Embedded hardware reference for engineers and makers

Arduino Pro Micro Pinout & Reference

24-pin interactive pinout

Arduino Pro Micro is an ATmega32U4 board for compact USB controllers. This model follows SparkFun v13 5V/16 MHz; compatible boards can use different connectors, regulators and bootloaders.

  • SparkFun / Open Source Hardware
  • Verified source
  • Updated Oct 2026

Interactive pinout diagramTop

  • GPIO
  • Power
  • Ground
  • Analog
  • Control

Tap a row of pins to see it up close

Arduino Pro Micro Pinout Vector DiagramInteractive vector pinout diagram of Arduino Pro Micro (top view) showing pin headers, power rails, components, and hardware interfaces.ATmega32U416MHz CST MIC5219Micro-B USBATmega32U4TXORXIGNDGND2~34~5~678~9RAWGNDRSTVCCA3A2A1A0151416~10

BOARD SUMMARY

ATmega32U4

Arduino Pro Micro

ATmega32U4

SparkFun / Open Source Hardware
MCU
ATmega32U4
CPU core
8-bit AVR RISC
Clock speed
16 MHz
SRAM
2.5 KB
Flash
32 KB
GPIO count
18
Logic voltage
5.0 V
Form factor
24-pin, Native USB 2.0 Full-Speed (ATmega32U4)

Before you wire

5 V logic — level-shift 3.3 V peripherals

  • GPIO uses 5V levels and internal 20–50 kΩ pull-ups. External interrupts: D0,D1,D2,D3,D7. Check level compatibility before connecting 3.3V peripherals.
  • SparkFun recommends RAW above 6V and no more than 12V for the 5V board. The 16V regulator maximum in older diagrams is not a recommended board input. Check LDO heating and load.
  • SparkFun Caterina: short RST to GND twice quickly for an 8-second upload window. Select the correct 5V/16 MHz or 3.3V/8 MHz target; other bootloaders can behave differently.

QUICK LINKS

Pin table

Showing 24 of 24 pins
Arduino Pro Micro pin table: physical pin, name, GPIO, functions, ADC, touch, default role, flags
PinNameGPIOFunctionsADCDefault roleFlags
left:1 leftTXOGPIO1
gpiouart
—GPIO
left:2 leftRXIGPIO0
gpiouart
—GPIO
left:3 leftGND—
gnd
—Ground
left:4 leftGND—
gnd
—Ground
left:5 left2GPIO2
gpioi2c
—GPIO
left:6 left~3GPIO3
gpioi2cpwm
—GPIO
left:7 left4GPIO4
gpioadc
ADC_CH8GPIO
left:8 left~5GPIO5
gpiopwm
—GPIO
left:9 left~6GPIO6
gpiopwmadc
ADC_CH10GPIO
left:10 left7GPIO7
gpio
—GPIO
left:11 left8GPIO8
gpioadc
ADC_CH11GPIO
left:12 left~9GPIO9
gpiopwmadc
ADC_CH12GPIO
right:1 rightRAW—
power
—7 - 12 V PowerAlways-on power rail
right:2 rightGND—
gnd
—Ground
right:3 rightRST—
reset
—Reset / Enable
right:4 rightVCC—
power
—5.0 V PowerAlways-on power rail
right:5 rightA3GPIO21
gpioadc
ADC_CH4GPIO
right:6 rightA2GPIO20
gpioadc
ADC_CH5GPIO
right:7 rightA1GPIO19
gpioadc
ADC_CH6GPIO
right:8 rightA0GPIO18
gpioadc
ADC_CH7GPIO
right:9 right15GPIO15
gpiospi
—GPIO
right:10 right14GPIO14
gpiospi
—GPIO
right:11 right16GPIO16
gpiospi
—GPIO
right:12 right~10GPIO10
gpiopwmadc
ADC_CH13GPIO

Grounded reference

Board overview

Arduino Pro Micro is an ATmega32U4 board for compact USB controllers. This model follows SparkFun v13 5V/16 MHz; compatible boards can use different connectors, regulators and bootloaders.

Canonical CAD Blueprint

Reference model: SparkFun Pro Micro DEV-12640, Eagle v13, 5V/16 MHz.24 source contacts, top SJ1 and mirrored underside. Shell/body landmarks follow CAD; fine surface details are schematic styling. Verify each clone separately.

Power inputs

  • Micro-B supplies USB data and power. Closed SJ1 directly ties USB UVCC to VCC; the fuse/diode path feeds RAW. Do not assume the fuse protects every VCC path.
  • SparkFun recommends RAW above 6V and no more than 12V for the 5V board. The 16V regulator maximum in older diagrams is not a recommended board input. Check LDO heating and load.
  • VCC is the 5V system rail and can accept a regulated 5V supply. It bypasses the LDO; prevent independent supplies and USB from feeding one another.

Hardware Variants, Clones & Traps

  • 5V/16 MHz and 3.3V/8 MHz require matching supply, oscillator and firmware targets; the reference uses MIC5219 and native ATmega32U4 USB.
  • USB-C derivatives can change the connector, protection circuit and pin labeling. Compare their own schematic; pin compatibility is not assumed.
  • For USB-C derivatives, verify CC1/CC2 configuration against their schematic. A cable-dependent power fault is not proof that every clone omits resistors.
  • Support the Micro-B connector and avoid sideways cable force. Mechanical retention varies with the connector and PCB revision.
  • SparkFun Caterina: short RST to GND twice quickly for an 8-second upload window. Select the correct 5V/16 MHz or 3.3V/8 MHz target; other bootloaders can behave differently.

Common use cases

  • USB keyboards and macro pads, including supported QMK targets.
  • USB gamepads and custom control panels.
  • USB sensor interfaces and compact data loggers.

Notes

  • GPIO uses 5V levels and internal 20–50 kΩ pull-ups. External interrupts: D0,D1,D2,D3,D7. Check level compatibility before connecting 3.3V peripherals.
  • Serial is native USB; Serial 1 uses RXI/D0 and TXO/D1. I2C: D2/SDA,D3/SCL. SPI: D15/SCK,D14/MISO,D16/MOSI. SS/D17 drives the onboard RX LED and is not a header contact.
  • 20 mA GPIO guidance;40 mA absolute per pin,200 mA aggregate and port limits. MIC5219 and fuse ratings are not guaranteed spare current for peripherals.

Before you wire

  • GPIO uses 5V levels and internal 20–50 kΩ pull-ups. External interrupts: D0,D1,D2,D3,D7. Check level compatibility before connecting 3.3V peripherals.
  • SparkFun recommends RAW above 6V and no more than 12V for the 5V board. The 16V regulator maximum in older diagrams is not a recommended board input. Check LDO heating and load.
  • SparkFun Caterina: short RST to GND twice quickly for an 8-second upload window. Select the correct 5V/16 MHz or 3.3V/8 MHz target; other bootloaders can behave differently.

Specifications

MCU
ATmega32U4
CPU core
8-bit AVR RISC
Clock
16 MHz
SRAM
2.5 KB
Flash
0.03125 MB
GPIO count
18
Logic voltage
5.0 V
Operating voltage (VIN)
USB/VCC 5 V; RAW >6–12 V (SparkFun guidance)

Pin usage guide

Safe GPIO pins

5V logic. GPIO guidance: at most 20 mA per pin;40 mA per I/O and 200 mA through VCC/GND are absolute ratings, not operating loads. Port-group limits also apply.

ADC and analog pins

Nine ADC inputs: A0–A3 and D4/D6/D8/D9/D10. Arduino analog aliases differ from silicon channels: D6/A7 is ADC10, not ADC9.

I2C, SPI and UART pins

Serial is native USB; Serial 1 uses RXI/D0 and TXO/D1. I2C: D2/SDA,D3/SCL. SPI: D15/SCK,D14/MISO,D16/MOSI. SS/D17 drives the onboard RX LED and is not a header contact.

Strapping and boot pins

Top-side SJ1 is closed on the 5V board and connects USB UVCC to VCC, bypassing regulation. It is not a switch that converts a 16 MHz board into the 3.3V/8 MHz variant.

Input-only pins

GPIO uses 5V levels and internal 20–50 kΩ pull-ups. External interrupts: D0,D1,D2,D3,D7. Check level compatibility before connecting 3.3V peripherals.

Related board pinouts

Compare Arduino boards

Frequently asked questions

Short answers to the questions people ask about this board, each checked against the manufacturer or project documents linked under it.

Which Pro Micro pins support analog input?

A0–A3 and D4,D6,D8,D9,D10 provide nine inputs. Their physical ADC channels are 7,6,5,4,8,10,11,12,13 respectively. In particular, Arduino A7/D6 maps to ADC10; analog aliases are not silicon channel numbers.

Sources:

How can I recover Pro Micro USB uploading?

For the SparkFun Caterina bootloader, briefly connect RST to GND twice to open an 8-second upload window. Select the matching voltage/clock target and bootloader port. If the bootloader itself is lost, use ISP; other bootloader variants have different procedures.

Sources:

Can I power a 5V Pro Micro from RAW or VCC?

SparkFun recommends RAW above 6V and at most 12V, subject to regulator heating and load. VCC needs a regulated 5V supply and bypasses regulation. Closed SJ1 ties USB UVCC to VCC, so prevent separate supplies from feeding one another. The old 16V regulator maximum and 500 mA component rating are not guaranteed board operating conditions.

Sources:

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