About String used in ESP32 testing result

Using Arduino Programming Questions
1

Hi all.
I knew it is not a good practice to use String in ESP32, just simply to do a test with these sketches:

one used String and one not, the String one output good result, and non String one got rebooting, I know this mean nothing, cause of they are simple small codes.
but why?

I have tried to use 'Backtrace: ' in esp32 exception decoder ', didn't get any results after paste the address into esp32 exception decode's window.

Thanks for help.
Adam

String code:

#include <SPI.h>
#include <SD.h>

const byte chipSelect = 10;
String parameter;
byte line;
String theArray[10];

void setup()
{
  Serial.begin(115200);
  while (!Serial);
  Serial.println("Initializing SD card...");
  if (!SD.begin(chipSelect))
  {
    Serial.println("Card failed, or not present");
    while (true);
  }
  Serial.println("card initialized.");
  File myFile = SD.open("params.txt");
  if (myFile)
  {
    while (myFile.available())
    {
      char c = myFile.read();
      if (isPrintable(c))
      {
        parameter.concat(c);
      }
      else if (c == '\n')
      {
        //        Serial.println(parameter);
        theArray[line] = parameter;
        parameter = "";
        line++;
      }
    }
  }
  myFile.close();
  printArray();
}

void loop()
{
}

void printArray()
{
  Serial.println("\nThe array contains :\n");
  for (int line = 0; line < 4; line++)
  {
    Serial.println(theArray[line]);
  }
}

String code output:

17:55:25.928 -> The array contains :
17:55:25.928 -> 
17:55:25.928 -> IPADDRESS = 192.168.1.1
17:55:25.928 -> SSID = WIFI1
17:55:25.928 -> PW = PASS1
17:55:25.928 -> NAME = MYNAME

non String code:

#include <SPI.h>
#include <SD.h>
char recordArray[4][30];
char aRecord[30];
byte recordNum;
byte charNum;

File myFile;

void setup()
{
  Serial.begin(115200);
  while (!Serial)
  {
  }
  Serial.print("Initializing SD card...");
  if (!SD.begin(10))
  {
    Serial.println("initialization failed!");
    while (1);
  }
  Serial.println("initialization done.");
  myFile = SD.open("params.txt");
  if (myFile)
  {
    Serial.println("params.txt:");
    while (myFile.available())
    {
      char inChar = myFile.read();
      if (inChar == '\n')
      {
        strcpy(recordArray[recordNum], aRecord);
        recordNum++;
        charNum = 0;
      }
      else
      {
        aRecord[charNum++] = inChar;
        aRecord[charNum] = '\0';
      }
    }
    myFile.close();
  }
  else
  {
    Serial.println("error opening params.txt");
  }
  printArray();
}

void loop()
{
}

void printArray()
{
  Serial.println("from the array :");
  for (int index = 0; index < 4; index++)
  {
    Serial.println(recordArray[index]);
  }
}

non String code output:

18:06:35.605 -> Initializing SD card...initialization done.
18:06:35.605 -> params.txt:
18:06:35.605 -> Guru Meditation Error: Core  1 panic'ed (LoadProhibited). Exception was unhandled.
18:06:35.605 -> 
18:06:35.605 -> Core  1 register dump:
18:06:35.605 -> PC      : 0x4008a5b0  PS      : 0x00060230  A0      : 0x800d1959  A1      : 0x3ffb1fd0  
18:06:35.652 -> A2      : 0x000d7d98  A3      : 0xffffffff  A4      : 0x000d7d98  A5      : 0x3ffb8dd8  
18:06:35.652 -> A6      : 0x007bf328  A7      : 0x003fffff  A8      : 0x800e4b18  A9      : 0x3ffb2110  
18:06:35.652 -> A10     : 0x3ffc4d4c  A11     : 0xffffffff  A12     : 0x00000000  A13     : 0x3ffb805c  
18:06:35.652 -> A14     : 0x00000002  A15     : 0x00000003  SAR     : 0x0000001a  EXCCAUSE: 0x0000001c  
18:06:35.652 -> EXCVADDR: 0x000d7dd8  LBEG    : 0x40086544  LEND    : 0x4008654e  LCOUNT  : 0x00000000  
18:06:35.652 -> 
18:06:35.652 -> 
18:06:35.652 -> Backtrace: 0x4008a5ad:0x3ffb1fd0 0x400d1956:0x3ffb2010 0x400d1c7f:0x3ffb2040 0x400d2031:0x3ffb2070 0x400e0d66:0x3ffb20a0 0x400e17ee:0x3ffb20c0 0x400e2c09:0x3ffb20e0 0x400e2cca:0x3ffb2110 0x400e4b15:0x3ffb2140 0x400de04f:0x3ffb2160 0x40086f4f:0x3ffb2180 0x4008570d:0x3ffb21a0 0x40085779:0x3ffb21d0 0x400d2bac:0x3ffb21f0 0x400d2b09:0x3ffb2210 0x400d1799:0x3ffb2240 0x400d5362:0x3ffb2290
2

I would guess your file has more than 4 lines.

1 Like
3

Thanks.
I would say you are right. there are some empty lines behind.

4

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