On Sat, 19 May 2018, David C Brown wrote:

> Use repeated subtraction of 100 to get the top nibble then use a 100 entr=
y
> lookup table for the two lower nibbles.  Fast and compact.

Yes I was just putting together some code to show this and you beat me to=20
it. Also take into account that the last two bits don't change with=20
repeated subtraction of 100 and you can speed the whole thing up by using
8 bit arithmetic instead of 16bit.

e.g.
// y =3D 0;
//
// while (x >=3D 100)
// {
//      y++;
//
//       x -=3D 100;
// }
//
// res =3D (arr[y] << 8) | arr[x];
//

// // 100 base 10 =3D 64 base 16 =3D 01100100 base 2
//
// uint8 x8, pl, ph;
// int16 res;
//
// convert 10 bit number to 8 bit number
// x8 =3D x >> 2;
//
// ph =3D 0;
//
// while (x8 >=3D (100 >> 2))
// {
//      ph++;
//      x8 -=3D (100 >> 2);
// }
//
// will always be 8 bits
// pl =3D (x & 3) | (x8 << 2);
//
// 2 x 8 bit BCD packed into 16 bit variable
// res =3D (arr[ph] << 8) | arr[pl];
//

where arr =3D
0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x08, 0x09
0x10, ... 0x19,
0x20, ... 0x29,
....
0x90, ... 0x99

Regards
Sergio Masci

>
>
> __________________________________________
> David C Brown
> 43 Bings Road
> Whaley Bridge
> High Peak                           Phone: 01663 733236
> Derbyshire                eMail: dcb.home@gmail.com
> SK23 7ND          web: www.bings-knowle.co.uk/dcb
> <http://www.jb.man.ac.uk/~dcb>
>
>
>
> *Sent from my etch-a-sketch*
>
> On 19 May 2018 at 17:25, Jean-Paul Louis <louijp@gmail.com> wrote:
>
>> Wayne,
>> With 9bit input and 10/11 bit output, a lookup table will be fast and
>> inexpensive.
>>
>> Just a thought,
>> Jean-Paul
>> N1JPL
>>
>> On Fri, May 18, 2018, 6:53 PM Dwayne Reid <dwayner@planet.eon.net> wrote=
:
>>
>>> Good day to all.
>>>
>>> I'm looking for a small, fast 9-bit binary-to-decimal conversion
>>> routine.  Somewhere between Scott Datallo's 8-bit-to-decimal and John
>>> Payson's 16-bit-to-decimal routines.
>>>
>>> Input range is [0..511] in binary, output in BCD or
>>> packed-BCD.  Actual input range for this project is 0..399 but I
>>> might as well try to get the full 9-bits of range.
>>>
>>> Short and fast if possible.
>>>
>>> I've been looking at PICLIST.com as well as my old email archives but
>>> haven't seen anything that is both short and fast.
>>>
>>> Does anyone have something that they can share?
>>>
>>> Many thanks!
>>>
>>> dwayne
>>>
>>> --
>>> Dwayne Reid   <dwayner@planet.eon.net>
>>> Trinity Electronics Systems Ltd    Edmonton, AB, CANADA
>>> 780-489-3199 voice   780-487-6397 fax   888-489-3199 Toll Free
>>> www.trinity-electronics.com
>>> Custom Electronics Design and Manufacturing
>>>
>>> --
>>> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
>>> View/change your membership options at
>>> http://mailman.mit.edu/mailman/listinfo/piclist
>>>
>> --
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>> View/change your membership options at
>> http://mailman.mit.edu/mailman/listinfo/piclist
>>
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>
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