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review.coreboot.org / coreboot / 0f8cd41be1fe6a6ed36c4e639e12e90b002085cf / . / util / spkmodem_recv / spkmodem-recv.c
blob: cd7bd483d09b3d6be6f9204af1325a4c667bf60a [file] [log] [blame]
Vladimir Serbinenko083d3552013-06-07 16:37:56 +0200[diff] [blame]1/* spkmodem-recv.c - decode spkmodem signals */
Patrick Georgi1afe2862020-05-10 17:34:15 +0200[diff] [blame]2/* SPDX-License-Identifier: GPL-2.0-or-later */
Vladimir Serbinenko083d3552013-06-07 16:37:56 +0200[diff] [blame]3
4#include <stdio.h>
5#include <stdlib.h>
6#include <string.h>
7
8/* Compilation: gcc -o spkmodem-recv spkmodem-recv */
Denis 'GNUtoo' Carikli217ecd1122018-02-24 19:24:21 +0100[diff] [blame]9/* Usage: parec --channels=1 --rate=48000 --format=s16le | ./spkmodem-recv */
Vladimir Serbinenko083d3552013-06-07 16:37:56 +0200[diff] [blame]10
11#define SAMPLES_PER_TRAME 240
12#define FREQ_SEP_MIN 5
13#define FREQ_SEP_MAX 15
14#define FREQ_DATA_MIN 15
15#define FREQ_DATA_THRESHOLD 25
16#define FREQ_DATA_MAX 60
17#define THRESHOLD 500
18
19#define DEBUG 0
20#define FLUSH_TIMEOUT 1
21
22static signed short trame[2 * SAMPLES_PER_TRAME];
23static signed short pulse[2 * SAMPLES_PER_TRAME];
24static int ringpos = 0;
25static int pos, f1, f2;
26static int amplitude = 0;
27static int lp = 0;
28
29static void
30read_sample (void)
31{
32 amplitude -= abs (trame[ringpos]);
33 f1 -= pulse[ringpos];
34 f1 += pulse[(ringpos + SAMPLES_PER_TRAME) % (2 * SAMPLES_PER_TRAME)];
35 f2 -= pulse[(ringpos + SAMPLES_PER_TRAME) % (2 * SAMPLES_PER_TRAME)];
36 fread (trame + ringpos, 1, sizeof (trame[0]), stdin);
37 amplitude += abs (trame[ringpos]);
38
39 if (pos ? (trame[ringpos] < -THRESHOLD)
40 : (trame[ringpos] > +THRESHOLD))
41 {
42 pulse[ringpos] = 1;
43 pos = !pos;
44 f2++;
45 }
46 else
47 pulse[ringpos] = 0;
48 ringpos++;
49 ringpos %= 2 * SAMPLES_PER_TRAME;
50 lp++;
51}
52
53int
54main ()
55{
56 int bitn = 7;
57 char c = 0;
58 int i;
59 int llp = 0;
60 while (!feof (stdin))
61 {
62 if (lp > 3 * SAMPLES_PER_TRAME)
63 {
64 bitn = 7;
65 c = 0;
66 lp = 0;
67 llp++;
68 }
69 if (llp == FLUSH_TIMEOUT)
70 fflush (stdout);
71 if (f2 > FREQ_SEP_MIN && f2 < FREQ_SEP_MAX
72 && f1 > FREQ_DATA_MIN && f1 < FREQ_DATA_MAX)
73 {
74#if DEBUG
75 printf ("%d %d %d @%d\n", f1, f2, FREQ_DATA_THRESHOLD,
76 ftell (stdin) - sizeof (trame));
77#endif
78 if (f1 < FREQ_DATA_THRESHOLD)
79 c |= (1 << bitn);
80 bitn--;
81 if (bitn < 0)
82 {
83#if DEBUG
84 printf ("<%c, %x>", c, c);
85#else
86 printf ("%c", c);
87#endif
88 bitn = 7;
89 c = 0;
90 }
91 lp = 0;
92 llp = 0;
93 for (i = 0; i < SAMPLES_PER_TRAME; i++)
94 read_sample ();
95 continue;
96 }
97 read_sample ();
98 }
99 return 0;
100}