7i77 and single ended MPG-Wheel encod er - read-out problem

If A and B swings from ~4V to ~0V then the 7I77 encoder should count
if the phase difference between them is 90 degrees:

Hm...
Before I left my workshop half hour ago, I tried again, with the encoder wired as single ended one to the 7i77s encoder input - did't count according to halshow (rawcounts)
Is there a possibility to see the values, which the card is meassuring on the individual input-chanels of the encoder input-plug?

You can read (and plot with halscope)  the digital values on the encoder input-a and input-b pins

Ok, I'll try again tomorrow.
I also had them on halshow but never was able to see them flickering

Thank you very much for your help so far!

P.S. I everytime put all encoders on halshow to ensure, that I don't check the wrong chanel

Now it's getting weird...

The yesterday meassured values where meassured with A / B unplugged from the 7i77 and just powered up by the card's encoder output.

Now I plugged A / B into the card and can see a/b - Signal in halshow - they are constantly there.
I meassured again while connected: Constantly 4V from GND to A/B (S0/S90)! As soon as I unplug A / B from the card, I have the same quadrature signal as described yesterday.

I think, It can't be an card issue as I tried the Encoder-Input with an (differential) linear encoder to ensure a working encoder-chanel

And yes, I change the jumpers between differnential / single-ended.

Is the 5V from the 7I77 OK? Low 5V would make the LEDs dimmer

The MPG A,B outputs are probably just the LM393 comparator outputs
with pullup resistors to +5V, so I would expect a full 5V signal swing

When plugged into the 7I77, the 7I77 adds an additional 2K pullup
resistor to 5V on each signal which should be OK since the LM393
can sink 6mA minimum and about 20 mA typical