Mercurial > hg > index.fcgi > lj > lj046

comparison tools/mktables.c @ 0:c84446dfb3f5

find changesets by author, revision, files, or words in the commit message
initial add
author paulo@localhost
date Fri, 13 Mar 2009 00:39:12 -0700
parents
children
comparison
equal deleted inserted replaced
-1:000000000000 0:82b9cb16b44a
1 #include <stdlib.h>
2 #include <stdio.h>
3 #include <math.h>
4
5 /*
6 Pin Eight standard tuning defines middle C as 2093/8 Hz.
7 It uses equal temperament: a semitone difference between two pitches
8 is a factor of 2^(1/12) between their frequencies.
9 Thus, MIDI 0 = 60, or 2093/256.
10 */
11 #define C_IN_OCTAVE(octave) \
12 ((double)((long int)2093 << octave) / 256.0)
13 #define TWELFTH_ROOT_OF_TWO 1.0594630943592952645618252949463
14
15 /*
16 DS note frequencies for the tone generator at 8 samples per period
17 are ((-0x1000000 / (n * 8)))
18 */
19 #define FREQ_TO_PSG_PERIOD(freq) \
20 ((unsigned short)(-0x1000000 / (freq * 8)))
21
22
23 int writePSG(FILE *fp) {
24
25 // write header
26 fputs(".section .rodata\n"
27 ".balign 4\n"
28 ".global midi2psgFreq\n"
29 "midi2psgFreq:", fp);
30
31 int octave = 0;
32
33 for (; octave < 2; ++octave) {
34 fprintf(fp, "\n@ unsupported octave %d\n.byte ", octave);
35 for (int semitone = 0; semitone < 12; ++semitone) {
36 if (semitone) {
37 fputs(", ", fp);
38 }
39 fputs(" 0, 0", fp);
40 }
41 }
42 for (; octave < 10; ++octave) {
43 double freq = C_IN_OCTAVE(octave);
44 fprintf(fp, "\n@ octave %d\n.byte ", octave);
45 for (int semitone = 0; semitone < 12; ++semitone) {
46 if (semitone) {
47 fputs(", ", fp);
48 freq *= TWELFTH_ROOT_OF_TWO;
49 }
50 unsigned int psgFreq = FREQ_TO_PSG_PERIOD(freq);
51 printf("midi %2d = %.2f = psg %5d\n",
52 octave * 12 + semitone,
53 freq,
54 psgFreq);
55 fprintf(fp, "%3u,%3u",
56 psgFreq & 0xFF,
57 (psgFreq >> 8) & 0xFF);
58 }
59 }
60
61 fputs("\n", fp);
62 return 0;
63 }
64
65 /**
66 * Writes lookup tables used by the ARM7 code.
67 * Currently, these include the PSG pitch values.
68 */
69 int writeARM7(const char *filename) {
70 FILE *fp = fopen(filename, "wt");
71 if (!fp) {
72 return -1;
73 }
74 if (writePSG(fp) < 0) {
75 fclose(fp);
76 return -1;
77 }
78 fclose(fp);
79 return 0;
80 }
81
82
83 int main(void) {
84 if (writeARM7("obj/ds/lookup_tables7.s") < 0) {
85 return EXIT_FAILURE;
86 }
87 return EXIT_SUCCESS;
88 }