 100 Mb is a simpler, non-error-correcting encoding. This means that even though the maximum frequency on the twisted pair goes up by an order of magnitude to ~660 MHz, requiring better cabling, better twist spacing, etc... it allows a "sloppier" job at both high and low frequencies, since the FEC really does hide a few errors. This can be spent on even worse filters for PoDL, on frequency-specific interference (e.g. an RF amp running nearby), etc.<p>Basically, I was surprised to find that 1 Gb was not only not more challenging at the system design level, it was often simpler. (I haven't played with 10 Mb in either of its two incarnations seriously yet.)
We built a Power over Data Line (PoDL) compliant device and power supply as part of a one-month 'sink or swim' approach to designing and testing new hardware, and getting to look at maturity of the 10Base-T1 ecosystem. The board was enclosed a submersible sensor node and field tested at a popular dive reef, SCUBA diving down and mounting it to the jetty.<p>It was also a nice excuse to get some macro shots of the PCB assembly process, including some nice footage of solder paste melting and the interesting surface tension interactions.<p>(I can't seem to get the videos to render in a format that iOS Safari will play, if anyone knows the ffmpeg incantation, please let me know, nothing I've tried has worked on my iPhone...)
> Single Pair Ethernet supports long range >1km cable runs<p>That's going to introduce a lot of people to the joys of outdoor long wires and their interaction with lighting. I've seen the induction current from ground surge turn 25 pair cat3 into <i>vapor</i> ... there's fun to be had there.
802.3cy recently added support for 25 Gb/s:<p>> <i>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 physical layers are intended for industrial and automotive applications[23] or as optional data channels in other interconnect applications.[24] The single pair operates at full duplex and has a maximum reach of 15 m or 49 ft (100BASE-T1, 1000BASE-T1 link segment type A) or up to 40 m or 130 ft (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]</i><p>* <a href="https://en.wikipedia.org/wiki/Ethernet_over_twisted_pair#Single-pair" rel="nofollow noreferrer">https://en.wikipedia.org/wiki/Ethernet_over_twisted_pair#Sin...</a><p>802.3dg is going for 100M and 1000M over distances of 500m
Also, since this doesn't really talk about the ethernet data, the signalling for 10Base-T1L is PAM3, 4B3T, 7.5 megabaud. So 4 bits of data get turned into 3 symbols, each symbol being either negative voltage, positive voltage, or zero voltage, and then the symbols are transmitted at 7.5MHz.<p>Something to note is that it has a much lower bandwidth requirement than 10BASE-T, because 10BASE-T uses manchester encoding with two symbols per bit (either 01 or 10). So 3.75MHz of bandwidth versus 10MHz of bandwidth.
As a side project I'm looking at making an autonomous vehicle of some kind, starting with a ground vehicle and eventually moving to something on or under the water.<p>It's mindboggling how many different ways there are to communicate with microcontrollers, sensors, etc. So many different standards with different data rates, capabilities, features, etc.<p>It's cool to see something like ethernet be able to be used in rough situations like this. I'm sure this is done already with some technology, but I'd love to see a buoy with solar/wind and batteries for power, with a tether going down into the water to supply power and data for sensor arrays underwater. Trying to communicate through water is tough - I even looked at acoustic modems to try and transfer data but it looks like they haven't gotten down to consumer/tinkerer level of electronics yet.<p>Single Pair ethernet with power seems very complicated for a fairly ignorant but interested hobbyist haha
But there are several types of ethernet that run over a single pair now. There's 802.3bu, 802.3cg, 802.3da, 802.3bw, and possibly more.<p>And I can't tell if any of them are compatible. I think da is compatible with cg, but the others are all little islands, all serving very similar needs in mutually-frustrating ways.<p>Whyyyyyyyyyyyyyyyyyyy?
I just started a job using PoDL and so far I'm quite impressed with it as a technology. I'd like to see consumer devices start to use it too.