diff -ruN Argyll_V1.6.3.orig/spectro/usbio.c Argyll_V1.6.3/spectro/usbio.c
--- Argyll_V1.6.3.orig/spectro/usbio.c	2014-01-31 05:08:57.000000000 +0100
+++ Argyll_V1.6.3/spectro/usbio.c	2015-03-13 09:04:25.067416774 +0100
@@ -353,7 +353,8 @@
 static int
 icoms_usb_ser_write(
 icoms *p,
-char *wbuf,
+char *wbuf,			/* null terminated unless nch > 0 */
+int nwch,			/* if > 0, number of characters to write */
 double tout)
 {
 	int len, wbytes;
@@ -385,7 +386,10 @@
 	else
 		type = icom_usb_trantype_interrutpt;
 
-	len = strlen(wbuf);
+	if (nwch != 0)
+		len = nwch;
+	else
+		len = strlen(wbuf);
 	tout *= 1000.0;		/* Timout in msec */
 
 	top = (int)(tout + 0.5);		/* Timeout period in msecs */
@@ -430,8 +434,9 @@
 icoms_usb_ser_read(icoms *p,
 char *rbuf,			/* Buffer to store characters read */
 int bsize,			/* Buffer size */
-char *tc,			/* Terminating characers, NULL if none */
-int ntc,			/* Number of terminating characters needed to terminate */
+int *pbread,		/* Bytes read (not including forced '\000') */
+char *tc,			/* Terminating characers, NULL for none or char count mode */
+int ntc,			/* Number of terminating characters or char count needed, if 0 use bsize */
 double tout)		/* Time out in seconds */
 {
 	int j, rbytes;
@@ -442,10 +447,6 @@
 	icom_usb_trantype type;	/* bulk or interrupt */
 	int retrv = ICOM_OK;
 
-#ifdef QUIET_MEMCHECKERS
-	memset(rbuf, 0, bsize);
-#endif
-
 	if (!p->is_open) {
 		a1loge(p->log, ICOM_SYS, "icoms_usb_ser_read: device is not open\n");
 		return ICOM_SYS;
@@ -472,7 +473,8 @@
 		return ICOM_SYS;
 	}
 
-	for (j = 0; j < bsize; j++) rbuf[j] = 0;
+	for (j = 0; j < bsize; j++)
+		rbuf[j] = 0;
  
 	bsize -= 1;				/* Allow space for null */
 	bsize -= p->ms_bytes;	/* Allow space for modem status bytes */
@@ -487,9 +489,11 @@
 	a1logd(p->log, 8, "\nicoms_usb_ser_read: ep 0x%x, ttop %d, quant %d\n", p->rd_ep, ttop, p->rd_qa);
 
 	/* Until data is all read, we time out, or the user aborts */
-	stime = msec_time();
+	etime = stime = msec_time();
 	top = ttop;
-	for (j = 0; top > 0 && bsize > 1 && j < ntc ;) {
+	j = (tc == NULL && ntc <= 0) ? -1 : 0;
+
+	for (; top > 0 && bsize > 0 && j < ntc ;) {
 		int c, rv;
 		int rsize = p->rd_qa < bsize ? p->rd_qa : bsize; 
 
@@ -503,9 +507,10 @@
 			/* Account for modem status bytes. Modem bytes are per usb read. */
 			if (p->ms_bytes) {		/* Throw away modem bytes */
 				int nb = rbytes < p->ms_bytes ? rbytes : p->ms_bytes;
+				a1logd(p->log, 8, "icoms_usb_ser_read: discarded %d modem bytes 0x%02x 0x%02x\n",nb,nb >= 1 ? (rbuf[0] & 0xff) : 0, nb >= 2 ? (rbuf[1] & 0xff) : 0);
 				rbytes -= nb;
 				memmove(rbuf, rbuf+nb, rbytes);
-				a1logd(p->log, 8, "icoms_usb_ser_read: discarded %d modem bytes\n",nb);
+				rbuf[rbytes] = 0;
 			}
 
 			a1logd(p->log, 8, "icoms_usb_ser_read: read %d bytes, rbuf = '%s'\n",rbytes,icoms_fix(rrbuf));
@@ -521,7 +526,10 @@
 						tcp++;
 					}
 				}
+				a1logd(p->log, 8, "icoms_usb_ser_read: tc count %d\n",j);
 			} else {
+				if (ntc > 0)
+					j += rbytes;
 				rbuf += rbytes;
 			}
 		}
@@ -534,14 +542,20 @@
 		}
 
 		top = ttop - (etime - stime);	/* Remaining time */
-		if (top <= 0) {					/* Run out of time */
-			a1logd(p->log, 8, "icoms_usb_ser_read: read ran out of time\n");
-			retrv |= ICOM_TO; 
-			break;
-		}
 	}
 
 	*rbuf = '\000';
+	a1logd(p->log, 8, "icoms_usb_ser_read: read %d total bytes\n",rbuf - rrbuf);
+	if (pbread != NULL)
+		*pbread = (rbuf - rrbuf);
+
+	/* If ran out of time and not completed */
+	a1logd(p->log, 8, "icoms_usb_ser_read: took %d msec\n",etime - stime);
+	if (top <= 0 && bsize > 0 && j < ntc) {
+		a1logd(p->log, 8, "icoms_usb_ser_read: read ran out of time\n");
+		a1logd(p->log, 8, "ttop %d, etime - stime %d\n",ttop,etime - stime);
+		retrv |= ICOM_TO; 
+	}
 
 	a1logd(p->log, 8, "icoms_usb_ser_read: returning '%s' ICOM err 0x%x\n",icoms_fix(rrbuf),retrv);
 
diff -ruN Argyll_V1.6.3.orig/spectro/usbio_lx.c Argyll_V1.6.3/spectro/usbio_lx.c
--- Argyll_V1.6.3.orig/spectro/usbio_lx.c	2014-01-31 05:08:58.000000000 +0100
+++ Argyll_V1.6.3/spectro/usbio_lx.c	2015-03-13 09:09:46.459415189 +0100
@@ -460,8 +460,11 @@
 			if ((rv = p->usbd->fd = open(p->usbd->dpath, O_RDWR)) < 0) {
 				a1logd(p->log, 8, "usb_open_port: open '%s' config %d failed (%d) (Permissions ?)\n",p->usbd->dpath,config,rv);
 				if (retries <= 0) {
-					if (kpc != NULL)
-						kpc->del(kpc); 
+					if (kpc != NULL) {
+						if (kpc->th->result < 0)
+							a1logw(p->log, "usb_open_port: killing competing processes failed\n");
+ 						kpc->del(kpc); 
+					}
 					a1loge(p->log, ICOM_SYS, "usb_open_port: open '%s' config %d failed (%d) (Permissions ?)\n",p->usbd->dpath,config,rv);
 					return ICOM_SYS;
 				}
@@ -636,25 +639,53 @@
 		pa[0].events = POLLIN | POLLOUT;
 		pa[0].revents = 0;
 	
+		/* Setup to wait for a shutdown signal via the sd_pipe */
 		pa[1].fd = p->usbd->sd_pipe[0];
 		pa[1].events = POLLIN;
 		pa[1].revents = 0;
 
-		/* Wait for fd to become ready or shutdown */
-		if ((rv = poll_x(pa, 2, -1)) < 0 || pa[1].revents || pa[0].revents == 0) {
-			a1logd(p->log, 6, "urb_reaper: poll returned %d and events %d %d\n",rv,pa[0].revents,pa[1].revents);
+		/* Wait for fd to become ready or fail */
+		rv = poll_x(pa, 2, -1);
+
+		/* Failed */
+		if (rv < 0) {
+			a1logd(p->log, 2, "urb_reaper: poll failed with %d\n",rv);
+				if (errc++ < 5) {
+				continue;
+			}
+			a1logd(p->log, 2, "urb_reaper: poll failed too many times - shutting down\n");
 			p->usbd->shutdown = 1;
 			break;
 		}
 
+		/* Shutdown event */
+		if (pa[1].revents != 0) {
+			a1logd(p->log, 6, "urb_reaper: poll returned events %d %d - shutting down\n",
+			                   pa[0].revents,pa[1].revents);
+			p->usbd->shutdown = 1;
+			break;
+		}
+
+		/* Hmm. poll returned without event from fd. */
+		if (pa[0].revents == 0) {
+			a1logd(p->log, 6, "urb_reaper: poll returned events %d %d - ignoring\n",
+			                   pa[0].revents,pa[1].revents);
+			continue;
+		}
+
 		/* Not sure what this returns if there is nothing there */
 		rv = ioctl(p->usbd->fd, USBDEVFS_REAPURBNDELAY, &out);
 
+		if (rv == EAGAIN) {
+			a1logd(p->log, 2, "urb_reaper: reap returned EAGAIN - ignored\n");
+			continue;
+		}
 		if (rv < 0) {
 			a1logd(p->log, 2, "urb_reaper: reap failed with %d\n",rv);
 				if (errc++ < 5) {
 				continue;
 			}
+			a1logd(p->log, 2, "urb_reaper: reap failed too many times - shutting down\n");
 			p->usbd->shutdown = 1;
 			break;
 		}
@@ -662,7 +693,7 @@
 		errc = 0;
 
 		if (out == NULL) {
-			a1logd(p->log, 2, "urb_reaper: reap returned NULL URB\n");
+			a1logd(p->log, 2, "urb_reaper: reap returned NULL URB - ignored\n");
 			continue;
 		}
 
@@ -803,7 +834,7 @@
 		bp += req.urbs[i].urb.buffer_length;
 		req.urbs[i].urb.status = -EINPROGRESS;
 	}
-a1logd(p->log, 8, "icoms_usb_transaction: reset req 0x%p nourbs to %d\n",&req,req.nourbs);
+a1logd(p->log, 8, "icoms_usb_transaction: reset req %p nourbs to %d\n",&req,req.nourbs);
 
 	/* Add our request to the req list so that it can be cancelled on reap failure */
 	pthread_mutex_lock(&p->usbd->lock);