How to get the buzzer work after storing Serial.read()?

Projects Programming
1

I am currently using a BLUNO (Arduino Uno + BLE).

I retrieve the RSSI value of the BLE under the loop. I would like to make the buzzer beep upon receiving the required responses as a result of executing the AT commands. However, if I were to assign Serial.read() to a char variable, I cannot evaluate the condition that contains the tone() codes in its block.

char inData[] = "";
int index = 0;
String inString = "";
String inParse[] = "";
byte charReceived = 0;
String responseString = "";
int responseLength = 0;
int inDataIndex = 0;
int rssi;

void setup() {
  Serial.begin(115200);
}

void serialEvent() {
  while(Serial.available()) {
    char inChar = Serial.read();  //if comment this 1
    inData[index] = inChar;        // and this 2
    index++;  
    inString += inChar;               //and this 3, buzzer will beep
    if (Serial.read() == 13) { // \r cannot be detected if I were to use buzzer. Use 13
      playAlarm();
      //delay(1000);
      index = 0;
      responseLength = strlen(inData) - 1; //Get rid of LF -1
      if(inData[0] != '-') //get rid of the first garbage) //inData[0]
        inDataIndex = 1;
       else
         inDataIndex = 0;
      for(int i=inDataIndex; i<responseLength; i++)
        responseString += inData[i];
      rssi = responseString.toInt();  //parse string to int
      if(responseString)
        responseString="";
    }
  }
}

void loop(){
  Serial.println("AT+RSSI=?");
  /*Some people suggests that it is best to retreive RSSI value
   * every 2 seconds. Anything faster than that, will make the RSSI
   * value too incnsistent
   */
  delay(150); //Must put delay. or else, it will return CMD error
}

void playAlarm() {
  tone(8, 2100, 150);  //21000 //Above is 9900 useless
  noTone(8);
  tone(8, 1000, 150);
}

void stopAlarm() {
  noTone(8);
}
2 
char inData[] = "";

An array of chars that contains one element. How is THAT useful?

String inParse[] = "";

An array of String objects containing one element. How is THAT useful?

    char inChar = Serial.read();  //if comment this 1
    inData[index] = inChar;        // and this 2
    index++;

You REALLY need to make sure that you don't store data beyond the end of your one element array.

    if (Serial.read() == 13) { // \r cannot be detected if I were to use buzzer. Use 13

Read another character, that may not have arrived. If it is something, do something. Otherwise, throw the value away. How is THAT useful?

At this point, I gave up. None of the rest of the code makes sense, because you have made fundamental errors before this.

3

Its always an error to read more characters than are available:

  while(Serial.available()) {
    char inChar = Serial.read();  //if comment this 1
    inData[index] = inChar;        // and this 2
    index++;  
    inString += inChar;               //and this 3, buzzer will beep
    if (Serial.read() == 13) { // \r cannot be detected if I were to use buzzer. Use 13

should be changed to something like this:

  while(Serial.available()) {  // pass this test, at least 1 char is available.
    char inChar = Serial.read();
    if (index < MAXCHARS)  // check for buffer over-run.
    {
      inData[index++] = inChar;
    }
    inString += inChar;  // why use string and String?
    if (inChar == 13) { // compare the character actually read

and change

char inData[] = "";

to

#define MAXCHARS 50  // or whatever is sensible
char inData[MAXCHARS+1] ;
4

@PaulS - I am sorry if it sounds so newbie, and have not reach your level yet. I just started and still learning. I got the sample codes somewhere and I simply copied it and did some changes to it. The codes work pretty well if I were to use LCD display instead of the buzzer though.

@MarkT - Thank you so much!! I got the buzzer working finally! I think I understand the rationale behind your modifications. Yeap. You hit on the nail. Before I posted these codes, I know there is 1 or 2 lines that is not relevant but I can't seem to find it as I was pretty in mess. You are right. I don't need the "inString"

  1. Can you explain this line? inData[index++] = inChar; If I understand correctly, it is a form of post-increment. So, the counter will automatically increase by 1 count after it store the char in one of its element? I guess its the same as
inData[index] = inChar;   
index++;

?