Switching between internal and external Ethernet connection with passive splitter? (internal wifi router) \ VOGONS

Switching between internal and external Ethernet connection with passive splitter? (internal wifi router)

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First post, by adalbert

Posted on 2020-08-28, 12:41

adalbert Offline

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I would like to solder an OpenWRT wifi module to 3C509B ISA card https://www.vogonswiki.com/index.php/3Com_3c509

so the machine would be able to connect to wifi through internal network card and packet driver. But I would like to retain the ability to connect external network cable (not simultaneously).
I understand that 10baseT can work with only 4 wires.

I thought about soldering 4 wires to internal wifi module and leaving 4 other wires for external device. I would also disconnect 4 pins used by internal module from RJ45 connector on the card.
When external ethernet device would be connected, I would swich off the +5V power from the OpenWRT module.

Would this setup work? Do I have to disconnect 4 pins used by internal module from the RJ45 connector, or it would be sufficient just to turn off that module when I want to connect external cable?
Is there any damage possible when external cable is connected and both devices are turned on?

BTW I would desolder the DB15 connector and install the device in such a way that wifi antenna is next to that hole.

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Reply 1 of 5, by Doornkaat

Posted on 2020-08-28, 15:49

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If I correctly understand what you're planning this won't work. You only need four pins/wires but can't just use any four pins for your ethernet connection.
Sorry if I completely misunderstood your question.

You could just use a four pole switch in a Y shaped cable to choose between connections.

Reply 2 of 5, by darry

Posted on 2020-08-28, 15:56

darry Offline

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Doornkaat wrote on 2020-08-28, 15:49:

If I correctly understand what you're planning this won't work. You only need four pins/wires but can't just use any four pins for your ethernet connection.
Sorry if I completely misunderstood your question.

You could just use a four pole switch in a Y shaped cable to choose between connections.

Why not get cheapest and smallest DD-WRT compatible router available ? It can be set to client bridge mode for WIFI access and will come with an integrated switch for optional wired access . If you can find one small enough you could hide it inside the PC case and possibly even power it using 12V from you PC PSU .

EDIT: You can also use OpenWRT , if you prefer, of course . My point was suggesting a device with a switch .

Reply 3 of 5, by adalbert

Posted on 2020-08-28, 16:50

adalbert Offline

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I already have this https://openwrt.org/toh/unbranded/a5-v11 flashed with OpenWRT and it works fine for me. Regular router won't do because i'm putting this inside T3200SXC laptop 😀 i will get +5V directly from the network card and the router will be piggybacked with RJ45 connector desoldered.

Doornkaat wrote on 2020-08-28, 15:49:
You only need four pins/wires but can't just use any four pins for your ethernet connection.

OK, I thought that the card would work with either pair 1 + pair 2 OR pair 3 + pair 4, but it will only work with pair 1 + pair 2? wiring a switch would be too much work for me because I most likely will not use the wired connection at all, I just wondered if it would be still accessible if needed (but I might do this in future).

So the last question: if I solder cables from the router to the network card internally, but the router will be turned off, would wired connection work and not be disrupted by the powered-down router which is still connected (the router would be isolated by the transformer, right)?