Un4Seen wrote:By the way, I was thinking about the following test: when it's finished, power on the clock from a non-Pi power source and simulate the signals from the Pi. Could this be done with the multimeter? I mean is there some mode on the multimeter (say, the diode test mode?) in which I could connect the negative lead of the multimeter to the pin where the PI's 0V pin is supposed to be and touch the pins which are supposed to be connected to the programmable GPIO pins with the multimeter's positive lead. Would this open the transistors in the ULN2003 ICs and would I see it working just like the signal was coming from the Pi? Perhaps I should use some other mode on the multimeter? Is this possible at all?
If your multimeter has a current range then yes.
A meter generally measures volts, but for current measurement it puts a small resistance in parrallel with the probes and measures the voltage across it that the current causes.
On a high (~2A) range the resistance is going to be quite low. Lower ranges will use progressively higher resistances, so that the same voltage will be produced.
It's instructive to connect two meters together. Put one on a current range, and the other on ohms. See what they each read.
A third set to voltage gives you something else to think about - though most people don't have three