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Author Topic: How to convert a number to binary ?  (Read 1277 times)
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I do not know how to convert a number to binary.

I have seen the way with Serial.print(x,bin) but what I want is a variable to take the binary and not just to print it.

For example :
When x is a random number
y = (x, BIN);
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Numbers are already stored in binary.

Perhaps you should give us a broader sense of what you are trying to do, rather than how you are trying to do it.
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Code:
unsigned long convToBin(unsigned int x) {'
  unsigned long ret = 0;
  for (unsigned char i=0; i<sizeof(x)*8; i++) {
    if (x & _BV(i)) ret += 10 * i;
  }
}
untested
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I do not know how to convert a number to binary.

It's not clear what you are trying to do. My guess is that you are trying to produce an ascii string of '1' and '0' characters containing a binary textual representation of an integer, similar to what you'd get if you printed the number to the Serial port with binary format. Is that right?
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If you are talking about a binary string: 3 = "00000011" for example, the following does it:

Code:
unsigned char *hex2binstr(unsigned char *str, unsigned char dat) {
  unsigned char mask = 0x80;
  do {
    if (dat & mask) *str='1'; //the bit is 1
    else *str='0'; //otherwise it is 0
    str+=1; //increment the pointer
    mask = mask >> 1; //shift mask
  } while (mask);
  return str;
}

It converts an unsigned char into an 8-char string.

You can then build on top of it routines that convert more complex structures into str.
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Here is what you can do to convert a short / long:

Code:
//convert a char type to a binary string
unsigned char * uc2binstr(unsigned char * str, unsigned char dat) {
...
}

//convert a short type to binary string
unsigned char * us2binstr(unsigned char *str, unsigned short dat) {
  str=uc2binstr(str, dat >> 8); //convert msb first
  str=uc2binstr(str, dat);
  return str;
}

//convert a long type to binary string
unsigned char * ul2binstr(unsigned char *str, unsigned long dat) {
  str=us2binstr(str, dat >> 16); //convert msw first
  str=us2binstr(str, dat);
  return str;
}

On longer types, you can simply use one of those routines successively, starting with the msb/msw first.
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There are four functions available in the AVR library that you might want to use:

char* itoa    ( int  __val, char *  __s, int  __radix)    

http://www.nongnu.org/avr-libc/user-manual/group__avr__stdlib.html#ga4f6b3dd51c1f8519d5b8fce1dbf7a665

Passing the __radix parameter the value 2 will give you a binary character string.

Cheers, Mikael
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Hello and welcome, maybe you just want to know how to write a number as binary?

By adding "0b" prefix (or "B" prefix, for bytes (8 bits) only), like this:

Code:
int x = 0b0011000000111001; //binary notation for 12345
byte y = B01111011;   //binary notation for 123
byte z = 0b01111011; //also valid of course

More infos here: http://en.wikipedia.org/wiki/Binary_numeral_system
« Last Edit: November 20, 2012, 12:25:20 am by guix » Logged

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I do not know how to convert a number to binary.

It's not clear what you are trying to do. My guess is that you are trying to produce an ascii string of '1' and '0' characters containing a binary textual representation of an integer, similar to what you'd get if you printed the number to the Serial port with binary format. Is that right?

First of all, thank you all for the immediate correspondence and really sorry for mine late correspondence, but I work too much and the free time is little."

PeterH , Yes ! This is what I want. For example I have an integer x = 100 and I want another variable y to take the binary of 100 => "0 1 1 0 0 1 0 0". As I am a newbie I do not know many things. Please be as simplest and more detailed (regarding commands) as you can!
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Quote
For example I have an integer x = 100 and I want another variable y to take the binary of 100
Code:
byte y = x;
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Quote
For example I have an integer x = 100 and I want another variable y to take the binary of 100
Code:
byte y = x;

Thank you for your answer but I am not sure that it works as when I create the program :

int x= 100;
void setup() {
 Serial.begin(9600);
}
void loop() {
  byte y = x;
   Serial.println (y);
}

It prints 100. Why ?
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Thank you for your answer but I am not sure that it works as when I create the program :

int x= 100;
void setup() {
 Serial.begin(9600);
}
void loop() {
  byte y = x;
   Serial.println (y);
}

It prints 100. Why ?
Because you told it to. What are you expecting it to do?

Serial.print() and Serial.println() convert 100 to '1', '0' and '0'. to print it to the screen. You can use Serial.write and it will send the binary value of 100 to the screen, which is 'd'.
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If you want to print the binary representation of the value, you have to tell Serial.print() that. Look at the documentation for how.
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If you want to print the binary representation of the value, you have to tell Serial.print() that. Look at the documentation for how.

Yes I know. Serial.print(y,bin).

Something else I would like to know is about how can I separate a 16 bin value of a variable into
 2 8bin variables. For example  x = 0B1111111100000001, I would like  y to be 0B11111111 and
 z = 0B00000001 in order to send them with shiftout (using 2 shift registers) to another chip.
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Quote
Something else I would like to know is about how can I separate a 16 bin value of a variable into
 2 8bin variables. For example  x = 0B1111111100000001, I would like  y to be 0B11111111 and
 z = 0B00000001 in order to send them with shiftout (using 2 shift registers) to another chip.
So, you WERE able to find the reference page. Too bad you didn't spend just a little bit longer there. That's a page well worth spending more then 2 minutes at. You should at least familiarize your self with the available functions, even if you don't study things like highByte and lowByte. Just knowing that they are there is useful.
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