Hi, I am having difficulty getting the Blue Robotics basic-esc to initialize on one brand of brushless thruster but not another. With the Esc connected to power and PWM wire connected to the pixhawk, I get 3 beeps, then 2 beeps and the thruster operates normally. Then, i power off the pixhawk and ESC and remove the PWM wire from the channel, then, I connect the second brand of thruster to the same ESC and insert the PWM wire into the same channel on the pixhawk and i get 3 beeps on power up, but no 2 beeps to follow and the motor dosent respond. I am using Qground Control, Any ideas?
Hi @wlocke, welcome to the forum 
The initial 3 beeps correspond to the ESC detecting the three phases of the motor. The next beep is the ESC detecting a valid input PWM signal (within the 1100-1900µs pulse-duration operating range), and the fifth beep occurs when it detects a consistent stop/neutral input signal (1500µs).
If the first three beeps are happening then the ESC is successfully detecting the motor and activating the separate phases (the beeps are caused by the ESC controlling each motor phase to vibrate at a specific frequency), and problems with the following two beeps mean there are issues with the detected input signal.
From the information you’ve provided my best guess is that you happened to plug the ESC input wires in backwards or into the wrong channel when you plugged it back in. If you’re powering off the system when swapping the thrusters I’m not sure why you would need to also remove the PWM wire, so perhaps it’s worth trying without doing that.
The only other thing I can think of is if you changed the Pixhawk firmware or parameters while changing the thrusters then you could have changed the output behaviours (although you didn’t mention doing that). If relevant you can check that the expected channel is being sent the intended signal via the SERVO_OUTPUT_RAW message in QGC’s MAVLink Inspector (or even better by probing the signal wire with an oscilloscope).