Arduino1 strings limit ?

Projects Programming
1

I run this sketch on Arduino 1:

/*
ARDUINO strings limits
 */

void setup() {
  // Open serial communications and wait for port to open:
  Serial.begin(9600);
  while (!Serial) {
    ; // wait for serial port to connect. Needed for native USB port only
  }

  // send an intro:
  Serial.println("Test ARDUINO strings limits");

  Serial.println();
}

void loop() {
  String test = ""; 

  for (int i = 1; i < 20; i++) {
    Serial.print("run n.");
    Serial.println(i);
    Serial.println("");

    test = test + "1";
    Serial.println(test);
    test = test + "2";
    Serial.println(test);
    test = test + "3";
    Serial.println(test);
    test = test + "4";
    Serial.println(test);
    test = test + "5";
    Serial.println(test);
    test = test + "6";
    Serial.println(test);
    test = test + "7";
    Serial.println(test);
    test = test + "8";
    Serial.println(test);
    test = test + "9";
    Serial.println(test);
    test = test + " ";
    Serial.println(test);
    

  }
}

The result is the expected one:

run n.1

1
12
123
1234
12345
123456
1234567
12345678
123456789
123456789
run n.2

123456789 1
123456789 12
123456789 123
123456789 1234
123456789 12345
123456789 123456
123456789 1234567
123456789 12345678
123456789 123456789
123456789 123456789
run n.3

123456789 123456789 1
123456789 123456789 12
123456789 123456789 123
123456789 123456789 1234
123456789 123456789 12345
123456789 123456789 123456
123456789 123456789 1234567
123456789 123456789 12345678
123456789 123456789 123456789
123456789 123456789 123456789
run n.4


.....    OMISSIS .......
.....    OMISSIS .......
.....    OMISSIS .......
.....    OMISSIS .......
.....    OMISSIS .......


run n.18

123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789
123456789 1
123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789
123456789 12
123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789
123456789 123
123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789
123456789 1234
123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789
123456789 12345
123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789
123456789 123456
123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789
123456789 1234567
123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789
123456789 12345678
123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789
123456789 123456789
123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789
123456789 123456789
run n.19

123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789
123456789 123456789 1
123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789
123456789 123456789 12
123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789
123456789 123456789 123
123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789
123456789 123456789 1234
123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789
123456789 123456789 12345
123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789
123456789 123456789 123456
123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789
123456789 123456789 1234567
123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789
123456789 123456789 12345678
123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789
123456789 123456789 123456789
123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789
123456789 123456789 123456789

Then a place function test in a big sketch with other code, and result is strange:

test arduino string limits
run n.1

1
12
123
1234
12345
123456
1234567
12345678
123456789
123456789 
run n.2

123456789 1
123456789 12
123456789 123
123456789 1234
123456789 12345
123456789 123456
123456789 1234567
123456789 12345678
123456789 123456789

run n.3

1
12
123
1234
12345
123456
1234567
12345678
123456789
123456789 
run n.4

123456789 1
123456789 12
123456789 123
123456789 1234
123456789 12345
123456789 123456
123456789 1234567
123456789 12345678
123456789 123456789
123456789 123456789 
run n.5

123456789 123456789 1
123456789 123456789 12

4
45
456
4567
45678
456789
456789 
run n.6

456789 1
456789 12
456789 123
456789 1234
456789 12345
456789 123456
456789 1234567
456789 12345678
456789 123456789
456789 123456789 
run n.7

456789 123456789 1
456789 123456789 12
456789 123456789 123
456789 123456789 1234
456789 123456789 12345

7
78
789
789 
run n.8

789 1
789 12
789 123
789 1234
789 12345
789 123456
789 1234567
789 12345678
789 123456789
789 123456789 
run n.9

789 123456789 1
789 123456789 12
789 123456789 123
789 123456789 1234
789 123456789 12345
789 123456789 123456
789 123456789 1234567
789 123456789 12345678

 
run n.10

 1
 12
 123
 1234
 12345
 123456
 1234567
 12345678
 123456789
 123456789 
run n.11

 123456789 1
 123456789 12
 123456789 123
 123456789 1234
 123456789 12345
 123456789 123456
 123456789 1234567
 123456789 12345678
 123456789 123456789
 123456789 123456789 
run n.12

 123456789 123456789 1

3
34
345
3456
34567
345678
3456789
3456789 
run n.13

3456789 1
3456789 12
3456789 123
3456789 1234
3456789 12345
3456789 123456
3456789 1234567
3456789 12345678
3456789 123456789
3456789 123456789 
run n.14

3456789 123456789 1
3456789 123456789 12
3456789 123456789 123
3456789 123456789 1234

6
67
678
6789
6789 
run n.15

6789 1
6789 12
6789 123
6789 1234
6789 12345
6789 123456
6789 1234567
6789 12345678
6789 123456789
6789 123456789 
run n.16

6789 123456789 1
6789 123456789 12
6789 123456789 123
6789 123456789 1234
6789 123456789 12345
6789 123456789 123456
6789 123456789 1234567

9
9 
run n.17

9 1
9 12
9 123
9 1234
9 12345
9 123456
9 1234567
9 12345678
9 123456789
9 123456789 
run n.18

9 123456789 1
9 123456789 12
9 123456789 123
9 123456789 1234
9 123456789 12345
9 123456789 123456
9 123456789 1234567
9 123456789 12345678
9 123456789 123456789
9 123456789 123456789 
run n.19


2
23
234
2345
23456
234567
2345678
23456789
23456789

WHAT ABOUT?

2

Then a place function test in a big sketch with other code, and result is strange:

Which you did not show us. It appears that you never, in the "big sketch", reset the String.

3 
  Serial.println("Test ARDUINO strings limits");

But you are using Strings not strings

 String test = "";

Using Strings (objects created by the String library) as opposed to using strings (zero terminated arrays of chars) is usually regarded as a bad thing in the Arduino community.

Without seeing your larger test program it is going to be difficult to provide help.