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Serial.readBytes()
Descripción
Serial.readBytes() lee caracteres desde el búfer del puerto serie. La función termina si la longitud determinada se ha leído, o el tiempo de espera (ver Serial.setTimeout()) de ha alcanzado.
Serial.readBytes() devuelve el número de caracteres colocados en el búfer. Un 0 significa que no se encontraron datos válidos.
Serial.readBytes() hereda de la clase Stream.
Sintaxis
Serial.readBytes(buffer, length)
Parámetros
- buffer: el buffer para almacenar los bytes (char [ ] o byte [ ])
- length: el número de bytes a leer (int)
Retornos
- Byte
Ejemplo
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
※ Nota:
- 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:
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
}
}
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