Hello everyone, I use mini ethernet module with w5500 with arduino nano. The problem is when I supply my board with dc current sometimes system works great but sometimes(unplug dc voltage and then plug it again ) I have connection problem. Leds on the ethernet socket like :
When I have connection problem : Firstly green led is on for 0.5 second or so and then green led is off, at the moment that green is off, yellow led is on for 0.5 second or so and then yellow led is off. Led status goes on like this repeatedly.
what might be the problem with ?
W5500 does not support auto-MDIX feature.
Thus, user should use straight-through cables to connect to other switches or routers and crossover cables to connect to devices such as servers, workstations or another W5500.
However, user can use either type of cable to connect to other devices with auto-MDIX enabled, and the interface automatically corrects for any incorrect cabling. Must work with your switch though, but you may try changing cables and try another switch to see if there will be a difference.
I tried many ways but finally I sort the problem out. I would supply ethernet board with arduino 3.3v pin. when I measure 3.3v pin and gnd, multimetre shows approx. 2.8 voltage and this makes me think problem may result from this voltage drop. Afterwards I supply ethernet board with another buck regulator with 3.4 volt dc. Problem has gone 
Thanks for your support
Good luck
Please inform us of any problems as soon as they occur.
