We have purchased a large quantity of Lockable Teensy 4.1 units. Initially we have set the encryption feature on these units by using the "Fuse Write Sketch" program and proceeded to download and test our application. All worked great. Now, it was our intention to lock the key using the "Lock Security Sketch". When that is performed, the Serial Monitor window shows that it was successfully locked. From this point forward the unit becomes unusable "bricked".
Brick definition in this instance: Powering on the unit, it still runs the lock sketch (since that was the last program downloaded). The serial monitor shows that the unit was successfully locked (again). Attempting to download the blink program at this point or any other for that matter, fails, the USB port drops out, (you here the windows USB dropout sound, and Windows indicates an error with the USB port. The USB no longer works again unless you repower the unit. (But again it will not take any program downloads)
I have now bricked 3 units in this way. The first I thought might be a fluke, so I tried it again with another unit. The second one also bricked. The third I tried to reset back to factory defaults first using the 13-17 second reset. It then bricked number 3.
Curiously, when I a start with a virgin Teensy 4.1 right out of the package, and perform the Fuse and Lock commands it works. I can then put my application on the unit successfully. Problem is, I have 24 units with our program on it that are not yet locked. And I am confident that they will brick as well unless I can determine the issue.
Thank you for any help that you can provide.
Brick definition in this instance: Powering on the unit, it still runs the lock sketch (since that was the last program downloaded). The serial monitor shows that the unit was successfully locked (again). Attempting to download the blink program at this point or any other for that matter, fails, the USB port drops out, (you here the windows USB dropout sound, and Windows indicates an error with the USB port. The USB no longer works again unless you repower the unit. (But again it will not take any program downloads)
I have now bricked 3 units in this way. The first I thought might be a fluke, so I tried it again with another unit. The second one also bricked. The third I tried to reset back to factory defaults first using the 13-17 second reset. It then bricked number 3.
Curiously, when I a start with a virgin Teensy 4.1 right out of the package, and perform the Fuse and Lock commands it works. I can then put my application on the unit successfully. Problem is, I have 24 units with our program on it that are not yet locked. And I am confident that they will brick as well unless I can determine the issue.
Thank you for any help that you can provide.