Problem with wiznet w5100

I am using the wiznet w5100 on one of my projects and I can't figure out how to get it to work when I am powering my board from an external power source. I have made a custom board that I am using, this is not through an arduino board. I have an "arduino breadboard" and the w5100 on my custom board. The arduino has a 5v voltage regulator and the w5100 a 3.3v regulator before it. Everything works fine when I am using an ftdi cable to power my board, however when I switch to the external power the w5100 stops working. I do not get any led indicators on the mag jack, and no response from ethernet requests. I have check the voltage on the power pin of the w5100 and I have 3.28v... I have attached an led to another pin of the arduino and ran a blink test through it and the atmega seems to work fine from the external power. Any ideas would greatly be appreciated.

Thanks, joe

The wiznet chip takes a lot of power. If you are supplying power thru the arduino barrel jack, make sure the supplied voltage is 7v or greater. Measure the voltage on the 5v pin and see if it is being maintained at 5v.

I am using a 7.5v 1a ps, the 5v is reading at about 4.98 and the 3.3 at 3.26, which is just slightly higher than when I use the ftdi cable which is 4.92, 3.25

I found that when only the ground and reset are hooked up from the external power the wiznet works. So, it's not a voltage issue, but more likely something with reset? So does anyone know why hooking only the reset and ground to the ftdi cable would allow this board to function?

Ok, I cut the resistor between reset and ground and it is working now. Not sure if I can still program it with the ftdi without that resistor, I think I read that you need it, but I'm sure glad to know how to get the Ethernet working.


Ah, and I see my error! The pull up should have been between 5v and reset, not ground…