Getting Error: invalid conversion from 'char' to 'const char*'

Community General Discussion
1

Hi at all,

coud you please help my tired brain, I'm quite new to C and I can't solve this issue:

invalid conversion from 'char' to 'const char*' [-fpermissive]

Here is my loop:

void loop() {
  // while loop begins here, continous loop:
  char Buf[50];
  if (Serial.available()) {    // check for incoming data --> if available
    delay(20); // just wait a little bit for more characters to arrive
    while (Serial.available())
    {
      inByte = Serial.read();      // store incoming data

      if ((!(inByte == '/')) && (!(inByte == ':'))) {
        text.concat(inByte);
      }
      if (inByte == ':') {
        data[count][0] = text;
        text = "";
      }
      if (inByte == '/') {
        data[count][1] = text;
        text = "";
        count++;
      }
      if (inByte == '#') {
        strip.clear();
        for (int i = 0; i < 154; i++) {
          for (int j = 0; j < count; j++) {
            if (data[j][0].toInt() == i) {
              if (String(data[j][1]) == 'g') {
                strip.setPixelColor(j, 0, 255, 0);
              }
              if (data[j][1] == 'b') {
                strip.setPixelColor(j, 0, 0, 255);
              }
              if (data[j][1] == 'l') {
                strip.setPixelColor(j, 148, 0, 211);
              }
              if (data[j][1] == 'r') {
                strip.setPixelColor(j, 255, 0, 0);
              }

              //Serial.print(i);
              //Serial.print(data[j][1]);
            }
            else {
              strip.setPixelColor(j, 0, 0, 0);
            }
          }
        }
        strip.show();
      }

    }

  }

I defined the variables as follows:

int count;
char inByte;  // incoming serial byte
String text = "";
String data[25][2];

Thank you!

2

The compiler told you exactly where the problem was, but you chose to make us go look for it.
Why?

(Your code is incomplete)

300 bytes of wasted RAM :open_mouth:

3

Sorry, was not my intension :wink:

C:\Users\xxx.ino: In function 'void loop()':
C:\Users\xxx.ino:65:41: warning: invalid conversion from 'char' to 'const char*' [-fpermissive]
               if (String(data[j][1]) == 'g') {
                                         ^~~
In file included from C:\Program Files (x86)\Arduino\hardware\arduino\avr\cores\arduino/Arduino.h:232:0,
                 from sketch\iNoWa.ino.cpp:1:
C:\Program Files (x86)\Arduino\hardware\arduino\avr\cores\arduino/WString.h:143:16: note:   initializing argument 1 of 'unsigned char String::operator==(const char*) const'
  unsigned char operator == (const char *cstr) const {return equals(cstr);}
                ^~~~~~~~
iNoWa:98:1: error: expected '}' at end of input
 }
 ^
exit status 1
expected '}' at end of input
4

why wasted?

5

Because an empty String takes 6 bytes.
You appear to be trying to store single characters in Strings.

6

Each String object takes 6 bytes of memory in addition to the content of the String (or its buffer).
For elements that seem to be mostly characters (1 byte long) this is a massive waste.

7

You are attempting to compare a string to a single character. The comparison needs to be between strings - put regular double quote marks around the letter "g" instead of single quotes 'g' if you really need to use a string for a single character comparison.

8

@anon73444976 @Whandall Thank you, ok now I undesrstand.
So for the data array, I should use char instead of string?

But then, how to

data[count][0] = text;

, as text is string type? Sorry, I'm really new into this :wink:

9

What does your incoming serial data look like?

10

Perhaps if @constantininthemountains posted their whole sketch we could provide more help

12

like this, eg:

140:g/120:g/55:b/44:l/67:r/#
13

Best to avoid Strings. They frequently cause memory problems and program crashes.

You may find this tutorial helpful: Serial Input Basics - updated

14

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