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Hot!Ethernet Troubleshooting

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DarioG
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Re: Ethernet Troubleshooting 2017/11/16 14:35:53 (permalink)
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post gone...

GENOVA :D :D ! GODO
#21
RISC
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Re: Ethernet Troubleshooting 2017/11/16 14:40:32 (permalink)
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Hi,
Could it be that the LED on REGOFF pin is mounted in the wrong direction....?
what is the voltage on LED1 ?
Regards
 
#22
matta
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Re: Ethernet Troubleshooting 2017/11/16 16:17:03 (permalink)
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RISC
Hi,
Could it be that the LED on REGOFF pin is mounted in the wrong direction....?
what is the voltage on LED1 ?
Regards
 


Don't think so, voltage on action LED on regoff pin is 0 as it is strapped to ground. In fact the action LED never comes on in the non-working version.  In the working prototype it blinks while it connects to the network (even without any program in the pic32, which I don't fully understand).
 
I did get the regulator voltage to read 1.25 by completely removing the LAN8720A, cleaning up the pads, and replacing it with a new one. But the result is still the same. I probably could have been a little more careful in decoupling this pin, I didn't think it would be so sensitive. I have the decoupling capacitors on the bottom and fed through a via which isn't ideal really. In any event it is putting out the right voltage now at least.
 
You were mentioning magnetics before, I use external magnetics TG110-E050N5.
#23
mrpackethead
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Re: Ethernet Troubleshooting 2017/11/17 00:30:35 (permalink)
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Without seeing your layout and schematics its a little hard to comment.   1.25V should be fine.   The transformer shoudl be ok, its a 1:1 ratios.    the placement of the caps and pullups etc makes a big differnece.
 
#24
matta
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Re: Ethernet Troubleshooting 2017/11/17 08:59:53 (permalink)
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I can't even post links to the files, much less images...I have had this account for over a decade, so you would think I have permissions but it always says access denied.
#25
DarioG
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Re: Ethernet Troubleshooting 2017/11/17 09:04:32 (permalink)
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they're just bugs on the forum. Use some external repository, or
http://picforum.ric323.com/

GENOVA :D :D ! GODO
#26
matta
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Re: Ethernet Troubleshooting 2017/11/17 09:34:04 (permalink)
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I can't post anything anymore
 
ok, I can, how did you post a link without getting access denied?
 
 
 
https://tinyurl.com/y8lsv6fq
y7p68pp7
y9keh2pg
post edited by matta - 2017/11/17 09:35:28
#27
matta
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Re: Ethernet Troubleshooting 2017/11/17 09:38:23 (permalink)
3 (1)
I had to make a post then go back and edit it...and now that it thinks there is a link it won't let me edit it anymore...really dumb.
 
Anyway, the second two are tinyurl links just like the first one.
#28
qhb
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Re: Ethernet Troubleshooting 2017/11/17 13:32:15 (permalink)
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matta
I had to make a post then go back and edit it...and now that it thinks there is a link it won't let me edit it anymore...really dumb.

Yep, that's part of the bug caused by the brain dead firewall running on this web server.
See: 
How to avoid errors when editing posts
#29
mrpackethead
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Re: Ethernet Troubleshooting 2017/11/17 18:56:41 (permalink)
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I can't see anything in your schemetics that jump out at mme too much.. Perhapas ERXERR shoudl be atached by a 33R resitor as well.   Have to say i dont' like yoru schematics much.. Have you not got symbols for VDD, GND VDDA?    
The choice of ferrite at L204 is important,    

I've ( sucessfully ) put a bigger cap on VddA ( say 4.7uF ) and then i also put some small caps ( 10nF ) right up against the center tap of the transformers. 

a sucessful design comes down to layout, its critical for this,   so, really need to see your design.  Have you got this a 4 layer ( or more ) pcb?    When i design this stuff, the decoupling caps are the first thing that gets put in, as i want them right next to the pins.
 
#30
friesen
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Re: Ethernet Troubleshooting 2017/11/20 06:44:20 (permalink)
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Can you post all or part of your pcb with layers that show traces to and from the MCU and PHY?
 
Ohming probably isn't as important as probing with a scope.  50mhz signalling is pretty fast.

Erik Friesen
#31
matta
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Re: Ethernet Troubleshooting 2017/11/20 16:03:42 (permalink)
3 (1)

Can you post all or part of your pcb with layers that show traces to and from the MCU and PHY?
 
Ohming probably isn't as important as probing with a scope.  50mhz signalling is pretty fast.

 
I can't for the life of me get the forum to reliably put a link in.  But if you got to tinyurl.com/y9keh2pg from my above post, it is the layout.
#32
friesen
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Re: Ethernet Troubleshooting 2017/11/20 16:08:55 (permalink)
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That doesn't show your MCU.
 
Its a bit unclear as well, is that only a 2 layer?  A capture of each layer would be good as well.

Erik Friesen
#33
matta
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Re: Ethernet Troubleshooting 2017/11/20 16:18:16 (permalink)
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Ok, I'll post some more/better shots.  It is a 4 layer board but the inner layers are power and ground planes so I turned them off so it would be easier to see. I also turned off the copper pour top and bottom because it seems like it makes it more confusing. I know it's hard to tell what is going on without being able to zoom in and out with the software.
 
tinyurl.com/ybxx44tn
tinyurl.com/yaspdwtu
tinyurl.com/y82nbq7q
#34
friesen
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Re: Ethernet Troubleshooting 2017/11/20 16:21:40 (permalink)
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Its a bit hard to tell, do you have series termination resistors on all the lines?

Erik Friesen
#35
matta
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Re: Ethernet Troubleshooting 2017/11/21 07:18:55 (permalink)
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I'm not sure exactly which lines you mean exactly.
The schematic is in tinyurl.com/y8lsv6fq
and
tinyurl.com/y7p68pp7
#36
friesen
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Re: Ethernet Troubleshooting 2017/11/21 07:23:18 (permalink)
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That is not the full schematic.  Basically, every line to and from the mcu to phy needs a series resistor.
 
ETXD0-2 for example? And ideally, the series resistors will be close to the tx source. 
 
Whether or not this would really break this I don't know.

Erik Friesen
#37
matta
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Re: Ethernet Troubleshooting 2017/11/21 07:29:47 (permalink)
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Oh OK, the MCU part of the schematic. I didn't show it because I have to zoom out so far but ECLK, ETXEN, ETXD0, ETXD1 all have a 33 ohm series resistor. I guess in reality I did it backwards and put the ETX resistors close to the MCU and the ERX ones close to the PHY. It is a fairly tight layout so I'm not sure if that could be an issue, 50 MHz is pretty fast though.
#38
friesen
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Re: Ethernet Troubleshooting 2017/11/21 07:39:20 (permalink)
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Here a while back I had a board that would not work right, it turns out my pcb cad sent in a pad that the pcb manufacture didn't rotated 45, so it shorted internally.

Erik Friesen
#39
matta
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Re: Ethernet Troubleshooting 2018/02/20 08:41:20 (permalink)
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So I eventually found that on the working hardware I had not soldered down one of the 50 termination resistors on the tx side. This led me to remove the termination resistors from the non-working version and sure enough it started the auto-negotiation process like it is suppose to. I came back and put 100 ohm resistors for all of the terminators and it is working perfectly. However, it feels like a hollow victory because I'm sure I must be doing something else wrong to make this the case. All the app notes for the lan8720 have 50 ohm terminators to VddA.
 
If anybody has experienced anything like this let me know, and thanks for the other help.
#40
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