使用电脑声卡来实现2FSK数据调制解调传输

此程序在物理层上使用10KHz的频率表示逻辑“0”，使用15KHz的频率表示逻辑“1”
在物理层之上（假设就叫传输层吧）用一个单位时间的0和一个单位时间的1表示逻辑“0”，用一个单位时间的0和两个单位时间的1表示逻辑“1”，并且每个字节的结尾都有一个偶校验位以及一个保持较长时间的0用于分隔字节
在传输层之上（假设就叫网络层吧），以包为单位传输数据，0x55表示包头，0xAA表示包尾，无校验

程序解调原理是：
首先利用10KHz和15KHz带通滤波器将声卡接收来的波形进行滤波，然后将两通道分别通过两个包络检波器，之后在门限噪声过滤后进行比较，谁幅度大判决结果就是谁
滤波器使用MATLAB生成的，值如下所示：
[C#] 纯文本查看 复制代码
private const int BandPass_Size = 45;

private static double[] BandPass_10KHz = new double[]{
0.0009781904976227,2.310687083045e-05,-0.001850921386016,-0.0009604556387189,
0.002732177361363, 0.002454026683306,-0.003530807893481,-0.005033359378625,
0.003268338256639, 0.008046002294271,-0.001785884965235, -0.01118839681511,
-0.001425109899399, 0.01337602169719, 0.005932600339844, -0.01398968593694,
-0.01124059666706, 0.01232758211354, 0.016159778255,-0.008524876132051,
-0.01973020933926, 0.003023046445069, 0.02098489087997, 0.003023046445069,
-0.01973020933926,-0.008524876132051, 0.016159778255, 0.01232758211354,
-0.01124059666706, -0.01398968593694, 0.005932600339844, 0.01337602169719,
-0.001425109899399, -0.01118839681511,-0.001785884965235, 0.008046002294271,
0.003268338256639,-0.005033359378625,-0.003530807893481, 0.002454026683306,
0.002732177361363,-0.0009604556387189,-0.001850921386016,2.310687083045e-05,
0.0009781904976227
};

private static double[] BandPass_15KHz = new double[]{
-0.0009981746791559, 0.000759180810415,0.0006404064214932,-0.002457709613472,
0.00238467384023,0.0007556946095888,-0.004687333695163, 0.004906581539168,
0.0005502824808439,-0.007567247883353, 0.00864646206089,-0.0006606208202895,
-0.01018615121518, 0.01288307335994,-0.002755953433256, -0.01205731207217,
0.01703290275592,-0.005710913930339, -0.01241906755974, 0.01996890238488,
-0.008755521713043, -0.01126587989407, 0.02109366603246, -0.01126587989407,
-0.008755521713043, 0.01996890238488, -0.01241906755974,-0.005710913930339,
0.01703290275592, -0.01205731207217,-0.002755953433256, 0.01288307335994,
-0.01018615121518,-0.0006606208202895, 0.00864646206089,-0.007567247883353,
0.0005502824808439, 0.004906581539168,-0.004687333695163,0.0007556946095888,
0.00238467384023,-0.002457709613472,0.0006404064214932, 0.000759180810415,
-0.0009981746791559
};

滤波程序如下（原理是将信号与滤波器进行卷积，卷积使用了一个滚动缓冲区来解决）：
[C#] 纯文本查看 复制代码
private int[] Filter_10KHz(int[] Data)
{
double[] dData = new double[Data.Length];
int i,j,k;

for(i = 0;i < dData.Length;i++)
{
dData[i] = 0;
k = BandPass_Size – 1;

for(j = i + 1;j < BandPass_Size;j++)
{
dData[i] += BandPassBuf_10KHz[j] * BandPass_10KHz[k–];
}

for(j = Math.Max(0,i – BandPass_Size + 1);j <= i;j++)
{
dData[i] += ((double)Data[j]) * BandPass_10KHz[k–];
}

if(k != -1)
{
throw new Exception();
}
}

for(i = Data.Length – 1,j = BandPass_Size – 1;j >= 0;i–,j–)
{
BandPassBuf_10KHz[j] = (double)Data[i];
}

int[] r = new int[Data.Length];

for(i = 0;i < Data.Length;i++)
{
r[i] = (int)dData[i];
}

return r;
}

private int[] Filter_15KHz(int[] Data)
{
double[] dData = new double[Data.Length];
int i,j,k;

for(i = 0;i < dData.Length;i++)
{
dData[i] = 0;
k = BandPass_Size – 1;

for(j = i + 1;j < BandPass_Size;j++)
{
dData[i] += BandPassBuf_15KHz[j] * BandPass_15KHz[k–];
}

for(j = Math.Max(0,i – BandPass_Size + 1);j <= i;j++)
{
dData[i] += ((double)Data[j]) * BandPass_15KHz[k–];
}

if(k != -1)
{
throw new Exception();
}
}

for(i = Data.Length – 1,j = BandPass_Size – 1;j >= 0;i–,j–)
{
BandPassBuf_15KHz[j] = (double)Data[i];
}

int[] r = new int[Data.Length];

for(i = 0;i < Data.Length;i++)
{
r[i] = (int)dData[i];
}

return r;
}

包络检波器代码如下（同样采用了滚动缓冲区）：
[C#] 纯文本查看 复制代码
private double env_3(double x,double rct)
{
if(rct == 0.0)
{
old_y = 0.0;
}
else
{
x = Math.Abs(x);

if(x > old_y)
{
old_y = x;
}
else
{
old_y *= rct / (rct + 1);
}
}

return old_y;
}

private void env_4(double[] x,out double[] y,int N,double rct)
{
double xx = 0.0;
int i;

old_y = 0.0;

y = new double[N];

y[0] = Math.Abs(x[0]);

for(i = 1; i < N; i++)
{
xx = Math.Abs(x[i]);

if(xx > y[i – 1])
{
y[i] = xx;
}
else
{
y[i] = y[i – 1] * rct / (rct + 1);
}
}
}

private int[] Env_10KHz(int[] Data)
{
double[] dData = null;
double[] dr;
int i,j,k;

if(Env10KHzInit)
{
dData = new double[Data.Length];

for(i = 0;i < Data.Length;i++)
{
dData[i] = Data[i];
}

Env10KHzInit = false;
}
else
{
dData = new double[Data.Length << 1];

for(i = 0;i < Data.Length;i++)
{
dData[i] = Env10KHzBuf[i];
}

for(i = 0;i < Data.Length;i++)
{
dData[Data.Length + i] = Data[i];
}
}

env_4(dData,out dr,dData.Length,rc);

int[] r = new int[Data.Length];

if(Data.Length == dr.Length)
{
for(i = 0;i < dr.Length;i++)
{
r[i] = (int)dr[i];
}
}
else
{
for(i = Data.Length;i < dr.Length;i++)
{
r[i – Data.Length] = (int)dr[i];
}
}

Env10KHzBuf = Data.ToArray();

return r;
}

private int[] Env_15KHz(int[] Data)
{
double[] dData = null;
double[] dr;
int i,j,k;

if(Env15KHzInit)
{
dData = new double[Data.Length];

for(i = 0;i < Data.Length;i++)
{
dData[i] = Data[i];
}

Env15KHzInit = false;
}
else
{
dData = new double[Data.Length << 1];

for(i = 0;i < Data.Length;i++)
{
dData[i] = Env15KHzBuf[i];
}

for(i = 0;i < Data.Length;i++)
{
dData[Data.Length + i] = Data[i];
}
}

env_4(dData,out dr,dData.Length,rc);

int[] r = new int[Data.Length];

if(Data.Length == dr.Length)
{
for(i = 0;i < dr.Length;i++)
{
r[i] = (int)dr[i];
}
}
else
{
for(i = Data.Length;i < dr.Length;i++)
{
r[i – Data.Length] = (int)dr[i];
}
}

Env15KHzBuf = Data.ToArray();

return r;
}

传输层数据接收程序：
[C#] 纯文本查看 复制代码
private void DataArrived_Audio(int[] audioData)
{
var r10 = Filter_10KHz(audioData);
var re10 = Env_10KHz(r10);
var r15 = Filter_15KHz(audioData);
var re15 = Env_15KHz(r15);
var v = 0;

for(int i = 0;i < re10.Length;i++)
{
statusChart1.Value = v = (((re10[i] < CurTValue) && (re15[i] < CurTValue)) ? 0 : (re10[i] > re15[i] ? 10000 : 30000));
statusChart2.Value = re10[i];
statusChart3.Value = re15[i];

if(v == 30000)
{
if(LastOne)
{
OneCnt++;
}
else
{
LastOne = true;
OneCnt = 1;
}
}
else if(v == 0)
{
//无效
ZeroCnt = 0;
OneCnt = 0;
LastOne = false;
CurBit = 0;
CurValue = 0;
}
else
{
if(LastOne)
{
//一个bit接收完成

if((ZeroCnt >= LowValue) && (OneCnt >= LowValue))
{
if(OneCnt > CenterValue)
{
//判定为1
CurValue |= (1 << CurBit);
CurBit++;
}
else
{
//判定为0
CurBit++;
}

if(CurBit >= 9)
{
var check = 0;

for(int j = 0;j < 8;j++)
{
check ^= (CurValue >> j) & 0x01;
}

if(check == (CurValue >> 8))
{
RevQ.Enqueue((byte)(CurValue & 0xFF));
}

ZeroCnt = 0;
CurBit = 0;
CurValue = 0;
}
}

LastOne = false;
ZeroCnt = 1;
}
else
{
ZeroCnt++;
}
}
}

}

传输层数据发送函数：
[C#] 纯文本查看 复制代码
private void DataSendThread()
{
while(true)
{
var check = 0;
var list = new List<byte>();

if(SendQ.Count > 0)
{
var x = SendQ.Dequeue();

for(int i = 0;i < 8;i++)
{
if((x & (1 << i)) == 0)
{
check ^= 0;
/*m_Fifo.Write(Signal10KHz,0,Signal10KHz.Length / 2);
m_Fifo.Write(Signal15KHz,0,Signal15KHz.Length / 2);*/
AddToList(list,Signal10KHz,Signal10KHz.Length / ZeroDiv);
AddToList(list,Signal15KHz,Signal15KHz.Length / ZeroDiv);
}
else
{
check ^= 1;
/*m_Fifo.Write(Signal10KHz,0,Signal10KHz.Length / 2);
m_Fifo.Write(Signal15KHz,0,Signal15KHz.Length);*/
AddToList(list,Signal10KHz,Signal10KHz.Length / ZeroDiv);
AddToList(list,Signal15KHz,Signal15KHz.Length / OneDiv);
}
}

if(check == 0)
{
AddToList(list,Signal10KHz,Signal10KHz.Length / ZeroDiv);
AddToList(list,Signal15KHz,Signal15KHz.Length / ZeroDiv);
}
else
{
AddToList(list,Signal10KHz,Signal10KHz.Length / ZeroDiv);
AddToList(list,Signal15KHz,Signal15KHz.Length / OneDiv);
}

AddToList(list,Signal10KHz,Signal10KHz.Length / 2);
}

m_Fifo.Write(list.ToArray(),0,list.Count);
}
}

该代码抗干扰能力很强，大声说话甚至喊叫都不会影响到声音传输，如果你那里一直接收不到数据，可能是你的扬声器发不出10KHz和15KHz的声音或者声音太小，这时可以采用音频线直接连接声卡的输入端和输出端
该程序在Windows 7 x64旗舰版下测试通过，由于受限于Windows的多任务调度机制，程序的实时性很难得到保证，因此传输速度只能达到4bit/s即0.5Byte/s或者说2s/Byte
发送速率可以由“speed”变量控制，该变量位于Form1类成员中

已经编译好的EXE需要在至少.net Framework 4.7.1的环境下启动（版本过低可能会报异常），并且可能需要在插入麦克风和扬声器之后才能成功启动，否则对于某些声卡可能会报异常
代码基于VS2017开发
窗口左下角的发送值只能填0-255之间的一个数，否则会报异常，那里是单字节的发送测试
右上角那个文本框可以输入任意文本，点击发送之后等待接收即可，那里是以包为单位发送的，因此若发送x个字符，实际发送的是(f(x)+2)*9个bit（包头一个字节，包尾一个字节，UTF-8编码表示编码的长度不定，所以x字符实际对应的字符数用f(x)表示，对于汉字而言，是三个字节表示一个字符），
下载链接：

音频数据传输GUI.rar

(476.74 KB, 下载次数: 150)

2019-4-9 08:41 上传

语美@五元普通

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