Content originally posted in LPCWare by johnnyfp on Tue Oct 21 11:29:55 MST 2014
No I ment 0.6v or 650mV. :p
And I sort of solved the problem. How very very embarassing, As a single solitary via was missing from pin 21 to ground! of all things. I think I would have liked it just to not have worked, so discovered this issue when revisiting the layout to gain access to the SWD port. But because I had the ISP line tied to ground it was enough to let the MCU run, unstable as it was but it was running and responding to the autobaud symbol.
As the old saying goes, Measure twice, cut once.
Anyway thanks for your help. Time to sort out that pesky via.