Serial Port selected disconnects after upload.

[ReeceM]

When I upload to my Sparkfun pro micro after selecting the port its on, after upload the selected port becomes deselected in the drop down and I can't upload again without going there and re-selecting the com port.

I am using a Hourly build when this happens :
Arduino 1.6.6 Hourly Build 2015/07/07 9:41

But if I use ver. 1.6.0 the serial port stays connected after upload.

Is this a localised problem or am I suffering from beta.

[matthijskooijman]

The micro disconnects and reconnects USB when switching from sketch to bootloader and back, perhaps this causes the problem? I haven't tried reproducing this, though.

[ReeceM]

I think the switching is causing the problem, because it switches to the port for uploading but never returns to the normal port. The IDE never reselects the port after an upload.

I think something that works with the Leonardo/micro upload style has been changed in the code, because it used to work correctly, i.e. it remembered the com port it is on after an upload.

[facchinm]

Hi @ReeceM , are you on Linux? Your problem can be triggered by the serial monitor (which is now kept in a "zombie" state during upload) respawning too soon and thus locking the previous port, so the sketch will get another one.
Can you post here your PC specs?

[ReeceM]

Hi @facchinm, I am on Windows XP, never had this problem before.

[facchinm]

Very strange, as Windows assigns different COM numbers to bootloader and sketch. Are you uploading with the serial monitor opened?

[ReeceM]

The serial monitor is not opened. The problem is that the IDE is not re-selecting the port after upload, even though it is there, example:
_BEFORE_

_AFTER_

[facchinm]

Ok, thanks for the screenshot, we'll analyze this issue as soon as @ffissore is back!

[ReeceM]

@facchinm cool 😃

[pablosun]

Hi, we can also reproduce this issue with a ATMega32U4 (3.3V/8MHz). The same cannot be reproduced with ATMega32U4(5V/16MHz) with Arduino IDE 1.6.5r2. This issue does not happen to Arduino IDE 1.6.4.

We suspect that this is related to uploadUsingPreferences() in Arduino/arduino-core/src/cc/arduino/packages/uploaders/SerialUploader.java

In recent changes, the uploader will set the BaseNoGui.selectSerialPort(uploadPort); after finishing uploading the sketch through the Bootloader COM port. However, uploadPort is actually set to Bootloader COM port at this moment - and thus overrides the setting from users (which should set to the sketch COM port). There was a logic that "detects" COM port with a 1000ms timeout in IDE 1.6.5r2 - and this timeout may not be sufficient enough for Pro Micro(3.3V/8MHz).

[NicoHood]

Does this only happen on Windows?
How does a 16mhz version behave?
Have you tried the official Bootloader as well, since the sparkfun bootloader is a bit different?

[pablosun]

Hi @NicoHood,

1. This does not happen on OS X(Yosemite) - but we also notice that on OS X, both Bootloader COM port and sketch COM port are registered as /dev/usbmodem1411 (the number may change on different machine, but keep the same when the board switches COM ports).
2. The official Leonardo (5V/16MHz) bootloader works without this issue.
3. We have only tried 8MHz version of Pro Micro bootloader - the result of Sparkfun Pro Micro bootloader at 5V/16MHz is unknown - sorry for a bit misleading when reporting this.

[NicoHood]

have you tried the 16mhz bootloader on a 16 mhz device? I mean you cannot use a slower/faster bootloader on a device with a different crystal.

You should try the sparkfun 16mhz bootloader for sure.

You could also try to recompile HoodLoader2 (see my repos) for 8mhz and see if this fixes the issue (since the original and modified bootloaders have some major problems)

[pablosun]

@NicoHood

1. Yes, we changed to 16MHz clock with 16MHz bootloaders
2. Sparkfun 5V/16MHz bootloader works fine without this issue
3. We haven't tried HoodLoader2 yet but reducing the timeout time of the Pro Micro bootloader can workaround this issue

But still I think the IDE code should have a more "formal" way to deal with Leonardo-derivatives which have disappearing COM ports after sketch uploads.