I am using a PS2205 to capture a triggered waveform with a custom
program (VB6). Skipping to the end: I am not succeeding in, um, triggering
Background: Sample rate is 6.25MSps, range is +/-5V. The trigger pulse is
active low (4.5V->0V), roughly 12us wide. I am using PS2000.dll from 19
Using the picoscope-6 application, I can capture using the trigger, and
both trigger and data look normal; I can even capture the trigger down to
to about 100kSps (trigger pulse is ~1 sample wide).
2) set_channel(A, enabled, DC,5V) ' data channel
3) set_channel(B, disabled, DC,5V) ' trigger channel
4) set_trigger(B, threshold, falling,delay=0)
If I set the threshold to the obvious one (2.5V = 16383) I get no
triggers at all. If I stepwise reduce the threshold, at some point (~320,
i.e. near 8-bit 0) I appear to get constant triggers. This in itself seems a
bit odd, since it suggests that
A) The trigger is actually level-sensitive, not edge-sensitive.
B) The trigger channel is reading as 0.
But (B) doesn't appear to be what picoscope-6 sees -- it sees a constant
4.5V level then a 12us 0V pulse.
Evidently picoscope-6 is doing something that I am not.
Another tidbit: Before the real system was ready, I cobbled-up a trigger
using a board I had lying around, the big difference being that this board
issued multiple (16x5us) "trigger" pulses, which appeared to work fine.
I saw that the sample programs issued set_ets(disable) calls, but doing
that didn't seem to help. Do I need to explicitly turn Off the advanced
triggering mechanisms in the 2205? Is there something else obvious I'm