Wait tx complete (#3165)

* Implement radio transmission drain mechanism and update shared memory structure
* don't wait for timeout if baseband already in shut down state

firmware/application/radio.cpp

@@ -50,7 +50,7 @@ using namespace hackrf::one;
 
 #include "portapack.hpp"
 #include "portapack_persistent_memory.hpp"
-
+#include "baseband_api.hpp"
 #include "hal.h"  // For LPC_SGPIO
 
 #include <array>
@@ -413,6 +413,19 @@ void set_rx_max283x_iq_phase_calibration(const size_t v) {
 }
 
 void disable() {
+    if (direction == rf::Direction::Transmit && baseband::is_image_running()) {
+        static constexpr uint32_t radio_tx_drain_timeout_ms = 100;
+        shared_memory.radio_tx_drain = 1;  // Request drain of the current DMA queue.
+        for (uint32_t waited_ms = 0;
+             shared_memory.radio_tx_drain && (waited_ms < radio_tx_drain_timeout_ms);
+             ++waited_ms) {
+            chThdSleepMilliseconds(1);
+        }
+    }
+    /* Never allow shutdown to block indefinitely waiting for a drain
+     * acknowledgement that may never arrive in normal operation. */
+    shared_memory.radio_tx_drain = 0;
+
     set_antenna_bias(false);
     baseband_codec.set_mode(max5864::Mode::Shutdown);
 #ifdef PRALINE