@jazzyhawk Hey, try doing a safeboot. It should skip your boot.py and main.py code and allow you back in. https://docs.pycom.io/gettingstarted/programming/safeboot.html

@tealbrains & @Xykon : thanks all , that was that ! sudo dfu-util -D ./expansion3_0.0.9.dfu -R -v (I had added my user to dialout group already : not enought)

@jmarcelino The only thing connected during update is PyTrack module which I use to connect USB.

@bucknall Thanks for your help the other evening - I'm up and running now, though I'm no closer to being able to update the firmware myself. For linux users I have a (useful?) bash script that beings up a console window and then waits up to 15s for me to plugin the device (that way I see any boot messages). I don't know if this will work on OSX as I don't have a Mac. I need to update my blog post as I've recently modified the script to allows me to select the which serial device to connect to and baud rate to use. Mike T.

@pascal probably you are connected to board by COM port from different program. You can not be connected to board bye e.g. pymark, putty. Updater tool must have exclusive access to com port (UART). Is this the case? also look here https://forum.pycom.io/topic/763/firmware-upgrade-troubleshooting-checklist-procedure

I found the problem, the jumper for the TX pins were missing, i used the BAT jumper for the time beeing. Now the upgrade works, Thanx for the link, that was one post i had not read yet.