Crowtail shield for Pico: specs and pinout
A plug-and-play expansion board for the Raspberry Pi Pico that adds Crowtail 4-pin sensor ports (2 I2C, 3 analog, 2 UART, 3 digital, 1 SPI), a battery port, an SWD debug connector and a 3.3 V / 5 V power switch. Elecrow says to use a Pico with pre-soldered header pins. Every port uses the Crowtail 4-pin connector, so a Crowtail cable is needed for each module; no Crowtail cable is sold here (the Crowtail pH sensor ships with one).
Specs
| Spec | Value | Source |
|---|---|---|
| Ports | 3 analog (A1, A2, A3), 3 digital (D1, D2, D3), 2 UART, 2 I2C, 1 SPI, 1 BAT, SWD debug | source Features |
| Power switch | 3.3 V / 5 V selectable | source Features |
| Platform support | MicroPython and Arduino | source Features |
| Operating temperature | -25 C to +85 C | source Features |
| Input power | Printed as 'Input power 3/5 V' (the 3.3 V / 5 V switch) | source Features |
| Size and weight | 65 x 56 mm; 26 g | source Features |
| Pico logic level | The Pico's GPIO is powered from its 3.3 V rail and is fixed at 3.3 V | source 4.2 General purpose I/O |
Power
| Value | Source | |
|---|---|---|
| Supply | Selectable 3.3 V or 5 V for the Crowtail ports with the on-board switch; the Pico is powered through its own USB or the shield | source Features; no current figure is published |
Pinout
The pin rows are the GPIO numbers used in Elecrow's own MicroPython examples on the shield wiki, not a pin table: the wiki and product page do not publish one. D3, A1 to A3, the second UART, the SPI port and the BAT port have no stated GPIO. The order of the four wires inside each Crowtail connector is not given. No analog port (A1 to A3) has a stated GPIO, although Elecrow's potentiometer example uses ADC pin 2.
| Pin | Function | Voltage | Notes | Source |
|---|---|---|---|---|
| D1 port | GPIO20 (the ultrasonic example also uses GPIO21 on this port) | Example code, not a pin table: LED, flashing and ultrasonic examples | source Program Example (Elecrow's own MicroPython code) | |
| D2 port | GPIO18 | Example code, not a pin table: Button example | source Program Example (Elecrow's own MicroPython code) | |
| I2C1 port | SDA = GPIO6, SCL = GPIO7 (I2C bus 1 in the example) | Example code, not a pin table: LCD example | source Program Example (Elecrow's own MicroPython code) | |
| I2C2 port | SDA = GPIO8, SCL = GPIO9 (I2C bus 0 in the example) | Example code, not a pin table: OLED example | source Program Example (Elecrow's own MicroPython code) | |
| UART1 port | TX = GPIO0, RX = GPIO1 (the example opens UART 0) | Example code, not a pin table: Bluetooth example | source Program Example (Elecrow's own MicroPython code) |
Build with it
Project ideas for the Crowtail shield for Pico. Each link opens Soldr with the prompt filled in; Soldr assigns the pins, checks power and shows how to wire every part.
- pH readout: The pH sensor ships with one 4-pin Crowtail cable, which plugs the sensor into an analog port. The pH board runs from 5 V and its output range is not published, while the Pico's ADC input must stay under about 3.6 V: measure the output with a meter before connecting it, and if it can exceed 3.3 V, use a voltage divider (two resistors) before the ADC pin; do not assume which GPIO the A1 port uses (the wiki gives no pin table). Learning project, not for water safety decisions.
- Soil moisture readout: The sensor is listed for 3.3 V to 5 V with a 4-pin connector, so set the switch to 3.3 V to keep its output inside the Pico's 3.3 V ADC range. Its package contains the sensor only. A 4-pin Crowtail cable you already own is required (not sold here). The GPIO behind the analog ports is not published. Learning project.
- Card ID logger: The Crowtail NFC module's wiki lists a 3.3 V working voltage, matching the 3.3 V switch position, and I2C as its default interface. This is a learning project for reading tag IDs, not an access-control system. A 4-pin Crowtail cable you already own is required (not sold here).
Common mistakes
- Leaving the power switch at 5 V for a 3.3 V sensor, or the other way round: the shield offers both and the wiki does not say that the ports shift logic levels, while the Pico's GPIO is fixed at 3.3 V (source: link, Features; link, 4.2 General purpose I/O).
- Sending more than about 3.6 V into an analog port: the Pico's ADC-capable pins have a diode to the 3.3 V rail, so the input must not exceed 3.3 V plus about 0.3 V (source: link, 4.2 General purpose I/O).
- Using a Pico without header pins: Elecrow's wiki says to plug a pre-soldered Pico into the shield (source: link, Description).
Not covered by the official source
- No schematic pin table is published; GPIO numbers come from the maker's example code only.
- The shield's board files are linked on the wiki as Pico_Shield_eagle but were not opened.
- The wiki does not say whether the shield's SWD, SPI and BAT ports are wired to specific Pico pins, and gives no current limit for the ports.
- Ideas 2 and 3 need a Crowtail cable you already own (not sold here); idea 1 uses the cable that ships with the pH sensor.