DSO NANO V3 does not trigger on 115 KBaud character

Pekstrom

My new DSO NANO V3 S/N DD1RE2120 does not trigger reliably when set to single trigger. Signals were 3.3V, threshold set near 1.5V, hysteresis 0.2V. The problem seems to be worst at fast sweep speeds. I found it unusable at 10uS for 115 KBaud serial comm characters. Consider them to be a short train of 9uSec pulses.
Experiments touching a probe to a 3V source by hand triggered a sweep sometimes at 0.1mS, very rarely at 10uS. Firmware version is 4.33.
Is this a known problem for which there is a firmware fix? If not, what is my next step?
This is the measurement I bought the unit for.

minidso

Do you have a screenshot of this?

Pekstrom

I have taken a screen shot and I think uploaded it, but I see no indication. I hope it worked.
I have a lot of trouble with your capchas.

Pekstrom

I had turned off the device, and when setting it back up to show how I had things set I chose the wrong sweep speed. I did do experiments at 0.1mS, as shown and could get it to single-trigger on slow signals  only rarely. The real measurements need to be done at 10usec scan, and I have never gotten it to trigger on a 115 KBaud (9uS pulses) signal with that fast sweep.

minidso

Please mail to service@minidso.com
We will help you.

Pekstrom

I e-mailed as requested in the last post by minidso, and found excellent attention to my messages. The problem is not yet resolved, but I understand it much better, and should correct my first claim.

When the DSO Nano V3 triggers it does just what the controls are set to do. Sweep speed and shape of a repeating signal do not matter. (My original report was wrong about this.)

However the scope usually does not trigger. When testing with isolated pulses or characters that do not repeat it takes a random number of tries to trigger it. I have seen it take several dozen tries. This affects both single and normal trigger modes.

When you test with a repeating signal, you can't see this problem. The scope eventually triggers and you get a perfect display.

I am hoping that a firmware update will fix this, but have heard no news so far.