I'm using AT91SAM256X with the Davicom DM9161A PHY in a configuration directly copied from the Atmel eval board (AT91SAM7X-EK).
I'm running the same software in both the Eval board and my board, and the eval board works 100%, so I think I'm looking at a hardware problem.
The problem is that I'm dropping data intermittently. Pinging 1000 times with a 256 byte packet gives me about 30% dropped. If I shorten the packet size, the error rate drops. At 32 byte long pings I'm at 2-4% dropped.
Been banging my head against this now for a couple of days, and not making much headway.
So my questions to this wise community; where should I look for problems?
Some more details :
I've looked at all the power pins for noise and my board is not significantly different than the Atmels eval board is.
I got a big improvement on the throughput when I changed my bandgap resistor from 6.2k (from the Atmel schematic) to 6.8k (which they really stuffed on the board). Is this a clue to something?
I have two deviations from the Davicom design guidelines;
1) My ground plane under the Rx/Tx pair is not AGND. It's DGND. 2) I'm running the Tx/Rx pairs close to each other. Do you thing this could be enough to cause these problems?Any ideas would be much appreciated. Thanx.