I’ve been able to read my R/C receiver nicely with my Arduino, with a solid refresh rate. My problem right now is that the signal often fluctuates between values that are 2, maybe 3 points away. This means the LEDs I’ve set up to test the system flicker quickly, and when I finally connect it to DC motors, I think the motors will move with jitters. Is there a hardware circuit I can set up to smooth the signal, or maybe software? Maybe it’s just the quality of my receiver/transmitter pair.
Well you could play around with some software 'filtering' options. Either take multiple PPM input readings and average them before outputting them. Or have a hysteresis value such that you don't change an output unless the input moves more then so many +/- counts from the prior reading.
Is there a hardware circuit I can set up to smooth the signal
It is called a filter. for a start see:-