[Coco] Detecting when CoCo is turned OFF

[Rick Ulland]

On 5/7/21 1:47 PM, Salvador Garcia via Coco wrote:
> Hello all!
> I am pondering on designing an Arduino based board to receive serial data coming from the CoCo's bit banger port. I would like for the Arduino board to do something when the CoCo is powered off...

In Linuxland we'd run 'heartbeat'. You could cobble your own version maybe.
Whenever the port is not actively in use, CoCo sends a unique byte 
string every minute? or so as a keepalive. If there has been no data and 
no special byte string in a reasonable time, the CoCo is off. 
Afterwards, if Arduino starts seeing the keepalive after a silent 
period, it is time to start looking for real data (not our special byte 
string) on the serial port again.