Serial Port not found - Seeeduino Lotus Cortext M0+

Hi All

My students are using Arduino IDE and Seeeduino Lotus Cortext M0+ (185 pcs.). Now the serial port of 14 of those boards is not found.
I can’t select the Serial Port via Tools > Ports*

How can I fix this?

These boards worked before. I found I can get boards manually into bootloader mode (doubleclick the Reset) But this does not work with the failing boards.

This is the problem (board/port not found - MAC):
errorSerialPort not found

It is not the Computer or USB cable, same setup with other Seeeduino works perfect - same MAC:

Thank you so mutch!
Hermanus van Vugt
(University of Amsterdam)

Hi @h.e.m.van.vugt
Have you used 1.8.0 version SAMD before? The bootloader interrupted which will need to re-flash the bootloader.
Please refer to the below forums.
Seeeduino Lotus Cortext M0 - 15 Pcs dead after uploading first code

Thank you

It looks you are right, it is caused by 1.8.0. Explained in this post:

They provide a ‘solution’ to the problem. But It is far too complex and will take me more than a day. I have to wait till someone writes a more specific howto for this situation. ;-(

Hi @h.e.m.van.vugt
If you have a raspberry pi then you can consider this way to solve it.