blob: b3d12b313e23bed401749cba44d7a3dcea7c3e6a (
plain)
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
|
/*
* Copyright 2019 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#ifndef ANALYZER_MANCHESTER_ENCODER_H
#define ANALYZER_MANCHESTER_ENCODER_H
#include <cstdint>
/**
* Encode bytes using Manchester Coding scheme.
*
* Manchester Code is self clocking.
* There is a transition in the middle of every bit.
* Zero is high then low.
* One is low then high.
*
* This avoids having long DC sections that would droop when
* passed though analog circuits with AC coupling.
*
* IEEE 802.3 compatible.
*/
class ManchesterEncoder {
public:
ManchesterEncoder(int samplesPerPulse)
: mSamplesPerPulse(samplesPerPulse)
, mSamplesPerPulseHalf(samplesPerPulse / 2)
, mCursor(samplesPerPulse) {
}
/**
* This will be called when the next byte is needed.
* @return
*/
virtual uint8_t onNextByte() = 0;
/**
* Generate the next floating point sample.
* @return
*/
virtual float nextFloat() {
advanceSample();
if (mCurrentBit) {
return (mCursor < mSamplesPerPulseHalf) ? -1.0f : 1.0f; // one
} else {
return (mCursor < mSamplesPerPulseHalf) ? 1.0f : -1.0f; // zero
}
}
protected:
/**
* This will be called when a new bit is ready to be encoded.
* It can be used to prepare the encoded samples.
* @param current
*/
virtual void onNextBit(bool current) {};
void advanceSample() {
// Are we ready for a new bit?
if (++mCursor >= mSamplesPerPulse) {
mCursor = 0;
if (mBitsLeft == 0) {
mCurrentByte = onNextByte();
mBitsLeft = 8;
}
--mBitsLeft;
mCurrentBit = (mCurrentByte >> mBitsLeft) & 1;
onNextBit(mCurrentBit);
}
}
bool getCurrentBit() {
return mCurrentBit;
}
const int mSamplesPerPulse;
const int mSamplesPerPulseHalf;
int mCursor;
int mBitsLeft = 0;
uint8_t mCurrentByte = 0;
bool mCurrentBit = false;
};
#endif //ANALYZER_MANCHESTER_ENCODER_H
|
