New Teensy 4.0 Suddenly Not Recognized

[Thundercat]

One further suggestion for your "new Teensy old carrier PCBA" test unit, is not to lock the Teensy. You then at least have the option of being able to do the 15 second restore, which I understand you can't do with a locked device. Given you're going to socket the Teensy, if it fails after a burn-in period, and can only be restored if unplugged, then that helps to narrow down the places to look.

There was a longish thread to do with a "startup bug", resolved in 1.59 but it seemed only to occur in limited circumstances - maybe it or something similar can still happen, with slightly different circumstances? I certainly encountered it in the Audio+TeensyDebug form, and the 15s restore appeared to be the only way out at the time.

EDIT: obviously, this is not a solution for production units - you want to lock those!

Hi h4yn0nnym0u5e,

That is very helpful. I really appreciate you sharing your experience, and the link. I'm blown away at how awesome you all are, and how great the forum is. Teensy is much more than a product - it's a legend, with caring people behind it.

So cool!

Thanks!

Mike

 

[Thundercat]

Hi, just an update - I thoroughly cleaned the boards with flux remover, scrubbed them, and let them dry well. They couldn't be more clean.

Behavior is unchanged. 3 boards fire up and run the sketch, but do not work correctly with attached button.

I took same working button from working unit and tried it in the 3 units - so it's not the button hardware, or the cable. I think the 3 units are just fried in some way. But they sort of work. Not OK for a product though, obvs.

The 4th board flashes but behaves strangely, and is effectively defunct.

5th board, I had desoldered and unfortunately ruined in the desoldering process.

Next step is to put a brand new Teensy 4.0 into a socket on one of the existing carrier boards.

I will do that in the next few days or week and post results.

As I said, I HAVE to solve this, because it goes into a product I make. Apologies for the slowness of my replies; I work another job and have been a bit busy.

Thank you all again for your tremendous support. Let's hope a new teensy with little to no high quality no-clean flux in soldering, works.

 

[PaulStoffregen]

For these latest tests, did you monitor the 3.3V power with your multimeter?

Do you have any way to monitor the USB current? If not, please buy (and use) one of these inexpensive USB power monitoring products.

 

[Thundercat]

For these latest tests, did you monitor the 3.3V power with your multimeter?

Do you have any way to monitor the USB current? If not, please buy (and use) one of these inexpensive USB power monitoring products.

View attachment 34333

I will buy one and use it.

I do have a multimeter; I guess I thought the point was moot if the board wasn't working right, since from same USB on brand new M3 MacBook Pro, other units work fine.

I will check 3.3V power on one of the defunct boards and report back. I'm assuming you just mean 3.3V to GND on the top of the Teensy? Or did you mean to check the computer USB power? In that case I will need to wait until I get the item you showed above, which I'll order today.

That product looks really neat; thank you for posting it.

And thank you again kindly for the amazing support.

EDIT: unit ordered. Will arrive in a few days. In the meantime, I'm going to test a carrier board with a new Teensy that is known to work. I will also check the Teensy voltage with a multimeter. Thank you again.

EDIT 2: Tested the new Teensy with multimeter installed in previous carrier board. 3.294V between 3.3v pin to GND, and 5.237 between VIN and GND. "Blink" has been running for a few mins without issue.

 

[defragster]

For these latest tests, did you monitor the 3.3V power with your multimeter?

Do you have any way to monitor the USB current? If not, please buy (and use) one of these inexpensive USB power monitoring products.

That looks like a nice device - with an important but rare to use feature: It will also show when current is flowing INTO USB Host.

That can make the Teensy act funny based on a T_3.x issue seen here with externally powered display matrix that wasn't grounded 'enough' to external power so the Teensy was carrying the current to the Host and that was making AUTO uploads unreliable. Don't recall how that was discovered (without this device) - but adding another GND wire from Matrix to the powered base board ribbon connector made it right.