I am using [BK Precision 2125C Dual Trace Oscilloscope (30 MHz)][1], which is analog. I'm trying to observe signal generated by the output of microprocessor. I'm seeing flickering signal (quickly moves left and right to the sides of scope) for which I know it's most probably not flickering like that in real "life" but that is most likely some scope's triggering issue. I'm almost sure that is the case since I observed normal square wave before this one and it also flickered like current one, at some trigger setting, but after re-setting trigger, there was no more flickering.

This flickering is **really** annoying when trying to observe little changes in the signal or read its period.

[Here][2] is the video to measurement of flickering signal.

Just for reference, for this measurement, I'm using following setup:

 - DC coupled input, CH1 (get same behavior with AC input coupling)
 - coupling: norm (same behavior with "auto" or "TV-V" or "TV-H")
 - source: CH1
 - main mode (not mix or delay mode)
 - voltage/div: 2V/div
 - time base/div: 2ms/div

Regarding "trigger level" and "hold off", however I turn both knobs (literally any combination), I always get flickering or unsynchronized signal. Otherwise, I'm measuring at output of MCU (10k pull-up, UART transmission) with normal passive probe (in 1:1 internal divider rate).

Any ideas how should achieve the view of "standing-still" looking signal at the screen of scope?


  [1]: https://www.bkprecision.com/products/oscilloscopes/2125C-30-mhz-delay-trace-analog-oscilloscope-with-probes.html#overview
  [2]: https://vimeo.com/532891476