Hi,

I am trying to connect the mbed directly to a windows box via ethernet (no swtich/hub!) for testing

I assume all I need is a crossover cable, but I am having trouble seeing any packets on the PC end (running simple http client and ethernet spam apps - my wiring is as per EMAC project)

Can someone please point out the (many) obvious things I am overlooking!

Thanks

Ok I figured out my own problem, posting here for others to see!

The wiring diagram at http://mbed.org/projects/cookbook/wiki/EMAC is for a ethernet jack with NON-STANDARD wiring (ie cable pin 2 does not map to the second output pin, etc.) (I think this is mentioned somewhere else in the forum...)

As at my end there are three different people programming, ordering parts, and wiring, the actual jack on the EMAC page was used but was wired for standard ethernet (1,2,3,6) not (1,3,4,6).

Fixing the wiring fixed the packet problem.

This should maybe be flagged more overtly on the EMAC page????

The wiring for these ethernet jacks are all different.

Simon, why don't we start a page for ethernet jack and correct wiring with all these different jacks. It seems that there is no real standard in these jacks and its giving people headaces from the beginning.

Hi all,

Vlad is right this is a good idea. I've started a page like this yesterday (Ethernet). And it seems like it was a good idea. Paul pointed out a mistake of my weiring, which might be responsible for some bad connection problems I've seen with "the fish". Just add a comment if you have another connector and I will add it.

The cookbook page was basically a project description therefore its only describes the connector I had.

I wonder who thought it's a good idea to have 8 wires in and 8 wires out even if they are not needed and never straight through ;-) It confusing.

Cheers

Rolf

Rolf,

you have a mistake in your Magjack diagram.  You have pin 4 listed twice.

Shareef.

Thanks, it's fixed

You shouldn't need a crossover cable, most modern PCs will swap the tx rx lines automatically so you can use a conventional Cat5 cable.

I have often wondered why the pairs on Ethernet cables don't go on consecutive connector pins.

The Ethernet 10BASE-T specification assumed that existing building telephone wiring would be used in many applications. Hence Ethernet wiring is based upon Bell System USOC (Uniform Service Order Codes). These codes applied to 4, 6 and 8 pin RJ connectors and arranged the pairs starting with the middle pins. The next pair went on the adjacent pins and so on.

So, a 4-pin RJ14 would be wired pair 1 = 2 and 3, pair 2 = 1 and 4.

A 6-pin RJ25 would be wired pair 1 = 3 and 4, pair 2 = 2 and 5, pair 3 = 1 and 6.

An 8-pin RJ61 would be wired pair 1 = 4 and 5, pair 2 = 3 and 6, pair 3 = 2 and 7, pair 4 = 1 and 8.

For RJ45 the EIA/TIA standards body modified the 8-pin RJ61 wiring to improve signal quality on the outer pairs. They kept the inner 4 signals the same but moved the outer pairs onto adjacent pins.

Hence RJ45 pairing is 1 and 2, 3 and 6,  4 and 5, 7 and 8.

The following web page describes all this in more detail: http://www.homephonewiring.com/jack-standards.html

Paul

Can someone describe what you should do with the two shield pins and pin 8 of the Magjack connector please. I can't find any info anywhere unless I'm searching for completely the wrong thing.

Are you supposed to connect them to DGND?  Their own GND?

Thanks, Shareef.