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View Full Version : Teensy 2 Use On-board pushbutton



johncc
11-29-2012, 03:52 PM
I just ordered some Teensy 2's and have a question.

For one application I have it would be best to be able to use the onboard (reset) pushbutton for the sole application input. Would it be feasible to, after programming the teensy, cut trace and/or re-wire the pushbutton so as to read the button state from my program? I have looked at the schematics but have not been able yet to see the routing of the traces...


Thanks!
John

PaulStoffregen
11-29-2012, 06:10 PM
The pushbutton is intended to get back to programming mode if your code crashes.

If you're using Arduino and you don't disable interrupts or fiddle directly with hardware much, the auto-reset upload pretty much always works. But if anything ever goes wrong, where interrupts or the USB are disabled by your code, then the board can't respond to the request to automatically reboot to programming mode. Then you have to push the button.

However, if you still want to cut a trace and repurpose the pushbutton after reading the cautionary message, on Teensy 2.0 the trace runs most of the distance from the button to the chip on the bottom side, where you can easily access it. Underneath the pushbutton are two vias, one for ground and the other for the reset signal. It's easy to see which is the reset signal, because it continues on to the pad on the right side. Unfortunately, you'll need to cut the trace between the chip and the via under the button, so it's not easy to leave the pad connected.

If you do this, it'd be smart to make the trace cut somewhere you can rejoin the original connection, in case you ever happen to load code which crashes and requires the physical reset to reprogram.

johncc
11-29-2012, 07:01 PM
That was just the type of input I was looking for, and expecting!

Thanks!
John