I've been seeing some very slow performance from MacENC for some time, but in the past few days it has reached the point that "no data" alarms are going off when I've selected nav on my autopilot. I do have an 8MB annotation file and hundreds of waypoints (most currently hidden) and I also record a track file on one minute intervals. Could any of these by the culprit?
Most of the alarms are generated when I change the chart scale, but yesterday I was getting alarms as I drove steadily across a small scale chart with no other apparent load on the processor. The alarm will go off two or three times in a few minutes and then there will be no trouble for several hours. Something definitely makes the program churn through some big delays. I've come to expect that scale changes will hang things up for 20-30 seconds (very slow screen redraws) but I haven't seen the no data alarms going off in the past.
Everything does work, just very very slowly.
I would try unchecking "Annotation" on the "View" menu and "Show Tracks" on the "Track" menu and see if things speed up.
Another possible culprit is you have a NMEA feedback loop, that is the NMEA data that you are sending to the autopilot is being sent back to MacENC. Make sure you do not have NMEA out from your autopilot coming back into MacENC.
Turning off annotation did speed things up. Oddly, I've tried that before without any effect in a previous version of MacENC. The track file does not like to turn off. I've unchecked it and restarted only to see the track line being drawn again. It does disappear until I quit the program if I leave it unchecked.
I have a large and ever growing annotation file. Charts need lots of annotation in the Aleutians. I wish there was some faster running way of adding data to cover all the gaps out here.
I don't think my autopilot can send out any NMEA data. I just went out for a day and the program was redrawing charts noticeably faster, but I continued to get faulty data and no data alarms. The strangest behavior is a sudden 40° turn hard to port, then after about .1 miles of cross track error builds, it will lurch back hard to starboard and return to the original track. That never happens on autopilot. Only the nav setting causes it.
There is no way to predict the lurch off course and back. It may happen twice in an hour, or only once in a day.
If MacENC does not receive a position via NMEA for more 1.5 minutes then it will display an alert dialog.
If "Capture" on the "Tracks" menu is enabled when MacENC starts, then "Show" will be turned on.
I am wondering about your NMEA connection and source. Faulty data? The best would be to capture the NMEA stream then email it to us for analysis.
My GPS feed comes from a BU-353 on one USB port and data goes out to the autopilot via a Miniplex on the other USB port. The faulty data and no data alarms mainly come during the very slow screen redraws. The sudden course swings tend to come out of the blue, with everything appearing to be working normally. I'm about to leave on another trip and I'll try to capture some NMEA data when this happens.
If connected, I would try removing the NMEA return from the autopilot to the mux in the event it is repeating NMEA. A feedback loop would exhibit the problems you described.