| At line 1 changed one line |
| !!!Sound in Forth (translation pending) |
| !!!Sound in Forth |
| At line 3 added 106 lines |
| %%tabbedSection |
| %%tab-english |
| This time we cover sounds. I have found the Basic Programm below to which creates a hoover sound. |
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| In VolksFORTH there is no build in SOUND command, so we have to build one that is compatible with the BASIC Sound command. |
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| With that new Word *SOUND* we can recreate the hoover sound in Forth. |
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| The BASIC Porgramm needs 5 variables (LOW, HIGH, P, AGAIN, WAIT), the Forth versions works without any variable declaration, all values are passed on the stack. This is one reason why Forth is memory efficient. |
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| The content of this word in detail |
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| CH# = Pokey Sound Channel 0-3 |
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| FREQ - Frequency |
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| DIST - distortion |
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| VOL - Sound volume |
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| The comment show what is on the Stack |
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| {{{ |
| : SOUND ( CH# FREQ DIST VOL -- ) |
| SWAP ( CH# FREQ VOL DIST -- we swap volume and distortion ) |
| $10 ( CH# FREQ VOL DIST $10 -- hexadecimal $10 or decimal 16 on the stack ) |
| \* ( CH# FREQ VOL DIST\*$10 -- distortion is now multiplied by 16 ) |
| + ( CH# FREQ VOL+DIST\*$10 -- volume and distortion are added together ) |
| ROT ( FREQ VOL+DIST\*$10 CH# -- we rotate the topmost 3 stack items, brining CH# on the top ) |
| DUP ( FREQ VOL+DIST\*$10 CH# CH# -- we duplicate the topmost stack item, the Channel ) |
| + ( FREQ VOL+DIST\*$10 CH#+CH# -- the Pokey Frequency Registers are two bytes apart, so we multiply the channel by 2 by adding the channel values ) |
| AUDBASE ( FREQ VOL+DIST\*$10 CH#\*2 $D200 -- we put the constant AUDBASE on the Stack, value is $D200, the first pokey frequency register ) |
| + ( FREQ VOL+DIST\*$10 CH#\*2+$D200 -- we add the channel to AUDBASE ) |
| ROT ( VOL+DIST\*$10 CH#\*2+$D200 FREQ -- we rotate the topmost 3 Stackitems, bringing the Frequency on top ) |
| OVER ( VOL+DIST\*$20 CH#\*2+$D200 FREQ CH#\*2+$D200 -- OVER copies the 2nd Stackitem on the Top of the Stack ) |
| C! ( VOL+DIST\*$20 CH#\*2+$D200 -- we store [think POKE] the Frequency value in the Pokey Frequency register ) |
| 1+ ( VOL+DIST\*$20 CH#\*2+$D200+1 -- we increment the topmosat stackvalue, which points now on the register for volume and distortion ) |
| C! ( -- we store volume and distortion in the Pokeys volume and distortion register ) |
| ; ( end of definition of SOUND word ) |
| }}} |
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| And now the same stuff with real values for the command 0 54 10 14 SOUND |
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| {{{ |
| : SOUND ( 0 54 10 14 -- ) |
| SWAP ( 0 54 14 10 -- we swap volume and distortion ) |
| $10 ( 0 54 14 10 16 -- hexadecimal $10 or decimal 16 on the stack ) |
| \* ( 0 54 14 160 -- distortion is now multiplied by 16 ) |
| + ( 0 54 174 -- volume and distortion are added together ) |
| ROT ( 54 174 0 -- we rotate the topmost 3 stack items, brining CH# on the top ) |
| DUP ( 54 174 0 0 -- we duplicate the topmost stack item, the Channel ) |
| + ( 54 174 0 -- the Pokey Frequency Registers are two bytes apart, so we multiply the channel by 2 by adding the channel values ) |
| AUDBASE ( 54 174 0 $D200 -- we put the constant AUDBASE on the Stack, value is $D200, the first pokey frequency register ) |
| + ( 54 174 $D200 -- we add the channel to AUDBASE ) |
| ROT ( 174 $D200 54 -- we rotate the topmost 3 Stackitems, bringing the Frequency on top ) |
| OVER ( 174 $D200 54 $D200 -- OVER copies the 2nd Stackitem on the Top of the Stack ) |
| C! ( 174 $D200 -- we store [think POKE] the Frequency value 64 in the Pokey Frequency register $D200 ) |
| 1+ ( 174 $D201 -- we increment the topmosat stackvalue, which points now on the register for volume and distortion ) |
| C! ( -- we store volume and distortion 174 in the Pokeys volume and distortion register $D201 ) |
| ; ( end of definition of SOUND word ) |
| }}} |
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| BASIC Version |
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| {{{ |
| 10 REM european hooter |
| 15 LOW=57:HIGH=45:P=45 |
| 20 FOR AGAIN=1 TO 20 |
| 30 SOUND 0,P,10,14 |
| 40 FOR WAIT = 1 TO 180: NEXT WAIT |
| 50 P=LOW:LOW=HIGH:HIGH=P |
| 60 NEXT AGAIN |
| 70 SOUND 0,0,0,0 |
| 80 END |
| }}} |
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| VolksForth Sound Command |
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| {{{ |
| \\ Atari 8bit Sound Command |
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| $D200 CONSTANT AUDBASE |
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| : SOUND ( CH# FREQ DIST VOL -- ) |
| SWAP $10 * + ROT DUP + AUDBASE + |
| ROT OVER C! 1+ C! ; |
| }}} |
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| {{{ |
| : hoover |
| 57 54 ( Sound values for hoover sound ) |
| 20 0 DO |
| OVER |
| 0 SWAP 10 14 SOUND |
| 500 0 DO LOOP ( delay loop ) |
| SWAP ( change sounds ) |
| LOOP |
| 0 0 0 0 SOUND ; |
| }}} |
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| /% |
| %%tab-german |
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| At line 149 added 5 lines |
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| /% |
| /% |
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, unless otherwise noted.