Hi James, bad news (for me). To swap COM2 with COM1 has not solved anything. The problem reappeared the day after.
So please forget all that I've written...Is an oscilloscope useful? Yes of course. It allows you not to only measure a voltage, but, mainly, it allows you to SEE THE SHAPE of your signal. I think that the reading of a DB9 pin voltage with a multimeter, even a very good one, is very hard (if not impossible) to interpret. The multimeter will read, e.g., "9.05 VRMS" if the byte is "00110011" then maybe "9,65 VRMS" if the byte change to "11110011" and so on...very quikly...but what will it really read finally ? With a scope, I think you'll see the byte itself. At last, it's not "my" scope, but one I've just borrowed at my job...thank for your superb links. |