How can I avoid destroying my Teensy?

K

kadukes

New member
I am still a beginner in microcontroller development and have so far developed small projects with the Arduino framework. I now want to try out a Teensy board, but a few things are still unclear to me.

In Arduino I once had the problem that I had accidentally overwritten the bootloader. I was able to fix this with a programmer (e.g. AVRISP MKII, Atmel ICE, ...) and the correct bootloader code.

I wonder how I could do these things with the Teensy in case I break something. I know that the bootloader cannot be overwritten. That's good news for me. But what do I need to bear in mind during development? Are there ways to make the Teensy unusable?
 
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@kadukes: The good news is that it is very unlikely that you could make the Teensy unusable strictly with the firmware that you load into it. The even better news is that the Teensy 4.x can easily be restored back to factory configuration using the procedure listed <here>, no matter how bad your loaded firmware may have hung it up. It is almost impossible to "brick" your Teensy 4.x by loading firmware into it.

The first hardware risk to be aware of is that the GPIO pins on the current Teensy 4.0/4.1devices are 3.3VDC compatible only - applying 5VDC to any pin (except the power pin) will damage/destroy the pin, and quite possibly take the entire processor with it. If you hook up any older external devices that provide 5VDC level signals, you must include some kind of level translation hardware in your design.

Another hardware risk is the necessity for flyback diode protection when driving inductive loads (e.g. motors) with the GPIO pins. Inductive loads can generate very large voltage spikes when changing states, and these spikes can easily damage/destroy the pin as well.

There are various other hardware risks to be aware of (e.g. don't connect output pins to anything that might accidentally drive a level into the pin which is different from whatever level the pin is set to output), but the two primary hardware risks mentioned above are the most common causes of physical damage as discussed here on this forum.

Good luck & have fun !! Hope that helps . . .

Mark J Culross
KD5RXT
 
@kd5rxt-mark
Thanks for the first impression about the pitfalls of development. I will take your tips into account when designing the hardware.

I just have a few questions:
1. do I still have a problem with inductive loads if I drive them via a dual H-bridge that already contains in-circuit protection diodes? Or do I need a separate protection diode in this setup as well?
2. I have read that you should not run the Teensy with USB power and external power at the same time. Does this also apply to the newer versions?

Thank you very much for your help!
 
kadukes said:
2. I have read that you should not run the Teensy with USB power and external power at the same time. Does this also apply to the newer versions?
Click to expand...

Teensy® 4.1

www.pjrc.com www.pjrc.com

"VIN PinWhen USB power is not used, 5V power may be applied to the VIN pin. Because VIN & VUSB are connected, power should not be applied to VIN while a USB cable is used, to prevent the possibility of power flowing back into your computer. Alternately, a pair of pads on the bottom side may be cut apart, to separate VUSB from VIN, allowing power to be safely applied while USB is in use. "
 
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