/
MagPhase.cpp
230 lines (197 loc) · 8.76 KB
/
MagPhase.cpp
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
/* Audio Library for Teensy 3.X
* Copyright (c) 2014, Paul Stoffregen, paul@pjrc.com
*
* Development of this audio library was funded by PJRC.COM, LLC by sales of
* Teensy and Audio Adaptor boards. Please support PJRC's efforts to develop
* open source software by purchasing Teensy or other PJRC products.
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice, development funding notice, and this permission
* notice shall be included in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
// find the magnitude and phase of the transmit audio I and Q streams
// it seems the general idea here is conversion from XY cartesian to polar form
// decimate by N version
#define DRATE 6 // decimation rate. Input should be lowpass filtered appropriately.
#define DC_OFFSET 0 // try a tx feature from the rx improved branch ( it reduces the suppression of the carrier )
#include <Arduino.h>
#include "MagPhase.h"
#include "utility/dspinst.h"
static int32_t val1, val2;
/*
// approx magnitude of I and Q channels
// 31 * I / 32 + 3 * Q / 8 where I > Q
// estimated async complex square law
static int32_t fastAM( int32_t i, int32_t q ){ // cpu 31-34
i = abs(i), q = abs(q);
if( q > i ){
q = (31 * q) >> 5;
i = ( 3 * i) >> 3;
}
else{
i = (31 * i) >> 5;
q = ( 3 * q) >> 3;
}
return ( i + q );
}
*/
static int32_t fastAM2( int32_t i, int32_t q ){ // this is quite a bit better ref: [2]
int32_t mb4; // return max or 7/8 max + 1/2 min, cpu 34
i = abs(i), q = abs(q);
if( q > i ){
mb4 = q >> 2;
if( i <= mb4 ) return q;
mb4 >>= 1;
q -= mb4; // 7/8 * q == q - 1/8q
i = i >> 1;
}
else{
mb4 = i >> 2;
if( q <= mb4 ) return i;
mb4 >>= 1;
i -= mb4;
q = q >> 1;
}
return ( i + q );
}
static int32_t arctan3( int32_t q, int32_t i ){ // from QCX-SSB code
#define _UA 44117/DRATE // can use arbitrary number
#define _atan2(z) (((_UA/8 + _UA/22) - _UA/22 * z ) * z) //uSDX original derived from equation 5 [1]. Perhaps smoother overall.
//#define _atan2(z) (((_UA/8 + _UA/23) - _UA/23 * z ) * z) // derived from equation 7 [1]. Don't notice much difference in result.
int32_t r;
int32_t ai, aq;
ai = abs(i); aq = abs(q);
if( aq > ai ) r = _UA / 4 - _atan2( ai / aq ); // arctan(z) = 90-arctan(1/z)
else r = (i == 0) ? 0 : _atan2( aq / ai ); // arctan(z)
r = (i < 0) ? _UA / 2 - r : r; // arctan(-z) = -arctan(z)
return (q < 0) ? -r : r; // arctan(-z) = -arctan(z)
}
/*
// a 31 tap +45 -45 Hilbert calculated in parallel using 1 set of constants. Increases cpu 34 to 42. The idea works fine.
static void process_hilbert2( int16_t val ){
static int32_t wi[31];
static int32_t wq[31];
const int32_t k[31] = {
(int32_t)(32767.5 * 0.002019498247804617 ),
(int32_t)(32767.5 *-0.000419042157951920 ),
(int32_t)(32767.5 * 0.005607599072179811 ),
(int32_t)(32767.5 *-0.000866624084253786 ),
(int32_t)(32767.5 * 0.012091307084456372 ),
(int32_t)(32767.5 *-0.001458857746966848 ),
(int32_t)(32767.5 * 0.022931742810751429 ),
(int32_t)(32767.5 *-0.002142121627251763 ),
(int32_t)(32767.5 * 0.040712336489107395 ),
(int32_t)(32767.5 *-0.002831235655617950 ),
(int32_t)(32767.5 * 0.071636004092801242 ),
(int32_t)(32767.5 *-0.003424899903708251 ),
(int32_t)(32767.5 * 0.138283590926794320 ),
(int32_t)(32767.5 *-0.003827202640866331 ),
(int32_t)(32767.5 * 0.445791135556372398 ),
(int32_t)(32767.5 * 0.702554327536345724 ),
(int32_t)(32767.5 *-0.445791135555810236 ),
(int32_t)(32767.5 *-0.003827202640430871 ),
(int32_t)(32767.5 *-0.138283590926741889 ),
(int32_t)(32767.5 *-0.003424899903512061 ),
(int32_t)(32767.5 *-0.071636004092789682 ),
(int32_t)(32767.5 *-0.002831235655510168 ),
(int32_t)(32767.5 *-0.040712336489104967 ),
(int32_t)(32767.5 *-0.002142121627190697 ),
(int32_t)(32767.5 *-0.022931742810750954 ),
(int32_t)(32767.5 *-0.001458857746932649 ),
(int32_t)(32767.5 *-0.012091307084457124 ),
(int32_t)(32767.5 *-0.000866624084236679 ),
(int32_t)(32767.5 *-0.005607599072180564 ),
(int32_t)(32767.5 *-0.000419042157944823 ),
(int32_t)(32767.5 *-0.002019498247804966 )
};
int i;
for( i = 0; i < 30; ++i ) wi[i] = wi[i+1]; // delay moves down
for( i = 30; i > 0; --i ) wq[i] = wq[i-1]; // delay moves up
wi[30] = wq[0] = val;
val1 = val2 = 0;
for( i = 0; i < 31; ++i ){
val1 += k[i] * wi[i];
val2 += k[i] * wq[i];
}
val1 >>= 15;
val2 >>= 15;
}
*/
// a 31 tap classic hilbert every other constant is zero, kaiser window
static void process_hilbert( int16_t val ){
static int32_t wi[31]; // delay terms
// static int32_t wq[31]; // extra redundant array
const int32_t k0 = (int32_t)( 32767.5 * 0.002972769320862211 );
const int32_t k1 = (int32_t)( 32767.5 * 0.008171666650726522 );
const int32_t k2 = (int32_t)( 32767.5 * 0.017465643081957562 );
const int32_t k3 = (int32_t)( 32767.5 * 0.032878923709314147 );
const int32_t k4 = (int32_t)( 32767.5 * 0.058021930268698417 );
const int32_t k5 = (int32_t)( 32767.5 * 0.101629404192315698 );
const int32_t k6 = (int32_t)( 32767.5 * 0.195583262432201366 );
const int32_t k7 = (int32_t)( 32767.5 * 0.629544595185021816 );
for( int i = 0; i < 30; ++i ) wi[i] = wi[i+1]; //, wq[i] = wq[i+1];
// wi[30] = wq[30] = val;
wi[30] = val;
val2 = wi[15]; // wq[15];
val1 = k0 * ( wi[0] - wi[30] ) + k1 * ( wi[2] - wi[28] ) + k2 * ( wi[4] - wi[26] ) + k3 * ( wi[6] - wi[24] );
val1 += k4 * ( wi[8] - wi[22] ) + k5 * ( wi[10] - wi[20]) + k6 * ( wi[12] - wi[18]) + k7 * ( wi[14] - wi[16]);
val1 >>= 15;
}
void AudioMagPhase1::update(void){
audio_block_t *blk1;
int16_t *dat1;
int i;
static int rem; // 128 by 6 has a remainder when done
// receiving, do nothing
if( mode == 0 ){
blk1 = receiveReadOnly(0);
if( blk1 ) release( blk1 );
return;
}
// transmitting
blk1 = receiveReadOnly(0);
if( blk1 == 0 ){
//release( blk1 );
return;
}
// decimate by DRATE, 6-> sample rate 7353, input must be lowpassed < 3.5k
dat1 = blk1->data;
for( i = 0; i < AUDIO_BLOCK_SAMPLES; i++ ){
++rem;
if( rem == DRATE ){
rem = 0;
if( mode == 1 ){ // SSB DATA mode
process_hilbert( *dat1 + DC_OFFSET ); // get val1 and val2
mag[count] = fastAM2( val1, val2);
ph[count] = arctan3( val1, val2 );
}
else{ // AM DSB modes
mag[count] = *dat1; // save just the plain audio signal
ph[count] = 0; // no phase changes
}
++count; count &= (AUDIO_BLOCK_SAMPLES-1); // assume power of two block size ( currently 128 )
}
dat1 += 1;
}
if( count >= AUDIO_BLOCK_SAMPLES / 2 ) avail = 1; // have buffered > 6ms of data, avail latches on
noInterrupts();
report_count = count; // only report the block ending position of the count
interrupts();
release( blk1 );
}
// [1] http://www-labs.iro.umontreal.ca/~mignotte/IFT2425/Documents/EfficientApproximationArctgFunction.pdf
// [2] http://www-labs.iro.umontreal.ca/~mignotte/IFT2425/Documents/ARootOfLessEvil.pdf