Power-on reset and ethernet shield?

Hello All --

I'm having trouble with my Arduino Duemilenova and an official ethernet shield. Everything works as it should, except that the ethernet shield doesn't get a link light from power-on. It works absolutely perfectly if you press the reset button.

Could someone who has an ethernet shield let me know if theirs works right from power-on? Or do you have to press the reset button?

My guess is that the ethernet chip W5100 isn't getting a reset signal; its datasheet doesn't say it resets on power-up; unlike the Atmega 168, which definitely does reset from power-up. The W5100 registers read and write perfectly, and I see the SPI perfectly on my scope. Just looks like it hasn't decided to do its negotiations. It's plugged into an Avaya 10/100 switch.

Many thanks if you can help.


There is a workaround for the problem.

In my case, the problem was fixed with inserting a 47nF capacitor between the RESET port and Gnd port.

See the replies #29 - #34 on the following link. http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1225354009/15

1 Like

Many thanks: exact same problem Iā€™m sure that will fix it.