Why do so many projects ask for the A0 pin to be connected to GND? What happens if you do that
jblack155:
Why do so many projects ask for the A0 pin to be connected to GND? What happens if you do that
Can you please provide links to some of the "many projects" that do this ?
approx 1/2 way down..
"""While this dialog has focus, ground pin A0 on the Arduino to activate the test script. The test script will test the game controller functionality in the following order:"""
You're sending a signal to that pin which is telling the program to do something. Mostly when you attach a button to a pin that button will pull the pin to ground when it is pressed. So that is something they've written into that program to allow you to put a button on A0 and use it to start some routine. They could have picked any pin. They picked A0.
The magic answer lies in the following paragraph...
JoystickTest
Simple test of the Joystick library. It exercises many of the Joystick library’s functions when pin A0 is grounded.
The Ground link across A0 is implemented to access a test routine.
This is not 'unusual' but frequently used when a temporary 'test' mode or configuration option is required.
It could otherwise be a UI option to 'enable' test mode.
A valid use of the idea.
Definitely not always.
Look at the JoystickTest example. It uses the state (HIGH or LOW) of A0 to change modes
Grounding A0 has no intrinsic meaning unless the program reads it and acts upon its state as in this example
Why do so many projects ask for the A0 pin to be connected to GND?
Never seen one, do they have the word instructables in the url? if they do ignore them unless you know where to spot the inevitable errors.
In the case of that page they are simply using A0 as a test input signal. Using the pinMode(A0, INPUT_PULLUP ) ; like they do ensures A0 will normally read high unless connected to ground when it will read a low. Note the A0 pin is being used as a digital input not an analogue one.
Just worth adding to the existing explanations...
Reading a configuration jumper or switches - can occur during initialisation - or during normal operation.
The choice is the developer's.
The first - is a 'setup' selection - which can't be 'changed' by a typical user during normal operation.
The second choice allows a knowledgable user to change the option states any time they can get to the link/switch.