CCF Tools

Conversion between RC5 and IRMan codes

If you use Girder intensively in conjonction with CCF Tools, may be you need to convert RC5 codes (extracted from CCF file) to IRMan codes (in order to generate Girder configuration file)

IRMAN code format

IRMan codes are defined by a 6 bytes hex string (12 hex digits).

Example :

14E000000000

RC5 format

RC5 codes are completely determined by 2 values named :

• system (between 0 and 31 included)
• command (between 0 and 127 included)

ProntoEdit writes this kind of code as a 6 short values string in hexadecimal format

5000 0000 0000 0001 system command

where system and command values are written as 4 digits hex strings prefilled with 0.

Example : For this RC5 code

5000 0000 0000 0001 001C 0021

• system is 001Ch = 28d
• command is 0021h = 33d

After some research, I discovered conversion formulas between these 2 formats :

RC5 to IRMan format conversion

By chance, RC5 codes are always translated like that : only the first 3 digits are important, the last 9 digits are always 0.

Let a,b,c these first 3 digits, x the system value and y the command value, the conversion formulas written in C code are :

	if (y >= 64)
	{
	  x = 31 - x;
	  y = 127 - y;
	}
	a = ( x >> 2 ) ^ 5;
	b = ( ( y << 4 ) + 4 * ( x & 3 ) ) ^ 5;
	c = ( y & 15 ) ^ 5;
  

Example :

	RC5 code = 5000 0000 0000 0001 001C 0021
	

gives

	x = 1Ch = 28d
	y = 21h = 33d

then

	a = ( 28 >> 4 ) ^ 5 = 7 ^ 5 = 2
	b = ( ( 33 >> 4 ) + 4 * ( 28 & 3 ) ) ^ 5 = ( 2 + 4 * 0 ) ^ 5 = 2 ^ 5 = 7
	c = ( 33 & 15 ) ^ 5 = 1 ^ 5 = 4
	

hence

	IRMan code = 274000000000
	

IRMan to RC5 format conversion

The previous formulas need to be reversed, you will notice that for given values a,b,c there will be 2 x,y possible couples.

	x = ( ( a ^ 5 ) << 2 ) + ( ( b ^ 5 ) >> 2 );
	y = ( ( ( b ^ 5 ) & 3 ) << 4 ) + ( c ^ 5 );
  

the first solution is

	x1 = x;
	y1 = y;
  

the second solution is

	x2 = 31 - x;
	y2 = 127 - y;
  

Example :

	IRMan code = 274000000000
	

gives

	a = 2		a ^ 5 = 7
	b = 7		b ^ 5 = 2
	c = 4		c ^ 5 = 1

then

	x1 = ( 7 << 2 ) + ( 2 >> 2 ) = 28 + 0 = 28 = 1Ch
	y1 = ( ( ( 2 & 3 ) << 4 ) + 1  = ( 2 << 4 ) + 1 = 33 = 21h
	x2 = 31 - 28 = 3
	y2 = 127 - 33 = 94 = 5Eh
	

hence

	RC5 code 1 = 5000 0000 0000 0001 001C 0021

or

	RC5 code 2 = 5000 0000 0000 0001 0003 005E

As a conclusion, 32 * 128 /2 = 2048 differents IRMan codes can be generated.

But I discovered, there are conflicts with some well known remote controls which use these codes

• Many Philips devices
• Canal+ and Canal Satellite decoder

Obviously there will be no problem if you don't own these types of devices.

Conversion between RC5x and IRMan codes

to be continued...