Turning my GPS logger shield off and on

Question

I have a Sparkfun GPS Logger Shield and I want to save power by shutting it off when I do not need GPS readings. Now reading the hookup guide it says that the "EN" pin can do this: "Active-high chip-enable – pull low to reset or turn off".

I wanted to ask some advice as to what this actually means and how I safely go about it. Is it as simple as:

pinMode(pin, OUTPUT);

//turn off    
digitalWrite(pin, LOW);

//turn on
digitalWrite(pin, HIGH);

Where the pin is a digital pin on the Arduino and it is connected to the "EN" pin of the GPS shield.

Answer 1

Yes, it is as simple as that.

However, since the pin is pulled up already you could also do this:

pinMode(pin, INPUT);
digitalWrite(pin, LOW);

// Turn off
pinMode(pin, OUTPUT);

// Turn on
pinMode(PIN, INPUT);

That then emulates an Open Drain pin which means you're not actively driving the pin when turned on, only when turned off.

Personally I prefer system that are active low not active high, and are pulled down by default (normally off) so that you don't waste power driving the pin in order to save power (it's kind of silly really) - you drive the pin to turn on and let the pin float to turn off (especially good with deep deep comatose sleep on some MCUs where the IO pins all switch off).

However the designers of this module decided otherwise, so you're stuck with driving the pin LOW to make it sleep.