Continuous Alarm Tone from D-180

RV-12 in flight checking AP74 AP - working fine, air very rough, so I turned off AP; got voice confirmation of AP off.

Then a continuous alarm tone sounded....could not determine its source.

Nothing highlighted
Nothing blinking
No alarm bar
No alarm menu
No voice announcement of alarm
No "Show [page]" button shown
No "silence" button displayed.
Engine analog indications of oil temp/pressue, etc normal
Made immediate landing.
Turned off power to D-180 and recycled power. Tone then gone. Taxi back to hangar..no alarms, engine fine.

What could have been the cause?

This was posted on the Dynon forum but no responses received.

Dynon software glitch?

John,
My guess is that there is a bug in the Dynon software. If it happens again, try holding in the left button of the Dynon D-180 to power it down. Then turn it back on and see if the alarm is gone. Have you upgraded to the latest Dynon software, version 5.4? If the Dynon serial port is readily accessible, you could download the data and analyze it for alarm conditions.
How did you shut off the autopilot, with the rocker switch or with the AP disconnect button next to the throttle?
Joe

Alarm Tone

I have 5.4 installed. Did power unit off via left push key off then on to clear tone.
I am not positive but suspect I used rocker power switch on panel, not on the AP74 to kill AP in flight. Next time up I will try it both ways and see if it makes any differece. I have killed the AP both ways quite a few times in the past with no trouble.

I suspect a transient occurence which hopefully will not reoccur, but we'll see.

The connector to the D180 is easily connected to to hook up a laptop, but the output is undecipderable as far as I am concerned.

Continuous Alarm Tone

Could not duplicate the alarm tone locked on today. No matter how the AP was turned off, with the instrument panel power switch, or with the AP 74 push button the tone did not show up.

A transient effect of the normal "beep" when the AP is turned off just 'stuck' on and gave me the un-ending alarm tone, but it was not an alarm tone, just the failure of the normal "beep" to stop.

End of incident.