Serial Ports (USB and UART)
The Arduino-Pico core implements a software-based Serial-over-USB port using the USB ACM-CDC model to support a wide variety of operating systems.
Serial is the USB serial port, and while
Serial.begin() does allow
specifying a baud rate, this rate is ignored since it is USB-based.
(Also be aware that this USB
Serial port is responsible for resetting
the RP2040 during the upload process, following the Arduino standard
of 1200bps = reset to bootloader).
The RP2040 provides two hardware-based UARTS with configurable pin selection.
Configure their pins using the
setXXX calls prior to calling
Serial1.setRX(pin); Serial1.setTX(pin); Serial1.begin(baud);
The size of the receive FIFO may also be adjusted from the default 32 bytes by
setFIFOSize call prior to calling
The FIFO is normally handled via an interrupt, which reduced CPU load and makes it less likely to lose characters.
For applications where an IRQ driven serial port is not appropriate, use
setPollingMode(true) before calling
For detailed information about the Serial ports, see the Arduino Serial Reference .