Annotation of sys/dev/ic/pt2254a.c, Revision 1.1.1.1
1.1 nbrk 1: /* $OpenBSD: pt2254a.c,v 1.1 2002/04/25 04:56:59 mickey Exp $ */
2: /*
3: * Copyright (c) 2002 Vladimir Popov <jumbo@narod.ru>.
4: *
5: * Redistribution and use in source and binary forms, with or without
6: * modification, are permitted provided that the following conditions
7: * are met:
8: * 1. Redistributions of source code must retain the above copyright
9: * notice, this list of conditions and the following disclaimer.
10: * 2. Redistributions in binary form must reproduce the above copyright
11: * notice, this list of conditions and the following disclaimer in the
12: * documentation and/or other materials provided with the distribution.
13: *
14: * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
15: * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
16: * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
17: * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
18: * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
19: * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
20: * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
21: * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
22: * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
23: * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
24: */
25: /*
26: * Princeton Technology Corp.'s Electronic Volume Controller IC PT2254A
27: * http://www.princeton.com.tw
28: *
29: * PT2254A is an electronic volume controller IC utilizing CMOS Technology
30: * specially designed for use in audio equipment. It has two built-in
31: * channels making it highly suitable for mono and stereo sound applications.
32: * Through the specially designated signals that are applied externally to
33: * the data, clock and strobe input pins, PT2254A can control attenuation
34: * and channel balance.
35: */
36:
37: #include <sys/param.h>
38:
39: #include <dev/ic/pt2254a.h>
40:
41: u_int32_t
42: pt2254a_encode_volume(u_int8_t *current, u_int8_t max) {
43: u_int32_t ret = 0ul;
44: u_int8_t vol, tens, ones;
45: int steps;
46:
47: /*
48: * Volume management is done nonlinear.
49: *
50: * Approximate the curve with three lines:
51: * low volume: y = - (48 /(max/3)) * x + 68
52: * middle volume: y = - (14 /(max/3)) * x + 34
53: * high volume: y = - (6 /(max/3)) * x + 18
54: */
55: if (*current > 0 && *current <= max / 3) {
56: vol = PT2254A_MAX_ATTENUATION - (144 * (int)(*current) / max);
57: } else if (*current > max / 3 && *current <= 2 * max / 3) {
58: vol = 34 - (42 * (int)(*current) / max);
59: } else if (*current > 2 * max / 3) {
60: vol = 18 - (18 * (int)(*current) / max);
61: } else vol = PT2254A_MAX_ATTENUATION;
62:
63: /* Report adjusted volume */
64: /* *current = max - (vol * max / PT2254A_MAX_ATTENUATION); */
65: steps = *current * PT2254A_MAX_ATTENUATION / max;
66: *current = steps * max / PT2254A_MAX_ATTENUATION;
67:
68: tens = vol / 10;
69: ones = vol - tens * 10;
70:
71: ret = PT2254A_ATTENUATION_MAJOR(tens) | PT2254A_ATTENUATION_MINOR(ones);
72:
73: return ret;
74: }
75:
76: u_int32_t
77: pt2254a_compose_register(u_int32_t lvol, u_int32_t rvol, int left, int right) {
78: u_int32_t ret = 0ul;
79:
80: if (left == USE_CHANNEL) {
81: ret |= PT2254A_LEFT_CHANNEL;
82: ret |= lvol;
83: }
84: if (right == USE_CHANNEL) {
85: ret |= PT2254A_RIGHT_CHANNEL;
86: ret |= rvol;
87: }
88:
89: ret |= PT2254A_ZERO_PADDING;
90: ret |= PT2254A_EMPTY_BIT;
91:
92: return ret;
93: }
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