Error conversion from 'char' to 'String' is ambiguous

Using Arduino Programming Questions
1

Hi
I am planning to use MIT app inventor as input for Arduino input via bluetooth serial mode.
App is sending serial data to uno but there is a programming error "conversion from 'char' to 'String' is ambiguous"

data from app to board as follow:

%
2
5
.
1
2
%
2
5
.
1
2
%

and so on...

I dont understand where I am mistaking and need help

My coding as follow:

 */
char Incoming_value = 0;                //Variable for storing Incoming_value
void setup() 
{
  Serial.begin(9600);         //Sets the data rate in bits per second (baud) for serial data transmission
  pinMode(13, OUTPUT);        //Sets digital pin 13 as output pin
}
void loop()
{
    Incoming_value = Serial.read();      //Read the incoming data and store it into variable Incoming_value
    Serial.println(Incoming_value);        //Print Value of Incoming_value in Serial monitor

String readString = Incoming_value;

// Split the readString by a pre-defined delimiter in a simple way. '%'(percentage) is defined as the delimiter in this project.
int delimiter, delimiter_1, delimiter_2, delimiter_3;
delimiter = readString.indexOf("%");
delimiter_1 = readString.indexOf("%", delimiter + 1);
delimiter_2 = readString.indexOf("%", delimiter_1 +1);
delimiter_3 = readString.indexOf("%", delimiter_2 +1);

// Define variables to be executed on the code later by collecting information from the readString as substrings.
String first = readString.substring(delimiter + 1, delimiter_1);
String second = readString.substring(delimiter_1 + 1, delimiter_2);
String third = readString.substring(delimiter_2 + 1, delimiter_3);

}
2

Incoming_value is declared as a char hence you cannot copy it to a String using

  String readString = Incoming_value;

In any case, each time that line of code is executed a new String variable is created so even if the copy worked it would only have a single character in it. Take a look at the Serial.readString() function

To compound the problem your code does not check whether there is any data available before reading from Serial

3

The serial input basics tutorial may be of interest.

4

Hi
or try this way:

String Incoming_value = "";                //Variable for storing Incoming_value
void setup()
{
  Serial.begin(9600);         //Sets the data rate in bits per second (baud) for serial data transmission
  pinMode(13, OUTPUT);        //Sets digital pin 13 as output pin
}
void loop()
{
  Incoming_value = Serial.readString();      //Read the incoming data and store it into variable Incoming_value
  Serial.println(Incoming_value);        //Print Value of Incoming_value in Serial monitor

//  String readString = Incoming_value;

  // Split the readString by a pre-defined delimiter in a simple way. '%'(percentage) is defined as the delimiter in this project.
  int delimiter, delimiter_1, delimiter_2, delimiter_3;
  delimiter = Incoming_value.indexOf("%");
  delimiter_1 = Incoming_value.indexOf("%", delimiter + 1);
  delimiter_2 = Incoming_value.indexOf("%", delimiter_1 + 1);
  delimiter_3 = Incoming_value.indexOf("%", delimiter_2 + 1);

  // Define variables to be executed on the code later by collecting information from the Incoming_value as substrings.
  String first = Incoming_value.substring(delimiter + 1, delimiter_1);
  String second = Incoming_value.substring(delimiter_1 + 1, delimiter_2);
  String third = Incoming_value.substring(delimiter_2 + 1, delimiter_3);

}
5

Thanks, it's working, I will add now IF condition to have a serial check and will post back with correct code.

6

readString blocks and waits for Serial timeout. You can reduce the wait with Serial.setTimeout(..) say 2mS for 9600 baud.
Or you can check my tutorial Arduino Software Solutions for a variety of non-blocking solutions to reading from Serial into Strings each with their pros and cons

7

Thanks, its working like a charme, below code are working, taking values from MIT app bluetooth and coverts it to numeric value.

String Incoming_value = "";                //Variable for storing Incoming_value
void setup()
{
  Serial.begin(9600);         //Sets the data rate in bits per second (baud) for serial data transmission
  pinMode(13, OUTPUT);        //Sets digital pin 13 as output pin
}
void loop()
{
  if (Serial.available() > 0) 
    
{
  Incoming_value = Serial.readString();      //Read the incoming data and store it into variable Incoming_value
  Serial.println(Incoming_value);        //Print Value of Incoming_value in Serial monitor

//  String readString = Incoming_value;

  // Split the readString by a pre-defined delimiter in a simple way. '%'(percentage) is defined as the delimiter in this project.
  int delimiter, delimiter_1, delimiter_2, delimiter_3;
  delimiter = Incoming_value.indexOf("%");
  delimiter_1 = Incoming_value.indexOf("%", delimiter + 1);
  delimiter_2 = Incoming_value.indexOf("%", delimiter_1 + 1);
  delimiter_3 = Incoming_value.indexOf("%", delimiter_2 + 1);

  // Define variables to be executed on the code later by collecting information from the Incoming_value as substrings.
  String first = Incoming_value.substring(delimiter + 1, delimiter_1);
  String second = Incoming_value.substring(delimiter_1 + 1, delimiter_2);
  String third = Incoming_value.substring(delimiter_2 + 1, delimiter_3);

//Converting strings to numbers
float  firstvalue=  first.toFloat();
float  secondvalue= second.toFloat();
float  thirdvalue=  third.toFloat();

Serial.print("first ");
Serial.println(firstvalue);
Serial.print("second ");
Serial.println(secondvalue);
Serial.print("third ");
Serial.println(thirdvalue);

}

}
8

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