Pull-Up Options for Alarm Using Data Logging Shield RTC

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schum
 
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Pull-Up Options for Alarm Using Data Logging Shield RTC

Post by schum »

Hello! I'm trying to use the PCF8523 SQ pin on the data logging shield to generate an interrupt to wake up my UNO, I currently have the SQ pin connected to a digital pin as an input. It says in the tutorial that "The output is open drain so a pullup (either physical resistor or enabled in software)."

Can someone please elaborate on either options (where does the physical resistor go, or how can the pullup be enabled in software)? What are the pro's and con's for each?

Thank you!

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Re: Pull-Up Options for Alarm Using Data Logging Shield RTC

Post by adafruit_support_bill »

The simplest way is to enable the internal pullup on your interrupt pin by setting it to INPUT_PULLUP via the PinMode command:
https://www.arduino.cc/en/Reference/PinMode

Then attach the interrupt via the AttachInterupt command.
https://www.arduino.cc/reference/en/lan ... interrupt/

This requires no additional components. You can just connect the SQ pin to the interrupt pin.
(Available interrupt pins on the UNO are pins 2 and 3)

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schum
 
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Re: Pull-Up Options for Alarm Using Data Logging Shield RTC

Post by schum »

I will try that and report back, thanks again!

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