From 6d01f9aa891b0262fdf64547b3275ab5ce0f093a Mon Sep 17 00:00:00 2001
From: GUVWAF <thijs@havinga.eu>
Date: Wed, 20 Apr 2022 20:04:44 +0200
Subject: [PATCH] Add isChannelActive() function to radio interface

---
 src/mesh/RF95Interface.cpp   | 19 +++++++++++++++++++
 src/mesh/RF95Interface.h     |  3 +++
 src/mesh/SX126xInterface.cpp | 17 +++++++++++++++++
 src/mesh/SX126xInterface.h   |  3 +++
 4 files changed, 42 insertions(+)

diff --git a/src/mesh/RF95Interface.cpp b/src/mesh/RF95Interface.cpp
index adaeead46..a96b95100 100644
--- a/src/mesh/RF95Interface.cpp
+++ b/src/mesh/RF95Interface.cpp
@@ -176,6 +176,25 @@ void RF95Interface::startReceive()
     enableInterrupt(isrRxLevel0);
 }
 
+bool RF95Interface::isChannelActive()
+{
+    // check if we can detect a LoRa preamble on the current channel
+    int16_t result;
+    setTransmitEnable(false);
+    setStandby();  // needed for smooth transition
+    result = lora->scanChannel();
+    
+    if (result == PREAMBLE_DETECTED) {
+        // DEBUG_MSG("Channel is busy!\n");
+        return true;
+    }
+
+    assert(result != ERR_WRONG_MODEM);
+    
+    // DEBUG_MSG("Channel is free!\n");
+    return false;
+}
+
 /** Could we send right now (i.e. either not actively receving or transmitting)? */
 bool RF95Interface::isActivelyReceiving()
 {
diff --git a/src/mesh/RF95Interface.h b/src/mesh/RF95Interface.h
index f62195a26..5e666ae8b 100644
--- a/src/mesh/RF95Interface.h
+++ b/src/mesh/RF95Interface.h
@@ -40,6 +40,9 @@ class RF95Interface : public RadioLibInterface
      */
     virtual void enableInterrupt(void (*callback)()) { lora->setDio0Action(callback); }
 
+    /** can we detect a LoRa preamble on the current channel? */
+    virtual bool isChannelActive() override;
+
     /** are we actively receiving a packet (only called during receiving state) */
     virtual bool isActivelyReceiving() override;
 
diff --git a/src/mesh/SX126xInterface.cpp b/src/mesh/SX126xInterface.cpp
index b0c48d55a..ac96aa70b 100644
--- a/src/mesh/SX126xInterface.cpp
+++ b/src/mesh/SX126xInterface.cpp
@@ -226,6 +226,23 @@ void SX126xInterface<T>::startReceive()
 #endif
 }
 
+/** Could we send right now (i.e. either not actively receving or transmitting)? */
+template<typename T>
+bool SX126xInterface<T>::isChannelActive()
+{
+    // check if we can detect a LoRa preamble on the current channel
+    int16_t result;
+
+    setStandby(); 
+    result = lora.scanChannel();
+    if (result == PREAMBLE_DETECTED) 
+        return true;
+    
+    assert(result != ERR_WRONG_MODEM);
+    
+    return false;
+}
+
 /** Could we send right now (i.e. either not actively receving or transmitting)? */
 template<typename T>
 bool SX126xInterface<T>::isActivelyReceiving()
diff --git a/src/mesh/SX126xInterface.h b/src/mesh/SX126xInterface.h
index 5168313e2..b0e5d9a32 100644
--- a/src/mesh/SX126xInterface.h
+++ b/src/mesh/SX126xInterface.h
@@ -46,6 +46,9 @@ class SX126xInterface : public RadioLibInterface
      */
     virtual void enableInterrupt(void (*callback)()) { lora.setDio1Action(callback); }
 
+    /** can we detect a LoRa preamble on the current channel? */
+    virtual bool isChannelActive() override;
+
     /** are we actively receiving a packet (only called during receiving state) */
     virtual bool isActivelyReceiving() override;