Gordon,

I've sent you an excel spreadsheet under separate cover in oorder to not
post a big attachemtn to the list.

Here is the idea:  Teach Excel to do some of your work for you.  The
spreadsheet does the following:

1.  Calculates 1/F,  1/F / 2, and converts it to microseconds, which is the
same as machine cycles in a 4mHz PIC.

2. Formats this info into an array:    int16 freqlookup[] = { 625, 588, etc
etc };  << All this tedious symtax is generated inside Excel

3.  Now cut and paste the array into your C code

4. Place it in a constant table like this:

BYTE CONST freqlookup[] = { 625, 588, etc etc };
warning, this works in CCS C, may not in Hitech

5.  Use it in your code like this:

freqlookup[5];


6.  Stuff this number into a timer preset, say you are using timer2, preset
Timer2 with 65535 - freqlookup[x], where x is incremented each timer
interrupt.

This is all off the top of my head, YMMV.

--Lawrence

----- Original Message -----
From: "Gordon Varney" <gordonv@IAMNEE.COM>
To: <PICLIST@MITVMA.MIT.EDU>
Sent: Wednesday, June 05, 2002 3:37 PM
Subject: [PIC]: incrementing in steps


> I need a pin to clock out a square wave at 800Hz. Simple, just set pin
high for 625us, set pin low for 625us, and
> repeat.
>
> Now I need to increment the clock frequency by 50Hz, do some work and
increment by 50Hz again, continue incrementing
> until complete. The step duration in a time period is not a constant. What
is the best method to incrementing the
> frequency by 50Hz.
>
> (Note: I am using a combination of Assembly and the CCS compiler for this
program.)
>
> Gordon Varney
> www.iamnee.com
>
> --
> http://www.piclist.com hint: To leave the PICList
> mailto:piclist-unsubscribe-request@mitvma.mit.edu
>
>

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