Every Arduino Mega 2560 pin with its capabilities (digital, PWM, ADC, I2C, SPI, UART) and the wiring gotchas that bite. The big UNO: 54 digital pins (15 PWM), 16 analog inputs and 4 hardware serial ports. For projects that simply run out of pins.
ATmega2560 @ 16 MHzLogic: 5 VPro in app
Arduino Mega 2560 pinout diagram
ICSP (2x3) on the far end; PWM on 2–13 and 44–46. Download SVG
Pin
Capabilities
Watch out
D0 (RX0)
DigitalUART RX
Shared with USB serial
D1 (TX0)
DigitalUART TX
Shared with USB serial
D2
DigitalPWMInterrupt
D3
DigitalPWMInterrupt
D4
DigitalPWM
D5
DigitalPWM
D6
DigitalPWM
D7
DigitalPWM
D8
DigitalPWM
D9
DigitalPWM
D10
DigitalPWM
D11
DigitalPWM
D12
DigitalPWM
D13
DigitalPWMBuilt-in LED
D14 (TX3)
DigitalUART3 TX
D15 (RX3)
DigitalUART3 RX
D16 (TX2)
DigitalUART2 TX
D17 (RX2)
DigitalUART2 RX
D18 (TX1)
DigitalUART1 TXInterrupt
D19 (RX1)
DigitalUART1 RXInterrupt
D20 (SDA)
DigitalI2C SDAInterrupt
D21 (SCL)
DigitalI2C SCLInterrupt
D22
Digital
D23
Digital
D24
Digital
D25
Digital
D26
Digital
D27
Digital
D28
Digital
D29
Digital
D30
Digital
D31
Digital
D32
Digital
D33
Digital
D34
Digital
D35
Digital
D36
Digital
D37
Digital
D38
Digital
D39
Digital
D40
Digital
D41
Digital
D42
Digital
D43
Digital
D44
DigitalPWM
D45
DigitalPWM
D46
DigitalPWM
D47
Digital
D48
Digital
D49
Digital
D50 (MISO)
DigitalSPI MISO
D51 (MOSI)
DigitalSPI MOSI
D52 (SCK)
DigitalSPI SCK
D53 (SS)
DigitalSPI SS
SS is convention, not hardwired — but keep D53 an OUTPUT whenever SPI is master, or the hardware drops into slave mode
A0
Analog inDigital
A1
Analog inDigital
A2
Analog inDigital
A3
Analog inDigital
A4
Analog inDigital
A5
Analog inDigital
A6
Analog inDigital
A7
Analog inDigital
A8
Analog inDigital
A9
Analog inDigital
A10
Analog inDigital
A11
Analog inDigital
A12
Analog inDigital
A13
Analog inDigital
A14
Analog inDigital
A15
Analog inDigital
AREF
Analog reference
Call analogReference(EXTERNAL) before feeding a voltage in, or it shorts against the internal reference
IOREF
Power out 5V
Logic-level reference for shields — output only, never feed power in
RESET
Reset
Active LOW — pull to GND to reset
5V
Power out 5V
3.3V
Power out 3.3V
Max ~50 mA
VIN
Power in 7–12V
GND
Ground
Arduino Mega 2560 gotchas & notes
I2C is on pin 20 (SDA) / 21 (SCL) — NOT A4/A5 like the UNO.
SPI is on 50 (MISO), 51 (MOSI), 52 (SCK), 53 (SS).
PWM on 2–13 and 44–46. Four UARTs: Serial, Serial1 (19/18), Serial2 (17/16), Serial3 (15/14).
External interrupts on 2, 3, 18, 19, 20, 21; pin-change interrupts (PCINT) only on 10–13, 50–53 and A8–A15.
ICSP header (2x3) at the far end: MISO, MOSI, SCK, RESET, 5V, GND — same SPI lines as 50–52. UNO shields that take SPI from ICSP work here unchanged.
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