So are you saying that the receiver or transmitter has failed and the Arduino part is working properly?
Yes, that's what I am thinking. I suspect the receiver because I had to double ground it (arduino AND sabertooth) to keep the receiver and maybe the arduino from freaking out since the receiver is connected to the arduino and the sabertooth. I suspect that the double grounding it was only a temporary fix.
In your original post you said " though it is still linking to the transmitter and also putting out something on the PPM out." What is that something?
"That something" is the link between the transmitter and the receiver. When I turn on the transmitter, an LED comes on on the receiver. The receiver also sends out some data on the PPM out and the arduino reads it and determines that the transmitter and receiver are online. The fact that there is an active link, I use that information to control some of the relays. If it's a first power on, that's a special scenario and the arduino behaves differently (does not time out and change the relays). The arduino is behaving as if it's a first power on and then it's not receiving anything else. That means either the transmitter is not transmitting, or the receiver is not passing PPM to the arduino. I also know, that in this case, the receiver is also not passing PWM to the sabertooth. The receiver has 2 strikes against it. the transmitter is also suspect because it was behaving oddly when I attempted to change some of the programming prior to all of this.
Someone on another board suggested using a servo on the PWM out, so I'll try that, though I suspect that will show the same thing as the sabertooth.
Have you any way (such as another Arduino) to simulate the output from the receiver?
I have other arduinos, but I wouldn't know where to start mocking that up. I have another arduino uno (2 actually), and an arduino Mega ADK I could feasibly use.
I have access to a wi-spy... that should help me know if the transmitter is transmitting or not.