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 a conflict. It would be nice if the pin was configurable, and if so, where can I change the config?
For instance, pins 7 and 9 can be used instead of pins 5 & 6. Pin 7 (GPIO4) is right next to pin 5, and is a general purpose GPIO pin and therefore has no conflict with any other functionality. It is also physically in proximity to the GND pin (pin 9), and so therefore the same shorting of the pin for Wake From Halt can still be achieved easily, right?
An external RTC like DS1337, DS1339 or DS3231 (which are usually I2C based) can be used in conjunction with a configurable "Wake From Halt" pin (GPIO4 or any other pin that doesn't conflict), to allow for scheduled shutdown, wake from halt that can be as long as the alarm time supported by the RTC (for example, wake up once a day and report some data) and allow for some power optimizations when running on battery/solar.
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?