public static DemodState EASInit(DemodState s)
{
// NOTE: Percision differences between C# and C
s.eas_2 = new State1();
s.eas = new State2();
float f;
int i;
for (f = 0, i = 0; i < CORRLEN; i++)
{
eascorr_mark_i[i] = (float)Math.Cos(f);
eascorr_mark_q[i] = (float)Math.Sin(f);
f += (float)(2.0 * Math.PI * FREQ_MARK / FREQ_SAMP);
}
for (f = 0, i = 0; i < CORRLEN; i++)
{
eascorr_space_i[i] = (float)Math.Cos(f);
eascorr_space_q[i] = (float)Math.Sin(f);
f += (float)(2.0 * Math.PI * FREQ_SPACE / FREQ_SAMP);
}
return(s);
}
public static DemodState EASDemod(DemodState s, float[] fbuffer, int length)
{
float f;
float dll_gain;
int idx = 0;
if (s.eas_2.subsamp != 0)
{
int numfill = SUBSAMP - (int)s.eas_2.subsamp;
if (length < numfill)
{
s.eas_2.subsamp += (uint)length;
return(s);
}
idx += numfill;
length -= numfill;
s.eas_2.subsamp = 0;
}
while (true)
{
length -= SUBSAMP;
if (length < SUBSAMP)
{
break;
}
idx += SUBSAMP;
f = (float)Math.Pow(Mac(fbuffer, idx, eascorr_mark_i, CORRLEN), 2.0) +
(float)Math.Pow(Mac(fbuffer, idx, eascorr_mark_q, CORRLEN), 2.0) -
(float)Math.Pow(Mac(fbuffer, idx, eascorr_space_i, CORRLEN), 2.0) -
(float)Math.Pow(Mac(fbuffer, idx, eascorr_space_q, CORRLEN), 2.0);
s.eas_2.dcd_shreg <<= 1;
s.eas_2.dcd_shreg |= (f > 0 ? (uint)1 : (uint)0);
if (f > 0 && s.eas_2.dcd_integrator < INTEGRATOR_MAXVAL)
{
s.eas_2.dcd_integrator += 1;
}
else if (f < 0 && s.eas_2.dcd_integrator > -INTEGRATOR_MAXVAL)
{
s.eas_2.dcd_integrator -= 1;
}
dll_gain = 0.5F;
if (((s.eas_2.dcd_shreg ^ (s.eas_2.dcd_shreg >> 1)) & 1) == 1)
{
if (s.eas_2.sphase < (0x8000u - (SPHASEINC / 8)))
{
if (s.eas_2.sphase > SPHASEINC / 2)
{
s.eas_2.sphase -= (uint)Math.Min((int)(s.eas_2.sphase * dll_gain), DLL_MAX_INC);
}
}
else
{
if (s.eas_2.sphase < (0x10000u - SPHASEINC / 2))
{
s.eas_2.sphase += (uint)Math.Min((int)(0x10000u - s.eas_2.sphase) * dll_gain, DLL_MAX_INC);
}
}
}
s.eas_2.sphase += SPHASEINC;
if (s.eas_2.sphase >= 0x10000u)
{
s.eas_2.sphase = 1;
s.eas_2.lasts >>= 1;
s.eas_2.lasts |= (byte)(((s.eas_2.dcd_integrator >= 0 ? 1 : 0) << 7) & 0x80u);
if (s.eas_2.lasts == PREAMBLE && s.eas.state != EAS_L2_READING_MESSAGE)
{
s.eas_2.state = EAS_L1_SYNC;
s.eas_2.byte_counter = 0;
}
else if (s.eas_2.state == EAS_L1_SYNC)
{
s.eas_2.byte_counter++;
if (s.eas_2.byte_counter == 8)
{
if (CharacterAllowed((char)s.eas_2.lasts))
{
s = EASFrame(s, (char)s.eas_2.lasts, idx);
}
else
{
s.eas_2.state = EAS_L1_IDLE;
s = EASFrame(s, (char)0x00, idx);
}
s.eas_2.byte_counter = 0;
}
}
}
}
s.eas_2.subsamp = (uint)length;
return(s);
}
static DemodState EASFrame(DemodState s, char data, int idx)
{
if (data != 0)
{
if (s.eas.state == EAS_L2_IDLE)
{
s.eas.state = EAS_L2_HEADER_SEARCH;
}
if (s.eas.state == EAS_L2_HEADER_SEARCH && s.eas.headlen < MAX_HEADER_LEN)
{
s.eas.head_buf[s.eas.headlen] = data;
s.eas.headlen++;
}
if (s.eas.state == EAS_L2_HEADER_SEARCH && s.eas.headlen >= MAX_HEADER_LEN)
{
if (IsEqualUpToN(s.eas.head_buf, HEADER_BEGIN, s.eas.headlen))
{
s.eas.state = EAS_L2_READING_MESSAGE;
s.headerStart = (uint)idx;
}
else if (IsEqualUpToN(s.eas.head_buf, EOM, s.eas.headlen))
{
s.eas.state = EAS_L2_READING_EOM;
s.eomStart = (uint)idx;
}
else
{
s.eas.state = EAS_L2_IDLE;
s.eas.headlen = 0;
}
}
else if (s.eas.state == EAS_L2_READING_MESSAGE && s.eas.msglen <= MAX_MSG_LEN)
{
s.eas.msg_buf[s.eas.msglen] = data;
s.eas.msglen++;
}
}
else
{
if (s.eas.state == EAS_L2_READING_MESSAGE)
{
int lastHyphen = -1;
for (int i = 0; i < s.eas.msg_buf.Length; i++)
{
if (s.eas.msg_buf[i] == '-')
{
lastHyphen = i;
}
}
if (lastHyphen != -1)
{
s.eas.msg_buf[lastHyphen + 1] = '\0';
}
string easMessage = "";
for (int i = 0; i < s.eas.msg_buf.Length; i++)
{
char c = s.eas.msg_buf[i];
if (c == 0)
{
break;
}
easMessage += c;
s.eas.msg_buf[i] = '\0';
}
s.message = $"{HEADER_BEGIN}{easMessage}";
Console.WriteLine($"EAS: {s.message}");
s.headerEnd = (uint)idx;
s.headerDetected = DateTime.Now;
}
else if (s.eas.state == EAS_L2_READING_EOM)
{
Console.WriteLine($"EAS: {EOM}");
s.eomEnd = (uint)idx;
s.eomDetected = DateTime.Now;
}
s.eas.state = EAS_L2_IDLE;
s.eas.msglen = 0;
s.eas.headlen = 0;
}
return(s);
}
