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Jorge
Asked: 2020-01-23 19:36:07 +0800 CST 2020-01-23 19:36:07 +0800 CST

How can I convert a number to hexadecimal in Arduino?

  • 772

I have tried to convert the number that a reading returns to me to hexadecimal. I have not found any reference.

This is the code:

byte dummy = 0x00;

byte readCard[4];

String datoWifi = "";

 for (int i = 0; i < 4; i++) {  //
    readCard[i] = mfrc522.uid.uidByte[i];
        //dummy = (readCard[i], HEX); //esto no funciona
    datoWifi += (String) mfrc522.uid.uidByte[i];
    Serial.print(readCard[i], HEX);//de esta manera se imprime correctamente
  }

Using Serial.print(readCard[i], HEX);the hexadecimal value is printed perfectly, however what I need is to be able to construct datoWifithat it is a type variable Stringnot with the returned numbers, but with the conversion already done.

I hope that there is some function already created for it and that the solution is not to create the function from scratch because that is what I want to avoid.

c++

2 Answers

  1. Best Answer

    What you need is to use the proper constructor :String

    byte dummy = 0x00;

byte readCard[4];

String datoWifi = "";

for (int i = 0; i < 4; i++) {
    readCard[i] = mfrc522.uid.uidByte[i];
    datoWifi += String(readCard[i], HEX);
}
    • 3

  2. For this type of conversions you have the library iomanip(IO MANIPulation). What happens is that this library only works with streams . So the solution is to use stringstreamand then dump the result to your variable string:

    #include <sstream>
#include <iomanip>

std::stringstream ss;
ss << std::hex << mrfc522.uid.uidByte[i];
datoWifi += ss.str();

    If you need the 0xtypical numbers in hexadecimal, you will have to add it manually:

    ss << "0x" << std::hex << mrfc522.uid.uidByte[i];
    • 2