Using 4-pin Ethernet on the Pi 3?

Hi Preston,

How long is the cable? It may be a very marginal connection that just-about works with the Mac. 4 wires is okay, but the cable needs to be twisted in specific pairs. Without the twists, you may only be able to go a metre or less (I've never measured it, but 1 metre sounds about realistic). You could twist yourself, but the amount of twists is important too (as is wire thickness and insulation material). All these factors determine how effective (in terms of error) and how far it can go. For these reasons, it is strongly advised to use the normal network cable i.e. Cat5.

Just FYI: I don't think the number of twists is that important. What IS important is that the four pairs in a cat5 cable each have a DIFFERENT twist frequency. If the twists-per-meter are the same, the pairs can influence each other. By having the twists-per-meter different this effect quickly cancels itself out: If there is a positive effect during a few turns that will be compensated by a negative effect a few turns later.

@preston: four wire cable is often "cat3". And that is not twisted. That's bad at 100mbps. A client of mine wired a whole building with CAT5, but used the wrong pinout. So effectively the pairs weren't pairs. That worked at 10mpbs but not at 100. (Actually it worked at 100, but lowsy, worse than at 10).

If the cable is RJ45 it usually has 8 wires connected. See RJ45 Wiring Diagram for Ethernet where they are coded. In actual usage only 2 pairs are needed. May sure we are not using RJ11 (4 wire) as in Wiring Termination Instructions and Diagrams - RJ11 and RJ45 Jacks Guide ,,,

Clem

So the cable is actually quite long. It is, to my understanding, Cat 5e cable that is running through the walls of my house. However, the brown and brown/white wires are missing from the cable. I have no real way of telling how long the cable actually is, but I would guess around 200ft. I know this length is fine as I have created ethernet cables that can run further. The wiring in the wall must be done at least somewhat correctly as my Mac can use it at the full 90 Mbits my ISP provides.

I read something online about the Pi's ethernet port being wired incorrectly or cheaply or something along those lines, but it was mostly people talking about PoE which I don't need.

Clem, the ending jacks are definitely RJ45 jacks; I just only have 6 wires to work with.

See Not All Ethernet Cables Are Equal: You Can Get Faster LAN Speeds By Upgrading . What is your CAT rating?

Clem

I would first try the RasPi 3 with a short Ethernet cable just to make sure its Ethernet port works at all.  If that's the case, it's probably that your long Ethernet cable through the walls is slightly flaky and it may work or not depending on how well the PHY chips at each end adapt to an iffy cable.

Another possiblity is that RasPi's Ethernet jack is making poor contact on one pin.  Ethernet uses differential pairs.  If one side of the pair is broken, you can often get enough signal through the other side to get some level of connectivity, but it's really unreliable.  Do a visual check to see that all the pins look good.

If you have a spare Ethernet switch lying around, try putting it between the RasPi 3 and your long cable.

Hi Roger,

Exactly as you say, cable length (and hence overall number of twists) is unimportant, I'd meant amount of twists for the cable length that he had. With no twists* at all for his length, he'd be lucky to achieve a metre perhaps (I once deliberately untwisted and separated a network cable to see what impact there was - I did need to separate perhaps 50cm to a metre of the twists before the eye-pattern completely degraded into complete uselessness, and probably high bit error prior to that).

However since he mentions 200ft further below, he's probably got some older standard as you say or generic 'phone extension' grade twisted wire which is still not as controlled as Cat5.

Preston, you really do need Cat5 over such a distance, otherwise you're at risk of either flakiness (or like complete unreachability) or high bit error which will give you network connectivity but will result in poor throughput.

*well, at a first level explanation to help the OP's practical situation; no twists could be fine providing they were well defined in their parallel-ness which is not the case here.

Hi hirolord (aka)@preston_turner

If you have another shorter patch lead, take the PI closer to the router and plug it in there.

If it works perfectly, then you know that the problem is with the "4-pin ethernet cable".

If it does not work, then you need to check the port or the setup/config of the Raspberry Pi.

I am of the opinion that it is not your cable.

Yunus