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MagTag button issue
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Please be positive and constructive with your questions and comments.

MagTag button issue

by joeycastillo on Thu Nov 19, 2020 1:51 pm

Hi, y'all. Just got my MagTag kit, and I'm experiencing an issue with one of the buttons.

When I first plugged the board in, the sketch that it came with was repeatedly printing that button B was pressed. Since then I installed CircuitPython, and even when setting all buttons up with an internal pull-up, button B remains in a low state no matter what. The other buttons work fine.

I've verified with a multimeter that the button is functional (open circuit normally, closed when the button is pressed). I also verified a good electrical connection between the button and the associated pin (IO14) on the ESP32-S2. It seems like it should work, and yet.

Anyway. When looking at the board files I noticed the unpopulated BUTTONB pull-up resistor footprint on the backside, so my next step in debugging the issue was going to be soldering a resistor on there. But when I emailed support@adafruit, the suggestion was to post here first. Open to any guidance or suggestions.

Thanks!

joeycastillo
 
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Re: MagTag button issue

by dastels on Thu Nov 19, 2020 2:36 pm

1) can you measure the voltage at the non-ground end of button B when pressed and not?

2) can you post a clear photo of both sides of the board?

Dave

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Re: MagTag button issue

by joeycastillo on Thu Nov 19, 2020 2:57 pm

Sure! The non-ground-end of button B reads 0.67 V when not pressed, and 0 V when pressed. (the other buttons all read 3.2 V when not pressed)

Here are photos of the board:

front.jpg
front.jpg (949.38 KiB) Viewed 75 times


back.jpg
back.jpg (986.39 KiB) Viewed 75 times

joeycastillo
 
Posts: 3
Joined: Wed Jan 21, 2015 8:38 pm

Re: MagTag button issue

by dastels on Thu Nov 19, 2020 9:43 pm

Yes, 0.67 would be a False.

If you've confirmed the resistor is missing (my MagTag hasn't been delivered yet so I'm flying blind for now) then soldering one in should do the trick. If so then we'll get you a new board. Out of curiosity, where is the missing resistor? I've compared your photo to the product shot and haven't found it.

Dave

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Re: MagTag button issue

by joeycastillo on Thu Nov 19, 2020 10:48 pm

I don't think they're missing; there are four resistor footprints (one for each of the buttons), but the board file says their values are DNP so I assume they're intentionally omitted. The guide also says to configure the pins with internal pull-ups, so I don't think they should be necessary.

Screen Shot 2020-11-19 at 9.35.27 PM.png
Screen Shot 2020-11-19 at 9.35.27 PM.png (220.63 KiB) Viewed 63 times


Having said that, when I added a 10K resistor to button B's pull-up footprint (next to the Stemma QT connector), button B started working as expected. Which means... maybe an issue with the ESP32's internal pull-up for that pin? Very strange! Definitely no need to send a new board now, but perhaps something to file away in case someone has a similar issue in the future.

Thanks!

joeycastillo
 
Posts: 3
Joined: Wed Jan 21, 2015 8:38 pm

Re: MagTag button issue

by dastels on Fri Nov 20, 2020 11:39 am

That is interesting.

Seeing external pullups on a digital input is unusual. I'm interested to check my board when it arrives.

Dave

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Re: MagTag button issue

by adafruit2 on Sat Nov 21, 2020 2:14 pm

this is a really weird rare issue we saw come up with 2 other boards. we have no idea why its happening and only on that one pin, but there's a spot for a pull up and we'll fabricate the next batches with the resistor in place

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Re: MagTag button issue

by dastels on Sat Nov 21, 2020 3:35 pm

To followup: my MagTag arrived and all seems to be as it should be.

dastels
 
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Please be positive and constructive with your questions and comments.