All Low

After the pull up experiment this one may seem boring at first glance. But read on.

//	Copyright 2011 Udo Klein
//	This program is free software: you can redistribute it and/or modify
//	it under the terms of the GNU General Public License as published by
//	the Free Software Foundation, either version 3 of the License, or
//	(at your option) any later version.
//	This program is distributed in the hope that it will be useful,
//	but WITHOUT ANY WARRANTY; without even the implied warranty of
//	GNU General Public License for more details.
//	You should have received a copy of the GNU General Public License
//	along with this program. If not, see

// This sketch will set all outputs to low.

void setup() { 
	for (uint8_t pin=0; pin<20; ++pin) {
		pinMode(pin, OUTPUT);
		digitalWrite(pin, LOW);

void loop() { }

Now all LEDs will be dark. This seems somewhat boring.

Blinkenlight Prototype Off

It is worth while to notice that this is NOT the default behavior. It is also important to see that even LED 0 is off. The serial interface will still default to high. Due to the 1k resistor in between this is not sufficient to have any significant impact on the voltage of pin 0. But it has some impact on the current. Pin 0 is sinking about 5mA. It follows that if you want to reduce current consumption of the Arduino the serial interface should be disconnected or pin 0 should not be defaulted to low.

Simplified Arduino Schematics

Simplified Arduino Schematics

The next experiment will complete the basic experiments by setting all LEDs to high.


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