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Below is a summary based on the official Raspberry Pi Pico (RP2040) datasheet and associated documentation. This information applies to the PICO (Raspberry Pi Pico Shield) in your project. For complete details, you can refer to the official Raspberry Pi Pico Datasheet available from Raspberry Pi’s website (for example, Raspberry Pi Pico Datasheet).
Below, the pins have been grouped by their general function along with key electrical characteristics and special considerations:
1. Power and System Control Pins
| Pin Name | Function | Electrical Characteristics | Special Considerations |
|---|---|---|---|
| VBUS | Supplies the 5 V from the USB input | 5 V input available from USB | Used to power on-board circuits; ensure USB supply stability |
| VSYS | Main system supply voltage | Accepts 1.8 V to 5.5 V (subject to on-board regulator specs) | Must be within range for proper regulator performance |
| 3V3(OUT) | Regulated 3.3 V output | Provides up to ~300 mA; outputs 3.3 V | Avoid overloading; ensure total current does not exceed regulator limits |
| GND / AGND | Ground references | 0 V potential reference | Use AGND for analog circuits (e.g., ADC); keep stable clean ground connections |
| 3V3_EN | Enables/disables the 3.3 V regulator | TTL-level input (typically high to enable) | Pull low to disable 3.3 V output if required by your design |
| RUN | Reset control for the RP2040 | Active low (pulling low resets the microcontroller) | Use proper debouncing if externally triggered |
2. General-Purpose I/O (GPIO) Pins
The Pico features multiple GPIO pins that can be configured as digital inputs or outputs. Their typical characteristics are:
Table
| Pin Group | Function | I/O Characteristics | Special Considerations |
|---|---|---|---|
| GPIO0 to GPIO28 (select examples below) | Digital I/O – configurable as input or output | Input: LOW if ≤0.8 V, HIGH if ≥2 V; Output: 0 V (LOW) or 3.3 V (HIGH) with drive strength options (2 mA, 4 mA, 8 mA, or 12 mA) | The combined cumulative current across all GPIOs should not exceed ~50 mA. Use pull-up or pull-down resistors where needed to ensure stable logic levels. |
| GPIO23 | (Specialized) May control power-saving functions (varies by firmware configuration) | Same as other GPIOs when used as digital pins | Refer to application notes for correct power-save configuration |
| GPIO24 | VBUS Sense | Digital input that goes HIGH when USB power is applied | Can be used to detect connection of a USB supply |
| GPIO25 | Onboard LED (default demo LED) | Digital output (0 V/3.3 V) | Often used as an activity indicator in examples |
3. Analog and ADC-Capable Pins
The RP2040 offers a built-in 12‑bit ADC over a few dedicated channels:
Table
| Pin Name | Function | I/O Characteristics | Special Considerations |
|---|---|---|---|
| GPIO26 (ADC0) | Analog input channel 0 | Reads analog voltages between 0 V and 3.3 V with 12‑bit resolution | Ensure input voltage does not exceed 3.3 V for accuracy and safety |
| GPIO27 (ADC1) | Analog input channel 1 | Identical ADC characteristics as ADC0 | Consider decoupling and low-noise design for accurate measurement |
| GPIO28 (ADC2) | Analog input channel 2 | Same as above | Use proper filtering if measuring low-level signals |
4. Communication Interfaces and PWM
The Pico supports several common protocols, and many GPIO pins serve dual functions:
Table
| Interface | Example Pin Assignments | I/O Characteristics | Special Considerations |
|---|---|---|---|
| UART | Default: GPIO0 (TX), GPIO1 (RX); alternative pairs available | Standard TTL levels (3.3 V logic) | Ensure matching baud rates; these pins are remappable if needed |
| I2C | Default: GPIO4 (SDA), GPIO5 (SCL) or alternate assignments | Open-drain configuration; require external pull-up resistors (e.g., 4.7 kΩ or 10 kΩ) | Proper bus termination and pull-ups are critical for reliable communication |
| SPI | Example: SPI0 uses GPIO16 (RX), GPIO19 (TX), GPIO18 (SCK), GPIO17 (CS) | High-speed CMOS digital signaling | Maintain short, impedance-controlled traces for high-speed data integrity |
| PWM | Many GPIOs may be assigned to PWM channels (e.g., GPIO0/16 to PWM channel 0A, etc.) | Digital output with configurable pulse widths | Ideal for controlling brightness of LEDs or motor speed; ensure proper slew rate for your load |
5. Debugging and Special Function Pins
| Pin Name | Function | I/O Characteristics | Special Considerations |
|---|---|---|---|
| SWD (SWDIO and SWCLK) | Used for Serial Wire Debug (programming and code debugging) | 3.3 V digital signals with precise timing requirements | Use a compatible debug probe; ensure these pins are not repurposed in your design |
Additional Considerations
- Configuration Flexibility: Most GPIO pins are multipurpose and can be remapped via software. Their configuration (input, output, alternate functions) is defined in your firmware.
- Electrical Limitations: While each GPIO can drive a maximum of about 12 mA, always check the combined current load to stay within the overall limit (~50 mA) to avoid stressing the microcontroller.
- Noise and Interference: For analog measurements (using ADC channels), ensure proper decoupling capacitors and low-noise layout practices.
- Programming and Debugging: Use the SWD interface carefully when programming the RP2040, and avoid conflict with any alternate functions assigned to SWD pins.
This summary covers the primary groups of pins on the Raspberry Pi Pico Shield. Each pin’s configuration is flexible; therefore, when designing your circuit, consult the official datasheet and application notes to ensure that every pin is employed correctly for its intended function.
Let me know if you need further help in applying this information to your schematic or if you'd like to connect any of these pins in your Flux project.
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