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MPR121 Capacitive touch hat: IRQ pin 37 (GPIO 26)
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MPR121 Capacitive touch hat: IRQ pin 37 (GPIO 26)

by glucose36 on Fri Jul 23, 2021 2:06 pm

Hey

I just got a Capacitive touch hat (this one exactly) and I realized a bit late that it uses the pin 37 (GPIO 26) for IRQ.
That information is not shown on pinout.xyz, and I had to dig down to the bottom of this page to discover the use of this pin by this HAT.

The thing is that I already use GPIO 26 for another purpose, and I would like to know if I can re-route the IRQ to another pin (for example by breaking the highlighted bridge on the PCB and re-wiring it), or if I can simply get rid of it, as it does not seem necessary (see examples with Arduino or non-raspberry boards).

In advance, thanks!

Glucose

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Re: MPR121 Capacitive touch hat: IRQ pin 37 (GPIO 26)

by adafruit_support_carter on Mon Jul 26, 2021 12:54 pm

Yep, I think you generally understand the options. The MPR121 IRQ pin is routed to #26 by default. You can cut the trace here to remove that:
caphat_irq.jpg
caphat_irq.jpg (148.96 KiB) Viewed 38 times


If you wanted to re-route it, you could use the solder pad next to the jumper to wire the IRQ line somewhere else. Or, you can just not use the IRQ feature and simply poll the MPR121 for any touch events.

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Re: MPR121 Capacitive touch hat: IRQ pin 37 (GPIO 26)

by glucose36 on Mon Jul 26, 2021 2:54 pm

Just tried that a few hours earlier and it worked as expected. Went here to say so and saw your message.
Thanks for your answer and picture!

I my case IRQ is not necessary as I check for touches only a few specific time with a CPU-friendly time period (about 0.1s).

glucose36
 
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Joined: Fri Jul 23, 2021 1:52 pm

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