Thank you all for your feedback!
Yes, nothing except the USB is connected to the Arduino Mega.
There are no exclamation marks by any Device Manager items, including COM and USB
I historically had used IDE 1.6.9
- At some point in the past I had downloaded a version IDE 1.8. and it didn't work
- I went back to IDE 1.6.9 and left a copy around when later I successfully downloaded IDE 1.8.5
Read all suggestions and attachments; lots of good ideas, but nothing seemed to apply here
Further actions I took today:
- Uninstalled and reinstalled IDE 1.8.5 - no change/improvement resulted
- Downloaded and installed the .zip file of IDE 1.8.5 in a separate location - no change/improvement resulted
- Unistalled and reinstalled the Chinese clone driver, CH341SER.EXE - no change/improvement resulted
- Note: the testing I'm doing at this point is with multiple Chinese clone Arduinos
- Did some snooping and noticed that the installation timestamp on COM2 and my Western Digital My Book Duo (MBD) USB device have the same timestamps - I am concluding that MBD must be using COM2
- Dismounted MBD and unplugged it from the USB port - now the mouse is still sluggish, but liveable
- Mouse clicks were frequently missed, as well as keyboard strokes - this is more of a problem
- Did several uploads to the Arduino, all successful but still a sluggish mouse
- Added a Serial.println statement to Blink - the Serial Monitor window opened but NO TEXT APPEARED
- Verified Serial Monitor baud rate (9600) and tried several other rates just for grins
- Reconnected the MBD (Arduino still connected, running Blink) and everything continued running sluggish
- Disconnected the Arduino and the PC performance returned to normal
- Reconnected the Arduino to USB and checked current draw - was only 10mA!!! - mouse still sluggish
- Left the USB attached to the Arduino, and in parallel supplied 9V to the Arduino's power jack
- PC mouse immediately became lively again
- Serial Monitor still not displaying any results
I should mention that when I first got the Chinese clones I didn't know in advance that they would show up differently on the list of ports. So, not knowing what they were, I have been known to attempt to upload a sketch to COM2. Who knows what this may have done - but until two days ago it didn't seem to have hurt anything.
These results are a bit confusing...sorting it out,
- I may have drawn too much current from my PC's USB port, damaging its ability to supply current(?)
- I may have somehow succeeded in damaging either the MBD driver or the Arduino driver. I appear to have replaced the Chinese clone driver with a known good one, but perhaps something else in the chain is still broken.
- I have no ideas why the Serial Monitor would not be working
Until I can figure out a solution at least I can supply power to the Arduino's power jack an continue development - without any Serial Monitor feedback :-(.