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Serial.readBytes()
Description
Serial.readBytes() reads characters from the serial port into a buffer. The function terminates if the specified length has been read, or it times out (see Serial.setTimeout()).
Serial.readBytes() returns the number of characters placed in the buffer. A 0 means no valid data was found.
Serial.readBytes() inherits from the Stream utility class.
Syntax
Serial.readBytes(buffer, length)
Parameter Values
- Serial: serial port object. See the list of available serial ports for each board on the Serial main page.
- buffer: the buffer to store the bytes in. Allowed data types: array of char or byte.
- length: the number of bytes to read. Allowed data types: int.
Return Values
- The number of bytes placed in the buffer. Data type: size_t.
Example Code
const int BUFFER_SIZE = 50;
char buf[BUFFER_SIZE];
void setup() {
Serial.begin(9600); // opens serial port, sets data rate to 9600 bps
}
void loop() {
// check if data is available
if (Serial.available() > 0) {
// read the incoming bytes:
int rlen = Serial.readBytes(buf, BUFFER_SIZE);
// prints the received data
Serial.print("I received: ");
for(int i = 0; i < rlen; i++)
Serial.print(buf[i]);
}
}
- Type "HELLO" on Serial Monitor and click Send button:
COM6
Autoscroll
Clear output
9600 baud
Newline
- The result on Serial Monitor:
COM6
I received: HELLO
Autoscroll
Clear output
9600 baud
Newline
※ NOTES AND WARNINGS:
- Serial.readBytes() may read a stream of bytes in multiple times (resulting in multiple fragments). To read a stream of bytes at one time, there are two ways:
- Based on the delimiter: Use Serial.readBytesUntil() with delimiter.
- Based on the fixed length: Wait until the fixed number of bytes is available. for example:
- Make sure that the read length does NOT exceed the buffer size. The below is the best practice:
- Serial functions are not only used for the communication between an Arduino board and Serial Monitor of Arduino IDE but also used for the communication between:
- An Arduino board and other Arduino board
- An Arduino board and other sensors/devices
- An Arduino board and computer (any Serial software on computer)
const int BUFFER_SIZE = 5;
char buf[BUFFER_SIZE];
void setup() {
Serial.begin(9600); // opens serial port, sets data rate to 9600 bps
}
void loop() {
// check if data is available
if (Serial.available() >= BUFFER_SIZE) {
// read the incoming bytes:
Serial.readBytes(buf, BUFFER_SIZE);
// TODO: PROCESS THE INCOMING DATA HERE
}
}
const int BUFFER_SIZE = 5;
char buf[BUFFER_SIZE]; // application buffer
void setup() {
Serial.begin(9600); // opens serial port, sets data rate to 9600 bps
}
void loop() {
// check if data is available
int rxlen = Serial.available(); // number of bytes available in Serial buffer
if (rxlen > 0) {
int rlen; // number of bytes to read
if (rxlen > BUFFER_SIZE) // check if the data exceeds the buffer size
rlen = BUFFER_SIZE; // if yes, read BUFFER_SIZE bytes. The remaining will be read in the next time
else
rlen = rxlen;
// read the incoming bytes:
rlen = Serial.readBytes(buf, rlen);
// TODO: PROCESS THE INCOMING DATA HERE
}
}
See Also
- Language : Arduino - Serial
- Language : Serial.available()
- Language : Serial.availableForWrite()
- Language : Serial.begin()
- Language : Serial.end()
- Language : Serial.find()
- Language : Serial.findUntil()
- Language : Serial.flush()
- Language : Serial.getTimeout()
- Language : if(Serial)
- Language : Serial.parseFloat()
- Language : Serial.parseInt()
- Language : Serial.peek()
- Language : Serial.print()
- Language : Serial.println()
- Language : Serial.read()
- Language : Serial.readBytesUntil()
- Language : Serial.readString()
- Language : Serial.readStringUntil()
- Language : serialEvent()
- Language : Serial.setTimeout()
- Language : Serial.write()
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