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Chapter #8: Frequency and Sound · Page 253
' -----[ Subroutine - Find Equals Character ]----------------------------FindEquals:
DO
READ RTTTL_File + counter, char
counter = counter + 1
LOOP UNTIL char = "="
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Go through characters in
RTTTL file looking for
'='. Increment counter
until '=' is found, then
return.
RETURN
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-----[ Subroutine - Read Tempo from RTTTL Header ]---------------------Each keyboard character has a unique number called an ASCII value.
The characters 0, 1, 2,...9 have ASCII values of 48, 49, 50,...57.
You can always convert from the character representing a digit to
to its value by subtracting 48 from the variable storing the digit.
You can examine this by comparing DEBUG DEC 49 and DEBUG 49.
GetTempo:
default_b = 0
DO
READ RTTTL_File + counter, char
IF char = ":" THEN
default_b = default_b / 10
counter = counter + 1
EXIT
ENDIF
default_b = default_b + char - 48
counter = counter + 1
default_b = default_b * 10
LOOP UNTIL char = ":"
RETURN
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Parse RTTTL file for Tempo.
Convert characters to
digits by subtracting 48
from each character's ASCII
value. Iteratively multiply
each digit by 10 if there
is another digit, then add
the most recent digit to
one's column.
For example, the string
"120" is (1 X 10 X 10)
+ (2 X 10) + 0. The '1'
is converted first, then
multiplied by 10. The '2'
is then converted/added.
0 is converted/added, done.
' -----[ Subroutine - Look up Octave ]-----------------------------------ProcessOctave:
READ RTTTL_File + counter, char
SELECT char
CASE "5" TO "8"
noteOctave = char - "0"
counter = counter + 1
CASE ELSE
noteOctave = default_o
ENDSELECT
IF default_o = 0 THEN
default_o = noteOctave
ENDIF
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Octave may or may not be
included in a given note
because any note that is
played in the default
octave does not specify
the octave. If a char
from '5' to '8' then use
it, else use default_o.
Characters are converted
to digits by subtracting
'0', which is the same as
subtracting 48. The first
time this subroutine is
called, default_o is 0.