Hi everyone,
I’ve faced with a problem about using ethernet cable, when i want to connect two BBB peer to peer.
When i connect one BBB through a ethernet cable to a switch or to my host computer, the link becomes successfully up and i can connect to BBB.
But when i connect two BBB peer to peer, result is different. in this case, link not brought up and the LEDs of ethernet ports not light up and hence i can’t ping from one BBB to another one.
Some points are here:
1- Sometimes, after a while about 1, 2, minutes… or more, the link becomes up.
2- If we reset one of the boards, link becomes up.
3- according to smsc.c driver notes, “Due to HW bug, LAN8700 sometimes does not detect presence of energy in the Ethernet cable in Energy Detect Power-Down mode”. So i disabled energy detect mode according to
https://git.backbone.ws/linux/backbone-sources/commit/d88ecb373bd1877acc43e13311a8e0e6daffc3d
but the resule is same.
4- The phy chip on BBB is LAN8710, and debian 8.3 as OS.
Best Regards.
On Sat, 28 May 2016 03:05:46 -0700 (PDT),
hussainali0935@gmail.com declaimed the
following:
But when i connect two BBB peer to peer, result is different. in this case,
link not brought up and the LEDs of ethernet ports not light up and hence i
can't ping from one BBB to another one.
Don't use a regular ethernet cable -- use a cross-over cable -- with a
regular cable you just connected Tx1 to Tx2 and Rx1 to Rx2, rather than Tx1
to Rx2 and Rx1 to Tx2
Routers/switches/hubs do the cross-over internally, and some even are
designed with auto-sense to work with either a cross-over or straight cable
(normally when linking two switches together when they don't have a
dedicated link port)
Some points are here:
1- Sometimes, after a while about 1, 2, minutes... or more, the link
becomes up.
Possibly something in the BBB is capable, after enough time, to
logically swap Tx and Rx in the PHY layer.
It might be cheaper to just buy an inexpensive hub, or switch. For a 5ft cross over patch cable we’re talking ~$6 usd . . . for less than twice that cost you can get a cheap 10/100 switch.
You can also make your own cables, but ethernet plug ends, and crimpers are pretty much out of reach( cost wise ) for the typical hobbyist.
Wow I take that back RJ45 crimp tools, and cable ends have dropped a lot in price since the last time I looked. But still cost wise for a one off cable it’s not worth it.
On Sat, 28 May 2016 03:05:46 -0700 (PDT),
hussain...@gmail.com declaimed the
following:
But when i connect two BBB peer to peer, result is different. in this case,
link not brought up and the LEDs of ethernet ports not light up and hence i
can’t ping from one BBB to another one.
Don’t use a regular ethernet cable – use a cross-over cable – with a
regular cable you just connected Tx1 to Tx2 and Rx1 to Rx2, rather than Tx1
to Rx2 and Rx1 to Tx2
using cross-over cable has no effect on result.
On Sat, 28 May 2016 13:10:05 -0700, William Hermans
<yyrkoon@gmail.com> declaimed the following:
Wow I take that back RJ45 crimp tools, and cable ends have dropped a lot in
price since the last time I looked. But still cost wise for a one off cable
it's not worth it.
That's what happens when they come out of the specialist stores into
Home Depot, next to the old phone cable stuff. {says someone who also has a
pair of lineman's test sets rotting away from lack of use, along with the
noise tracer and punch-down tools}