Devices API Overview: C7222 Pico W Board Interfaces and Pin Assignments

The C7222 Pico W board is a very simple I/O board intended as a getting-started platform for Raspberry Pi Pico W development. It provides a UART connector, a reset button, four user buttons, and three red/green LED pairs so core embedded workflows can be tested quickly with minimal hardware complexity.

The schematic is shown in the image above. The 3D board view below is for reference only.

C7222 Pico W Board 3D View

This document summarizes the external interfaces and GPIO assignments for the C7222 Pico W board, based on the schematic.

Board Overview

The board is built around a Raspberry Pi Pico W. It exposes:

1. A debug UART header.
2. Four push buttons with pull-ups.
3. Three dual‑color LED pairs (red/green).
4. A reset switch tied to RUN.

GPIO Assignments

LEDs (active‑low)

Each LED is tied to 3V3 through a 470 Ω resistor. The GPIO drives the LED low to turn it on (active‑low).

1. LED1_RED → GP21
2. LED1_GREEN → GP20
3. LED2_RED → GP19
4. LED2_GREEN → GP18
5. LED3_RED → GP17
6. LED3_GREEN → GP16

These match the C++ API enums:

1. PicoWBoard::LedId::LED1_RED = 21
2. PicoWBoard::LedId::LED1_GREEN = 20
3. PicoWBoard::LedId::LED2_RED = 19
4. PicoWBoard::LedId::LED2_GREEN = 18
5. PicoWBoard::LedId::LED3_RED = 17
6. PicoWBoard::LedId::LED3_GREEN = 16

Buttons (active‑low)

Each button pulls the GPIO to GND when pressed, with a 100 kΩ pull‑up to 3V3.

1. BUTTON_B1 → GP2
2. BUTTON_B2 → GP3
3. BUTTON_B3 → GP4
4. BUTTON_B4 → GP5

These match the C++ API enums:

1. PicoWBoard::ButtonId::BUTTON_B1 = 2
2. PicoWBoard::ButtonId::BUTTON_B2 = 3
3. PicoWBoard::ButtonId::BUTTON_B3 = 4
4. PicoWBoard::ButtonId::BUTTON_B4 = 5

Debug UART Header

The UART header exposes the Pico’s UART signals:

1. DBG_TX → GP0
2. DBG_RX → GP1
3. GND

Notes:

1. This is the default UART for Pico platforms and is enabled out of the box for stdio/printf output.
2. When using a Pico Debugger, the UART wires must be crossed: board DBG_TX goes to debugger RX, and board DBG_RX goes to debugger TX.
3. If using the Pico Debugger provided cables, the female and male pin cables can be attached as follows:
   • Female black ↔ male black
   • Female orange ↔ male yellow
   • Female yellow ↔ male orange

Reset

The RESET switch ties the Pico RUN pin to GND to reset the board.

Usage Notes

1. LEDs are active‑low: write 0 to turn on, 1 to turn off.
2. Buttons are active‑low: pressed = logic 0, released = logic 1.
3. The GPIO assignments are fixed by hardware; use the enums in c7222_pico_w_board.hpp for clarity.
4. LED drive relies on the Pico’s sink capability (drive strength). This is not optimized for low‑power operation.