RoboteQ AX500 manual Reception Watchdog

Reception Watchdog

the controller captures the full joystick movement, the AX500 defaults to the timing values shown in Figure 57. These vales can be changed and stored as new defaults.

joystick position: min center max

	1.05ms
		0.45ms
R/C pulse timing:
			0.9ms

FIGURE 57. Joystick position vs. pulse duration default values

The AX500 has a very accurate pulse capture input and is capable of detecting changes in joystick position (and therefore pulse width) as small as 0.4%. This resolution is superior to the one usually found in most low cost R/C transmitters. The AX500 will therefore be able to take advantage of the better precision and better control available from a higher quality R/C radio, although it will work fine with lesser expensive radios as well.

Internally, the measured pulse width is compared to the reference minimum, center and maximum pulse width values. From this is generated a number ranging from -127 (when the joystick is in the min. position), to 0 (when the joystick is in the center position) to +127 (when the joystick is in the max position). This number is then used to set the motors’ desired speed or position that the controller will then attempt to reach.

For best results, reliability and safety, the controller will also perform a series of correc- tions, adjustments and checks to the R/C commands, as described in the following sec- tions.

Reception Watchdog

Immediately after it is powered on, if in the R/C mode, the controller is ready to receive pulses from the R/C radio and move the motors accordingly.

If no pulses are present, the motors are disabled.After powering on the R/C radio receiver and transmitter, and if the wiring is correct, the controller will start receiving pulses. For a preset amount of time, the controller will monitor the pulse train to make sure that they are regular and therefore genuine R/C radio command pulses. After that, the motors are enabled.

This power-on Watchdog feature prevents the controller from becoming active from para- site pulses and from moving the motors erratically as a result.

Similarly, if the pulse train is lost while the motors were enabled, the controller will wait a short preset amount of time before it disables the motors. If the pulses reappear during that time, the controller continues without any breaks. If the communication is confirmed to be lost, the “no ctrl” message is displayed again.

AX500 Motor Controller User’s Manual 87