Did the comparator break

I have two inputs for my LM393P comparator (https://www.rcscomponents.kiev.ua/datasheets/texas_instruments-lm393p-datasheet.pdf). I have checked these two inputs with the analog inputs with my Arduino Uno and they are typically at ~0.5v. I have 5v from the Arduino running to Vcc of the comparator and the ground of the comparator running to the Arduino ground. I am using input 1 of the comparator, having checked that I am using the correct input and output ports. The output port is connected to the Digital port 10 of the Arduino (set to "input") with a 1k resistor in between.

One thing I am concerned about, is that the marking on the comparator isn't the same as in the datasheet. The comparator does note it is the LM393P however, but I might have mistaken which side was "up". I believe it to be the side of the small circular indentation now.

The readings almost always return 1, but periodically return 0. These periodic readings seem to be separated with a almost fixed timing (~0.5s).

Having the comparator been placed in reverse, should I expect it to be broken or is there possibly another cause to my problem?

I'm not sure of a website or application in which I can draw schematics easily, as I am a beginner to electronics, but I'm willing to sketch a schematic if that's of use.

Update

Just ordered some extra LM393's. I will keep this question open and check whether a new IC will fix the problem.

Update

Made some new observations. I've got the LM393N's in the mail, and they show the same scenario. If I connect a led to the output, I see a faint light with a 100 Ohm resistor, while the same led on 5V input shows full brightness. Wiring digital ports to + and – inputs of the comparator and writing low and high, doesn't do anything either. I would expect the led to change in brightness. Is it required to use all the ports on the 393 comparator for it to work?
To add some info, originally I was using photodiodes to compare the outputs of two of them and send the result to the Arduino.

Update

I've tried replacing some of the connections to no avail.

Update

I got the comparator working! I accidentally mistook delay() for being seconds, but it is instead milliseconds. Writing with the digital ports, high and low, alternated by a second, I got the comparator to play nice.
I placed a 1K resistor between Vcc and output. Now to get it to work with my photodiodes..

Update

It now works with my photodiodes, but the accuracy and responsiveness are very low.