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by sridharrajagopal
Tue Nov 06, 2018 6:53 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Using DS3231 RTC alarm reset/wake from halt
Replies: 2
Views: 1600

Re: Using DS3231 RTC alarm reset/wake from halt

You can use software I2C using any GPIO pins - that way, there is no conflict with pin3 for wake from halt. See https://github.com/raspberrypi/firmware/blob/master/boot/overlays/README for more details. Relevant section copy-pasted here: Name: i2c-gpio Info: Adds support for software i2c controller ...
by sridharrajagopal
Tue Oct 30, 2018 7:55 pm
Forum: General discussion
Topic: Alternate pin for "Wake From Halt" instead of GPIO3 ?
Replies: 5
Views: 706

Re: Alternate pin for "Wake From Halt" instead of GPIO3 ?

An alternate way to wake from halt is to use the RUN pin. If the safe shutdown feature is enabled: dtoverlay=gpio-shutdown, then that also defaults to GPIO3 so that a single switch can be used to shutdown or wake. However unlike the wake pin, the shutdown pin can be configured to any GPIO for those...
by sridharrajagopal
Tue Oct 30, 2018 7:52 pm
Forum: General discussion
Topic: Alternate pin for "Wake From Halt" instead of GPIO3 ?
Replies: 5
Views: 706

Re: Alternate pin for "Wake From Halt" instead of GPIO3 ?

So my question is whether the Wake From Halt pin can be changed from GPIO3 to another? Also, if it makes sense, can GPIO4 be considered for Wake From Halt for future purposes to avoid conflict with I2C? No, the pin is hard-coded into the Pi. It can't be changed. One reason that pin was chosen is be...
by sridharrajagopal
Tue Oct 30, 2018 2:27 am
Forum: General discussion
Topic: Alternate pin for "Wake From Halt" instead of GPIO3 ?
Replies: 5
Views: 706

Alternate pin for "Wake From Halt" instead of GPIO3 ?

Hi, I am interested in shutting down the RPi and then waking it up from halt as a means of power optimization. I see that GPIO3 (pin5 ) can be shorted to GND (pin6) to wake the RPi from halt. However, GPIO3 is also the default pin for I2C. If you have any I2C devices connected to your RPi, there is ...

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