The RP2040 Interfacer is a small low-cost USB to UART and I2C Adapter (both 3.3V) powered by an RP2040 microcontroller that plugs straight into a USB Type-A socket. Being powered by the RP2040 with 2MB FLASH it can be used with CircuitPython or Pico C SDK based firmware.
The serial UART connector is a 3-pin JST SH compatible socket as used on the Raspberry Pi 5 UART port.
The I2C ST/Qw connector is a 4-pin JST SH compatible with (3.3V) Qwiic/STEMMA QT. The SCL/SDA lines also have 1K resistors connected to additional GPIO lines allowing each one to have either pull up/down resistor enabled in software. The ST/Qw GPIO pins used are capable of analogue input allowing them to be used for non I2C uses, and when combined with the 1K pull resistors, can be used to measure and detect external pull up/down resistors.
On the reverse side of the connectors, there are three LEDs. In the middle is a red LED and over both UART and ST/Qw connectors are orange LEDs.
The RP2040 BOOTSEL button is dual-purpose, once the RP2040 has started up it can be used for user input.
You can also use a USB-C to USB-A adapter to allow the Interfacer to connect to many mobile phones for USB CDC Serial UART access (where supported)!
Pin Reference
The GPIO pin numbers for the connectors, LED, and button (as listed below) are also labelled on the PCB itself for quick reference
GPIO
Usage
GP12
UART TX
GP13
UART RX
GP14
UART orange LED
GP16
Red status LED
GP17
ST/Qw I2C orange LED
GP18
1K Resistor to SDA
GP19
1K Resistor to SCL
GP23
USER Button (active LOW)
GP26
ST/Qw I2C SDA/A0
GP27
ST/Qw I2C SCL/A1
Firmware
To upload the usb_interfacer_bridge firmware to the USB Interfacer:
Press and hold the BOOT button whilst plugging a USB cable from the device into your computer, then release the BOOT button.
After a few seconds, an RPI-RP2 drive should appear.
Skip to content
