Why do I keep getting 0? I tried several ways and then I took the sample codes on arduino site and that didnt work either. I always get Serial.available()=0
int incomingByte = 0; // for incoming serial data void setup() { Serial.begin(9600); // opens serial port, sets data rate to 9600 bps } void loop() { // send data only when you receive data: if (Serial.available() > 0) { // read the incoming byte: incomingByte = Serial.read(); // say what you got: Serial.print("I received: "); Serial.println(incomingByte, DEC); } else Serial.print("I received nothing "); } 4 Answers
Your program works fine on my Arduino although you need some delays to stop the rapid-fire "I received nothing " messages. I would change the "I received nothing " block to include a delay of a few seconds e.g. delay(3000) for a 3-second delay.
Also, consider changing your code to use a SerialEvent() procedure such as depicted here: SerialEvent example
String inputString = ""; // a string to hold incoming data boolean stringComplete = false; // whether the string is complete void setup() { // initialize serial: Serial.begin(9600); // reserve 200 bytes for the inputString: inputString.reserve(200); } void loop() { // print the string when a newline arrives: if (stringComplete) { Serial.println(inputString); // clear the string: inputString = ""; stringComplete = false; } } /* SerialEvent occurs whenever a new data comes in the hardware serial RX. This routine is run between each time loop() runs, so using delay inside loop can delay response. Multiple bytes of data may be available. */ void serialEvent() { while (Serial.available()) { // get the new byte: char inChar = (char)Serial.read(); // add it to the inputString: inputString += inChar; // if the incoming character is a newline, set a flag // so the main loop can do something about it: if (inChar == '\n') { stringComplete = true; } } } What is wrong? Nothing. The code is ok the hardware is ok. Serial.available() returns the number of characters in the buffer waiting to be read, so if you don't send it anything it will always return zero/false.
int incomingByte = 0; void setup() {Serial.begin(9600);} void loop() { if (Serial.available() > 0) { incomingByte = Serial.read(); Serial.print("I received: "); Serial.println(incomingByte, DEC); } else Serial.print("I received nothing\n"); delay(1000); } Uploading this code and sending 'ss' into the serial buffer will produce:
0:00:00.000 -> I received:115 //s 0:00:00.000 -> I received:115 //s 0:00:00.000 -> I received:10 //newline I had a similar problem and solved it by including short delay() statements. It seems that Arduino reads the first byte and is interrupted with the following...
Some boards restart when a serial connection is initiated. This way when you do echo smth > /dev/serial/xxxx board resets, doesn't receive smth and Serial.available() never happens. This behavior can be overridden, or you can communicate with cat > /dev/serial/xxxx.
Took me a good while to figure out, hope it helps someone.
