feat: add TX writeStream with loopback buffer for TX→RX testing

CMakeLists.txt

@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 2.8.7)
+cmake_minimum_required(VERSION 3.10)
 project(SoapyLoopback CXX)
 
 find_package(SoapySDR "0.8.0" NO_MODULE REQUIRED)

Settings.cpp

@@ -48,7 +48,18 @@ SoapyLoopback::SoapyLoopback(const SoapySDR::Kwargs &args):
     bufferedElems(0),
     resetBuffer(false),
     gainMin(0.0),
-    gainMax(0.0)
+    gainMax(0.0),
+    // TX/loopback state
+    _txActive(false),
+    _txBufferLength(DEFAULT_BUFFER_LENGTH),
+    _txNumBuffers(DEFAULT_NUM_BUFFERS),
+    _loopbackFormat(""),
+    _loopbackBytesPerSample(8),  // Default to CF32, will be set in setupStream
+    _loopback_head(0),
+    _loopback_tail(0),
+    _loopback_count(0),
+    _loopback_overflow(false),
+    _loopbackEnabled(false)
 {
 
 }
@@ -96,7 +107,7 @@ size_t SoapyLoopback::getNumChannels(const int dir) const
 
 bool SoapyLoopback::getFullDuplex(const int direction, const size_t channel) const
 {
-    return false;
+    return true;  // Support simultaneous TX and RX for loopback testing
 }
 
 /*******************************************************************
@@ -113,10 +124,7 @@ std::vector<std::string> SoapyLoopback::listAntennas(const int direction, const
 
 void SoapyLoopback::setAntenna(const int direction, const size_t channel, const std::string &name)
 {
-    if (direction != SOAPY_SDR_RX)
-    {
-        throw std::runtime_error("setAntena failed: RTL-SDR only supports RX");
-    }
+    // Accept any antenna setting for both RX and TX
 }
 
 std::string SoapyLoopback::getAntenna(const int direction, const size_t channel) const

SoapyLoopback.hpp

@@ -95,6 +95,14 @@ class SoapyLoopback: public SoapySDR::Device
             long long &timeNs,
             const long timeoutUs = 100000);
 
+    int writeStream(
+            SoapySDR::Stream *stream,
+            const void * const *buffs,
+            const size_t numElems,
+            int &flags,
+            const long long timeNs = 0,
+            const long timeoutUs = 100000);
+
     /*******************************************************************
      * Direct buffer access API
      ******************************************************************/
@@ -306,4 +314,23 @@ class SoapyLoopback: public SoapySDR::Device
     std::atomic<bool> resetBuffer;
 
     double gainMin, gainMax;
+
+    // TX state
+    bool _txActive;
+    size_t _txBufferLength;
+    size_t _txNumBuffers;
+
+    // Loopback format tracking
+    std::string _loopbackFormat;  // Store the format for loopback operations
+    size_t _loopbackBytesPerSample;  // Bytes per sample for the loopback format
+
+    // Loopback ring buffer (TX writes here, RX reads from here)
+    std::mutex _loopback_mutex;
+    std::condition_variable _loopback_cond;
+    std::vector<Buffer> _loopback_buffs;
+    size_t _loopback_head;
+    size_t _loopback_tail;
+    std::atomic<size_t> _loopback_count;
+    std::atomic<bool> _loopback_overflow;
+    bool _loopbackEnabled;  // when true, RX reads from loopback buffer instead of synthetic data
 };