implement OSP_SNDCP_CH_GNT (this commit just adds support to respond to an ISP_SNDCP_CH_REQ, it does not mean data services will work);

p25/TrunkPacket.cpp

@@ -309,9 +309,7 @@ bool TrunkPacket::process(uint8_t* data, uint32_t len, bool preDecoded)
                         m_rfTSBK.getDataServiceOptions(), m_rfTSBK.getDataAccessControl(), srcId);
                 }
 
-                // SNDCP data channel requests are currently unsupported -- maybe in the future?
-
-                writeRF_TSDU_Deny(P25_DENY_RSN_SYS_UNSUPPORTED_SVC, TSBK_ISP_SNDCP_CH_REQ);
+                writeRF_TSDU_Grant(false, false, false, true);
                 break;
             case TSBK_IOSP_STS_UPDT:
                 // validate the source RID
@@ -2017,8 +2015,9 @@ void TrunkPacket::queueRF_TSBK_Ctrl(uint8_t lco)
 /// <param name="grp"></param>
 /// <param name="skip"></param>
 /// <param name="net"></param>
+/// <param name="sndcpGrant"></param>
 /// <returns></returns>
-bool TrunkPacket::writeRF_TSDU_Grant(bool grp, bool skip, bool net)
+bool TrunkPacket::writeRF_TSDU_Grant(bool grp, bool skip, bool net, bool sndcpGrant)
 {
     uint8_t lco = m_rfTSBK.getLCO();
 
@@ -2101,6 +2100,7 @@ bool TrunkPacket::writeRF_TSDU_Grant(bool grp, bool skip, bool net)
 
                 m_grantChTable[m_rfTSBK.getDstId()] = chNo;
                 m_rfTSBK.setGrpVchNo(chNo);
+                m_rfTSBK.setDataChnNo(chNo);
 
                 m_grantTimers[m_rfTSBK.getDstId()] = Timer(1000U, GRANT_TIMER_TIMEOUT);
                 m_grantTimers[m_rfTSBK.getDstId()].start();
@@ -2112,11 +2112,30 @@ bool TrunkPacket::writeRF_TSDU_Grant(bool grp, bool skip, bool net)
         else {
             uint32_t chNo = m_grantChTable[m_rfTSBK.getDstId()];
             m_rfTSBK.setGrpVchNo(chNo);
+            m_rfTSBK.setDataChnNo(chNo);
 
             m_grantTimers[m_rfTSBK.getDstId()].start();
         }
     }
 
+    if (sndcpGrant) {
+        if (!net) {
+            ::ActivityLog("P25", true, "SNDCP grant request from to %u", m_rfTSBK.getDstId());
+        }
+
+        if (m_verbose) {
+            LogMessage((net) ? LOG_NET : LOG_RF, P25_TSDU_STR ", TSBK_OSP_SNDCP_CH_GNT (SNDCP Data Channel Grant), chNo = %u, dstId = %u",
+                m_rfTSBK.getDataChnNo(), m_rfTSBK.getDstId());
+        }
+
+        // transmit SNDCP grant
+        m_rfTSBK.setLCO(TSBK_OSP_SNDCP_CH_GNT);
+        writeRF_TSDU_SBF(false, true, net);
+
+        m_rfTSBK.setLCO(lco);
+        return true;
+    }
+
     if (grp) {
         if (!net) {
             ::ActivityLog("P25", true, "group grant request from %u to TG %u", m_rfTSBK.getSrcId(), m_rfTSBK.getDstId());

p25/TrunkPacket.h

@@ -196,7 +196,7 @@ namespace p25
         void queueRF_TSBK_Ctrl(uint8_t lco);
 
         /// <summary>Helper to write a grant packet.</summary>
-        bool writeRF_TSDU_Grant(bool grp, bool skip = false, bool net = false);
+        bool writeRF_TSDU_Grant(bool grp, bool skip = false, bool net = false, bool sndcpGrant = false);
         /// <summary>Helper to write a unit to unit answer request packet.</summary>
         void writeRF_TSDU_UU_Ans_Req(uint32_t srcId, uint32_t dstId);
         /// <summary>Helper to write a acknowledge packet.</summary>

p25/lc/TSBK.cpp

@@ -590,6 +590,26 @@ void TSBK::encode(uint8_t* data, bool rawTSBK, bool noTrellis)
         tsbkValue = (tsbkValue << 32) + m_dstId;                                    // Target Radio Address
         tsbkValue = (tsbkValue << 24) + m_srcId;                                    // Source Radio Address
         break;
+    case TSBK_OSP_SNDCP_CH_GNT:
+    {
+        uint32_t calcSpace = (uint32_t)(m_siteIdenEntry.chSpaceKhz() / 0.125);
+        float calcTxOffset = m_siteIdenEntry.txOffsetMhz() * 1000000;
+
+        uint32_t txFrequency = (uint32_t)((m_siteIdenEntry.baseFrequency() + ((calcSpace * 125) * m_dataChannelNo)));
+        uint32_t rxFrequency = (uint32_t)(txFrequency + calcTxOffset);
+
+        uint32_t rootFreq = rxFrequency - m_siteIdenEntry.baseFrequency();
+        uint32_t rxChNo = rootFreq / (m_siteIdenEntry.chSpaceKhz() * 1000);
+
+        tsbkValue = 0U;
+        tsbkValue = (tsbkValue << 8) + m_dataServiceOptions;                        // Data Service Options
+        tsbkValue = (tsbkValue << 4) + m_siteData.channelId();                      // Channel (T) ID
+        tsbkValue = (tsbkValue << 12) + m_dataChannelNo;                            // Channel (T) Number
+        tsbkValue = (tsbkValue << 4) + m_siteData.channelId();                      // Channel (R) ID
+        tsbkValue = (tsbkValue << 12) + (rxChNo & 0xFFFU);                          // Channel (R) Number
+        tsbkValue = (tsbkValue << 24) + m_dstId;                                    // Target Radio Address
+    }
+    break;
     case TSBK_IOSP_STS_UPDT:
         tsbkValue = 0U;
         tsbkValue = (tsbkValue << 16) + m_statusValue;                              // Status Value
@@ -1111,6 +1131,9 @@ TSBK::TSBK(SiteData siteData) :
     m_messageValue(0U),
     m_statusValue(0U),
     m_extendedFunction(P25_EXT_FNCT_CHECK),
+    m_dataServiceOptions(0U),
+    m_dataAccessControl(0U),
+    m_dataChannelNo(0U),
     m_adjCFVA(P25_CFVA_FAILURE),
     m_adjRfssId(0U),
     m_adjSiteId(0U),
@@ -1176,6 +1199,8 @@ void TSBK::copy(const TSBK& data)
 
     m_extendedFunction = data.m_extendedFunction;
 
+    m_dataChannelNo = data.m_dataChannelNo;
+
     m_adjCFVA = data.m_adjCFVA;
     m_adjRfssId = data.m_adjRfssId;
     m_adjSiteId = data.m_adjSiteId;

p25/lc/TSBK.h

@@ -148,6 +148,9 @@ namespace p25
             /// <summary>SNDCP Data Access Control</summary>
             __PROPERTY(uint32_t, dataAccessControl, DataAccessControl);
 
+            /// <summary>SNDCP grant channel number.</summary>
+            __PROPERTY(uint32_t, dataChannelNo, DataChnNo);
+
             /** Adjacent Site Data */
             /// <summary>Adjacent site CFVA flags.</summary>
             __PROPERTY(uint8_t, adjCFVA, AdjSiteCFVA);