µTasker Forum
µTasker Forum => NXPTM M522XX, KINETIS and i.MX RT => Topic started by: alager on February 10, 2009, 11:28:47 PM
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I'm looking for guidance on trouble shooting the lack of link on my board. I've run out of ideas.
I can program the 52235eval board, and it establishes link and runs, as long as I force the mode to 10Mb or 100Mb. But using the same S19 file on my board, I can not get the link to establish.
I've tried both the utasker and the coldfire lite systems and I get the same result.
I'm pretty sure it's my hardware, but I don't understand this chip enough to trouble shoot it.
What is going on when the chip is trying to establish link? How can I monitor it?
Thanks,
Aaron
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Hi Aaron
If you monitor the TX lines and compare the two boards you may see a difference in the pulses which will give an idea.
Check the circuits carefully for any mistakes in wiring. Also the current resistor - it should be accurate (12,4k). I have heard of this being forgotten and then it doesn't work.
One problem that I once had was that a discrete transformer was used on the board. I spend a long time trying to find out why it wasn't working. Only after changing the LAN connector - when it then finally started operating properly - it became obviously that someone had soldered in a LAN connector with internal transformer on the board!! Two transformers doesn't work... and you don't actually see whether the connector has one it it or not...
Regards
Mark
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Mark,
The pulses pretty much look the same. print_006 is my board TXp & TXn, print_007 is the eval board.
The Rbias is 1% 12.4k. I only have one transformer, a magjack SI-50196-F, integrated transformer and jack.
But I even took the H2019 off the eval board, ran little wires to it and a jack, with nearly the same resultant waveforms and still no link.
One odd think I've found is that if I have the bypass caps on the centertap of the magnetics, the Tx pulse becomes a runt. The attached plots are with no bypass caps on the centertaps, just the series connected 49.9ohm resistors: TXp--R--CT--R--TXn.
Keep the ideas coming please.
Aaron
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Just updating to close this thread. I forgot to pull up the center tap of the magnetics. Now I have link and can serve up web pages.
Thanks for the help.
Aaron