Merge branch 'UHD-3.9.LTS' into maint

This provides the GPS fixes.

Conflicts:
	host/CMakeLists.txt
	tools/debs/upload_debs.sh

6 files changed, 174 insertions, 159 deletions

diff --git a/host/lib/usrp/b200/b200_impl.cpp b/host/lib/usrp/b200/b200_impl.cpp
index aed1204d3..33f0850eb 100644
--- a/host/lib/usrp/b200/b200_impl.cpp
+++ b/host/lib/usrp/b200/b200_impl.cpp
@@ -461,6 +461,10 @@ b200_impl::b200_impl(const uhd::device_addr_t& device_addr, usb_device_handle::s
     ////////////////////////////////////////////////////////////////////
     _async_task_data.reset(new AsyncTaskData());
     _async_task_data->async_md.reset(new async_md_type(1000/*messages deep*/));
+    if (_gpsdo_capable)
+    {
+        _async_task_data->gpsdo_uart = b200_uart::make(_ctrl_transport, B200_TX_GPS_UART_SID);
+    }
     _async_task = uhd::msg_task::make(boost::bind(&b200_impl::handle_async_task, this, _ctrl_transport, _async_task_data));
 
     ////////////////////////////////////////////////////////////////////
@@ -481,10 +485,6 @@ b200_impl::b200_impl(const uhd::device_addr_t& device_addr, usb_device_handle::s
     ////////////////////////////////////////////////////////////////////
     if (_gpsdo_capable)
     {
-        _async_task_data->gpsdo_uart = b200_uart::make(_ctrl_transport, B200_TX_GPS_UART_SID);
-        _async_task_data->gpsdo_uart->set_baud_divider(B200_BUS_CLOCK_RATE/115200);
-        _async_task_data->gpsdo_uart->write_uart("\n"); //cause the baud and response to be setup
-        boost::this_thread::sleep(boost::posix_time::seconds(1)); //allow for a little propagation
 
         if ((_local_ctrl->peek32(RB32_CORE_STATUS) & 0xff) != B200_GPSDO_ST_NONE)
         {
diff --git a/host/lib/usrp/b200/b200_uart.cpp b/host/lib/usrp/b200/b200_uart.cpp
index 4682a79b9..065aa49ce 100644
--- a/host/lib/usrp/b200/b200_uart.cpp
+++ b/host/lib/usrp/b200/b200_uart.cpp
@@ -16,12 +16,14 @@
 //
 
 #include "b200_uart.hpp"
+#include "b200_impl.hpp"
 #include <uhd/transport/bounded_buffer.hpp>
 #include <uhd/transport/vrt_if_packet.hpp>
 #include <uhd/utils/byteswap.hpp>
 #include <uhd/utils/msg.hpp>
 #include <uhd/types/time_spec.hpp>
 #include <uhd/exception.hpp>
+#include <boost/foreach.hpp>
 
 using namespace uhd;
 using namespace uhd::transport;
@@ -32,10 +34,10 @@ struct b200_uart_impl : b200_uart
         _xport(xport),
         _sid(sid),
         _count(0),
-        _char_queue(4096)
+        _baud_div(std::floor(B200_BUS_CLOCK_RATE/115200 + 0.5)),
+        _line_queue(4096)
     {
-        //this default baud divider is over 9000
-        this->set_baud_divider(9001);
+        /*NOP*/
     }
 
     void send_char(const char ch)
@@ -67,23 +69,16 @@ struct b200_uart_impl : b200_uart
 
     void write_uart(const std::string &buff)
     {
-        for (size_t i = 0; i < buff.size(); i++)
+        BOOST_FOREACH(const char ch, buff)
         {
-            if (buff[i] == '\n') this->send_char('\r');
-            this->send_char(buff[i]);
+            this->send_char(ch);
         }
     }
 
     std::string read_uart(double timeout)
     {
         std::string line;
-        char ch = '\0';
-        while (_char_queue.pop_with_timed_wait(ch, timeout))
-        {
-            if (ch == '\r') continue;
-            line += std::string(&ch, 1);
-            if (ch == '\n') return line;
-        }
+        _line_queue.pop_with_timed_wait(line, timeout);
         return line;
     }
 
@@ -95,19 +90,20 @@ struct b200_uart_impl : b200_uart
         packet_info.num_packet_words32 = buff->size()/sizeof(boost::uint32_t);
         vrt::if_hdr_unpack_le(packet_buff, packet_info);
         const char ch = char(uhd::wtohx(packet_buff[packet_info.num_header_words32+1]));
-        _char_queue.push_with_pop_on_full(ch);
-    }
-
-    void set_baud_divider(const double baud_div)
-    {
-        _baud_div = size_t(baud_div + 0.5);
+        _line += ch;
+        if (ch == '\n')
+        {
+            _line_queue.push_with_pop_on_full(_line);
+            _line.clear();
+        }
     }
 
     const zero_copy_if::sptr _xport;
     const boost::uint32_t _sid;
     size_t _count;
     size_t _baud_div;
-    bounded_buffer<char> _char_queue;
+    bounded_buffer<std::string> _line_queue;
+    std::string _line;
 };
 
 
diff --git a/host/lib/usrp/b200/b200_uart.hpp b/host/lib/usrp/b200/b200_uart.hpp
index 1c8e44ddc..f58479888 100644
--- a/host/lib/usrp/b200/b200_uart.hpp
+++ b/host/lib/usrp/b200/b200_uart.hpp
@@ -29,7 +29,6 @@ public:
     typedef boost::shared_ptr<b200_uart> sptr;
     static sptr make(uhd::transport::zero_copy_if::sptr, const boost::uint32_t sid);
     virtual void handle_uart_packet(uhd::transport::managed_recv_buffer::sptr buff) = 0;
-    virtual void set_baud_divider(const double baud_div) = 0;
 };
 
 
diff --git a/host/lib/usrp/e100/e100_ctrl.cpp b/host/lib/usrp/e100/e100_ctrl.cpp
index cdbbff6dd..c164a6fb0 100644
--- a/host/lib/usrp/e100/e100_ctrl.cpp
+++ b/host/lib/usrp/e100/e100_ctrl.cpp
@@ -232,10 +232,13 @@ public:
 
             //got a character -> process it
             if (ret == 1){
-                const bool flush  = ch == '\n' or ch == '\r';
-                if (flush and line.empty()) continue; //avoid flushing on empty lines
-                line += std::string(1, ch);
-                if (flush) break;
+                _line += ch;
+                if (ch == '\n')
+                {
+                    line = _line;
+                    _line.clear();
+                    break;
+                }
             }
 
             //didnt get a character, check the timeout
@@ -251,7 +254,9 @@ public:
         return line;
     }
 
-private: int _node_fd;
+private:
+    int _node_fd;
+    std::string _line;
 };
 
 uhd::uart_iface::sptr e100_ctrl::make_gps_uart_iface(const std::string &node){
diff --git a/host/lib/usrp/gps_ctrl.cpp b/host/lib/usrp/gps_ctrl.cpp
index 207ef10ab..908f84a00 100644
--- a/host/lib/usrp/gps_ctrl.cpp
+++ b/host/lib/usrp/gps_ctrl.cpp
@@ -28,6 +28,7 @@
 #include <boost/tokenizer.hpp>
 #include <boost/format.hpp>
 #include <boost/regex.hpp>
+#include <boost/thread/mutex.hpp>
 
 #include "boost/tuple/tuple.hpp"
 #include "boost/foreach.hpp"
@@ -48,24 +49,68 @@ gps_ctrl::~gps_ctrl(void){
 
 class gps_ctrl_impl : public gps_ctrl{
 private:
-  std::map<std::string, boost::tuple<std::string, boost::system_time, bool> > sensors;
+    std::map<std::string, boost::tuple<std::string, boost::system_time, bool> > sentences;
+    boost::mutex cache_mutex;
+    boost::system_time _last_cache_update;
 
-  std::string get_cached_sensor(const std::string sensor, const int freshness, const bool once, const bool touch=true) {
-    boost::system_time time = boost::get_system_time();
-    try {
-      // this is nasty ...
-      //std::cout << boost::format("Requested %s - seen? ") % sensor << sensors[sensor].get<2>() << " once? " << once << std::endl;
-      if(time - sensors[sensor].get<1>() < milliseconds(freshness) && (!once or !sensors[sensor].get<2>())) {
-        sensors[sensor] = boost::make_tuple(sensors[sensor].get<0>(), sensors[sensor].get<1>(), touch);
-        return sensors[sensor].get<0>();
-      } else {
-          return update_cached_sensors(sensor);
-      }
-    } catch(std::exception &e) {
-      UHD_MSG(warning) << "get_cached_sensor: " << e.what();
+    std::string get_sentence(const std::string which, const int max_age_ms, const int timeout, const bool wait_for_next = false)
+    {
+        std::string sentence;
+        boost::system_time now = boost::get_system_time();
+        boost::system_time exit_time = now + milliseconds(timeout);
+        boost::posix_time::time_duration age;
+
+        if (wait_for_next)
+        {
+            boost::lock_guard<boost::mutex> lock(cache_mutex);
+            update_cache();
+            //mark sentence as touched
+            if (sentences.find(which) != sentences.end())
+                sentences[which].get<2>() = true;
+        }
+        while (1)
+        {
+            try
+            {
+                boost::lock_guard<boost::mutex> lock(cache_mutex);
+
+                // update cache if older than a millisecond
+                if (now - _last_cache_update > milliseconds(1))
+                {
+                    update_cache();
+                }
+
+                if (sentences.find(which) == sentences.end())
+                {
+                    age = milliseconds(max_age_ms);
+                } else {
+                    age = boost::get_system_time() - sentences[which].get<1>();
+                }
+                if (age < milliseconds(max_age_ms) and (not (wait_for_next and sentences[which].get<2>())))
+                {
+                    sentence = sentences[which].get<0>();
+                    sentences[which].get<2>() = true;
+                }
+            } catch(std::exception &e) {
+                UHD_MSG(warning) << "get_sentence: " << e.what();
+            }
+
+            if (not sentence.empty() or now > exit_time)
+            {
+                break;
+            }
+
+            sleep(boost::posix_time::milliseconds(1));
+            now = boost::get_system_time();
+        }
+
+        if (sentence.empty())
+        {
+            throw uhd::value_error("gps ctrl: No " + which + " message found");
+        }
+
+        return sentence;
     }
-    return std::string();
-  }
 
     static bool is_nmea_checksum_ok(std::string nmea)
     {
@@ -88,33 +133,39 @@ private:
         return (string_crc == calculated_crc);
     }
 
-  std::string update_cached_sensors(const std::string sensor) {
-    if(not gps_detected() || (gps_type != GPS_TYPE_INTERNAL_GPSDO)) {
+  void update_cache() {
+    if(not gps_detected() or (_gps_type != GPS_TYPE_INTERNAL_GPSDO)) {
         UHD_MSG(error) << "get_stat(): unsupported GPS or no GPS detected";
-        return std::string();
+        return;
     }
 
-    const std::list<std::string> list = boost::assign::list_of("GPGGA")("GPRMC")("SERVO");
-    static const boost::regex status_regex("\\d\\d-\\d\\d-\\d\\d");
+    const std::list<std::string> keys = boost::assign::list_of("GPGGA")("GPRMC")("SERVO");
+    static const boost::regex servo_regex("^\\d\\d-\\d\\d-\\d\\d.*$");
     static const boost::regex gp_msg_regex("^\\$GP.*,\\*[0-9A-F]{2}$");
     std::map<std::string,std::string> msgs;
 
     // Get all GPSDO messages available
     // Creating a map here because we only want the latest of each message type
-    for (std::string msg = _recv(); msg.length(); msg = _recv())
+    for (std::string msg = _recv(0); not msg.empty(); msg = _recv(0))
     {
         // Strip any end of line characters
         erase_all(msg, "\r");
         erase_all(msg, "\n");
 
+        if (msg.empty())
+        {
+            // Ignore empty strings
+            continue;
+        }
+
         if (msg.length() < 6)
         {
-            UHD_LOGV(regularly) << __FUNCTION__ << ": Short NMEA string: " << msg << std::endl;
+            UHD_LOGV(regularly) << __FUNCTION__ << ": Short GPSDO string: " << msg << std::endl;
             continue;
         }
 
         // Look for SERVO message
-        if (boost::regex_search(msg, status_regex, boost::regex_constants::match_continuous))
+        if (boost::regex_search(msg, servo_regex, boost::regex_constants::match_continuous))
         {
             msgs["SERVO"] = msg;
         }
@@ -124,62 +175,63 @@ private:
         }
         else
         {
-            UHD_LOGV(regularly) << __FUNCTION__ << ": Malformed NMEA string: " << msg << std::endl;
+            UHD_LOGV(regularly) << __FUNCTION__ << ": Malformed GPSDO string: " << msg << std::endl;
         }
     }
 
     boost::system_time time = boost::get_system_time();
 
-    // Update sensors with newly read data
-    BOOST_FOREACH(std::string key, list) {
-        if (msgs[key].length())
-            sensors[key] = boost::make_tuple(msgs[key], time, !sensor.compare(key));
+    // Update sentences with newly read data
+    BOOST_FOREACH(std::string key, keys)
+    {
+        if (not msgs[key].empty())
+        {
+            sentences[key] = boost::make_tuple(msgs[key], time, false);
+        }
     }
 
-    // Return requested sensor if it was updated
-    if (msgs[sensor].length())
-        return msgs[sensor];
-
-    return std::string();
+    _last_cache_update = time;
   }
 
 public:
-  gps_ctrl_impl(uart_iface::sptr uart){
-    _uart = uart;
-
+  gps_ctrl_impl(uart_iface::sptr uart) :
+      _uart(uart),
+      _gps_type(GPS_TYPE_NONE)
+  {
 
     std::string reply;
     bool i_heard_some_nmea = false, i_heard_something_weird = false;
-    gps_type = GPS_TYPE_NONE;
 
     //first we look for an internal GPSDO
     _flush(); //get whatever junk is in the rx buffer right now, and throw it away
-    _send("HAAAY GUYYYYS\n"); //to elicit a response from the GPSDO
-
-    //wait for _send(...) to return
-    sleep(milliseconds(GPSDO_COMMAND_DELAY_MS));
+    _send("*IDN?\r\n"); //request identity from the GPSDO
 
     //then we loop until we either timeout, or until we get a response that indicates we're a JL device
     const boost::system_time comm_timeout = boost::get_system_time() + milliseconds(GPS_COMM_TIMEOUT_MS);
     while(boost::get_system_time() < comm_timeout) {
       reply = _recv();
-      if(reply.find("Command Error") != std::string::npos) {
-        gps_type = GPS_TYPE_INTERNAL_GPSDO;
+      //known devices are JL "FireFly" and "LC_XO"
+      if(reply.find("FireFly") != std::string::npos or reply.find("LC_XO") != std::string::npos) {
+        _gps_type = GPS_TYPE_INTERNAL_GPSDO;
         break;
+      } else if(reply.substr(0, 3) == "$GP") {
+          i_heard_some_nmea = true; //but keep looking
+      } else if(not reply.empty()) {
+          i_heard_something_weird = true; //probably wrong baud rate
       }
-      else if(reply.substr(0, 3) == "$GP") i_heard_some_nmea = true; //but keep looking for that "Command Error" response
-      else if(reply.length() != 0) i_heard_something_weird = true; //probably wrong baud rate
     }
 
-    if((i_heard_some_nmea) && (gps_type != GPS_TYPE_INTERNAL_GPSDO)) gps_type = GPS_TYPE_GENERIC_NMEA;
+    if((i_heard_some_nmea) && (_gps_type != GPS_TYPE_INTERNAL_GPSDO)) _gps_type = GPS_TYPE_GENERIC_NMEA;
 
-    if((gps_type == GPS_TYPE_NONE) && i_heard_something_weird) {
+    if((_gps_type == GPS_TYPE_NONE) && i_heard_something_weird) {
       UHD_MSG(error) << "GPS invalid reply \"" << reply << "\", assuming none available" << std::endl;
     }
 
-    switch(gps_type) {
+    switch(_gps_type) {
     case GPS_TYPE_INTERNAL_GPSDO:
-      UHD_MSG(status) << "Found an internal GPSDO" << std::endl;
+      erase_all(reply, "\r");
+      erase_all(reply, "\n");
+      UHD_MSG(status) << "Found an internal GPSDO: " << reply << std::endl;
       init_gpsdo();
       break;
 
@@ -193,6 +245,9 @@ public:
       break;
 
     }
+
+    // initialize cache
+    update_cache();
   }
 
   ~gps_ctrl_impl(void){
@@ -215,7 +270,7 @@ public:
     or key == "gps_gprmc") {
         return sensor_value_t(
                  boost::to_upper_copy(key),
-                 get_cached_sensor(boost::to_upper_copy(key.substr(4,8)), GPS_NMEA_NORMAL_FRESHNESS, false, false),
+                 get_sentence(boost::to_upper_copy(key.substr(4,8)), GPS_NMEA_NORMAL_FRESHNESS, GPS_TIMEOUT_DELAY_MS),
                  "");
     }
     else if(key == "gps_time") {
@@ -225,7 +280,10 @@ public:
         return sensor_value_t("GPS lock status", locked(), "locked", "unlocked");
     }
     else if(key == "gps_servo") {
-        return sensor_value_t("GPS servo status", get_servo(), "");
+        return sensor_value_t(
+                 boost::to_upper_copy(key),
+                 get_sentence(boost::to_upper_copy(key.substr(4,8)), GPS_SERVO_FRESHNESS, GPS_TIMEOUT_DELAY_MS),
+                 "");
     }
     else {
         throw uhd::value_error("gps ctrl get_sensor unknown key: " + key);
@@ -238,40 +296,20 @@ private:
     //none of these should issue replies so we don't bother looking for them
     //we have to sleep between commands because the JL device, despite not acking, takes considerable time to process each command.
      sleep(milliseconds(GPSDO_COMMAND_DELAY_MS));
-    _send("SYST:COMM:SER:ECHO OFF\n");
+    _send("SYST:COMM:SER:ECHO OFF\r\n");
      sleep(milliseconds(GPSDO_COMMAND_DELAY_MS));
-    _send("SYST:COMM:SER:PRO OFF\n");
+    _send("SYST:COMM:SER:PRO OFF\r\n");
      sleep(milliseconds(GPSDO_COMMAND_DELAY_MS));
-    _send("GPS:GPGGA 1\n");
+    _send("GPS:GPGGA 1\r\n");
      sleep(milliseconds(GPSDO_COMMAND_DELAY_MS));
-    _send("GPS:GGAST 0\n");
+    _send("GPS:GGAST 0\r\n");
      sleep(milliseconds(GPSDO_COMMAND_DELAY_MS));
-    _send("GPS:GPRMC 1\n");
+    _send("GPS:GPRMC 1\r\n");
      sleep(milliseconds(GPSDO_COMMAND_DELAY_MS));
-    _send("SERV:TRAC 0\n");
+    _send("SERV:TRAC 1\r\n");
      sleep(milliseconds(GPSDO_COMMAND_DELAY_MS));
   }
 
-  //retrieve a raw NMEA sentence
-  std::string get_nmea(std::string msgtype) {
-    std::string reply;
-
-    const boost::system_time comm_timeout = boost::get_system_time() + milliseconds(GPS_COMM_TIMEOUT_MS);
-    while(boost::get_system_time() < comm_timeout) {
-        if(!msgtype.compare("GPRMC")) {
-          reply = get_cached_sensor(msgtype, GPS_NMEA_FRESHNESS, true);
-        }
-        else {
-          reply = get_cached_sensor(msgtype, GPS_NMEA_LOW_FRESHNESS, false);
-        }
-        if(reply.size()) {
-          if(reply.substr(1, 5) == msgtype) return reply;
-        }
-        boost::this_thread::sleep(milliseconds(GPS_TIMEOUT_DELAY_MS));
-    }
-    throw uhd::value_error(str(boost::format("get_nmea(): no %s message found") % msgtype));
-  }
-
   //helper function to retrieve a field from an NMEA sentence
   std::string get_token(std::string sentence, size_t offset) {
     boost::tokenizer<boost::escaped_list_separator<char> > tok(sentence);
@@ -286,12 +324,12 @@ private:
   }
 
   ptime get_time(void) {
-    _flush();
     int error_cnt = 0;
     ptime gps_time;
     while(error_cnt < 2) {
         try {
-            std::string reply = get_nmea("GPRMC");
+            // wait for next GPRMC string
+            std::string reply = get_sentence("GPRMC", GPS_NMEA_NORMAL_FRESHNESS, GPS_COMM_TIMEOUT_MS, true);
 
             std::string datestr = get_token(reply, 9);
             std::string timestr = get_token(reply, 1);
@@ -314,7 +352,6 @@ private:
 
         } catch(std::exception &e) {
             UHD_MSG(warning) << "get_time: " << e.what();
-            _flush();
             error_cnt++;
         }
     }
@@ -328,46 +365,24 @@ private:
   }
 
   bool gps_detected(void) {
-    return (gps_type != GPS_TYPE_NONE);
+    return (_gps_type != GPS_TYPE_NONE);
   }
 
   bool locked(void) {
     int error_cnt = 0;
     while(error_cnt < 3) {
         try {
-            std::string reply = get_cached_sensor("GPGGA", GPS_LOCK_FRESHNESS, false, false);
-            if(reply.size() <= 1) return false;
-
-            return (get_token(reply, 6) != "0");
+            std::string reply = get_sentence("GPGGA", GPS_LOCK_FRESHNESS, GPS_COMM_TIMEOUT_MS);
+            if(reply.empty())
+                error_cnt++;
+            else
+                return (get_token(reply, 6) != "0");
         } catch(std::exception &e) {
             UHD_MSG(warning) << "locked: " << e.what();
             error_cnt++;
         }
     }
-    throw uhd::value_error("Timeout after no valid message found");
-    return false;
-  }
-
-  std::string get_servo(void) {
-
-    //enable servo reporting
-    _send("SERV:TRAC 1\n");
-    sleep(milliseconds(GPSDO_COMMAND_DELAY_MS));
-
-    std::string reply;
-
-    const boost::system_time comm_timeout = boost::get_system_time() + milliseconds(GPS_COMM_TIMEOUT_MS);
-    while(boost::get_system_time() < comm_timeout) {
-        reply = get_cached_sensor("SERVO", GPS_NMEA_LOW_FRESHNESS, false);
-        if(reply.size())
-        {
-            //disable it before leaving function
-            _send("SERV:TRAC 0\n");
-            return reply;
-        }
-        boost::this_thread::sleep(milliseconds(GPS_TIMEOUT_DELAY_MS));
-    }
-    throw uhd::value_error("get_stat(): no servo message found");
+    throw uhd::value_error("locked(): unable to determine GPS lock status");
   }
 
   uart_iface::sptr _uart;
@@ -390,13 +405,11 @@ private:
     GPS_TYPE_INTERNAL_GPSDO,
     GPS_TYPE_GENERIC_NMEA,
     GPS_TYPE_NONE
-  } gps_type;
+  } _gps_type;
 
   static const int GPS_COMM_TIMEOUT_MS = 1300;
-  static const int GPS_NMEA_FRESHNESS = 10;
-  static const int GPS_NMEA_LOW_FRESHNESS = 2500;
   static const int GPS_NMEA_NORMAL_FRESHNESS = 1000;
-  static const int GPS_SERVO_FRESHNESS = 2500;
+  static const int GPS_SERVO_FRESHNESS = 1000;
   static const int GPS_LOCK_FRESHNESS = 2500;
   static const int GPS_TIMEOUT_DELAY_MS = 200;
   static const int GPSDO_COMMAND_DELAY_MS = 200;
diff --git a/host/lib/usrp/x300/x300_fw_uart.cpp b/host/lib/usrp/x300/x300_fw_uart.cpp
index b0fae124d..7f60e26fc 100644
--- a/host/lib/usrp/x300/x300_fw_uart.cpp
+++ b/host/lib/usrp/x300/x300_fw_uart.cpp
@@ -30,28 +30,36 @@ using namespace uhd;
 struct x300_uart_iface : uart_iface
 {
     x300_uart_iface(wb_iface::sptr iface):
-        rxoffset(0), txoffset(0), txword32(0), rxpool(0), txpool(0), poolsize(0)
+        _iface(iface),
+        rxoffset(0),
+        txword32(0),
+        _last_device_rxoffset(0)
     {
-        _iface = iface;
-        rxoffset = _iface->peek32(SR_ADDR(X300_FW_SHMEM_BASE, X300_FW_SHMEM_UART_RX_INDEX));
         txoffset = _iface->peek32(SR_ADDR(X300_FW_SHMEM_BASE, X300_FW_SHMEM_UART_TX_INDEX));
         rxpool = _iface->peek32(SR_ADDR(X300_FW_SHMEM_BASE, X300_FW_SHMEM_UART_RX_ADDR));
         txpool = _iface->peek32(SR_ADDR(X300_FW_SHMEM_BASE, X300_FW_SHMEM_UART_TX_ADDR));
         poolsize = _iface->peek32(SR_ADDR(X300_FW_SHMEM_BASE, X300_FW_SHMEM_UART_WORDS32));
         _rxcache.resize(poolsize);
-        _last_device_rxoffset = rxoffset;
         //this->write_uart("HELLO UART\n");
         //this->read_uart(0.1);
     }
 
     void putchar(const char ch)
     {
-        txoffset = (txoffset + 1) % (poolsize*4);
         const int shift = ((txoffset%4) * 8);
         if (shift == 0) txword32 = 0;
         txword32 |= boost::uint32_t(ch) << shift;
-        _iface->poke32(SR_ADDR(txpool, txoffset/4), txword32);
-        _iface->poke32(SR_ADDR(X300_FW_SHMEM_BASE, X300_FW_SHMEM_UART_TX_INDEX), txoffset);
+        // Write out full 32 bit words or whatever we have if end of string
+        if (txoffset % 4 == 3 or ch == '\n')
+        {
+            _iface->poke32(SR_ADDR(txpool, txoffset/4), txword32);
+        }
+        txoffset = (txoffset + 1) % (poolsize*4);
+        if (ch == '\n')
+        {
+            // Tell the X300 to write the string
+            _iface->poke32(SR_ADDR(X300_FW_SHMEM_BASE, X300_FW_SHMEM_UART_TX_INDEX), txoffset);
+        }
     }
 
     void write_uart(const std::string &buff)
@@ -59,7 +67,6 @@ struct x300_uart_iface : uart_iface
         boost::mutex::scoped_lock(_write_mutex);
         BOOST_FOREACH(const char ch, buff)
         {
-            if (ch == '\n') this->putchar('\r');
             this->putchar(ch);
         }
     }
@@ -128,18 +135,13 @@ struct x300_uart_iface : uart_iface
             // Get available characters
             for (int ch = this->getchar(); ch != -1; ch = this->getchar())
             {
-                // skip carriage returns
-                if (ch == '\r')
-                    continue;
-
                 // store character to buffer
-                _rxbuff += std::string(1, (char)ch);
+                _rxbuff.append(1, ch);
 
                 // newline found - return string
                 if (ch == '\n')
                 {
-                    buff = _rxbuff;
-                    _rxbuff.clear();
+                    buff.swap(_rxbuff);
                     return buff;
                 }
             }