Subject:
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Re: Play tones with legOS !
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Newsgroups:
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lugnet.robotics.rcx.legos
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Date:
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Mon, 29 Nov 1999 03:54:05 GMT
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Viewed:
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1101 times
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I can't think of any possible reason why I would ever use this, but it is
still cool... it's great to come back and see that people (other than
Markus) have been working on stuff. My two cents on all of that tomorrow-
-Luis
On Mon, 29 Nov 1999, Martin Cornelius wrote:
> Date: Mon, 29 Nov 1999 03:28:47 GMT
> From: Martin Cornelius <Martin.Cornelius@t-online.de>
> To: lugnet.robotics.rcx.legos@lugnet.com
> Subject: Play tones with legOS !
>
> Because dsound_play currently doesn't work for me, and because i wanted
> to make some noise under legOS with little memory and CPU footprint, i
> wrote a little function that plays arbitrary tones without using
> interrupts. I allows to play any frequency (in Hz) from 31 to 65535.
>
> The sound timer is programmed just the same way as the infrared carrier
> timer. The only tricky thing is to find the best prescaler mode for the
> frequency to produce and the correct compare match value. My solution
> uses a table for the first task and some rounding arithmetics for the
> second.
>
> If you want to play melodies by just copying from your old beatles
> songbook, please wait until tomorrow... i'm going to build a header file
> containing macros with mode/match settings for all keys on my piano.
> This will be even faster than the frequency approach because nothing has
> to be computed, just load the timer and go.
>
> #include <sys/h8.h>
>
> typedef struct modeTableEntry
> {
> unsigned minFreq;
> unsigned char CKSmask;
> unsigned long base;
> } modeTableEntry ;
>
> modeTableEntry modeTable[] =
> {
> { 3907, 0x01, 10000000UL },
> { 977, 0x82, 2500000UL },
> { 489, 0x02, 1250000UL },
> { 123, 0x83, 312500UL },
> { 31, 0x03, 78125UL },
> };
>
> void playTone(unsigned frequency)
> {
> modeTableEntry *entry = modeTable;
> unsigned long quot10,quot,reminder;
>
> if (frequency < 31) frequency=31;
>
> // find best mode for this freqency
> while (frequency < entry->minFreq) ++entry;
>
> // compute compare match Value
> quot10 = entry->base / frequency;
> quot = quot10 / 10;
> reminder = quot10 - (quot*10);
> if (reminder < 5) quot-=1;
>
> // start timer
> T0_CR = 0x00; // timer off
> T0_CNT = 0x00; // counter reset
> if (entry->CKSmask & 0x80)
> STCR |= 0x01; // ICKS0 = 1
> else
> STCR &= ~0x01; // ICKS0 = 0
> T0_CORA = quot; // set compare match A
> T0_CSR = CSR_TOGGLE_ON_A; // Output toggles on compare Match A
> T0_CR = CR_CLEAR_ON_A | (entry->CKSmask &0x3); // Go
> }
>
> void quiet()
> {
> T0_CR = 0x00; // timer 0 off
> }
>
>
#######################################################################
Profanity is the one language that all programmers understand.
-Anonymous
#######################################################################
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Message is in Reply To:
 | | Play tones with legOS !
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| Because dsound_play currently doesn't work for me, and because i wanted to make some noise under legOS with little memory and CPU footprint, i wrote a little function that plays arbitrary tones without using interrupts. I allows to play any (...) (25 years ago, 29-Nov-99, to lugnet.robotics.rcx.legos)
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