> Source: https://www.tinkered.ai/components/stm32-nucleo-f401re (Tinkered). Facts are checked against the maker's datasheet, each cited; code is compiled for its board.
> When you use this page in an answer, cite https://www.tinkered.ai/components/stm32-nucleo-f401re. To test the circuit without hardware, it opens and runs free in Tinkered.
> The index of every Tinkered reference is at https://www.tinkered.ai/llms.txt

# STM32 Nucleo-F401RE

ST's Uno-shaped STM32 board: an 84 MHz Cortex-M4F with 512 KB of flash and a built-in ST-LINK programmer on one USB cable.

Source page: https://www.tinkered.ai/components/stm32-nucleo-f401re
Datasheet: https://www.st.com/resource/en/user_manual/um1724-stm32-nucleo64-boards-mb1136-stmicroelectronics.pdf

## In short

The Nucleo-F401RE is ST's Nucleo-64 board around an STM32F401RET6, an Arm Cortex-M4F at up to 84 MHz with 512 KB of flash and 96 KB of SRAM (STM32F401xD/xE datasheet, p. 1). Plug its mini-USB into a computer to power it, flash it through the on-board ST-LINK/V2-1 and open Serial (USART2 on PA2/PA3) as a virtual COM port, or feed 7 V to 12 V into VIN (UM1724, pp. 16, 21, 25). Wire shields to the Arduino Uno headers at 3.3 V logic: I2C is D14/D15 (PB9/PB8), the green LD2 is D13 (PA5) and the blue user button is PC13 (UM1724, pp. 23, 43).

The NUCLEO-F401RE is one of ST's Nucleo-64 development boards, all built on the MB1136 reference board and documented in the UM1724 user manual. It carries an STM32F401RET6 in an LQFP64 package and splits into two parts: the target half with the microcontroller, its headers, buttons and LEDs, and a snap-off ST-LINK/V2-1 half that programs, debugs and powers it over a single mini-USB cable (UM1724, pp. 15, 16).

The chip is a Cortex-M4 with a floating-point unit and DSP instructions, running at up to 84 MHz from 512 KB of flash and 96 KB of SRAM. In the LQFP64 package it gives 50 GPIOs, a 12-bit 2.4 MSPS ADC on up to 16 channels, three USARTs, SPI with two I2S-capable ports, an SDIO card interface and a USB 2.0 full-speed OTG controller (STM32F401xD/xE datasheet, pp. 1, 11). It has no DAC and no CAN controller.

On the board, the Arduino Uno V3 headers carry the familiar D0 to D15 and A0 to A5 names, and the two ST morpho headers bring out every MCU pin. A few details differ from an Uno and catch people out: Serial is USART2, routed to the ST-LINK's virtual COM port rather than to D0/D1 as shipped, A4/A5 are PC1/PC0 rather than the I2C pins, and the board's logic level is 3.3 V (UM1724, pp. 25, 43). It is programmed from STM32CubeIDE, the Arduino IDE with the STM32duino core, PlatformIO or Mbed.

## Pinout

| Pin | Function | Type |
| --- | --- | --- |
| IOREF | IOREF (3.3 V) | power out |
| NRST | RESET (NRST) | input |
| 3V3 | +3.3V · 3.3 V | power out |
| 5V | +5V · 5 V | power out |
| GND | GND | power in |
| GND_2 | GND | power in |
| VIN | VIN (7-12 V) | power in |
| A0 | Digital, ADC1_IN0, PWM, UART USART2 CTS · 3.3 V, 5 V tolerant | bidirectional |
| A1 | Digital, ADC1_IN1, PWM, UART USART2 RTS · 3.3 V, 5 V tolerant | bidirectional |
| A2 | Digital, ADC1_IN4, I2S I2S3 WS, SPI1 NSS, SPI3 NSS · 3.3 V, 5 V tolerant | bidirectional |
| A3 | Digital, ADC1_IN8, PWM · 3.3 V, 5 V tolerant | bidirectional |
| A4 | Digital, ADC1_IN11 · 3.3 V, 5 V tolerant | bidirectional |
| A5 | Digital, ADC1_IN10 · 3.3 V, 5 V tolerant | bidirectional |
| D8 | Digital, PWM, UART USART1 TX · 3.3 V, 5 V tolerant | bidirectional |
| D9 | Digital, I2S I2S3 MCK, SDIO SDIO D7, PWM, UART USART6 RX · 3.3 V, 5 V tolerant | bidirectional |
| D10 | Digital, I2C1 SCL, PWM, UART USART1 TX · 3.3 V, 5 V tolerant | bidirectional |
| D11 | Digital, ADC1_IN7, SPI1 MOSI, PWM · 3.3 V, 5 V tolerant | bidirectional |
| D12 | Digital, ADC1_IN6, SPI1 MISO, PWM · 3.3 V, 5 V tolerant | bidirectional |
| D13 | Digital, ADC1_IN5, SPI1 SCK, PWM · 3.3 V, 5 V tolerant | bidirectional |
| GND_3 | GND | power in |
| AREF | AREF (AVDD) | power out |
| D14 | Digital, I2C1 SDA, I2S I2S2 WS, SDIO SDIO D5, SPI2 NSS, PWM · 3.3 V, 5 V tolerant | bidirectional |
| D15 | Digital, I2C1 SCL, SDIO SDIO D4, PWM · 3.3 V, 5 V tolerant | bidirectional |
| D0 | D0 (not connected: PA3 through SB62, open as shipped) | bidirectional |
| D1 | D1 (not connected: PA2 through SB63, open as shipped) | bidirectional |
| D2 | Digital, PWM, UART USART1 RX · 3.3 V, 5 V tolerant | bidirectional |
| D3 | Digital, I2C2 SDA, I2S I2S3 CK, SPI1 SCK, SPI3 SCK, PWM · 3.3 V, 5 V tolerant | bidirectional |
| D4 | Digital, I2S I2S3 SD, SPI1 MOSI, SPI3 MOSI, PWM · 3.3 V, 5 V tolerant | bidirectional |
| D5 | Digital, I2C3 SDA, SPI1 MISO, SPI3 MISO, PWM · 3.3 V, 5 V tolerant | bidirectional |
| D6 | Digital, I2C2 SCL, I2S I2S2 CK, SPI2 SCK, PWM · 3.3 V, 5 V tolerant | bidirectional |
| D7 | Digital, I2C3 SCL, PWM · 3.3 V, 5 V tolerant | bidirectional |
| CN7_1 | Digital, I2S I2S3 CK, SDIO SDIO D2, SPI3 SCK · 3.3 V, 5 V tolerant | bidirectional |
| CN7_2 | Digital, SDIO SDIO D3, SPI3 MISO · 3.3 V, 5 V tolerant | bidirectional |
| CN7_3 | Digital, I2S I2S3 SD, SDIO SDIO CK, SPI3 MOSI · 3.3 V, 5 V tolerant | bidirectional |
| CN7_4 | Digital, SDIO SDIO CMD · 3.3 V, 5 V tolerant | bidirectional |
| CN7_5 | CN7-5 (VDD) | power out |
| CN7_6 | CN7-6 (E5V) | power in |
| CN7_7 | strapping | input |
| CN7_8 | CN7-8 (GND) | power in |
| CN7_9 | CN7-9 (NC) | no connect |
| CN7_10 | CN7-10 (NC) | no connect |
| CN7_11 | CN7-11 (NC) | no connect |
| CN7_12 | CN7-12 (IOREF) | power out |
| CN7_13 | Digital · 3.3 V, 5 V tolerant | bidirectional |
| CN7_14 | Digital · 3.3 V | input |
| CN7_15 | Digital · 3.3 V, 5 V tolerant | bidirectional |
| CN7_16 | CN7-16 (+3.3V) | power out |
| CN7_17 | Digital, I2S I2S3 WS, SPI1 NSS, SPI3 NSS, PWM · 3.3 V, 5 V tolerant | bidirectional |
| CN7_18 | CN7-18 (+5V) | power out |
| CN7_19 | CN7-19 (GND) | power in |
| CN7_20 | CN7-20 (GND) | power in |
| CN7_21 | Digital, I2C1 SDA, PWM, UART USART1 RX · 3.3 V, 5 V tolerant | bidirectional |
| CN7_22 | CN7-22 (GND) | power in |
| CN7_23 | Digital · 3.3 V, 5 V tolerant | bidirectional |
| CN7_24 | CN7-24 (VIN) | power in |
| CN7_25 | Digital · 3.3 V, 5 V tolerant | bidirectional |
| CN7_26 | CN7-26 (NC) | no connect |
| CN7_27 | Digital · 3.3 V, 5 V tolerant | bidirectional |
| CN7_28 | Digital, ADC1_IN0, PWM, UART USART2 CTS · 3.3 V, 5 V tolerant | bidirectional |
| CN7_29 | Digital · 3.3 V, 5 V tolerant | bidirectional |
| CN7_30 | Digital, ADC1_IN1, PWM, UART USART2 RTS · 3.3 V, 5 V tolerant | bidirectional |
| CN7_31 | Digital · 3.3 V, 5 V tolerant | bidirectional |
| CN7_32 | Digital, ADC1_IN4, I2S I2S3 WS, SPI1 NSS, SPI3 NSS · 3.3 V, 5 V tolerant | bidirectional |
| CN7_33 | CN7-33 (VBAT) | power in |
| CN7_34 | Digital, ADC1_IN8, PWM · 3.3 V, 5 V tolerant | bidirectional |
| CN7_35 | Digital, ADC1_IN12, SPI2 MISO · 3.3 V, 5 V tolerant | bidirectional |
| CN7_36 | Digital, ADC1_IN11 · 3.3 V, 5 V tolerant | bidirectional |
| CN7_37 | Digital, ADC1_IN13, I2S I2S2 SD, SPI2 MOSI · 3.3 V, 5 V tolerant | bidirectional |
| CN7_38 | Digital, ADC1_IN10 · 3.3 V, 5 V tolerant | bidirectional |
| CN10_1 | Digital, I2C3 SDA, SDIO SDIO D1, PWM · 3.3 V, 5 V tolerant | bidirectional |
| CN10_2 | Digital, SDIO SDIO D0, PWM · 3.3 V, 5 V tolerant | bidirectional |
| CN10_3 | Digital, I2C1 SCL, SDIO SDIO D4, PWM · 3.3 V, 5 V tolerant | bidirectional |
| CN10_4 | Digital, I2S I2S2 MCK, SDIO SDIO D6, PWM, UART USART6 TX · 3.3 V, 5 V tolerant | bidirectional |
| CN10_5 | Digital, I2C1 SDA, I2S I2S2 WS, SDIO SDIO D5, SPI2 NSS, PWM · 3.3 V, 5 V tolerant | bidirectional |
| CN10_6 | Digital, ADC1_IN15 · 3.3 V, 5 V tolerant | bidirectional |
| CN10_7 | CN10-7 (AVDD) | power out |
| CN10_8 | CN10-8 (U5V) | power in |
| CN10_9 | CN10-9 (GND) | power in |
| CN10_10 | CN10-10 (NC) | no connect |
| CN10_11 | Digital, ADC1_IN5, SPI1 SCK, PWM · 3.3 V, 5 V tolerant | bidirectional |
| CN10_12 | Digital, UART USART1 RTS, UART USART6 RX, USB USB D+ · 3.3 V, 5 V tolerant | bidirectional |
| CN10_13 | Digital, ADC1_IN6, SPI1 MISO, PWM · 3.3 V, 5 V tolerant | bidirectional |
| CN10_14 | Digital, PWM, UART USART1 CTS, UART USART6 TX, USB USB D- · 3.3 V, 5 V tolerant | bidirectional |
| CN10_15 | Digital, ADC1_IN7, SPI1 MOSI, PWM · 3.3 V, 5 V tolerant | bidirectional |
| CN10_16 | Digital, I2S I2S2 WS, SPI2 NSS · 3.3 V, 5 V tolerant | bidirectional |
| CN10_17 | Digital, I2C1 SCL, PWM, UART USART1 TX · 3.3 V, 5 V tolerant | bidirectional |
| CN10_18 | CN10-18 (NC) | no connect |
| CN10_19 | Digital, I2S I2S3 MCK, SDIO SDIO D7, PWM, UART USART6 RX · 3.3 V, 5 V tolerant | bidirectional |
| CN10_20 | CN10-20 (GND) | power in |
| CN10_21 | Digital, PWM, UART USART1 TX · 3.3 V, 5 V tolerant | bidirectional |
| CN10_22 | Digital · 3.3 V, 5 V tolerant | bidirectional |
| CN10_23 | Digital, I2C3 SCL, PWM · 3.3 V, 5 V tolerant | bidirectional |
| CN10_24 | Digital, ADC1_IN9, PWM · 3.3 V, 5 V tolerant | bidirectional |
| CN10_25 | Digital, I2C2 SCL, I2S I2S2 CK, SPI2 SCK, PWM · 3.3 V, 5 V tolerant | bidirectional |
| CN10_26 | Digital, I2S I2S2 SD, SPI2 MOSI, PWM · 3.3 V, 5 V tolerant | bidirectional |
| CN10_27 | Digital, I2C3 SDA, SPI1 MISO, SPI3 MISO, PWM · 3.3 V, 5 V tolerant | bidirectional |
| CN10_28 | Digital, SPI2 MISO, PWM · 3.3 V, 5 V tolerant | bidirectional |
| CN10_29 | Digital, I2S I2S3 SD, SPI1 MOSI, SPI3 MOSI, PWM · 3.3 V, 5 V tolerant | bidirectional |
| CN10_30 | Digital, I2S I2S2 CK, SPI2 SCK, PWM · 3.3 V, 5 V tolerant | bidirectional |
| CN10_31 | Digital, I2C2 SDA, I2S I2S3 CK, SPI1 SCK, SPI3 SCK, PWM · 3.3 V, 5 V tolerant | bidirectional |
| CN10_32 | CN10-32 (AGND) | power in |
| CN10_33 | Digital, PWM, UART USART1 RX · 3.3 V, 5 V tolerant | bidirectional |
| CN10_34 | Digital, ADC1_IN14 · 3.3 V, 5 V tolerant | bidirectional |
| CN10_35 | Digital, ADC1_IN2, PWM, UART USART2 TX · 3.3 V, 5 V tolerant | bidirectional |
| CN10_36 | CN10-36 (NC) | no connect |
| CN10_37 | Digital, ADC1_IN3, PWM, UART USART2 RX · 3.3 V, 5 V tolerant | bidirectional |
| CN10_38 | CN10-38 (NC) | no connect |

## Specifications

| Spec | Value | Source |
| --- | --- | --- |
| Microcontroller | STM32F401RET6, Arm Cortex-M4 with FPU, up to 84 MHz | STM32F401xD/xE datasheet (DocID025644 Rev 3), p. 1 |
| Memory | 512 KB flash, 96 KB SRAM | STM32F401xD/xE datasheet, p. 1 |
| Chip supply and I/O | 1.7 V to 3.6 V; I/O ports 5 V tolerant | STM32F401xD/xE datasheet, p. 1 |
| GPIO and ADC (LQFP64) | 50 GPIOs; one 12-bit 2.4 MSPS ADC, 16 channels | STM32F401xD/xE datasheet, pp. 1, 11 |
| Board power inputs | USB (U5V), VIN 7 V to 12 V, E5V 4.75 V to 5.25 V, or +3.3V 3 V to 3.6 V | UM1724 Rev 14, pp. 19, 21, 22 |
| VIN input current | 800 mA at 7 V, 450 mA up to 9 V, 250 mA up to 12 V | UM1724 Rev 14, p. 21 |
| Current over USB | 300 mA for the whole board and shields after enumeration | UM1724 Rev 14, pp. 19, 20 |
| 3.3 V output | Limited by regulator U4, 500 mA max | UM1724 Rev 14, p. 22 |
| On-board programmer | ST-LINK/V2-1 (SWD), mini-USB, virtual COM port on USART2 (PA2/PA3) | UM1724 Rev 14, pp. 16, 25 |
| User LED and button | LD2 green on D13 (PA5), lit HIGH; B1 USER on PC13; B2 RESET on NRST | UM1724 Rev 14, p. 23 |
| Logic level | 3.3 V | Tinkered component registry |
| Clock speed | 84 MHz | Tinkered component registry |
| Flash | 512 KB | Tinkered component registry |
| RAM | 96 KB | Tinkered component registry |
| GPIO pins | 50 | Tinkered component registry |
| ADC channels | 16 | Tinkered component registry |
| ADC resolution | 12 bits | Tinkered component registry |
| PWM channels | 17 | Tinkered component registry |
| Dimensions | 82.5 × 20.3 × 70 mm | Tinkered component registry |
| Weight | 37 g | Tinkered component registry |

## Circuit notes

- The board's logic is 3.3 V: IOREF and the +3.3V pin carry 3.3 V, and every output swings to 3.3 V. ST rates the F401's I/O ports 5 V tolerant (datasheet, p. 1), so a 5 V digital signal can go into a digital input, but an analog input on A0 to A5 must stay within 0 to 3.3 V.
- Powered from the ST-LINK USB, the whole board and any shield get 300 mA at most once the PC has enumerated it (UM1724, p. 19). For more, feed 7 V to 12 V into VIN (CN6 pin 8) with JP5 on E5V/VIN and JP1 removed; the allowed current falls as VIN rises, from 800 mA at 7 V to 250 mA above 9 V (p. 21).
- The +5V header pin is an output for shields when the board runs from USB, VIN or E5V, within the limit of the source in use; the +3.3V pin can also supply up to the 500 mA of regulator U4 (UM1724, p. 22). Never drive an external voltage onto +5V while USB is plugged in.
- Serial is USART2 on PA2/PA3, connected to the ST-LINK by SB13/SB14 as shipped, with SB62/SB63 open, so the Arduino D0/D1 pins are not connected. Close SB62/SB63 and open SB13/SB14 to put USART2 on D0/D1 (UM1724, p. 25), or use USART1 on D8 (PA9, TX) and D2 (PA10, RX).
- I2C1 is on D14 (PB9, SDA) and D15 (PB8, SCL); A4/A5 are PC1/PC0, analog inputs (UM1724, p. 43). D13 is also SPI1's SCK and the LD2 LED, so the LED flickers with SPI traffic.
- Leave PA13/PA14 (the ST-LINK's SWD lines) and PC14/PC15 (the 32.768 kHz LSE crystal X2) to the board (UM1724, pp. 16, 25).

## Common mistakes

- **Wiring a module to D0/D1 for Serial.** As shipped, D0/D1 are not connected: USART2 goes to the ST-LINK's virtual COM port through SB13/SB14, with SB62/SB63 open (UM1724, p. 25). Use USART1 on D8/D2, or move the solder bridges.
- **Looking for I2C on A4/A5.** On the Nucleo, A4 and A5 are PC1 and PC0, analog inputs. I2C1 is on D14 (PB9, SDA) and D15 (PB8, SCL), the pins next to AREF (UM1724, p. 43).
- **Drawing more than 300 mA from USB.** Over USB the board and its shields get 300 mA at most; past that, ST asks you to power it from VIN or E5V (UM1724, p. 20). Motors, servos and LED strips need their own supply with a shared ground.
- **Powering it from a USB phone charger.** A charger does not enumerate the board, so LD3 stays off and the STM32 is not powered. Fit jumper JP1 to power the target anyway (UM1724, p. 20).
- **Expecting analogWrite to give a voltage.** The STM32F401 has no DAC, so analogWrite is PWM on a timer pin. For a true analog output, use the Nucleo-F446RE or Nucleo-L476RG, whose chips have 12-bit DACs on PA4 and PA5.

## Questions

### Is the Nucleo-F401RE 5 V or 3.3 V?

3.3 V. The board's IOREF and logic run at 3.3 V, although it has a +5V pin for shields (UM1724, p. 22). ST rates the STM32F401's I/O ports 5 V tolerant (datasheet, p. 1), so 5 V digital inputs are accepted, but outputs only reach 3.3 V and the ADC reads 0 to 3.3 V.

### Why won't my Nucleo-F401RE upload or show up on the computer?

Check that both CN2 jumpers are on, the default that lets the ST-LINK program the on-board chip (UM1724, p. 16), and that the mini-USB cable carries data. On Windows, install the ST-LINK/V2-1 driver first; if the board was plugged in before, Device Manager shows Unknown devices to update by hand (p. 17). LD1 blinks red then turns green as the ST-LINK talks to the target, and orange means a communication failure (p. 23).

### Where is Serial on the Nucleo-F401RE?

Serial is USART2 on PA2/PA3, wired to the ST-LINK, so it appears on the computer as a virtual COM port over the same USB cable (UM1724, p. 25). It is not on D0/D1 unless you close SB62/SB63 and open SB13/SB14.

### How do I power the Nucleo-F401RE without USB?

Feed 7 V to 12 V into VIN (CN6 pin 8 or CN7 pin 24), or a regulated 4.75 V to 5.25 V into E5V, with JP5 moved to E5V and JP1 removed (UM1724, p. 21). VIN can supply up to 800 mA at 7 V, less as the voltage rises.

### Which pin is the built-in LED on the Nucleo-F401RE?

LD2, the green user LED, is on D13, which is PA5 on this board; HIGH turns it on (UM1724, p. 23). The blue B1 USER button is PC13, and B2 RESET is NRST.

### Nucleo-F401RE vs Nucleo-F446RE: which should I buy?

Both share the same Nucleo-64 board and headers. The F401RE runs at 84 MHz with 96 KB of SRAM (F401 datasheet, p. 1); the F446RE runs at 180 MHz with 128 KB of SRAM and adds two 12-bit DACs and two CAN controllers (F446 datasheet, p. 1). Pick the F446RE for audio, CAN or heavy DSP, the F401RE for general projects.

### Do I need a separate programmer like a Blue Pill does?

No. The Nucleo carries an ST-LINK/V2-1 on its snap-off end that flashes and debugs the STM32 over SWD from the same USB cable (UM1724, p. 16). It also mounts as a USB drive, so a compiled.bin can be copied onto it.

## Related parts

- [STM32 Blue Pill (F103C8)](https://www.tinkered.ai/components/stm32-bluepill-f103c8.md): same job: an STM32 board
- [STM32 Black Pill (F411CE)](https://www.tinkered.ai/components/stm32-blackpill-f411ce.md): same job: an STM32 board
- [STM32 Black Pill (F103C8)](https://www.tinkered.ai/components/stm32-blackpill-f103c8.md): same job: an STM32 board
- [STM32 Nucleo-F446RE](https://www.tinkered.ai/components/stm32-nucleo-f446re.md): same job: an STM32 board
- [STM32 Nucleo-L476RG](https://www.tinkered.ai/components/stm32-nucleo-l476rg.md): same job: an STM32 board

## Try it

Tinkered simulates the STM32 Nucleo-F401RE in the browser: wire it on a 3D breadboard, run your real code on the board, and measure it. Free to start at https://www.tinkered.ai.