ChrisCurl

So I measured the voltages on the pins when plugged into the USB port. The voltage between 5V <--> GND has 5.18V. The voltage betwen 3V <--> GND jumps around in the low mV range.

It must be bricked. I tried a different cable that I know to be good (it also worked exatly as expected with the Pico), and still nothing from the Teensy. Not even the red LED when I release the program-mode button. Time to buy a new Teensy I...

Something is wrong. The red LED should turn on after pressing the Program button. But please understand Teensy uses HID protocol in programming mode, not Serial. So if you look only for a /dev/ttyACM device, you'll miss Teensy when it's using...

I should have mentioned that I also have a RPI Pico and, with it connected to the same cable, the Pico shows up as (/dev/ttyACM0), and the Serial Monitor comes up and behaves as expected. I'll try a different cable anyway. The red LED does not...

The most common problem for Teensy not detected is use of a power-only cable. They're incredibly common in drawers of leftover USB cables. On Linux, the 2nd most common problem is not having the udev rules file installed. But lacking udev...

I am using Arduino 2.3.2, Teensy 1.59.0, Debian 12 Linux, with a Teensy 4.0 I recently received (from my daughter - she bought in on Amazon). I get this message, and I don't know how to fix it. Teensy should be selected from "teensy ports"...