how can I caculate with numbers bigger than a word using 16F88 ?

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- 11th May 2010, 20:52
Mugelpower

how can I caculate with numbers bigger than a word using 16F88 ?

Hi Guys & Dolls,

to make my tripmaster accurate I need to crunch bigger numbers.

my code works like this:

'---[INT - interrupt handler]---------------------------------------------------
ToggleLED1:
cnt = cnt +1
cntb = cnt * 20
meter = cntb / f0
If meter = x Then
meter = 0
km = km + 1
cnt = 0
else
Endif
@ INT_RETURN

but to get more accuracy I need cntb = cnt * 1000 with a maximum of cnt around 4000.

makes 4000000 maximum for cntb .

How could I do that fast enough in my interrupt routine?

Regards
Mugelpower
- 12th May 2010, 01:23
mackrackit

The easy way would be using an 18Fxxx with PBP 2.50 or greater. That way you have LONGs.

Other wise you are stuck with dividing down and messing with HIGH BYTE/LOW BYTE stuff. Just not worth is these days.
- 12th May 2010, 02:02
Charles Linquis

I'm trying to rid the world of 16F chips, but try this

http://www.picbasic.co.uk/forum/show...ght=n-bit_math
- 12th May 2010, 05:08
Jerson

What is x20?
what is f0?
what is x?

A little more detail and it is possible that a different solution exists.

The last time I did something similar, I had a pulses per mile count. After that the mile count would increase by 1. To handle numbers as big as 99999999 you can do it in code like I did

Pseudo code begins

Code:

miles[4] var byte ' lsb to msb on input pulse, pulses=pulses+1 if pulses >= Pulsespermile pulses = 0 ' start counting again till we reach pulses per mile miles[0] = miles[0]+1 if miles[0] > 99 then miles[0] =0 miles[1] = miles[1]+1 if miles[1] > 99 then miles[1] = 0 miles[2] = miles[2]+1 if miles[2] > 99 then miles[2] = 0 miles[3] = miles[3]+1 if miles[3] > 99 then miles[3] = 0 ' roll over to all zero endif endif endif endif endif

Now, displaying this is easy.

Code:

Num = miles[0] dig 1 ' first digit to display digitpos = 0 gosub displaynum ' show the number Num = miles[0] dig 0 ' 2nd digit to display digitpos = 1 gosub displaynum ' show the number Num = miles[1] dig 1 ' 3rd digit to display digitpos = 2 gosub displaynum ' show the number Num = miles[1] dig 0 ' 4th digit to display digitpos = 3 gosub displaynum ' show the number and so on
- 13th May 2010, 02:53
NullDevice

Quote:

Originally Posted by Charles Linquis

I'm trying to rid the world of 16F chips...

I'm with you, Charles, but is there a PIC18 that is nearly the same price as a PIC16F88? I'm doing a low cost consumer product right now where 40 cents makes a big difference. Until that time, that evil PIC16F architecture lives on.
- 13th May 2010, 03:31
Charles Linquis

In some cases,(like high-volume applications), the 16F series makes sense. But too often I see people that work hours (or tens of hours) longer to get something to work because they started out with an inadequate chip on a one-off project.
- 13th May 2010, 04:12
rmteo

Quote:

Originally Posted by NullDevice

I'm with you, Charles, but is there a PIC18 that is nearly the same price as a PIC16F88? I'm doing a low cost consumer product right now where 40 cents makes a big difference. Until that time, that evil PIC16F architecture lives on.

According to here PIC16F88 the lowest cost device is $2.20 - if you go here PIC18 Product Family and do a sort on ascending price, you will find about 45 PIC18's that cost less than a PIC16F88. That said, I use several competitive 32-bit devices that are about half that price.
- 13th May 2010, 07:47
Darrel Taylor

Not sure, but maybe you can just change 1-line.

Code:

'---[INT - interrupt handler]--------------------------------------------------- ToggleLED1: cnt = cnt +1 cntb = cnt * 20 ; could be * 1000 meter = DIV32 f0 If meter = x Then meter = 0 km = km + 1 cnt = 0 Endif @ INT_RETURN

Depends on what f0 and x are.
- 16th May 2010, 23:27
BigWumpus

If you are looking for costs ... forget all this old 16F... or 18F...-devices.

Take new cheap dsPic33 or ...J... or ...K... -devices.
The new devices are very cheap, the old stuff is expensive !!!!
- 17th May 2010, 02:51
Bill Legge

Big Numbers

Not an economic solution but great fun is the 'floating point co-processor' from Micromega. Costs about $20. the free IDE make developing the code a doddle.

Regards Bill Legge