Teensy 4.1 bricked

Hello,

I bought a Teensy 4.1 through the official pjrc shop some months ago. It recently just died on me and is now bricked. When powering it the red bootloader LED flashes twice, then waits for 5 seconds and then flashes twice again, repeating infinitely. The physical pushbutton does nothing and I can't connect through Arduino IDE anymore. What can I do to make it work again?

Best regards
 
Hi,
You may have already tried this but... I understand that the 4.1 has a restore feature. You need to hold the reset button down for 15 seconds. Then the board will wipe itself and restore the original out of the box "Blink" sketch. Apparently it takes about a min to complete the process.

Good luck - Martin
 
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Do you have a voltmeter? Since it's not responding, before spending a lot more time on the communication, check if your Teensy is getting properly powered. Measure both the 5V and 3.3V power pins, located just above the USB connector, of course with the negative lead touching GND.
 
My best guess is somehow you've lost connectivity between the U1 and U2 chips. These are the areas where their connections are located.

pcb.png

First visually check for any damage. If nothing is obviously visible, try pressing on that corner of U1. Sometimes thermal or physical stress to the BGA chip can cause some of its pins to come disconnected, where pressing can cause them to touch.
 
I never exposed my teensy to physical or thermal stress. There is no visible damage to the board and pressing the marked corner changes nothing.
 
Well, I'm running out of guesses based on the available info.

Earlier you said the 15 sec button press didn't work. Can you be more specific about exactly what you saw? While holding the button, I'm guessing you probably did get the quick blink at 13 sec to indicate you're within the 4 second window to release the button.

When you released the button, did the red LED turn on bright? How long did it run before failing?

When you first power up your Teensy, without touching the button, is it showing any signs of still running a previously written program?
 
I chose the word bricked for a reason. The teensy is not reacting to anything at all.

To answer your questions:
Earlier you said the 15 sec button press didn't work. Can you be more specific about exactly what you saw? While holding the button, I'm guessing you probably did get the quick blink at 13 sec to indicate you're within the 4 second window to release the button.
The bootloader LED blinks red twice, waits, then repeats infinitely. If I press and hold the button for 15 seconds the same LED pattern occurs for the time pressing it and afterwards. It is not reacting to pressing the button.

When you released the button, did the red LED turn on bright? How long did it run before failing?
No, the LED keeps repeating the same blinking pattern no matter what I do, if I press the button or release it doesn't matter. It was working fine for at least 6 months.

When you first power up your Teensy, without touching the button, is it showing any signs of still running a previously written program?
No, it goes straight to the blinking twice pattern on the red bootloader LED.
 
2 blinks on the red LED comes from the bootloader chip (U2) which means it can't communicate with U1.

The main processor (U1) may or may not still be running a program if U2 isn't connected to it. In other words, U1 might still be working fine and the lack of communication between the chips might be physical connectivity related. But it's also possible U1 got damaged in some strange way. Very difficult to know what really happened.
 
I verified there is no program running by connecting my PS3 Controller to the USB Host, it is not being powered and not passing through inputs (Which it would be doing if my program was running)
 
Hi, did we ever get anywhere with this?

So I've been using a 4.1 for a few years and have encountered this numerous times but put it down to an error on my board or soldering problem, reflow or hot air issue etc. I am using the t4.1 soldered to a custom 'carrier board' my board is at v1.

This time I captured the error perfectly.

Finished soldering yesterday, powered up, programmed multiple times (simple blink sketches) all was well for at least an hour so it was time for the overnight soak test (blink without delay program left to run at a ridiculous 100ms interval). I've returned to a dead t4.1 with no led13 flashing..... no usb detected, just 2 blinks - 3sec delay 2 blinks 3 sec delay on the bootloader red led....

I get 5v, and 3v3 on the t4.1, and i am able to use the on/off button to power up/down the 4.1. However, the usb is not seen at all, and it would seem the blink program isn't running either.

When holding the rest button, it does nothing, before or after.

Any guidance would be much appreciated. Its like my 6th 4.1 via various diffrent projects where i have encountered this isssue. Whats strange is I know if I get a new 4.1, add it to the board its likely to work just fine, but would really like to understand why this is happening.
 
OK slight update to aid the discussion:

Power off > Reset button held > power on > reset released > usb recognised! > teensy loader sees the 4.1 > program > seems sucessfull > reboot.

After reboot, no led13 flashing... just the bootloader sequence described above + usb completely disappears as if its not plugged in.
 
Power off > Reset button held > power on > reset released > usb recognised!
Note: The Teensy has no Reset Button. It is a Program button where the bootloader halts the Teensy inviting an upload as occurred.
When the Bootloader is in control it presents as a valid USB HID device to facilitate the upload.

Try again with a known valid sketch with USB Serial for the Teensy and have it blink and print something in loop()
 
It is a Program button where the bootloader halts the Teensy inviting an upload as occurred.
Could you explain what you mean by the above sentence. I think I know what you mean, but we have a large number of members who DO NOT have English as a first language and may not understand your sentence, especially the halts the Teensy inviting an upload as occurred. part.
 
With a Teensy 4.x there is a RED LED by the USB connector. Only the bootloader can power that RED LED.
Anytime the RED LED is on the PJRC bootloader chip is in control of the Teensy MCU/Processor.
> This includes any non-solid blink patterns that indicate the MCU will be 'offline' with the bootloader in control, or attempting control (as indicated by the blink code).

A Teensy has a single factory button. That button places the Teensy into Program mode, where the card also has a pin hole labeled 'Program' in the row across the Teensy - that pin is shared electronically with the Button and when pulled to GND, like pushing the Button, will cause the onboard PJRC bootloader processor to halt and take control of the primary MCU to facilitate programming over the USB connection.

The "as occured" was in reference to the comment included in that p#17 explaining that Pressing the "Program [not reset]" caused the 'usb recognised' as a result of the just added preceding text: Reset button held > power on > reset released > usb recognised!
 
So, the use of the word 'reset' was used out of habit. I know its a 'Program' button but thanks for double checking my knowledge on the matter (or rather correcting my terminology). So, Its certainly bricked. I have put this down to a faulty connection (probably caused by a microscopic :-( solder ball that I failed to capture on the microscope before powering up). I can confirm I have successfully repopulated another PCB (luckily I have 5 and only need 2), hot aired the teensy 4.1 onto it and now all is working. Lessons learnt: Check, clean, check clean check clean, check again...wait a day, check again, then power up!
 
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