are you suddenly getting this error:

File “/usr/lib/python2.7/dist-packages/serial/serialposix.py”, line 460, in read
raise SerialException(’device reports readiness to read but returned no data (device disconnected?)’)
SerialException: device reports readiness to read but returned no data (device disconnected?)

where you didn’t before using pyserial? Me too. Boot with the previous kernel (linux-3.13.0-63-generic) and your problems will go away.

I hope you read my blog before spending as much time with your oscilloscope as I just did.

With thanks to this https://www.mail-archive.com/kernel-packages@lists.launchpad.net/msg137077.html post. It’s reported https://bugs.launchpad.net/ubuntu/+source/linux-lts-trusty/+bug/1500860 here