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P25 PDU Tweaks;

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lwvmobile
2022-10-08 07:07:45 -04:00
parent 3f31d4ffe0
commit 215594a2a8
3 changed files with 47 additions and 5 deletions
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2
src/p25p1_block.cpp
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@@ -18,7 +18,7 @@ typedef std::vector<bool> bit_vector;
/* deinterleave and trellis1_2 decoding, count_bits, and find_min*/
/* buf is assumed to be a buffer of 12 bytes */
typedef std::vector<bool> bit_vector;
//typedef std::vector<bool> bit_vector;
//ugly copy and paste below
static int count_bits(unsigned int n) {

19
src/p25p1_tsbk.c
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@@ -79,8 +79,22 @@ void processTSBK(dsd_opts * opts, dsd_state * state)
//fprintf (stderr, "BAD CRC16");
}
//shuffle corrected bits back into tsbk_byte
k = 0;
for (i = 0; i < 12; i++)
{
int byte = 0;
for (x = 0; x < 8; x++)
{
byte = byte << 1;
byte = byte | tsbk_decoded_bits[k];
k++;
}
tsbk_byte[i] = byte;
}
//convert tsbk_byte to PDU and send to vPDU handler...may or may not be entirely compatible,
PDU[0] = 07; //P25p1 TSBK Duid 0x07
PDU[0] = 0x07; //P25p1 TSBK Duid 0x07
PDU[1] = tsbk_byte[0];
PDU[2] = tsbk_byte[2];
PDU[3] = tsbk_byte[3];
@@ -96,7 +110,7 @@ void processTSBK(dsd_opts * opts, dsd_state * state)
PDU[1] = PDU[1] ^ 0x40; //flip bit to make it compatible with MAC_PDUs, i.e. 3D to 7D
//Don't run NET_STS out of this, or will set wrong NAC/CC
if (err == 0 && ec == 0 && PDU[1] != 0x7B && PDU[1] != 0xFB)
if (err == 0 && ec == 0 && PDU[1] != 0x7B && PDU[1] != 0xFB && PDU[1] != 0x49 && PDU[1] != 0x45) //0x49 is telephone grant, 0x46 Unit to Unit Channel Answer Request
{
fprintf (stderr, "%s",KMAG);
process_MAC_VPDU(opts, state, 0, PDU);
@@ -122,7 +136,6 @@ void processTSBK(dsd_opts * opts, dsd_state * state)
{
fprintf (stderr, "%s",KCYN);
fprintf (stderr, "\n P25 PDU Payload ");
fprintf (stderr, " BD = %d CRC = %d \n ", ec, err);
for (i = 0; i < 12; i++)
{
fprintf (stderr, "[%02X]", tsbk_byte[i]);

31
src/p25p2_vpdu.c
View File

@@ -132,7 +132,36 @@ void process_MAC_VPDU(dsd_opts * opts, dsd_state * state, int type, unsigned lon
//Synchronization Broadcast (SYNC_BCST)
if (MAC[1+len_a] == 0x70)
{
fprintf (stderr, "\n Synchronization Broadcast (SYNC_BCST)");
fprintf (stderr, "\n Synchronization Broadcast \n");
int ist = (MAC[3+len_a] >> 2) & 0x1; //IST bit tells us if time is realiable, synced to external source
int ltoff = (MAC[4+len_a] & 0x3F);
int year = MAC[5+len_a] >> 1;
int month = ((MAC[5+len_a] & 0x1) << 3) | (MAC[6+len_a] >> 5);
int day = (MAC[6+len_a] & 0x1F);
int hour = MAC[7+len_a] >> 3;
int min = ((MAC[7+len_a] & 0x7) << 3) | (MAC[8+len_a] >> 5);
int slots = ((MAC[8+len_a] & 0x1F) << 8) | MAC[9+len_a];
int sign = (ltoff & 0b100000) >> 5;
float offhour = 0;
//calculate local time (on system) by looking at offset and subtracting 30 minutes increments, or divide by 2 for hourly
if (sign == 1)
{
offhour = -( (ltoff & 0b11111 ) / 2);
}
else offhour = ( (ltoff & 0b11111 ) / 2);
int seconds = slots / 135; //very rough estimation, but may be close enough for grins
if (seconds > 60) seconds = 60; //sanity check for rounding error
fprintf (stderr, " Date: 20%02d.%02d.%02d Time: %02d:%02d:%02d UTC\n",
year, month, day, hour, min, seconds);
fprintf (stderr, " Local Time Offset: %.01f Hours;", offhour);
//if ist bit is set, then time on system may be considered invalid (i.e., no external time sync)
if (ist == 1)
{
fprintf (stderr, " Invalid System Time ");
}
else fprintf (stderr, " Valid System Time ");
}
//identifier update VHF/UHF