Unable to download after certain previous downloads

[PropGit]

Parallax IDE may not be flushing it's receive buffer after a reset condition is delivered to the BASIC Stamp, or not waiting long enough before flushing. See BASIC Stamp Programming Protocol v1.1 page 5.

After the following program is downloaded to the BS2 module, Parallax IDE is often unable to identify (or download) to the BS2 again whereas on the same computer the BSE software is able to do both with no problem. See this demo video for an example. Sometimes Parallax IDE is able to identify again, but unable to download and it displays a toast saying "Serial port not open."

UPDATE: Here's a more in-depth video using a different PBASIC program to cause the problem.

' BRANCH.BS2
' This program shows how the value of idx controls the destination of the
' BRANCH instruction.

' {$STAMP BS2}
' {$PBASIC 2.5}

idx             VAR     Nib


Main:
  DEBUG "idx: ", DEC1 idx, " "
  BRANCH idx, [Task_0, Task_1, Task_2]          ' branch to task
  DEBUG "BRANCH target error...", CR, CR        ' ... unless out of range

Next_Task:
  idx = idx + 1 // 4                            ' force idx to be 0..3
  PAUSE 250
  GOTO Main

Task_0:
  DEBUG "BRANCHed to Task_0", CR
  GOTO Next_Task

Task_1:
  DEBUG "BRANCHed to Task_1", CR
  GOTO Next_Task

Task_2:
  DEBUG "BRANCHed to Task_2", CR
  GOTO Next_Task

[2fast2fourier]

I was able to replicate this issue and tracked a connection leak to the serialport library. I've submitted a PR (garrows/browser-serialport/pull/38) and I will resolve this issue once the fix is verified and merged.

[PropGit]

We have a customer in our educator's course today that is experiencing this; at least the pattern fits. Very frustrating. I hope this actually fixes it, but I'm skeptical. Please test using multiple programs that contain repetitive DEBUG output- that's where I see it happen most often.

I don't remember having to restart Parallax IDE in order to solve this particular problem; I just have to use the BSE software to reprogram the BS2-IC with a simple PBASIC program containing a STOP command, then Parallax IDE can recognize it and reprogram it.

[phated]

This should be fixed with dependency updates. However, we were never able to duplicate this problem with the supplied source code, so it should be thoroughly tested by @PropGit. Please re-open if the problem persists.

[PropGit]

This problem is not entirely fixed.

The original problem still exists exactly as before using the Branch code and demonstrated by the first video in the first post.

The second and likely related problem noted by the second video and the Debug_Debugin code (below) still occurs, but not with as much frequency. Sometimes it fails, sometimes it does not. Perhaps the dependency updates improved things?

[phated]

Requires more research and information, as we are not able to duplicate with the given code.