Serial

write()

Writes binary data to the serial port. This data is sent as a byte or series of bytes; to send the characters representing the digits of a number use the print() function instead.

// PROTOTYPES
virtual size_t write(uint8_t);
size_t write(uint16_t);
virtual size_t write(const uint8_t *buffer, size_t size);

// SYNTAX
Serial.write(val);
Serial.write(str);
Serial.write(buf, len);

// EXAMPLE USAGE

void setup()
{
  Serial.begin(9600);
}

void loop()
{
  Serial.write(45); // send a byte with the value 45

  int bytesSent = Serial.write(“hello”); //send the string “hello” and return the length of the string.
}

Parameters:

• val: a value to send as a single byte
• str: a string to send as a series of bytes
• buf: an array to send as a series of bytes
• len: the length of the buffer

write() will return the number of bytes written, though reading that number is optional.

Since 6.5.0:

On hardware UART ports (Serial1, etc.) and USB serial (Serial, USBSerial1), the Serial.write(buf, len) form transfers the buffer directly instead of writing it one byte at a time, which is significantly faster for larger buffers. It honors blockOnOverrun(): with blocking enabled (the default), the call waits for room in the buffer as needed until all of len bytes have been written; with blocking disabled, it writes as many bytes as currently fit and returns immediately, so the returned count may be less than len.