SoftwareSerial

Introduction

The SoftwareSerial library emulates a UART on any pair of GPIO pins. Its API follows the official Arduino SoftwareSerial library and it derives from Stream, so print(), println(), read() and available() are available.

Usage

#include <SoftwareSerial.h>

SoftwareSerial mySerial(10, 11); // RX, TX

void setup() {
  mySerial.begin(4800);
  mySerial.println("Hello, world?");
}

void loop() {
  if (mySerial.available()) {
    Serial.write(mySerial.read());
  }
}

See the SoftwareSerialExample and TwoPortReceive examples of the library.

Implementation

A hardware timer generates an interrupt at frequency = baudrate * OVERSAMPLE (by default 3 * baudrate) to handle the reception and the transmission. This increases the CPU load, especially at a high baud rate.

Several instances can be created, but only one can receive at a time. Use listen() to select the receiving instance.
The receive buffer holds _SS_MAX_RX_BUFF (64) bytes. overflow() reports that bytes were dropped.
If the RX and TX pins are the same, the instance works in half-duplex mode.

API

Method	Description
`SoftwareSerial(pin_size_t receivePin, pin_size_t transmitPin, bool inverse_logic = false)`	Creates an instance. Use the same pin for RX and TX for half-duplex. `inverse_logic` inverts the data level.
`void begin(long speed)`	Sets the baud rate and initializes the pins. Starts listening unless the instance is half-duplex.
`void end()`	Stops the instance and disables the timer interrupt.
`bool listen()`	Makes this instance the listening one. Returns `true` if it replaced another one or was not listening, `false` if it was already listening.
`bool isListening()`	Returns `true` if this instance is listening.
`bool stopListening()`	Stops listening. Waits for the pending output.
`bool overflow()`	Returns `true` if the receive buffer overflowed since the last call, then clears the flag.
`int available()`	Number of bytes in the receive buffer.
`int read()`	Reads a byte, `-1` if the buffer is empty.
`int peek()`	Returns the next byte without removing it, `-1` if the buffer is empty.
`size_t write(uint8_t byte)`	Sends a byte, waiting for any previous transmission.
`void flush()`	Clears the receive buffer and waits for the pending transmission.
`static void setInterruptPriority(uint32_t preemptPriority, uint32_t subPriority)`	Sets the priority of the timer interrupt shared by all instances.

Note

Define FORCE_BAUD_RATE to override the speed passed to begin().