Printing the array using print and serial write function in Arduino Uno

Question

I have, one program with only using printing array and other with serial write and print function for the array, while using serial write and print function I get these extra characters between the data as shown below, can anyone help me with this

Printing the array with print function

uint8_t a[13] = {0x11, 0x22, 0x33, 0x44, 0x55, 0x66, 0X77, 0x88,
                 0x01, 0x02, 0x03, 0x04, 0x05};
int i;
void Print_Hexa(uint8_t num) {
  char Hex_Array[2];
sprintf(Hex_Array, "%02X", num);
  Serial.print(Hex_Array);
}
void setup() {
  Serial.begin(9600);
}
void loop() {
  for (i = 0; i <= 12; i++) {
    //Serial.write(a[i]);
    Print_Hexa(a[i]);
  }
  Serial.println();
  delay(100);
}

Using with serial write and print function for array

uint8_t a[13] = {0x11, 0x22, 0x33, 0x44, 0x55, 0x66, 0X77, 0x88,
                 0x01, 0x02, 0x03, 0x04, 0x05};
int i;
void Print_Hexa(uint8_t num) {
  char Hex_Array[2];
sprintf(Hex_Array, "%02X", num);
  Serial.print(Hex_Array);
}
void setup() {
  Serial.begin(9600);
}
void loop() {
  for (i = 0; i <= 12; i++) {
    Serial.write(a[i]);
    Print_Hexa(a[i]);
  }
  Serial.println();
  delay(100);
}

score 6 · Answer 1 · answered Jul 29 '21 at 13:58

Serial.write(some_byte) writes a byte on the serial output. The Arduino serial monitor tries to interpret the bytes it receives as text:

0x11 is a control character, displayed as “□”
0x22 is the ASCII code for the double quote (")
0x33 is the ASCII code for the digit 3.
0x44 is the ASCII code for the uppercase letter “D”
etc.

score 1 · Answer 2 · answered Jul 29 '21 at 13:39

To store a 2 character string you need a 3 byte array, not a 2 byte array. This is because in C a string consists of the actual string data and a zero ("NULL") byte at the end to indicate where the end of the string is.

So you would need:

char Hex_Array[3];

so it can store, for the number 0x69: 69\0. Otherwise you overrun the array and corrupt other data that follows in the stack, and changing that other data corrupts your string by changing the "end of string" marker to some other random ASCII character.

Printing the array using print and serial write function in Arduino Uno

2 Answers2