Thread: Convert BCD to Binary

Hi anyone knows how to Convert BCD to Binary in PIC18F2620 using c language?

I do it by hand.
Supposing you have an array of BCD numbers.

int BCD_numbers[] = {3, 2, 7, 6, 8};
int result, i;

result = 0;
for(i=0;i<5;i++)
result *= 10 + BCD_numbers[i];

result now should contain 0x7FFF.

Assuming it's packed BCD in an integer then the following should work,

Code:

unsigned int BCDtoI(unsigned int BCD){
unsigned int result;
    result=(BCD>>12)*1000;
    result+=((BCD>>8)&0x0f)*100;
    result+=((BCD>>4)&0x0f)*10;
    result+=((BCD)&0x0f);
    return result;
}

Mike.

is it okie to write in this way:

int BCD2BINARY(int x)
{
int binary;
binary = ((x & 0xF0 )>>4 ) * 10 + (x & 0x0F);
return (binary);
}

Originally Posted by Pommie

Assuming it's packed BCD in an integer then the following should work,

Code:

unsigned int BCDtoI(unsigned int BCD){
unsigned int result;
    result=(BCD>>12)*1000;
    result+=((BCD>>8)&0x0f)*100;
    result+=((BCD>>4)&0x0f)*10;
    result+=((BCD)&0x0f);
    return result;
}

Mike.

hi pommie can u explain ur coding,i am new in c,but i am very much interested to learn,please

All the code is doing is getting the relevant digit and multiplying by the decimal value. So, BCD>>12 will get the thousands digit which is then multiplied by 1000.

Mike.

Hi pommie,

Thanks for the reply, however i was wondering why must it shift by 3 and times 3?

Originally Posted by apricot_star

Hi pommie,

Thanks for the reply, however i was wondering why must it shift by 3 and times 3?

The way to convert a BCD number to it's binary equivalent is to divide the high digit by 16 and then multiply by 10. Another way to do the same thing is to subtract the high digit * 6 (16-10). To do this in code you do BCD>>4 to get the high digit and then multiply by 6. As 6 is 3*2 then you can reduce the number of shifts by 1 and multiply by 3. This is just the same as saying that BCD/16*6 is the same as BCD/8*3.

The less efficient (but more logical) way to write the same thing is,
bcd-=((bcd&0xf0)>>4)*6;

Mike.

Convert BCD to Binary
Hi anyone knows how to Convert BCD to Binary in Psoc using assembly language?

Ha, was just looking at the 18F data sheet instructions. The assembler instruction, DAW, looks custom fit for the BCD to BIN decode. Would this do the trick?

Code:

;Decode say a DS1307 minutes from BCD to binary
;minutes = 0x27 BCD
	call	FN_READ8BIT
	movff	   READ8BIT,MIN
	movf	   MIN,W,BANKED
	daw
	movwf  MIN,BANKED 
;MIN is now 27 minutes in binary?