OK, I already need some additional help. (I told you!)
Let me first tell you what I'm trying to do.....
I fly R/C airplanes, and several of the older members of my club have had accidents with their electric powered models. With a lot of the less-expensive ESCs, once you connect the battery the motor is "hot", and any accidental bump to the throttle stick, or a dropped transmitter, or even turning the transmitter off before disconnecting the battery, can result in an unexpected prop strike. My idea is to have a circuit that plugs between the ESC and the receiver that essentially "hi-jacks" the throttle output from the receiver. Once you connect the battery, the circuit assumes control and sends a LOW throttle signal (90ms) to the ESC, which keeps the motor off and allows you to check all the other servos, make trim adjustments, etc., and carry your plane out to the runway without worrying about the motor starting. A red LED is on to tell you the model is in the "safe" mode. When you're ready to fly, you depress and hold a small tactile switch, during which time the red LED flashes rapidly. If the switch is held for 3 seconds, the LED turns green, and the program goes into a loop in which it checks the pulse width from the receiver and sends it immediatley to the ESC. This simply continues until the battery is disconnected. The only other thing I'd like for it to do is to check the pulse width and if it's less than ~90ms, output a LOW pulse to the ESC, so that if you forget and turn your Tx off with the battery still in the plane, the circuit will hold the ESC at off and not allow the motor to start up via a random signal.
OK, now here's my problem. I have all the above working perfectly except for one minor thing. I'm using a normal servo to check the function of the program, instead of an ESC/motor combo, and every time the PULSIN command is executed, it seems to interfere with the sevo command, and it's causing the servo to jitter. I have the servo on it's own battery, isolated from the chip's power supply, I have a .01mfd cap across the servo's + and -, and I have a 330ohm resistor in line with the servo's signal wire. I've tried both the servo and the servopos commands, both behave the same way. And I'm pretty sure it isn't anything to do with the servo itself, because at the start of the program I have a line that sets the servo's output LOW (90ms), and it moves there and doesn't jitter at all until the program moves on to the later parts where the PULSIN command is called. It may not cause any problems with an ESC, since it doesn't actually move, it may only cause the motor speed to fluctuate slightly, but I'd like to figure it out and eliminate it if possible.
Does the PULSIN command interfere with a timer or something used by the servo/servopos commands? Is there any way around it, or some other technique I can use? Thanks again!