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[on:]

I thought I handled the harder part already, soldering the W5100 ethernet chip on my new boards.  Nooooo... dealing with power is giving me headaches.

Question:
1) What is the recommended power supply for use with the Arduino?  5vDC 1A?  9vDC 650mA?

2) I seem to have a timing issue with bootup from a cold start.  When I plug the DC adapter the board starts, the sketch starts, the ethernet board starts... but the board and ethernet are not communicating.   The solution is to press the reset on the Arduino (using Mega).   I have decoupled the RESET of the Wiznet chip from the board RESET to be able to reset the W5100 independently.

So why would warm reboot (manually pressing reset on the Arduino) fix the issue?   I'd like it to work from a cold boot too!  Capacitor issue?

[Reply #1 on:]

What is the recommended power supply for use with the Arduino?  5vDC 1A?  9vDC 650mA?

At least 7V is needed to get past the linear regulator and get 5V out. The current depends upon what you are powering. The Arduino itself is likely going to be <50mA. You can use higher voltages (>7V) but then you just waste more power in the regulator.

So why would warm reboot (manually pressing reset on the Arduino) fix the issue?

There are LOTS of variables here, roughly broken up into "hardware" and "software". Without knowing what they are and how they interact, I can't speculate. Though I doubt it's a capacitor issue.

--
The Gadget Shield: accelerometer, RGB LED, IR transmit/receive, light sensor, potentiometers, pushbuttons

[Reply #2 on:]

This is a well known issue with the original ethernet shields.  Heres a thread with the solution http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1225354009/30  posts #29 onwards

A 50 - 100 nf capacitor between ground and reset seems to work.