From 3861559f87c6191c8a9a7d74cbb6852c47a282b8 Mon Sep 17 00:00:00 2001
From: Bryan Biedenkapp <gatekeep@gmail.com>
Date: Wed, 26 Jun 2024 12:17:54 -0400
Subject: [PATCH] add support to send SNDCP disabled annoucement messages
 properly;

---
 src/common/p25/lc/tsbk/OSP_SNDCP_CH_ANN.cpp | 20 ++++++++++++++++----
 src/common/p25/lc/tsbk/OSP_SNDCP_CH_ANN.h   |  6 +++++-
 src/host/p25/packet/ControlSignaling.cpp    | 12 +++++++++---
 3 files changed, 30 insertions(+), 8 deletions(-)

diff --git a/src/common/p25/lc/tsbk/OSP_SNDCP_CH_ANN.cpp b/src/common/p25/lc/tsbk/OSP_SNDCP_CH_ANN.cpp
index afa77096..8115f462 100644
--- a/src/common/p25/lc/tsbk/OSP_SNDCP_CH_ANN.cpp
+++ b/src/common/p25/lc/tsbk/OSP_SNDCP_CH_ANN.cpp
@@ -28,6 +28,7 @@ using namespace p25::lc::tsbk;
 /// Initializes a new instance of the OSP_SNDCP_CH_ANN class.
 /// </summary>
 OSP_SNDCP_CH_ANN::OSP_SNDCP_CH_ANN() : TSBK(),
+    m_implicitChannel(false),
     m_sndcpAutoAccess(true),
     m_sndcpDAC(1U)
 {
@@ -76,10 +77,21 @@ void OSP_SNDCP_CH_ANN::encode(uint8_t* data, bool rawTSBK, bool noTrellis)
     tsbkValue = (tsbkValue << 8) +
         (m_sndcpAutoAccess ? 0x80U : 0x00U) +                                       // Autonomous Access
         (m_sndcpAutoAccess ? 0x40U : 0x00U);                                        // Requested Access
-    tsbkValue = (tsbkValue << 4) + m_siteData.channelId();                          // Channel (T) ID
-    tsbkValue = (tsbkValue << 12) + m_siteData.channelNo();                         // Channel (T) Number
-    tsbkValue = (tsbkValue << 4) + m_siteData.channelId();                          // Channel (R) ID
-    tsbkValue = (tsbkValue << 12) + (rxChNo & 0xFFFU);                              // Channel (R) Number
+
+    if (m_implicitChannel) {
+        tsbkValue = (tsbkValue << 16) + 0xFFFFU;
+    } else {
+        tsbkValue = (tsbkValue << 4) + m_siteData.channelId();                      // Channel (T) ID
+        tsbkValue = (tsbkValue << 12) + m_siteData.channelNo();                     // Channel (T) Number
+    }
+
+    if (m_implicitChannel) {
+        tsbkValue = (tsbkValue << 16) + 0xFFFFU;
+    } else {
+        tsbkValue = (tsbkValue << 4) + m_siteData.channelId();                      // Channel (R) ID
+        tsbkValue = (tsbkValue << 12) + (rxChNo & 0xFFFU);                          // Channel (R) Number
+    }
+
     tsbkValue = (tsbkValue << 16) + m_sndcpDAC;                                     // Data Access Control
 
     std::unique_ptr<uint8_t[]> tsbk = TSBK::fromValue(tsbkValue);
diff --git a/src/common/p25/lc/tsbk/OSP_SNDCP_CH_ANN.h b/src/common/p25/lc/tsbk/OSP_SNDCP_CH_ANN.h
index fde10624..5a757ba3 100644
--- a/src/common/p25/lc/tsbk/OSP_SNDCP_CH_ANN.h
+++ b/src/common/p25/lc/tsbk/OSP_SNDCP_CH_ANN.h
@@ -7,7 +7,7 @@
 * @package DVM / Common Library
 * @license GPLv2 License (https://opensource.org/licenses/GPL-2.0)
 *
-*   Copyright (C) 2022 Bryan Biedenkapp, N2PLL
+*   Copyright (C) 2022,2024 Bryan Biedenkapp, N2PLL
 *
 */
 #if !defined(__P25_LC_TSBK__OSP_SNDCP_CH_ANN_H__)
@@ -40,6 +40,10 @@ namespace p25
                 /// <summary>Returns a string that represents the current TSBK.</summary>
                 std::string toString(bool isp = false) override;
 
+            public:
+                /// <summary>Flag indicating explicit channel frequncies should not be transmitted.</summary>
+                __PROPERTY(bool, implicitChannel, ImplicitChannel);
+
             private:
                 bool m_sndcpAutoAccess;
                 uint16_t m_sndcpDAC;
diff --git a/src/host/p25/packet/ControlSignaling.cpp b/src/host/p25/packet/ControlSignaling.cpp
index 24044453..73657d3d 100644
--- a/src/host/p25/packet/ControlSignaling.cpp
+++ b/src/host/p25/packet/ControlSignaling.cpp
@@ -2051,11 +2051,17 @@ void ControlSignaling::queueRF_TSBK_Ctrl(uint8_t lco)
             }
             break;
         case TSBKO::OSP_SNDCP_CH_ANN:
+        {
             // transmit SNDCP announcement
-            tsbk = std::make_unique<OSP_SNDCP_CH_ANN>();
-            tsbk->siteIdenEntry(m_p25->m_idenEntry);
+            std::unique_ptr<OSP_SNDCP_CH_ANN> osp = std::make_unique<OSP_SNDCP_CH_ANN>();
+            osp->siteIdenEntry(m_p25->m_idenEntry);
+            if (!m_p25->m_sndcpSupport) {
+                osp->setImplicitChannel(true);
+            }
+            tsbk = std::move(osp);
             DEBUG_LOG_TSBK(tsbk->toString());
-            break;
+        }
+        break;
         case TSBKO::OSP_SYNC_BCAST:
         {
             // transmit sync broadcast