3 files changed, 110 insertions, 15 deletions

diff --git a/gr-uhd/lib/Makefile.am b/gr-uhd/lib/Makefile.am
index c27682f7f..c322c6124 100644
--- a/gr-uhd/lib/Makefile.am
+++ b/gr-uhd/lib/Makefile.am
@@ -31,7 +31,8 @@ lib_LTLIBRARIES = libgnuradio-uhd.la
 
 libgnuradio_uhd_la_SOURCES = \
 	gr_uhd_usrp_source.cc \
-	gr_uhd_usrp_sink.cc
+	gr_uhd_usrp_sink.cc \
+	gr_uhd_amsg_source.cc
 
 libgnuradio_uhd_la_LIBADD = \
 	$(GNURADIO_CORE_LA) \
diff --git a/gr-uhd/lib/gr_uhd_amsg_source.cc b/gr-uhd/lib/gr_uhd_amsg_source.cc
new file mode 100644
index 000000000..f2958f115
--- /dev/null
+++ b/gr-uhd/lib/gr_uhd_amsg_source.cc
@@ -0,0 +1,88 @@
+/*
+ * Copyright 2011 Free Software Foundation, Inc.
+ * 
+ * This file is part of GNU Radio
+ * 
+ * GNU Radio is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 3, or (at your option)
+ * any later version.
+ * 
+ * GNU Radio is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ * 
+ * You should have received a copy of the GNU General Public License
+ * along with GNU Radio; see the file COPYING.  If not, write to
+ * the Free Software Foundation, Inc., 51 Franklin Street,
+ * Boston, MA 02110-1301, USA.
+ */
+
+#include <gr_uhd_amsg_source.h>
+#include <boost/bind.hpp>
+#include <gruel/thread.h>
+
+/***********************************************************************
+ * UHD Asynchronous Message Source Impl
+ **********************************************************************/
+class uhd_amsg_source_impl : public uhd_amsg_source{
+public:
+    uhd_amsg_source_impl(
+        const uhd::device_addr_t &device_addr,
+        gr_msg_queue_sptr msgq
+    ):
+        _msgq(msgq), _running(true)
+    {
+        _dev = uhd::usrp::multi_usrp::make(device_addr);
+        _amsg_thread =
+            gruel::thread(boost::bind(&uhd_amsg_source_impl::recv_loop, this));
+    }
+
+    ~uhd_amsg_source_impl()
+    {
+        _running = false;
+        _amsg_thread.join();
+    }
+
+    void recv_loop()
+    {
+        gr_message_sptr msg;
+        uhd::async_metadata_t *md;
+
+        while (_running) {
+            msg = gr_make_message(0, 0.0, 0.0, sizeof(uhd::async_metadata_t));
+            md = (uhd::async_metadata_t *) msg->msg();
+
+            while (!_dev->get_device()->recv_async_msg(*md, 0.1)) {
+                if (!_running)
+                    return;
+            }
+
+            post(msg);
+        }
+    }
+
+    void post(gr_message_sptr msg)
+    {
+        _msgq->insert_tail(msg);
+    }
+
+protected:
+    uhd::usrp::multi_usrp::sptr _dev;
+    gruel::thread _amsg_thread;
+    gr_msg_queue_sptr _msgq;
+    bool _running;
+};
+
+/***********************************************************************
+ * Make UHD Asynchronous Message Source
+ **********************************************************************/
+boost::shared_ptr<uhd_amsg_source> uhd_make_amsg_source(
+    const uhd::device_addr_t &device_addr,
+    gr_msg_queue_sptr msgq
+){
+    return boost::shared_ptr<uhd_amsg_source>(
+        new uhd_amsg_source_impl(device_addr, msgq)
+    );
+}
diff --git a/gr-uhd/lib/gr_uhd_usrp_source.cc b/gr-uhd/lib/gr_uhd_usrp_source.cc
index 9983489c3..669f890ea 100644
--- a/gr-uhd/lib/gr_uhd_usrp_source.cc
+++ b/gr-uhd/lib/gr_uhd_usrp_source.cc
@@ -182,19 +182,37 @@ public:
         gr_vector_const_void_star &input_items,
         gr_vector_void_star &output_items
     ){
-        //wait for a packet to become available
+        //In order to allow for low-latency:
+        //We receive all available packets without timeout.
+        //This call can timeout under regular operation...
         size_t num_samps = _dev->get_device()->recv(
             output_items, noutput_items, _metadata,
-            _type, uhd::device::RECV_MODE_ONE_PACKET, 1.0
+            _type, uhd::device::RECV_MODE_FULL_BUFF, 0.0
         );
 
+        //If receive resulted in a timeout condition:
+        //We now receive a single packet with a large timeout.
+        if (_metadata.error_code == uhd::rx_metadata_t::ERROR_CODE_TIMEOUT){
+            num_samps = _dev->get_device()->recv(
+                output_items, noutput_items, _metadata,
+                _type, uhd::device::RECV_MODE_ONE_PACKET, 1.0
+            );
+        }
+
         //handle possible errors conditions
         switch(_metadata.error_code){
         case uhd::rx_metadata_t::ERROR_CODE_NONE:
+            //TODO insert tag for time stamp
             break;
 
+        case uhd::rx_metadata_t::ERROR_CODE_TIMEOUT:
+            //Assume that the user called stop() on the flow graph.
+            //However, a timeout can occur under error conditions.
+            return WORK_DONE;
+
         case uhd::rx_metadata_t::ERROR_CODE_OVERFLOW:
             //ignore overflows and try work again
+            //TODO insert tag for overflow
             return work(noutput_items, input_items, output_items);
 
         default:
@@ -204,18 +222,6 @@ public:
             return num_samps;
         }
 
-        //advance the pointers and count by num_samps
-        noutput_items -= num_samps;
-        for (size_t i = 0; i < _nchan; i++){
-            _tmp_buffs[i] = static_cast<char *>(output_items[i]) + num_samps*_type.size;
-        }
-
-        //receive all available packets without timeout
-        num_samps += _dev->get_device()->recv(
-            _tmp_buffs, noutput_items, _metadata,
-            _type, uhd::device::RECV_MODE_FULL_BUFF, 0.0
-        );
-
         return num_samps;
     }