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P25 -- Fix MPDU Valid Dibit/Status Dibit Gathering;

This commit is contained in:
lwvmobile 2023-12-12 13:39:40 -05:00
parent 6d56db17f4
commit a01a01b533
1 changed files with 35 additions and 16 deletions
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51
src/p25p1_mdpu.c
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@ -130,7 +130,6 @@ void processMPDU(dsd_opts * opts, dsd_state * state)
memset (ec, -2, sizeof(ec));
memset (err, -2, sizeof(err));
int skipdibit = 14; //initial status dibit will occur at 14, then add 36 each time it occurs
int MFID = 0xFF; //Manufacturer ID
uint8_t mpdu_byte[18*129];
@ -165,33 +164,53 @@ void processMPDU(dsd_opts * opts, dsd_state * state)
int stop = 101;
int start = 0;
//collect x-len reps of 101 dibits (98 valid dibits with status dibits interlaced)
//now using modulus on skipdibit values
int skipdibit = 36-14; //when we arrive here, we are at this position in the counter after reading FS, NID, DUID, and Parity dibits
int status_count = 1; //we have already skipped the Status 1 dibit before arriving here
int dibit_count = 0; //number of gathered dibits
UNUSED(status_count); //debug counter
//collect x-len reps of 100 or 101 dibits (98 valid dibits with two or three status dibits sprinkled in)
for (j = 0; j < end; j++)
{
k = 0;
if (j == 3) //may need to do this for multiple alignments, unsure, or change this part to work more...better....still need to triple check this
start = 1; //fixes decoding error past j 2 repitition, since the status dibit is perfectly aligned at the starting value at that point
else start = 0;
dibit_count = 0;
for (i = start; i < stop; i++)
{
dibit = getDibit(opts, state);
if (i+(j*101) != skipdibit) //
if ( (skipdibit / 36) == 0)
{
tsbk_dibit[k] = dibit;
tsbkbit[k*2] = (dibit >> 1) & 1;
tsbkbit[k*2+1] = (dibit & 1);
k++;
dibit_count++;
tsbk_dibit[k++] = dibit;
}
if (i+(j*101) == skipdibit)
else
{
skipdibit += 36;
}
skipdibit = 0;
status_count++;
// fprintf (stderr, " S:%02d; D:%03d; i:%03d;", status_count, (j*101)+i+57, i); //debug Status Count, Total Dibit Count, and i (compare to symbol rx table)
// fprintf (stderr, " S:%02d; CD:%02d; i:%03d; d:%d;", status_count, dibit_count, i, dibit); //debug Status Count, Current Dibit Count, i, and status dibit
//debug, intepret status dibit (no fec or parity, so could easily be errroneous, could also be different on a data channel vs conventional?)
// if (dibit == 0) fprintf (stderr, " Unknown - Use for Talk Around;");
// if (dibit == 1) fprintf (stderr, " Inbound Channel Busy;");
// if (dibit == 2) fprintf (stderr, " Unknown - Use for Inbound or Outbound;");
// if (dibit == 3) fprintf (stderr, " Inbound Channel Idle;");
//this is used to skip gathering one dibit as well since we only will end up skipping 2 status dibits (getting 99 instead of 98, throwing alignment off)
// if (i > 92) start = 1; //testing values (i > 101-(36*3)-101)? may need longer 3/4 rata messages for comparison/correction (fall back to this if issues arise)
// else start = 0;
}
skipdibit++; //increment
//this is used to skip gathering one dibit as well since we only will end up skipping 2 status dibits (getting 99 instead of 98, throwing alignment off)
if (dibit_count == 98) //this could cause an issue though if the next bit read is supposed to be a status dibit (unsure) it may not matter, should be handled as first read in next rep
break;
}
// fprintf (stderr, " DC: %d\n", dibit_count); //debug
//send header to p25_12 and return tsbk_byte
if (j == 0) ec[j] = p25_12 (tsbk_dibit, tsbk_byte);