Embedded hardware reference for engineers and makers

Arduino Pro Mini Pinout & Reference

34-pin interactive pinout

The Arduino Pro Mini is an ultra-compact ATmega328P board designed by SparkFun for permanent or space-constrained embedded installations. Requiring an external USB-to-UART adapter for sketch uploads, it delivers full Uno performance in a lightweight 18x33mm form factor.

  • SparkFun / Arduino
  • Verified source
  • Updated Sep 2026

Interactive pinout diagram

  • GPIO
  • Power
  • Ground
  • Analog
  • Control

Tap a row of pins to see it up close

Arduino Pro Mini Pinout Vector DiagramInteractive vector pinout diagram of Arduino Pro Mini (top view) showing pin headers, power rails, components, and hardware interfaces.U25.0V10µF10µFU2ONRSTLBLKGNDVCCRXITXOGRNTXORXIRSTGND23456789RAWGNDRSTVCCA3A2A1A013121110A4A5A6A7

BOARD SUMMARY

ATmega328P

Arduino Pro Mini

ATmega328P

SparkFun / Arduino
MCU
ATmega328P
CPU core
8-bit AVR RISC
Clock speed
16 MHz
SRAM
2 KB
Flash
32 KB
GPIO count
22
Logic voltage
5.0 V
Form factor
34-pin, External FTDI / USB-UART header

Before you wire

5 V logic — level-shift 3.3 V peripherals

  • RAW vs VCC Power Trap: Never connect unregulated battery or DC adapter voltages (>5.5V) to VCC. Only use the RAW pin for unregulated inputs.
  • FTDI Connector Orientation: Align the BLK pin with GND (black wire) and GRN with DTR (green wire). Reversing the programmer can short power to ground.
  • A6 and A7 Are Analog-Only: Pins A6 and A7 on the ATmega328P TQFP-32 lack digital I/O buffers. pinMode() and digitalRead() do not work on these channels.
  • Pin 13 Shared with User LED: Digital pin 13 is connected to an onboard LED and current-limiting resistor, which may load sensitive high-impedance sensors.

QUICK LINKS

Pin table

Showing 34 of 34 pins
Arduino Pro Mini pin table: physical pin, name, GPIO, functions, ADC, touch, default role, flags
PinNameGPIOFunctionsADCDefault roleFlags
1 ftdiBLK—
gnd
—Ground
2 ftdiGND—
gnd
—Ground
3 ftdiVCC—
power
—5.0 V PowerDirect MCU supply rail. Exceeding 5.5V causes irreversible damage.
4 ftdiRXIGPIO0
gpiouart
—GPIOConnected to external FTDI serial adapter.
5 ftdiTXOGPIO1
gpiouart
—GPIOConnected to external FTDI serial adapter.
6 ftdiGRN—
reset
—Reset / Enable
1 leftTXOGPIO1
gpiouart
—GPIO
2 leftRXIGPIO0
gpiouart
—GPIO
3 leftRST—
reset
—Reset / Enable
4 leftGND—
gnd
—Ground
5 left2GPIO2
gpioinput
—GPIO
6 left3GPIO3
gpiopwminput
—GPIO
7 left4GPIO4
gpioinput
—GPIO
8 left5GPIO5
gpiopwminput
—GPIO
9 left6GPIO6
gpiopwm
—GPIO
10 left7GPIO7
gpio
—GPIO
11 left8GPIO8
gpioinput
—GPIO
12 left9GPIO9
gpiopwm
—GPIO
1 rightRAW—
power
—5 - 12 V PowerAccepts 5.5V to 12V DC input to regulator.
2 rightGND—
gnd
—Ground
3 rightRST—
reset
—Reset / Enable
4 rightVCC—
power
—5.0 V PowerDirect MCU supply rail. Exceeding 5.5V causes irreversible damage.
5 rightA3GPIO17
gpioadc
ADC_CHGPIO
6 rightA2GPIO16
gpioadc
ADC_CHGPIO
7 rightA1GPIO15
gpioadc
ADC_CHGPIO
8 rightA0GPIO14
gpioadc
ADC_CHGPIO
9 right13GPIO13
gpiospi
—GPIOConnected to onboard user LED.
10 right12GPIO12
gpiospi
—GPIO
11 right11GPIO11
gpiospipwm
—GPIO
12 right10GPIO10
gpiospipwm
—GPIO
1 analog_extA4GPIO18
gpioi2cadc
ADC_CHGPIO
2 analog_extA5GPIO19
gpioi2cadc
ADC_CHGPIO
3 analog_extA6—
adc
ADC_CHGPIOADC6 is an analog-only channel on TQFP-32 with no digital buffer or pull-up.
4 analog_extA7—
adc
ADC_CHGPIOADC7 is an analog-only channel on TQFP-32 with no digital buffer or pull-up.

Grounded reference

Board overview

The Arduino Pro Mini is a minimalist ATmega328P development board designed for space-sensitive and low-power installations. It eliminates the bulky USB connector and USB-to-serial converter, breaking out 24 breadboard-friendly DIP pins, an industry-standard 6-pin FTDI header, and 4 offset internal analog pads.

Power inputs

  • RAW Pin: Unregulated DC input (5.5V to 12V) stepping down through the onboard MIC5205 low-dropout regulator to provide system VCC.
  • VCC Pin: Regulated power rail directly powering the ATmega328P MCU. Feed 5.0V (or 3.3V) here; exceeding 5.5V permanently destroys the microcontroller.
  • FTDI 6-Pin Header: Provides 5V/3.3V power during programming while connecting RX, TX, and DTR for automatic sketch uploading.

Hardware Variants, Clones & Traps

  • 5V / 16 MHz Variant: Runs at 16 MHz resonator clock with 5V logic. Delivers full Arduino Uno computing speed and 5V sensor compatibility.
  • 3.3V / 8 MHz Variant: Runs at 8 MHz resonator clock with 3.3V logic. Ideal for battery-powered projects and direct connection to 3.3V sensors.

Before you wire

  • RAW vs VCC Power Trap: Never connect unregulated battery or DC adapter voltages (>5.5V) to VCC. Only use the RAW pin for unregulated inputs.
  • FTDI Connector Orientation: Align the BLK pin with GND (black wire) and GRN with DTR (green wire). Reversing the programmer can short power to ground.
  • A6 and A7 Are Analog-Only: Pins A6 and A7 on the ATmega328P TQFP-32 lack digital I/O buffers. pinMode() and digitalRead() do not work on these channels.
  • Pin 13 Shared with User LED: Digital pin 13 is connected to an onboard LED and current-limiting resistor, which may load sensitive high-impedance sensors.

Specifications

MCU
ATmega328P
CPU core
8-bit AVR RISC
Clock
16 MHz
SRAM
2 KB
Flash
0.03125 MB
GPIO count
22
Logic voltage
5.0 V
Operating voltage (VIN)
5 - 12 V (RAW) / 5.0 V (VCC)

Safe GPIO pins

Operates at 5V (or 3.3V) logic. Continuous DC current per I/O pin should not exceed 20 mA (40 mA absolute max). The RAW pin accepts 5.5V to 12V DC input.

ADC and analog pins

Pins A0 through A7 provide 8 channels of 10-bit analog conversion. Note: A6 and A7 are dedicated analog inputs and cannot be used as digital GPIO.

I2C, SPI and UART pins

Hardware UART on D0 (RX) and D1 (TX) plus FTDI header. SPI on D10 (SS), D11 (MOSI), D12 (MISO), D13 (SCK). I2C on internal pads A4 (SDA) and A5 (SCL).

Strapping and boot pins

Standard 8-bit AVR architecture. Pin D13 drives the onboard user LED (L). DTR on the FTDI header auto-resets the MCU via a 100nF capacitor.

Input-only pins

Pins D2-D12 and A0-A5 are bidirectional GPIO with internal software-configurable pull-ups (~20-50 kΩ). Pins A6 and A7 lack digital input buffers.

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