The Complete Raspberry Pi Pico Pinouts Reference Table
Whether you are prototyping on a breadboard or designing a custom PCB, the 40-pin DIP footprint of the Raspberry Pi Pico (and the newer Pico 2) is the foundation of your build. Below is the complete physical pinout map, reading from Pin 1 (top-left, square pad) down to Pin 40.
| Pin | Function (Left Bank) | Function (Right Bank) | Pin |
|---|---|---|---|
| 1 | GP0 (UART0 TX / I2C0 SDA) | GP16 (SPI0 RX / UART0 TX) | 21 |
| 2 | GP1 (UART0 RX / I2C0 SCL) | GP17 (SPI0 CSn / UART0 RX) | 22 |
| 3 | GND | GND | 23 |
| 4 | GP2 (I2C1 SDA) | GP18 (SPI0 SCK) | 24 |
| 5 | GP3 (I2C1 SCL) | GP19 (SPI0 TX) | 25 |
| 6 | GP4 (SPI0 RX / I2C0 SDA) | GP20 (SPI0 RX) | 26 |
| 7 | GP5 (SPI0 CSn / I2C0 SCL) | GP21 (SPI0 CSn) | 27 |
| 8 | GND | GND | 28 |
| 9 | GP6 (SPI0 SCK / I2C1 SDA) | GP22 (I2C1 SDA) | 29 |
| 10 | GP7 (SPI0 TX / I2C1 SCL) | RUN (Reset / Enable) | 30 |
| 11 | GP8 (UART1 TX / I2C0 SDA) | GP26 / ADC0 (I2C1 SDA) | 31 |
| 12 | GP9 (UART1 RX / I2C0 SCL) | GP27 / ADC1 (I2C1 SCL) | 32 |
| 13 | GND | AGND (Analog Ground) | 33 |
| 14 | GP10 (SPI1 CSn / I2C1 SDA) | GP28 / ADC2 (SPI1 CSn) | 34 |
| 15 | GP11 (SPI1 SCK / I2C1 SCL) | ADC_VREF (3.3V Reference) | 35 |
| 16 | GP12 (SPI1 TX / I2C0 SDA) | 3V3 (Main 3.3V Output) | 36 |
| 17 | GP13 (SPI1 RX / I2C0 SCL) | 3V3_EN (Regulator Enable) | 37 |
| 18 | GND | GND | 38 |
| 19 | GP14 (SPI1 SCK / I2C1 SDA) | VSYS (Main Power Input 1.8-5.5V) | 39 |
| 20 | GP15 (SPI1 TX / I2C1 SCL) | VBUS (USB 5V Output/Input) | 40 |
Rows People Get Wrong: VSYS, VBUS, and ADC Limits
When troubleshooting fried boards or erratic sensor readings, the culprit almost always traces back to a misunderstanding of the power and analog pins on the right bank.
- Pin 39 (VSYS) vs. Pin 40 (VBUS): VSYS is the main power input for the board (accepting 1.8V to 5.5V). VBUS is the raw 5V from the USB connector. Never backfeed 5V into VBUS if the USB cable is plugged in. The Pico uses a Schottky diode to OR the USB and VSYS power paths; forcing 5V into VBUS while USB is connected can bypass protection and release the magic smoke from your PC's USB port or the Pico's onboard regulator.
- Pin 35 (ADC_VREF): This pin provides the 3.3V reference for the Analog-to-Digital Converter. While it can technically be used as a standard GPIO, doing so introduces noise into your ADC readings. If you need precise analog measurements, leave Pin 35 unconnected or use it strictly as a reference tie-point.
- Pico W Wireless Pins (GP23, GP24, GP25): If you are using the Pico W (or Pico 2 W), the physical pins for GP23, GP24, and GP25 do not route to the RP2040/RP2350 silicon. They are consumed internally by the Infineon CYW43439 wireless chip to control the WLAN ON state, antenna switching, and busy flags. Do not attempt to use them for external I/O.
Mapping GPIO to External Harness Color Codes (IEC vs NEC)
When moving a Pico project from a breadboard to a permanent DIN-rail enclosure or industrial control panel, you transition from loose jumper wires to ferrule-crimped wiring harnesses. You must map the Pico's low-voltage DC logic to the regional wiring standards governing your enclosure to pass inspection and ensure safe maintenance.
| Pico Pin / Function | IEC 60446 (EU/UK/AU Standard) | NEC / NFPA 79 (US Standard) |
|---|---|---|
| VSYS / VBUS (+5V DC) | Brown (or Red for internal DC+) | Red (or Orange for DC+) |
| 3V3 (OUT) | Orange (Internal DC+ < 5V) | Yellow (Internal DC+ < 5V) |
| GND / AGND | Blue (DC Ground) | Black (DC Ground) or Blue |
| Signal (I2C/SPI/UART) | White or Grey | White or Grey |
Faded Silk and Missing Markings: Safe Pin Identification
Clone boards, heavily used development units, or boards exposed to flux and heat often suffer from faded silkscreen text. If you cannot read the pin labels, use these physical and electrical verification methods before applying power.
- The Pin 1 Indicator: Locate the micro-USB or USB-C port at the top of the board. Pin 1 is always the top-left pin. On the PCB, Pin 1 will have a square copper pad (all other pins are circular). On the silicon RP2040/RP2350 chip itself, there is a small dimple or dot indicating Pin 1 orientation.
- The GND Continuity Test: If the board is unpowered, set your multimeter to continuity mode. Probe the suspected GND pins against the metal shielding of the USB port (which is tied to ground). The Pico has eight dedicated digital ground pins (3, 8, 13, 18, 23, 28, 33, 38). If you get a beep on an odd-numbered pin on the left bank (like 3, 13, 23), you have confirmed the left-side orientation.
- Identifying RUN (Pin 30): Pin 30 is the only non-GPIO, non-power pin on the right bank that sits directly below GP22 and above ADC0. It routes directly to the chip's reset circuitry. Probing it to GND with a jumper wire will instantly reset the board if it is powered.
Decision Tree: Choosing Your Pico Variant and Pin Strategy
With the original Pico, Pico W, and the newer Pico 2 (RP2350) sharing the same 40-pin footprint, selecting the right board and pin strategy requires matching your project's physical and logical constraints. Use this decision matrix to lock in your hardware.
| Project Requirement | Constraint / Edge Case | Concrete Pick |
|---|---|---|
| Standard sensor logging, basic I2C/SPI, low cost | Need maximum available GPIOs without wireless overhead. | Original Pico (RP2040). Use GP0-GP22 for digital, GP26-28 for analog. |
| IoT dashboard, MQTT telemetry, remote OTA updates | Requires WiFi/BLE. Consumes internal pins for the radio chip. | Pico W (or Pico 2 W). Avoid GP23-25. Use the cyw43 library for the onboard LED instead of standard GPIO. |
| Complex motor control, 5V logic interfacing, high PIO demand | RP2040 PIO is limited; 3.3V logic requires level shifters for 5V industrial sensors. | Pico 2 (RP2350). Utilizes 5V-tolerant GPIO pads (on specific variants) and doubled PIO blocks. Default pick for new 2026 industrial designs. |
| Battery-powered wearable or remote node | Needs deep sleep and precise ADC for battery voltage monitoring. | Pico (Any). Feed battery voltage through a 100k/100k divider into GP28 (ADC2). Tie VSYS directly to the LiPo BMS output. |
For 90% of hobbyist and prototyping builds in 2026, the Original Pico (RP2040) remains the default, most cost-effective pick. Reserve the Pico 2 for projects that explicitly demand 5V-tolerant I/O or advanced cryptographic hardware accelerators, and only reach for the Pico W when wireless telemetry is a hard requirement. Always verify your harness color codes against your local AHJ (Authority Having Jurisdiction) before closing up any mains-adjacent enclosures.
References: Raspberry Pi Pico Datasheet (Official), Raspberry Pi Pico Hardware Documentation.
