diff --git a/include/hamlib/rig.h b/include/hamlib/rig.h
index f58dfa387..9e174d0fa 100644
--- a/include/hamlib/rig.h
+++ b/include/hamlib/rig.h
@@ -1984,6 +1984,17 @@ struct rig_caps {
     const char *clone_combo_set;    /*!< String describing key combination to enter load cloning mode */
     const char *clone_combo_get;    /*!< String describing key combination to enter save cloning mode */
     const char *macro_name;     /*!< Rig model macro name */
+
+    int async_data_supported;
+    int (*read_frame_direct)(RIG *rig,
+                             size_t buffer_length,
+                             const unsigned char *buffer);
+    int (*is_async_frame)(RIG *rig,
+                          size_t frame_length,
+                          const unsigned char *frame);
+    int (*process_async_frame)(RIG *rig,
+                               size_t frame_length,
+                               const unsigned char *frame);
 };
 //! @endcond
 
@@ -2186,6 +2197,10 @@ typedef struct hamlib_port {
     } parm;                 /*!< Port parameter union */
     int client_port;      /*!< client socket port for tcp connection */
     RIG *rig;             /*!< our parent RIG device */
+
+    int async;            /*!< enable asynchronous data handling if true */
+    int fd_sync_write;    /*!< file descriptor for writing synchronous data */
+    int fd_sync_read;     /*!< file descriptor for reading synchronous data */
 } hamlib_port_t;
 //! @endcond
 
diff --git a/rigs/icom/frame.c b/rigs/icom/frame.c
index 964277a13..2137df20e 100644
--- a/rigs/icom/frame.c
+++ b/rigs/icom/frame.c
@@ -46,7 +46,8 @@
  * NB: the frame array must be big enough to hold the frame.
  *      The smallest frame is 6 bytes, the biggest is at least 13 bytes.
  */
-int make_cmd_frame(char frame[], char re_id, char ctrl_id, char cmd, int subcmd,
+int make_cmd_frame(unsigned char frame[], unsigned char re_id, unsigned char ctrl_id,
+                   unsigned char cmd, int subcmd,
                    const unsigned char *data, int data_len)
 {
     int i = 0;
@@ -121,7 +122,7 @@ int icom_frame_fix_preamble(int frame_len, unsigned char *frame)
  * return RIG_OK if transaction completed,
  * or a negative value otherwise indicating the error.
  */
-int icom_one_transaction(RIG *rig, int cmd, int subcmd,
+int icom_one_transaction(RIG *rig, unsigned char cmd, int subcmd,
                          const unsigned char *payload, int payload_len, unsigned char *data,
                          int *data_len)
 {
@@ -134,7 +135,7 @@ int icom_one_transaction(RIG *rig, int cmd, int subcmd,
     unsigned char buf[200];
     unsigned char sendbuf[MAXFRAMELEN];
     int frm_len, frm_data_len, retval;
-    int ctrl_id;
+    unsigned char ctrl_id;
 
     ENTERFUNC;
     rig_lock();
@@ -146,7 +147,7 @@ int icom_one_transaction(RIG *rig, int cmd, int subcmd,
 
     ctrl_id = priv_caps->serial_full_duplex == 0 ? CTRLID : 0x80;
 
-    frm_len = make_cmd_frame((char *) sendbuf, priv->re_civ_addr, ctrl_id, cmd,
+    frm_len = make_cmd_frame(sendbuf, priv->re_civ_addr, ctrl_id, cmd,
                              subcmd, payload, payload_len);
 
     /*
@@ -158,7 +159,7 @@ int icom_one_transaction(RIG *rig, int cmd, int subcmd,
 
     if (data_len) { *data_len = 0; }
 
-    retval = write_block(&rs->rigport, (char *) sendbuf, frm_len);
+    retval = write_block(&rs->rigport, sendbuf, frm_len);
 
     if (retval != RIG_OK)
     {
@@ -234,7 +235,7 @@ int icom_one_transaction(RIG *rig, int cmd, int subcmd,
             RETURNFUNC(-RIG_EPROTO);
         }
 
-        if (memcmp(buf, sendbuf, frm_len))
+        if (memcmp(buf, sendbuf, frm_len) != 0)
         {
             /* Frames are different? */
             /* Problem on ci-v bus? */
@@ -466,17 +467,17 @@ static const char icom_block_end[2] = { FI, COL};
 #define icom_block_end_length 2
 
 /*
- * read_icom_frame
- * read a whole CI-V frame (until 0xfd is encountered)
+ * Read a whole CI-V frame (until 0xfd is encountered).
+ *
  * TODO: strips padding/collisions
  * FIXME: check return codes/bytes read
  */
-int read_icom_frame(hamlib_port_t *p, unsigned char rxbuffer[],
-                    int rxbuffer_len)
+static int read_icom_frame_generic(hamlib_port_t *p, const unsigned char rxbuffer[],
+                                   size_t rxbuffer_len, int direct)
 {
     int read = 0;
     int retries = 10;
-    char *rx_ptr = (char *)rxbuffer;
+    unsigned char *rx_ptr = (unsigned char *) rxbuffer;
 
     ENTERFUNC;
     // zeroize the buffer so we can still check contents after timeouts
@@ -484,13 +485,20 @@ int read_icom_frame(hamlib_port_t *p, unsigned char rxbuffer[],
 
     /*
      * OK, now sometimes we may time out, e.g. the IC7000 can time out
-     * during a PTT operation. So, we will insure that the last thing we
+     * during a PTT operation. So, we will ensure that the last thing we
      * read was a proper end marker - if not, we will try again.
      */
     do
     {
-        int i = read_string(p, rx_ptr, MAXFRAMELEN - read,
-                            icom_block_end, icom_block_end_length, 0);
+        int i;
+        if (direct)
+        {
+            i = read_string_direct(p, rx_ptr, MAXFRAMELEN - read, icom_block_end, icom_block_end_length, 0);
+        }
+        else
+        {
+            i = read_string(p, rx_ptr, MAXFRAMELEN - read, icom_block_end, icom_block_end_length, 0);
+        }
 
         if (i < 0 && i != RIG_BUSBUSY) /* die on errors */
         {
@@ -518,6 +526,17 @@ int read_icom_frame(hamlib_port_t *p, unsigned char rxbuffer[],
     RETURNFUNC(read);
 }
 
+int read_icom_frame(hamlib_port_t *p, const unsigned char rxbuffer[],
+                    size_t rxbuffer_len)
+{
+    return read_icom_frame_generic(p, rxbuffer, rxbuffer_len, 0);
+}
+
+int read_icom_frame_direct(hamlib_port_t *p, const unsigned char rxbuffer[],
+                           size_t rxbuffer_len)
+{
+    return read_icom_frame_generic(p, rxbuffer, rxbuffer_len, 1);
+}
 
 /*
  * convert mode and width as expressed by Hamlib frontend
diff --git a/rigs/icom/frame.h b/rigs/icom/frame.h
index 0ffc7e0e9..acd03c5cd 100644
--- a/rigs/icom/frame.h
+++ b/rigs/icom/frame.h
@@ -27,11 +27,14 @@
 /*
  * helper functions
  */
-int make_cmd_frame(char frame[], char re_id, char ctrl_id, char cmd, int subcmd, const unsigned char *data, int data_len);
+int make_cmd_frame(unsigned char frame[], unsigned char re_id, unsigned char ctrl_id,
+                   unsigned char cmd, int subcmd,
+                   const unsigned char *data, int data_len);
 int icom_frame_fix_preamble(int frame_len, unsigned char *frame);
 
 int icom_transaction (RIG *rig, int cmd, int subcmd, const unsigned char *payload, int payload_len, unsigned char *data, int *data_len);
-int read_icom_frame(hamlib_port_t *p, unsigned char rxbuffer[], int rxbuffer_len);
+int read_icom_frame(hamlib_port_t *p, const unsigned char rxbuffer[], size_t rxbuffer_len);
+int read_icom_frame_direct(hamlib_port_t *p, const unsigned char rxbuffer[], size_t rxbuffer_len);
 
 int rig2icom_mode(RIG *rig, vfo_t vfo, rmode_t mode, pbwidth_t width, unsigned char *md, signed char *pd);
 void icom2rig_mode(RIG *rig, unsigned char md, int pd, rmode_t *mode, pbwidth_t *width);
diff --git a/rigs/icom/ic7300.c b/rigs/icom/ic7300.c
index d2c6b79e7..e9fb53598 100644
--- a/rigs/icom/ic7300.c
+++ b/rigs/icom/ic7300.c
@@ -692,6 +692,11 @@ const struct rig_caps ic7300_caps =
         },
     },
 
+    .async_data_supported = 1,
+    .read_frame_direct = icom_read_frame_direct,
+    .is_async_frame = icom_is_async_frame,
+    .process_async_frame = icom_process_async_frame,
+
     .cfgparams =  icom_cfg_params,
     .set_conf =  icom_set_conf,
     .get_conf =  icom_get_conf,
diff --git a/rigs/icom/icom.c b/rigs/icom/icom.c
index 4a3e17ac0..6ad781007 100644
--- a/rigs/icom/icom.c
+++ b/rigs/icom/icom.c
@@ -929,6 +929,7 @@ icom_rig_open(RIG *rig)
     struct rig_state *rs = &rig->state;
     struct icom_priv_data *priv = (struct icom_priv_data *) rs->priv;
     int retry_flag = 1;
+    int echo_off;
 
     ENTERFUNC;
 
@@ -937,9 +938,9 @@ icom_rig_open(RIG *rig)
     rig_debug(RIG_DEBUG_VERBOSE, "%s: %s v%s\n", __func__, rig->caps->model_name,
               rig->caps->version);
 retry_open:
-    retval = icom_get_usb_echo_off(rig);
+    echo_off = icom_get_usb_echo_off(rig);
 
-    if (retval == RIG_OK) // then echo is on so let's try freq now
+    if (echo_off == 0) // then echo is on so let's try freq now
     {
         rig->state.current_vfo = icom_current_vfo(rig);
         // some rigs like the IC7100 still echo when in standby
@@ -967,9 +968,9 @@ retry_open:
         }
 
         // Now that we're powered up let's try again
-        retval = icom_get_usb_echo_off(rig);
+        echo_off = icom_get_usb_echo_off(rig);
 
-        if (retval < 0)
+        if (echo_off < 0)
         {
             rig_debug(RIG_DEBUG_ERR, "%s: Unable to determine USB echo status\n", __func__);
             RETURNFUNC(retval);
@@ -7675,7 +7676,7 @@ int icom_set_powerstat(RIG *rig, powerstat_t status)
         // we'll just send a few more to be sure for all speeds
         memset(fe_buf, 0xfe, fe_max);
         // sending more than enough 0xfe's to wake up the rs232
-        write_block(&rs->rigport, (char *) fe_buf, fe_max);
+        write_block(&rs->rigport, fe_buf, fe_max);
 
         // we'll try 0x18 0x01 now -- should work on STBY rigs too
         pwr_sc = S_PWR_ON;
@@ -8601,9 +8602,9 @@ static int icom_parse_spectrum_frame(RIG *rig, int length,
     RETURNFUNC(RIG_OK);
 }
 
-int icom_is_async_frame(RIG *rig, int frame_len, const unsigned char *frame)
+int icom_is_async_frame(RIG *rig, size_t frame_length, const unsigned char *frame)
 {
-    if (frame_len < ACKFRMLEN)
+    if (frame_length < ACKFRMLEN)
     {
         return 0;
     }
@@ -8613,7 +8614,7 @@ int icom_is_async_frame(RIG *rig, int frame_len, const unsigned char *frame)
                                    && frame[5] == S_SCP_DAT);
 }
 
-int icom_process_async_frame(RIG *rig, int frame_len,
+int icom_process_async_frame(RIG *rig, size_t frame_length,
                              const unsigned char *frame)
 {
     struct rig_state *rs = &rig->state;
@@ -8670,7 +8671,7 @@ int icom_process_async_frame(RIG *rig, int frame_len,
     case C_CTL_SCP:
         if (frame[5] == S_SCP_DAT)
         {
-            icom_parse_spectrum_frame(rig, frame_len - (6 + 1), frame + 6);
+            icom_parse_spectrum_frame(rig, frame_length - (6 + 1), frame + 6);
         }
 
         break;
@@ -8706,6 +8707,7 @@ int icom_decode_event(RIG *rig)
     {
         rig_debug(RIG_DEBUG_VERBOSE,
                   "%s: got a timeout before the first character\n", __func__);
+        RETURNFUNC(-RIG_ETIMEOUT);
     }
 
     if (frm_len < 1)
@@ -8755,6 +8757,11 @@ int icom_decode_event(RIG *rig)
     RETURNFUNC(icom_process_async_frame(rig, frm_len, buf));
 }
 
+int icom_read_frame_direct(RIG *rig, size_t buffer_length, const unsigned char *buffer)
+{
+    return read_icom_frame_direct(&rig->state.rigport, buffer, buffer_length);
+}
+
 int icom_set_raw(RIG *rig, int cmd, int subcmd, int subcmdbuflen,
                  unsigned char *subcmdbuf, int val_bytes, int val)
 {
@@ -9216,11 +9223,11 @@ DECLARE_PROBERIG_BACKEND(icom)
         for (civ_addr = 0x01; civ_addr <= 0x7f; civ_addr++)
         {
 
-            frm_len = make_cmd_frame((char *) buf, civ_addr, CTRLID,
+            frm_len = make_cmd_frame(buf, civ_addr, CTRLID,
                                      C_RD_TRXID, S_RD_TRXID, NULL, 0);
 
             rig_flush(port);
-            write_block(port, (char *) buf, frm_len);
+            write_block(port, buf, frm_len);
 
             /* read out the bytes we just sent
              * TODO: check this is what we expect
@@ -9290,11 +9297,11 @@ DECLARE_PROBERIG_BACKEND(icom)
         for (civ_addr = 0x80; civ_addr <= 0x8f; civ_addr++)
         {
 
-            frm_len = make_cmd_frame((char *) buf, civ_addr, CTRLID,
+            frm_len = make_cmd_frame(buf, civ_addr, CTRLID,
                                      C_CTL_MISC, S_OPTO_RDID, NULL, 0);
 
             rig_flush(port);
-            write_block(port, (char *) buf, frm_len);
+            write_block(port, buf, frm_len);
 
             /* read out the bytes we just sent
              * TODO: check this is what we expect
diff --git a/rigs/icom/icom.h b/rigs/icom/icom.h
index 20176f2a2..10d23fdd9 100644
--- a/rigs/icom/icom.h
+++ b/rigs/icom/icom.h
@@ -398,8 +398,9 @@ int icom_set_custom_parm_time(RIG *rig, int parmbuflen, unsigned char *parmbuf,
 int icom_get_custom_parm_time(RIG *rig, int parmbuflen, unsigned char *parmbuf,
                               int *seconds);
 int icom_get_freq_range(RIG *rig);
-int icom_is_async_frame(RIG *rig, int frame_len, const unsigned char *frame);
-int icom_process_async_frame(RIG *rig, int frame_len, const unsigned char *frame);
+int icom_is_async_frame(RIG *rig, size_t frame_length, const unsigned char *frame);
+int icom_process_async_frame(RIG *rig, size_t frame_length, const unsigned char *frame);
+int icom_read_frame_direct(RIG *rig, size_t buffer_length, const unsigned char *buffer);
 
 extern const struct confparams icom_cfg_params[];
 extern const struct confparams icom_ext_levels[];
diff --git a/rigs/kenwood/tmd710.c b/rigs/kenwood/tmd710.c
index 8012f654f..f8e7e58a5 100644
--- a/rigs/kenwood/tmd710.c
+++ b/rigs/kenwood/tmd710.c
@@ -588,6 +588,7 @@ static int tmd710_resolve_vfo(RIG *rig, vfo_t vfo, vfo_t *resolved_vfo,
     switch (vfo)
     {
     case RIG_VFO_CURR:
+    case RIG_VFO_MEM:
         return tmd710_get_vfo_num(rig, resolved_vfonum, resolved_vfo);
 
     case RIG_VFO_A:
diff --git a/src/iofunc.c b/src/iofunc.c
index 232bc3fb0..6483d2e18 100644
--- a/src/iofunc.c
+++ b/src/iofunc.c
@@ -55,6 +55,18 @@
 #include "cm108.h"
 #include "gpio.h"
 
+static void close_sync_data_pipe(hamlib_port_t *p)
+{
+    if (p->fd_sync_read != -1) {
+        close(p->fd_sync_read);
+        p->fd_sync_read = -1;
+    }
+    if (p->fd_sync_write != -1) {
+        close(p->fd_sync_write);
+        p->fd_sync_write = -1;
+    }
+}
+
 /**
  * \brief Open a hamlib_port based on its rig port type
  * \param p rig port descriptor
@@ -64,10 +76,30 @@ int HAMLIB_API port_open(hamlib_port_t *p)
 {
     int status;
     int want_state_delay = 0;
+    int sync_pipe_fds[2];
 
     ENTERFUNC;
 
     p->fd = -1;
+    p->fd_sync_write = -1;
+    p->fd_sync_read = -1;
+
+    if (p->async)
+    {
+        status = pipe2(sync_pipe_fds, O_NONBLOCK);
+        if (status != 0)
+        {
+            rig_debug(RIG_DEBUG_ERR, "%s: synchronous data pipe open status=%d, err=%s\n", __func__,
+                    status, strerror(errno));
+            close_sync_data_pipe(p);
+            RETURNFUNC(-RIG_EINTERNAL);
+        }
+
+        p->fd_sync_read = sync_pipe_fds[0];
+        p->fd_sync_write = sync_pipe_fds[1];
+
+        rig_debug(RIG_DEBUG_VERBOSE, "%s: created synchronous data pipe\n", __func__);
+    }
 
     switch (p->type.rig)
     {
@@ -78,6 +110,7 @@ int HAMLIB_API port_open(hamlib_port_t *p)
         {
             rig_debug(RIG_DEBUG_ERR, "%s: serial_open(%s) status=%d, err=%s\n", __func__,
                       p->pathname, status, strerror(errno));
+            close_sync_data_pipe(p);
             RETURNFUNC(status);
         }
 
@@ -92,6 +125,7 @@ int HAMLIB_API port_open(hamlib_port_t *p)
         if (status != 0)
         {
             rig_debug(RIG_DEBUG_ERR, "%s: set_rts status=%d\n", __func__, status);
+            close_sync_data_pipe(p);
             RETURNFUNC(status);
         }
 
@@ -105,6 +139,7 @@ int HAMLIB_API port_open(hamlib_port_t *p)
         if (status != 0)
         {
             rig_debug(RIG_DEBUG_ERR, "%s: set_dtr status=%d\n", __func__, status);
+            close_sync_data_pipe(p);
             RETURNFUNC(status);
         }
 
@@ -124,6 +159,7 @@ int HAMLIB_API port_open(hamlib_port_t *p)
 
         if (status < 0)
         {
+            close_sync_data_pipe(p);
             RETURNFUNC(status);
         }
 
@@ -134,6 +170,7 @@ int HAMLIB_API port_open(hamlib_port_t *p)
 
         if (status < 0)
         {
+            close_sync_data_pipe(p);
             RETURNFUNC(status);
         }
 
@@ -144,6 +181,7 @@ int HAMLIB_API port_open(hamlib_port_t *p)
 
         if (status < 0)
         {
+            close_sync_data_pipe(p);
             RETURNFUNC(-RIG_EIO);
         }
 
@@ -157,6 +195,7 @@ int HAMLIB_API port_open(hamlib_port_t *p)
 
         if (status < 0)
         {
+            close_sync_data_pipe(p);
             RETURNFUNC(status);
         }
 
@@ -174,12 +213,14 @@ int HAMLIB_API port_open(hamlib_port_t *p)
 
         if (status < 0)
         {
+            close_sync_data_pipe(p);
             RETURNFUNC(status);
         }
 
         break;
 
     default:
+        close_sync_data_pipe(p);
         RETURNFUNC(-RIG_EINVAL);
     }
 
@@ -231,6 +272,8 @@ int HAMLIB_API port_close(hamlib_port_t *p, rig_port_t port_type)
         p->fd = -1;
     }
 
+    close_sync_data_pipe(p);
+
     RETURNFUNC(ret);
 }
 
@@ -370,16 +413,18 @@ static int port_select(hamlib_port_t *p,
 
 /* POSIX */
 
-static ssize_t port_read(hamlib_port_t *p, void *buf, size_t count)
+static ssize_t port_read_generic(hamlib_port_t *p, void *buf, size_t count, int direct)
 {
+    int fd = direct ? p->fd : p->fd_sync_read;
+
     if (p->type.rig == RIG_PORT_SERIAL && p->parm.serial.data_bits == 7)
     {
         unsigned char *pbuf = buf;
 
-        int ret = read(p->fd, buf, count);
+        ssize_t ret = read(fd, buf, count);
 
         /* clear MSB */
-        int i;
+        ssize_t i;
 
         for (i = 0; i < ret; i++)
         {
@@ -390,12 +435,12 @@ static ssize_t port_read(hamlib_port_t *p, void *buf, size_t count)
     }
     else
     {
-        return read(p->fd, buf, count);
+        return read(fd, buf, count);
     }
 }
 
 //! @cond Doxygen_Suppress
-#define port_write(p,b,c) write((p)->fd,(b),(c))
+#define port_write_generic(p,b,c,d) write((d) ? (p)->fd : (p)->fd_sync_write,(b),(c))
 #define port_select(p,n,r,w,e,t) select((n),(r),(w),(e),(t))
 //! @endcond
 
@@ -430,7 +475,7 @@ static ssize_t port_read(hamlib_port_t *p, void *buf, size_t count)
  * it could work very well also with any file handle, like a socket.
  */
 
-int HAMLIB_API write_block(hamlib_port_t *p, const char *txbuffer, size_t count)
+static int write_block_generic(hamlib_port_t *p, const unsigned char *txbuffer, size_t count, int direct)
 {
     int ret;
 
@@ -468,7 +513,7 @@ int HAMLIB_API write_block(hamlib_port_t *p, const char *txbuffer, size_t count)
 
         for (i = 0; i < count; i++)
         {
-            ret = port_write(p, txbuffer + i, 1);
+            ret = port_write_generic(p, txbuffer + i, 1, direct);
 
             if (ret != 1)
             {
@@ -487,7 +532,7 @@ int HAMLIB_API write_block(hamlib_port_t *p, const char *txbuffer, size_t count)
     }
     else
     {
-        ret = port_write(p, txbuffer, count);
+        ret = port_write_generic(p, txbuffer, count, direct);
 
         if (ret != count)
         {
@@ -530,31 +575,55 @@ int HAMLIB_API write_block(hamlib_port_t *p, const char *txbuffer, size_t count)
 
 
 /**
- * \brief Read bytes from an fd
+ * \brief Write a block of characters to an fd.
  * \param p rig port descriptor
- * \param rxbuffer buffer to receive text
- * \param count number of bytes
- * \return count of bytes received
+ * \param txbuffer command sequence to be sent
+ * \param count number of bytes to send
+ * \return 0 = OK, <0 = NOK
  *
- * Read "num" bytes from "fd" and put results into
- * an array of unsigned char pointed to by "rxbuffer"
+ * Write a block of count characters to port file descriptor,
+ * with a pause between each character if write_delay is > 0
  *
- * Blocks on read until timeout hits.
+ * The write_delay is for Yaesu type rigs..require 5 character
+ * sequence to be sent with 50-200msec between each char.
  *
- * It then reads "num" bytes into rxbuffer.
+ * Also, post_write_delay is for some Yaesu rigs (eg: FT747) that
+ * get confused with sequential fast writes between cmd sequences.
+ *
+ * input:
+ *
+ * fd - file descriptor to write to
+ * txbuffer - pointer to a command sequence array
+ * count - count of byte to send from the txbuffer
+ * write_delay - write delay in ms between 2 chars
+ * post_write_delay - minimum delay between two writes
+ * post_write_date - timeval of last write
  *
  * Actually, this function has nothing specific to serial comm,
  * it could work very well also with any file handle, like a socket.
  */
 
-int HAMLIB_API read_block(hamlib_port_t *p, char *rxbuffer, size_t count)
+int HAMLIB_API write_block(hamlib_port_t *p, const unsigned char *txbuffer, size_t count)
+{
+    return write_block_generic(p, txbuffer, count, 1);
+}
+
+int HAMLIB_API write_block_sync(hamlib_port_t *p, const unsigned char *txbuffer, size_t count)
+{
+    return write_block_generic(p, txbuffer, count, 0);
+}
+
+static int read_block_generic(hamlib_port_t *p, unsigned char *rxbuffer, size_t count, int direct)
 {
     fd_set rfds, efds;
+    int fd;
     struct timeval tv, tv_timeout, start_time, end_time, elapsed_time;
     int total_count = 0;
 
     rig_debug(RIG_DEBUG_VERBOSE, "%s called\n", __func__);
 
+    fd = direct ? p->fd : p->fd_sync_read;
+
     /*
      * Wait up to timeout ms.
      */
@@ -571,10 +640,10 @@ int HAMLIB_API read_block(hamlib_port_t *p, char *rxbuffer, size_t count)
         tv = tv_timeout;    /* select may have updated it */
 
         FD_ZERO(&rfds);
-        FD_SET(p->fd, &rfds);
+        FD_SET(fd, &rfds);
         efds = rfds;
 
-        retval = port_select(p, p->fd + 1, &rfds, NULL, &efds, &tv);
+        retval = port_select(p, fd + 1, &rfds, NULL, &efds, &tv);
 
         if (retval == 0)
         {
@@ -605,7 +674,7 @@ int HAMLIB_API read_block(hamlib_port_t *p, char *rxbuffer, size_t count)
             return -RIG_EIO;
         }
 
-        if (FD_ISSET(p->fd, &efds))
+        if (FD_ISSET(fd, &efds))
         {
             rig_debug(RIG_DEBUG_ERR,
                       "%s(): fd error after %d chars\n",
@@ -619,7 +688,7 @@ int HAMLIB_API read_block(hamlib_port_t *p, char *rxbuffer, size_t count)
          * grab bytes from the rig
          * The file descriptor must have been set up non blocking.
          */
-        rd_count = port_read(p, rxbuffer + total_count, count);
+        rd_count = (int) port_read_generic(p, rxbuffer + total_count, count, direct);
 
         if (rd_count < 0)
         {
@@ -643,38 +712,61 @@ int HAMLIB_API read_block(hamlib_port_t *p, char *rxbuffer, size_t count)
 
 
 /**
- * \brief Read a string from an fd
- * \param p Hamlib port descriptor
- * \param rxbuffer buffer to receive string
- * \param rxmax maximum string size + 1
- * \param stopset string of recognized end of string characters
- * \param stopset_len length of stopset
- * \return number of characters read if the operation has been successful,
- * otherwise a negative value if an error occurred (in which case, cause is
- * set appropriately).
+ * \brief Read bytes from the device directly or from the synchronous data pipe, depending on the device caps
+ * \param p rig port descriptor
+ * \param rxbuffer buffer to receive text
+ * \param count number of bytes
+ * \return count of bytes received
  *
- * Read a string from "fd" and put result into
+ * Read "num" bytes from "fd" and put results into
  * an array of unsigned char pointed to by "rxbuffer"
  *
  * Blocks on read until timeout hits.
  *
- * It then reads characters until one of the characters in
- * "stopset" is found, or until "rxmax-1" characters was copied
- * into rxbuffer.  String termination character is added at the end.
+ * It then reads "num" bytes into rxbuffer.
  *
  * Actually, this function has nothing specific to serial comm,
  * it could work very well also with any file handle, like a socket.
- *
- * Assumes rxbuffer!=NULL
  */
-int HAMLIB_API read_string(hamlib_port_t *p,
-                           char *rxbuffer,
-                           size_t rxmax,
-                           const char *stopset,
-                           int stopset_len,
-                           int flush_flag)
+
+int HAMLIB_API read_block(hamlib_port_t *p, unsigned char *rxbuffer, size_t count)
+{
+    return read_block_generic(p, rxbuffer, count, !p->async);
+}
+
+/**
+ * \brief Read bytes directly from the device file descriptor
+ * \param p rig port descriptor
+ * \param rxbuffer buffer to receive text
+ * \param count number of bytes
+ * \return count of bytes received
+ *
+ * Read "num" bytes from "fd" and put results into
+ * an array of unsigned char pointed to by "rxbuffer"
+ *
+ * Blocks on read until timeout hits.
+ *
+ * It then reads "num" bytes into rxbuffer.
+ *
+ * Actually, this function has nothing specific to serial comm,
+ * it could work very well also with any file handle, like a socket.
+ */
+
+int HAMLIB_API read_block_direct(hamlib_port_t *p, unsigned char *rxbuffer, size_t count)
+{
+    return read_block_generic(p, rxbuffer, count, 1);
+}
+
+static int read_string_generic(hamlib_port_t *p,
+                               unsigned char *rxbuffer,
+                               size_t rxmax,
+                               const char *stopset,
+                               int stopset_len,
+                               int flush_flag,
+                               int direct)
 {
     fd_set rfds, efds;
+    int fd;
     struct timeval tv, tv_timeout, start_time, end_time, elapsed_time;
     int total_count = 0;
     int i=0;
@@ -694,6 +786,8 @@ int HAMLIB_API read_string(hamlib_port_t *p,
         return 0;
     }
 
+    fd = direct ? p->fd : p->fd_sync_read;
+
     /*
      * Wait up to timeout ms.
      */
@@ -707,15 +801,16 @@ int HAMLIB_API read_string(hamlib_port_t *p,
 
     while (total_count < rxmax - 1) // allow 1 byte for end-of-string
     {
-        int rd_count;
+        ssize_t rd_count;
         int retval;
+
         tv = tv_timeout;    /* select may have updated it */
 
         FD_ZERO(&rfds);
-        FD_SET(p->fd, &rfds);
+        FD_SET(fd, &rfds);
         efds = rfds;
 
-        retval = port_select(p, p->fd + 1, &rfds, NULL, &efds, &tv);
+        retval = port_select(p, fd + 1, &rfds, NULL, &efds, &tv);
 
         if (retval == 0)
         {
@@ -743,7 +838,7 @@ int HAMLIB_API read_string(hamlib_port_t *p,
 
         if (retval < 0)
         {
-            dump_hex((unsigned char *) rxbuffer, total_count);
+            dump_hex(rxbuffer, total_count);
             rig_debug(RIG_DEBUG_ERR,
                       "%s(): select() error after %d chars: %s\n",
                       __func__,
@@ -753,7 +848,7 @@ int HAMLIB_API read_string(hamlib_port_t *p,
             return -RIG_EIO;
         }
 
-        if (FD_ISSET(p->fd, &efds))
+        if (FD_ISSET(fd, &efds))
         {
             rig_debug(RIG_DEBUG_ERR,
                       "%s(): fd error after %d chars\n",
@@ -769,13 +864,12 @@ int HAMLIB_API read_string(hamlib_port_t *p,
          */
         do 
         {
-            rd_count = port_read(p, &rxbuffer[total_count], 1);
+            rd_count = port_read_generic(p, &rxbuffer[total_count], 1, direct);
             if (errno == EAGAIN)
             {
                 hl_usleep(5*1000);
                 rig_debug(RIG_DEBUG_WARN, "%s: port_read is busy?\n", __func__);
             }
-
         } while( ++i < 10 && errno == EBUSY); // 50ms should be enough
 
         /* if we get 0 bytes or an error something is wrong */
@@ -793,7 +887,7 @@ int HAMLIB_API read_string(hamlib_port_t *p,
         // check to see if our string startis with \...if so we need more chars
         if (total_count == 0 && rxbuffer[total_count] == '\\') { rxmax = (rxmax - 1) * 5; }
 
-        total_count += rd_count;
+        total_count += (int) rd_count;
 
         if (stopset && memchr(stopset, rxbuffer[total_count - 1], stopset_len))
         {
@@ -817,4 +911,77 @@ int HAMLIB_API read_string(hamlib_port_t *p,
     return total_count;           /* return bytes count read */
 }
 
+/**
+ * \brief Read a string from the device directly or from the synchronous data pipe, depending on the device caps
+ * \param p Hamlib port descriptor
+ * \param rxbuffer buffer to receive string
+ * \param rxmax maximum string size + 1
+ * \param stopset string of recognized end of string characters
+ * \param stopset_len length of stopset
+ * \return number of characters read if the operation has been successful,
+ * otherwise a negative value if an error occurred (in which case, cause is
+ * set appropriately).
+ *
+ * Read a string from "fd" and put result into
+ * an array of unsigned char pointed to by "rxbuffer"
+ *
+ * Blocks on read until timeout hits.
+ *
+ * It then reads characters until one of the characters in
+ * "stopset" is found, or until "rxmax-1" characters was copied
+ * into rxbuffer.  String termination character is added at the end.
+ *
+ * Actually, this function has nothing specific to serial comm,
+ * it could work very well also with any file handle, like a socket.
+ *
+ * Assumes rxbuffer!=NULL
+ */
+
+int HAMLIB_API read_string(hamlib_port_t *p,
+        unsigned char *rxbuffer,
+        size_t rxmax,
+        const char *stopset,
+        int stopset_len,
+        int flush_flag)
+{
+    return read_string_generic(p, rxbuffer, rxmax, stopset, stopset_len, flush_flag, !p->async);
+}
+
+
+/**
+ * \brief Read a string directly from the device file descriptor
+ * \param p Hamlib port descriptor
+ * \param rxbuffer buffer to receive string
+ * \param rxmax maximum string size + 1
+ * \param stopset string of recognized end of string characters
+ * \param stopset_len length of stopset
+ * \return number of characters read if the operation has been successful,
+ * otherwise a negative value if an error occurred (in which case, cause is
+ * set appropriately).
+ *
+ * Read a string from "fd" and put result into
+ * an array of unsigned char pointed to by "rxbuffer"
+ *
+ * Blocks on read until timeout hits.
+ *
+ * It then reads characters until one of the characters in
+ * "stopset" is found, or until "rxmax-1" characters was copied
+ * into rxbuffer.  String termination character is added at the end.
+ *
+ * Actually, this function has nothing specific to serial comm,
+ * it could work very well also with any file handle, like a socket.
+ *
+ * Assumes rxbuffer!=NULL
+ */
+
+int HAMLIB_API read_string_direct(hamlib_port_t *p,
+                                  unsigned char *rxbuffer,
+                                  size_t rxmax,
+                                  const char *stopset,
+                                  int stopset_len,
+                                  int flush_flag)
+{
+    return read_string_generic(p, rxbuffer, rxmax, stopset, stopset_len, flush_flag, 1);
+}
+
 /** @} */
diff --git a/src/iofunc.h b/src/iofunc.h
index 8055acfa8..5def45bf4 100644
--- a/src/iofunc.h
+++ b/src/iofunc.h
@@ -25,24 +25,38 @@
 #include <sys/types.h>
 #include <hamlib/rig.h>
 
-
 extern HAMLIB_EXPORT(int) port_open(hamlib_port_t *p);
 extern HAMLIB_EXPORT(int) port_close(hamlib_port_t *p, rig_port_t port_type);
 
 
 extern HAMLIB_EXPORT(int) read_block(hamlib_port_t *p,
-                                     char *rxbuffer,
+                                     unsigned char *rxbuffer,
                                      size_t count);
 
+extern HAMLIB_EXPORT(int) read_block_direct(hamlib_port_t *p,
+                                            unsigned char *rxbuffer,
+                                            size_t count);
+
 extern HAMLIB_EXPORT(int) write_block(hamlib_port_t *p,
-                                      const char *txbuffer,
+                                      const unsigned char *txbuffer,
                                       size_t count);
 
+extern HAMLIB_EXPORT(int) write_block_sync(hamlib_port_t *p,
+                                           const unsigned char *txbuffer,
+                                           size_t count);
+
 extern HAMLIB_EXPORT(int) read_string(hamlib_port_t *p,
-                                      char *rxbuffer,
+                                      unsigned char *rxbuffer,
                                       size_t rxmax,
                                       const char *stopset,
                                       int stopset_len,
                                       int flush_flag);
 
+extern HAMLIB_EXPORT(int) read_string_direct(hamlib_port_t *p,
+                                             unsigned char *rxbuffer,
+                                             size_t rxmax,
+                                             const char *stopset,
+                                             int stopset_len,
+                                             int flush_flag);
+
 #endif /* _IOFUNC_H */
diff --git a/src/rig.c b/src/rig.c
index c709b1857..3c22b6976 100644
--- a/src/rig.c
+++ b/src/rig.c
@@ -227,6 +227,18 @@ void rig_lock() {};
 void rig_unlock() {};
 #endif
 
+#ifdef HAVE_PTHREAD
+volatile int async_data_handler_thread_run = 0;
+pthread_t async_data_handler_thread_id;
+
+struct async_data_handler_args_s
+{
+    RIG *rig;
+} async_data_handler_args;
+
+void *async_data_handler(void *arg);
+#endif
+
 /*
  * track which rig is opened (with rig_open)
  * needed at least for transceive mode
@@ -365,13 +377,13 @@ static int rig_check_rig_caps()
     if (&caps_test.rig_model != caps_test_rig_model)
     {
         rc = -RIG_EINTERNAL;
-        rig_debug(RIG_DEBUG_WARN, "%s: shared libary change#1\n", __func__);
+        rig_debug(RIG_DEBUG_WARN, "%s: shared library change#1\n", __func__);
     }
 
     if (&caps_test.macro_name != caps_test_macro_name)
     {
         rc = -RIG_EINTERNAL;
-        rig_debug(RIG_DEBUG_WARN, "%s: shared libary change#2\n", __func__);
+        rig_debug(RIG_DEBUG_WARN, "%s: shared library change#2\n", __func__);
     }
 
     //if (rc != RIG_OK)
@@ -467,6 +479,9 @@ RIG *HAMLIB_API rig_init(rig_model_t rig_model)
     rs->pttport.fd = -1;
     rs->comm_state = 0;
     rs->rigport.type.rig = caps->port_type; /* default from caps */
+    rs->rigport.async = caps->async_data_supported;
+    rs->rigport.fd_sync_write = -1;
+    rs->rigport.fd_sync_read = -1;
 
     switch (caps->port_type)
     {
@@ -1039,6 +1054,22 @@ int HAMLIB_API rig_open(RIG *rig)
         RETURNFUNC(status);
     }
 
+    if (caps->async_data_supported)
+    {
+        async_data_handler_thread_run = 1;
+        async_data_handler_args.rig = rig;
+        int err = pthread_create(&async_data_handler_thread_id, NULL,
+                async_data_handler, &async_data_handler_args);
+
+        if (err)
+        {
+            rig_debug(RIG_DEBUG_ERR, "%s(%d) pthread_create error: %s\n", __FILE__, __LINE__,
+                    strerror(errno));
+            port_close(&rs->rigport, rs->rigport.type.rig);
+            return -RIG_EINTERNAL;
+        }
+    }
+
     add_opened_rig(rig);
 
     rs->comm_state = 1;
@@ -1053,6 +1084,8 @@ int HAMLIB_API rig_open(RIG *rig)
 
         if (status != RIG_OK)
         {
+            // TODO: stop async reader
+            port_close(&rs->rigport, rs->rigport.type.rig);
             RETURNFUNC(status);
         }
     }
@@ -1177,6 +1210,22 @@ int HAMLIB_API rig_close(RIG *rig)
 
 #endif
 
+    async_data_handler_thread_run = 0;
+
+    if (async_data_handler_thread_id != 0)
+    {
+        int err = pthread_join(async_data_handler_thread_id, NULL);
+
+        if (err)
+        {
+            rig_debug(RIG_DEBUG_ERR, "%s(%d): pthread_join error: %s\n", __FILE__, __LINE__,
+                    strerror(errno));
+            // just ignore the error
+        }
+
+        async_data_handler_thread_id = 0;
+    }
+
     if (!rig || !rig->caps)
     {
         RETURNFUNC(-RIG_EINVAL);
@@ -7139,3 +7188,64 @@ HAMLIB_EXPORT(void) sync_callback(int lock)
 
 /*! @} */
 
+#ifdef HAVE_PTHREAD
+
+#define MAX_FRAME_LENGTH 1024
+
+void *async_data_handler(void *arg)
+{
+    struct async_data_handler_args_s *args = (struct async_data_handler_args_s *)arg;
+    unsigned char frame[MAX_FRAME_LENGTH];
+    RIG *rig = args->rig;
+    struct rig_state *rs = &rig->state;
+    int result;
+
+    rig_debug(RIG_DEBUG_TRACE, "%s(%d): Starting async data handler thread\n", __FILE__,
+            __LINE__);
+
+    while (async_data_handler_thread_run)
+    {
+        int frame_length;
+        int async_frame;
+
+        result = rig->caps->read_frame_direct(rig, sizeof(frame), frame);
+        if (result < 0)
+        {
+            // TODO: error handling
+            rig_debug(RIG_DEBUG_ERR, "%s: read_frame_direct() failed, result=%d\n", __func__, result);
+            continue;
+        }
+
+        frame_length = result;
+
+        async_frame = rig->caps->is_async_frame(rig, frame_length, frame);
+
+        rig_debug(RIG_DEBUG_VERBOSE, "%s: received frame: len=%d async=%d\n", __func__, frame_length, async_frame);
+
+        if (async_frame)
+        {
+            result = rig->caps->process_async_frame(rig, frame_length, frame);
+            if (result < 0)
+            {
+                // TODO: error handling
+                continue;
+            }
+        }
+        else
+        {
+            result = write_block_sync(&rs->rigport, frame, frame_length);
+            if (result < 0)
+            {
+                // TODO: error handling
+                rig_debug(RIG_DEBUG_ERR, "%s: write_block_sync() failed, result=%d\n", __func__, result);
+                continue;
+            }
+        }
+    }
+
+    rig_debug(RIG_DEBUG_TRACE, "%s(%d): Stopping async data handler thread\n", __FILE__,
+            __LINE__);
+
+    return NULL;
+}
+#endif
diff --git a/src/serial.c b/src/serial.c
index 959b546a9..9af2624d9 100644
--- a/src/serial.c
+++ b/src/serial.c
@@ -643,6 +643,7 @@ int HAMLIB_API serial_flush(hamlib_port_t *p)
     int timeout_save;
     unsigned char buf[4096];
     ENTERFUNC;
+    RETURNFUNC(RIG_OK);
 
     if (p->fd == uh_ptt_fd || p->fd == uh_radio_fd || p->flushx)
     {
diff --git a/tests/rigctl_parse.c b/tests/rigctl_parse.c
index bf8798d49..df9f281cd 100644
--- a/tests/rigctl_parse.c
+++ b/tests/rigctl_parse.c
@@ -4144,11 +4144,11 @@ static int myspectrum_event(RIG *rig, struct rig_spectrum_line *line,
 {
     ENTERFUNC;
 
-    if (rig_need_debug(RIG_DEBUG_TRACE))
+    if (rig_need_debug(RIG_DEBUG_ERR))
     {
         char spectrum_debug[line->spectrum_data_length * 4];
         print_spectrum_line(spectrum_debug, sizeof(spectrum_debug), line);
-        rig_debug(RIG_DEBUG_TRACE, "%s: ASCII Spectrum Scope: %s\n", __func__,
+        rig_debug(RIG_DEBUG_ERR, "%s: ASCII Spectrum Scope: %s\n", __func__,
                   spectrum_debug);
     }
 
@@ -4198,7 +4198,8 @@ declare_proto_rig(set_trn)
         rig_set_spectrum_callback(rig, myspectrum_event, NULL);
     }
 
-    RETURNFUNC(rig_set_trn(rig, trn));
+    RETURNFUNC(RIG_OK);
+    //RETURNFUNC(rig_set_trn(rig, trn));
 }
 
 
@@ -4932,7 +4933,7 @@ declare_proto_rig(send_cmd)
 
     rig_debug(RIG_DEBUG_TRACE, "%s: rigport=%d, bufcmd=%s, cmd_len=%d\n", __func__,
               rs->rigport.fd, hasbinary(bufcmd, cmd_len) ? "BINARY" : bufcmd, cmd_len);
-    retval = write_block(&rs->rigport, (char *)bufcmd, cmd_len);
+    retval = write_block(&rs->rigport, (unsigned char *) bufcmd, cmd_len);
 
     if (retval != RIG_OK)
     {
@@ -4957,7 +4958,7 @@ declare_proto_rig(send_cmd)
         }
 
         /* Assumes CR or LF is end of line char for all ASCII protocols. */
-        retval = read_string(&rs->rigport, (char *)buf, rxbytes, eom_buf,
+        retval = read_string(&rs->rigport, buf, rxbytes, eom_buf,
                              strlen(eom_buf), 0);
 
         if (retval < 0)