Alarms and recovery¶

How to read alarms and recover from them. The methods are documented in Alarms and the exceptions in Exceptions. Examples assume a connected Magician named bot.

Reading alarms¶

get_alarms returns an AlarmSet. Its format() method gives one line per alarm with a remedy.

alarms = bot.get_alarms()
if alarms:
    for line in alarms.format():
        print(line)

When an alarm occurs¶

While an alarm is active, the status LED of the arm is red and the arm does not move: a move queued during an alarm is dropped. The next command that waits for the arm, such as ptp, raises a DobotAlarmError subclass, which stops the program unless it is caught. Commands still queued are discarded, so clearing the alarm does not resume them. The control panel shows the active alarms in its banner.

Clear the alarm with clear_alarm or the Clear Alarm button of the panel. The LED turns green. A joint-limit alarm ends by itself when the joint is jogged back off the limit. set_home and the panel's Home button work also during an alarm: the arm homes, and the alarms are cleared when homing ends.

Recovering from a failed move¶

from pydobotlab import DobotAlarmError, DobotKinematicError

try:
    bot.ptp(mode=1, x=400, y=0, z=0, r=0)  # MOVJ_XYZ, outside the workspace
except DobotKinematicError as error:
    print(error)  # one line per alarm, with a remedy
    bot.clear_alarm()
except DobotAlarmError as error:
    print("alarms:", error.alarms)
    bot.clear_alarm()

How each alarm ends is listed under Alarm, and the exception for each code range under Alarm groups.

Recovery by alarm type¶

Alarm	Recovery
Planning or motion (`PLAN_`, `MOVE_`)	Call `clear_alarm()`, then retry with a reachable target.
Joint or parallelogram limit (`LIMIT_*`)	Jog the joint back off the limit; the alarm ends by itself.
Overspeed (`OVERSPEED_J*`)	Lower `motion_params`, then call `clear_alarm()`.
Lost step (`LOST_STEP_J*`)	Call `set_home()`.
System (`PUBLIC_*`)	`PUBLIC_RESET` and `PUBLIC_UNDEFINED_INSTRUCTION`: call `clear_alarm()`. Others: power-cycle the arm.

Clearing¶

clear_alarm reads the alarms again after clearing. If the cause persists, for example a joint still pressed against its limit, the alarm becomes active again at once and stays active, and clear_alarm raises its exception. The Clear Alarm button of the panel shows the same message.

try:
    bot.clear_alarm()
except DobotAlarmError as error:
    print("still active:", error.alarms)