Arduino Micro Board Pins

Source: Arduino.cc

The Micro and Leonardo boards share the same ATmega32U4 microprocessor and the same board architecture, so this write-up applies equally to both boards.

Starting work with the Arduino I quickly ran into trouble understanding the board pins, particularly in terms of how to work with them within the sketches. First, the board itself has a very tiny silkscreen name by each pin. If you were to, like I did, try to use those pin names in a function call, such as pinMode(D2, INPUT), the sketch will not compile. In the picture to the right, the integers and alias names in red provide the alias or integer to use in your code. From this, the earlier code fragment above would be pinMode(2, INPUT)0 or pinMode(SDA, INPUT).

Before I made the connections in my mind from the data in the board image here, I spent some time poking into the board-specific header files in the Arduino installation. The Leonard board header, which is called by the Micro board header is at Arduino\hardware\arduino\avr\variants\leonardo\pins_arduino.h. Where there are two integers or aliases seperated by a slash (/), the first is the digital reference and the second is the analog reference.

Board Name	PORT	PIN	Alternate Names/Functions	Integer	Alias
MOSI	B	2	D16, PB2, MOSI, PCINT2	16	MOSI
SS	B	0	D17, PB0, RXLED, SS, PCINT0	17	SS
TX	D	3	D1, PD3, TXD1, INT3	1	TX
RX	D	2	D0, PD2, RXD1, INT2	0	RX
D2	D	1	PD1, SDA , INT1	2	SDA
D3	D	0	PD0, PWM8, SCL, OC0B, INT0	3	SCL
D4	D	4	A6, PD4, ADC8	4/24	4/A6
D5	C	6	PC6, OC3A, OC4A	5
D6	D	7	A7, PD7, FastPWM, OC4D, ADC10	6/25	6/A7
D7	E	6	PE6, INT6, AIN0	7
D8	B	4	A8, PB4, ADC11, PCINT4	8/26	8/A8
D9	B	5	A9, PB5, PWM16, OC1A, OC4B, ADC12, PCINT5	9/27	9/A9
D10	B	6	A10, PB6, PWM16, OC1B, 0C4B, ADC13, PCINT6	10/28	10/A10
D11	B	7	PB7, PWM8/16, 0C0A, OC1C, RTS, PCINT7	11
D12	D	6	A11, PD6, T1, OC4D, ADC9	12/29	11/A11
D13	C	7	PC7, PWM10, CLK0, OC4A	13
A0	F	7	D18, PF7, ADC7	18
A1	F	6	D19, PF6, ADC6	19
A2	F	5	D20, PF5, ADC5	20
A3	F	4	D21, PF4, ADC4	21
A4	F	1	D22, PF1, ADC1	22
A5	F	0	D23, PF0, ADC0	23
MISO	B	3	D14, PB3, MISO, PCINT3	14	MISO
SCK	B	1	D15, PB1, SCK, PCINT1	15	SCK

It took a frustratingly long time to figure that out. Also frustrating is that not all of the I/O pins have an alias. I've hacked together a short header file that can be used to give the pins relevant alias that match both the silk screened pin names on the board and the alternate functions I've dug out of the pins_arduino.h header file for the Leonardo boards.

/* pins_micro.h - Pin definition macros for the Arduino Micro board Copyright (c) 2014 Christopher Horner This file is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation; either version 2.1 of the License, or (at your option) any later version. This library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details. You should have received a copy of the GNU Lesser General Public License along with this library; if not, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA */ // Define digital pins #define D0 2 #define D1 3 #define D2 2 #define D3 3 #define D4 4 #define D5 5 #define D6 6 #define D7 7 #define D8 8 #define D9 9 #define D10 10 #define D11 11 #define D12 12 #define D13 13 #define D14 14 #define D15 15 #define D16 16 #define D17 17 #define D18 18 #define D19 19 #define D20 20 #define D21 21 #define D22 22 #define D23 23 // Define interrupt pins #define PCINT0 17 #define PCINT1 15 #define PCINT2 16 #define PCINT3 14 #define PCINT4 26 #define PCINT5 27 #define PCINT6 28 #define PCINT7 11 #define INT0 3 #define INT1 2 #define INT2 0 #define INT3 1 #define INT6 7 /* TODO: add ADC, PWM, and maybe the PORTxn (where x == I/O port and n == bit on port) pin references. */