I tried to hook a 5V DC-DC switching supply but some of my units are not responding to sketch upload. The one unit I have at hand is ok. The problematic ones are in the field so I don't know quite what happened.
So are there any way to replace the crappy supply with switching supply? I guess not. I searched for a while whether there is a part that is SOT-223 and switching. A switching supply needs an inductor. That won't fit on the foot print. Any recommendations?
You could make a little daughter card that plugs into the power connector on the Uno, inputs from Vin and outputs to 5V (or make it part of a shield.) Then all you have to do is disable the existing regulator.
(It's disappointing that you're having regulator problems. My perception is that few projects end up using the regulator, so it doesn't get as much testing as it should. IIRC, some of the clones had regulator problems from the beginning.)
(And I'm glad that I ended up using a boring 7805-style regulator on the freeduino design!)
Thanks! I'll give it a try. I'll probably just remove the arduino regulator to see if it improves. The issue affects all new arduino official boards that I've come across. None has the original good-quality regulator and all had the cheaper ones that give up easily. I'm still puzzled why back feeding with a 5V switching regulator made some units refuse to accept firmware. I'll have to get one of these units to test out. Hope it's just a bad switching regulator.
