Q: The plan is for all of this to eventually go in to a cabinet, but I pieced it together the dry-run on a card-table. The source is a Raspberry Pi 3b. The output is sent to an Envision H170L monitor. When I attach and activate the scanline generator, the screen begins to randomly flicker on the Retropie main menu. Once in an arcade game, the screen flickers in a mostly repeating pattern, with four lighter areas pulsing and working their way from the top to bottom. If I flip the dipswitch to turn off the scanlines, the screen flicker and pulsing ceases. I am able to leave the scanline generator plugged in and turned off and there is no interference or flickering. As soon as the first dipswitch is thrown, the pulsating begins again. I have tried all possible dipswitch combinations, and the outcome is the same as previously described.
The scanlines look fantastic, and I am thrilled with how they may be manipulated with the dipswitches and R/G/B pots, however the flickering is obviously not a desired effect. Please let me know if there is something that I can try to overcome the issues that I've described, or if a return and swap to another unit is the preferred outcome.
A: Test run the scanline generator between a PC and monitor. The issue can appear based on monitor. The configuration file of the raspberry pi can lessen the screen flicker while in game. It's just a matter of trial and error now that I know it's a software issue. View this linked video for more info RaspberryPi/RetroPie - How to fix flickering HDMI output | ONE LINE FIX
For an alternate answer, please visit http://backtothearcade.net/2017/02/27/adding-scanline-generator/