I’ve always wondered how that worked exactly, but what i have noticed that if i want to see a vco’s waveform nicely, sometimes it helps to also put that same audio rate signal in the ext. So maybe it works like a clock input on how fast the visual is sampled for you to see? would be curious of the proper answer though…
The trigger sets the triggering threshold. When the input crosses the threshold, it goes. As you are observing. It it for sure not a one shot storage scope. Submarine makes a nice logic analyzer that does that (sort of).
Gee - didn’t you people have analog oscilloscopes in the 70’s?
I’m sorry to appear as thick as the Prince Regent from Blackadder, but I don’t understand. The horizontal scan is always running. I disconnect the X IN to get a flat trace then reconnect it only for the scan to start straightaway, I don’t get a chance to manually trip EXT IN.
Maybe, but it’s very much quicker than 1 second. And to be honest, and no disrespect intended, I don’t see the point of this “timed out” feature. If scope is waiting for an EXT IN but starts scanning anyway it defeats the purpose of EXT IN.
And if it’s not a one shot scan and capture as @Squinky alluded to then it’s not what I’m after anyway.
But I’m damned sure I would like to understand that EXT IN
From the looks of the code, it looks like it’s actually 0.5s. I kind of agree that this threshold should be longer (or even not implemented); if the user’s intent is to do a manual trigger and a scan is already happening when we didn’t call for it, it will not retrigger and the external trigger is ignored.
This is how analog oscilloscope works. Some scopes had a “trig-blank” switch that would blank the trace if there’s no trigger lock, but that’s not the idea here. The idea of the trig input is to lock the pattern on the scope to get a stable image where the scan always starts at the same phase point of the input waveform. Try this out: Hookup the scope X IN to the SIN out of VCO-1 and switch the scope to EXT trig mode. If you adjust the frequency of the VCO the pattern on the scope will be running around. Now hookup a cable from the SQR out of VCO-1 to the scope EXT input. The pattern will lock and you’ll have a nice stable pattern.
And if you wanna have even more fun, have the SQR input connected to a delay plugin such as MSM Dual Delay. Connect the Delay out to the EXT trig input, dial the DRY/WET to full wet and the delay time to the minimum 1ms. Now when dialing the Time slowly up, you can get the sin wave start at different points of the cycle on the scope which really illustrates how this trig works. Sorry for getting carried away, but I’m really an electrical engineer at heart