Teensy 4.1 not responding to pressing button for sketch upload

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jimmie

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I have a brand new Teensy 4.1 that worked fine for a couple of days.

Now, when I try to upload a program to it, nothing happens. When I press the programming button, the LED stops flashing and the sketch is not uploaded. Also, the computer loses the connection to the com port.

I tried restarting the computer but it did not help. I also tried with another Teensy 4.1 with the same computer and everything works normally with another board.

When that problem board is powered, it runs the last sketch that was uploaded to it. I am using Arduino 1.8.9 with Teensyduino 1.53. Is the board bricked?

Is this potentially a fake chip or are there other reasons?

Thanks in advance for the community's help.
 
Thank you, I tried but it does not help.

The first time I plug the board in, LED lights up and computer recognizes it. When a sketch tries to be uploaded, nothing happens. Pressing the programming button does not do anything.

If I press the button and hold it pressed while plugging in the cable (as the article recommends), this causes the computer to beep but com port is not recognized and LED is off.

What else should I try?
 
Not clear what is going on there ...

Assuming the cable used for the working T_4.1 is also used when plugging in the other one?

Unplug all the Teensys.

Have the IDE open with a simple BLINK or other sketch done with a VERIFY build

With TeensyLoader Open go to Help and select Verbose - that will have any interaction with the T_4.1 shown in the verbose window.

Using that good cable hold the program Button when plugging it in and wait a second before releasing - that should leave it in Bootloader ready to upload a simple BLINK sketch. And it should log in the Verbose window and then have TeensyLoader program it if in 'Auto' mode.

Results?

If that works and it is ready to upload another sketch - maybe the same blink with a faster or slower blink that is obvious.

If not try the 15 sec Restore. Press the Button and watch for a RED LED flash about 15 seconds and release the button at that point and the RED LED should then go ON for the duration of the FLASH Erase and restoring of the Factory blink code, and the steps above should then work.
 
Thank you @defragster.

I loaded and verified the Blink app. I have also uploaded the verbose logs. Tried all the above but nothing helped.

When I unplug the cable then replug it, the board is recognized. Once I press the button, the com port is gone ....

I am happy to try anything else.
 

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Good you uploaded the Verbose - Paul might scan it.

If it won't program that is not right, but one the button is pressed it will never show a COM port - it goes into HID mode for bootloader.

Any notes on the 15 Sec Restore? Did the RED LED Flash and then stay on when Button was released?
 
When first connecting the board to the PC, the com port is found and the LED lights up.

At that point, I measured a voltage under the button (Program Pin?) of 2.0 V. When I pressed the button, the 2.0V remain. But in the latter case, the computer no longer sees the COM port and the LED is off.
 
T41.png

Paul
 
When I touch the program button with a single Voltmeter tip, the PC beeps.

The voltage between Program pin and Ground is 3.3. When I press the program button, it goes to zero.
 
When I touch the program button with a single Voltmeter tip, the PC beeps.

Does the same PC beep happen when you press & release the pushbutton?

Sure sounds like it's trying to work, but can't.

All signs point to both the main IMXRT processor and the MKL02 bootloader both working, but unable to communicate with each other. Obviously the main chip is working because it's still running your previously programmed code (which is USB Serial, not USB RawHID as originally shipped from PJRC). The bootloader chip also seems to be alive, because it's turning on the CPU voltage (powerup sequence step 7), and it's giving 3.3V on the Program pin which comes from its internal pullup. That it's doing *something* when Program changes is also a good sign that chip is alive. At least the good news is all the chips seem to be operating, so there's a chance this board might work again if whatever has gone wrong with the connection between them gets fixed.

Is there any sign of damage to the PCB in the area just below pins 23-17? If pins 22 & 23 were soldered and any stray solder got onto the tiny pins of the nearby bootloader chip, that sort of shorting signals together would explains the way this board is behaving.
 
Thanks Paul.

I think I understand now what has caused the problem. I am using a custom board which also has the Ethernet connection. To use that board, I desoldered the 2-row 6-pin connector to place a different one that connects directly to the board with the built-in Ethernet. Most likely, it is damage to that area is what has caused the problem. I did check the area again and while I cannot see any damage, I must have damaged something. I wish an RJ45 came integrated with that board :).

Thanks again for your help. I will be more careful next time.
 
Oh how I wish we could integrate a RJ45. It kinda doesn't really fit...

If you can carefully desolder the part and get the location where something went wrong, there's a pretty good chance this board might be salvageable, since both the chips appear to be alive. Then again, that much work might not be worthwhile to save only 1 board.
 
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