newbie - int to char* and more.

[rebelo55]

Hello,

I am new to QT on Linux. I've been a .NET programmer and now working on Beaglebone Black. I'm using C++ to communicate with a motor controller which requires a command's parameter to be sent one byte at a time.

My function receives an int (decimal) and this needs to be converted to Hex and then sent to another function one byte at a time.
For example,

Function parameter -> 16000 (decimal)
convert it to Hex -> 3E80
format the number as 000000 -> 003E80
now this number must be sent one byte at a time so it must be broken down like this:
char x[3];
x[0] = 0x00;
x[1] = 0x3E;
x[2] = 0x80;

How can I achieve this? Sorry I'm a real newbie in C++/QT.

Thanks

[d_stranz]

This is C++ 101. You should be able to use a union for this:

union myConverter
{
  std::uint32_t intVal;
  unsigned char[4] charVal;
}
 
myConverter c;
c.intVal = 16000;
 
// c.charVal[0] - [3] now contains the unsigned hex values

union myConverter
{
  std::uint32_t intVal;
  unsigned char[4] charVal;
}

myConverter c;
c.intVal = 16000;

// c.charVal[0] - [3] now contains the unsigned hex values

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Of course, this assumes you have the same byte order on your target device. If not, you'll need to swap bytes around.

[ChrisW67]

Or something like this

quint32 value = 16000;  // or 0x00003e80
char x[3];
x[0] = (value >> 16) & 0xff ;
x[1] = (value >>  8) & 0xff ;
x[2] =  value & 0xff ;

quint32 value = 16000;  // or 0x00003e80
char x[3];
x[0] = (value >> 16) & 0xff ;
x[1] = (value >>  8) & 0xff ;
x[2] =  value & 0xff ;

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The question really has nothing to do with hex, which is a human friendly string representation of a binary value.

[rebelo55]

Both the solutions worked. thanks experts!!