strange QT4 behavior

Discussion created by ROB LUND on Oct 19, 2006
Latest reply on Nov 9, 2006 by ROB LUND
Hey all,

I've got some QT4's on a mature design that are behaving strangely. On a controlled test environment, I'm seeing a few boards fail at random times while others from the same batch are not. All QT's are from the same date code batch (RMCGWm).

The method of failure is the same. I have input switches that are "freezing up". In other words, immediately upon power up these switches are not functioning when they very clearly should be. I have (what I thought to be) very stable state machines and adequate COP timer resets such that these switches are polled constantly.

Unfortunately, it's difficult to debug this problem. I have the QT4 demo board, but that requires porting the code into that board. Plus, that is different hardware, so I could be chasing a phantom bug that might be hardware related.

After swapping out boards, I no longer saw the problem. Here's the question: what is it about this problem board that would cause this? I've already tested for intermittent shorts on the inputs. I'm thinking it's something about the microcontroller. Any thoughts?