Teensy 4.1, F1 fuse causing problems

T

TriangleThesis

Member
Hello, I have a Teensy 4.1 that I connected to a USB hub, this caused the Teensy to not be detectable from Arduino IDE or Device Manager. Eventually, I connected the ground of the USB port to one side of the F1 component and there was a slight spark, then the board connected.

Is it ok to bypass this fuse by soldering a wire from a ground to one side of the fuse? It seems that connecting either side of the F1 fuse to the usb ground will allow the board to turn on.

EDIT:
It seems that briefly, connecting the usb ground to the usb power will turn the board on as well, what could be causing this?
 
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The fuse is a self resetting thermal fuse. Given that there was a spark you may have taken out the fuse and/or other devices.
You should not need to connect either side of the fuse to cause the board to turn on.
I suggest you connect the T4.1 directly to the computer to see if it still functions.
If it does not function try carrying out the Memory Wipe & LED Blink Restore process.

Memory Wipe & LED Blink Restore
Click to expand...
Teensy 4.1 will fully erase its non-volatile memory and return the flash memory to a simple LED blink program if the program button is held between 13 to 17 seconds. The red LED flashes briefly at the beginning of this time window. During flash erase, the red LED is on bright. When completed, Teensy 4.1 will automatically reboot and run the LED blink program, causing the orange LED to blink slowly.
Click to expand...
 
The fuse is connected inline with the positive supply current, connecting it to ground would turn the Teensy into a short circuit that would likely kill anything you connected it to.
 
I have done the Memory Wipe and LED Blink Restore process, it does connect to the computer and I can access it with the Arduino IDE. I have not taken out the fuse. I can't detect the Teensy through USB until after I short the USB power pin to the USB ground pin. Could the USB interface on the Teensy be the issue? I have tried multiple USB cables and other USB ports
 
It sounds like the hub is either designed for USB-C and there's unmentioned adapters involved, or it's just really cheap/badly designed and doesn't check for a connected device unless it detects significant current draw.
 
Yes, so it was a very cheap hub and I think it fried something in the teensy when it was connected. I am no longer using it and my Teensy is connected directly to a USB port on a computer using a different micro USB wire. I still can only detect the teensy when I do that short quickly.
 
I don't get any error messages when flashing sketches to it, I've just flashed a modified blink sketch and it seems to work fine. Also, when trying to do the memory wipe and blink restore, it doesn't seem to work. I held the button down for a long time and I just saw one red flash from the red led, but the teensy still runs my modified blink sketch.
 
TriangleThesis said:
I don't get any error messages when flashing sketches to it, I've just flashed a modified blink sketch and it seems to work fine. Also, when trying to do the memory wipe and blink restore, it doesn't seem to work. I held the button down for a long time and I just saw one red flash from the red led, but the teensy still runs my modified blink sketch.
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Did you release the button when you saw that LED flash? That should happen after 13-15 seconds or so. After you release the button, the erase process should start, and should take about a minute-ish.
 
So it seems like the teensy functions just fine, I can reset it to blink, I can flash different sketches to it. But it just will not turn on or be detected by the computer until I short the USB connector ground to the USB power.
 
Can you describe what external components are attached to Teensy?
And, upload a photo of Teensy with all the external peripherals connected.

BTW, T4.x are not 5Volt tolerant. Hopefully you don't have anything attached that would exceed 3.3V on T4.1 pins.

Shorting USB 5V to ground is not a good thing. Please don't do that.
 
TriangleThesis said:
So it seems like the teensy functions just fine, I can reset it to blink, I can flash different sketches to it. But it just will not turn on or be detected by the computer until I short the USB connector ground to the USB power.
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You say the Teensy functions just fine but then you say that it will not turn on or be detected by the computer until I short the USB connector ground to the USB power.
Those would seem to me to be two contradictory statements.
Can you reset it to blink, and flash different sketches to it without shorting the USB connector ground to the USB power?
 
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