diff --git a/main.c b/main.c
index 2d8fd45..aff2ac1 100644
--- a/main.c
+++ b/main.c
@@ -12,6 +12,7 @@ int overlay = 0;
 long delay = 500;
 char * directory = NULL;
 char pathname[18];
+uint8_t targetPortNo = 99;
 
 int out_ep;
 int in_ep;
@@ -40,6 +41,7 @@ void usage(int error)
 	fprintf(dest, "        -m delay         : Microseconds delay between checking for new devices (default 500)\n");
 	fprintf(dest, "        -v               : Verbose\n");
 	fprintf(dest, "        -s               : Signed using bootsig.bin\n");
+	fprintf(dest, "        -0/1/2/3/4/5/6   : Only look for CMs attached to USB port number 0-6\n");
 	fprintf(dest, "        -h               : This help\n");
 
 	exit(error ? -1 : 0);
@@ -54,7 +56,8 @@ libusb_device_handle * LIBUSB_CALL open_device_with_vid(
 	struct libusb_device_handle *handle = NULL;
 	uint32_t i = 0;
 	int r, j, len;
-	uint8_t path[8];
+	uint8_t path[8];	// Needed for libusb_get_port_numbers
+	uint8_t portNo = 0;
 
 	if (libusb_get_device_list(ctx, &devs) < 0)
 		return NULL;
@@ -80,6 +83,14 @@ libusb_device_handle * LIBUSB_CALL open_device_with_vid(
 			}
 		}
 
+		/*
+		  http://libusb.sourceforge.net/api-1.0/group__dev.html#ga14879a0ea7daccdcddb68852d86c00c4
+
+		  The port number returned by this call is usually guaranteed to be uniquely tied to a physical port,
+		  meaning that different devices plugged on the same physical port should return the same port number.
+		*/
+		portNo = libusb_get_port_number(dev);
+
 		if(verbose == 2)
 		{
 			printf("Found device %u idVendor=0x%04x idProduct=0x%04x\n", i, desc.idVendor, desc.idProduct);
@@ -90,9 +101,23 @@ libusb_device_handle * LIBUSB_CALL open_device_with_vid(
 			if(desc.idProduct == 0x2763 ||
 			   desc.idProduct == 0x2764)
 			{
-				if(verbose) printf("Device located successfully\n");
-				found = dev;
-				break;
+				if(verbose == 2)
+				      printf("Found candidate Compute Module...");
+
+				///////////////////////////////////////////////////////////////////////
+				// Check if we should match against a specific port number
+				///////////////////////////////////////////////////////////////////////
+				if (targetPortNo == 99 || portNo == targetPortNo)
+				{
+					if(verbose) printf("Device located successfully\n");
+					found = dev;
+					break;
+				}
+				else
+				{
+					if(verbose == 2)
+					      printf("...Wrong Port, Trying again\n");
+				}
 			}
 		}
 	}
@@ -241,6 +266,34 @@ void get_options(int argc, char *argv[])
 		{
 			signed_boot = 1;
 		}
+		else if(strcmp(*argv, "-0") == 0)
+		{
+			targetPortNo = 0;
+		}
+		else if(strcmp(*argv, "-1") == 0)
+		{
+			targetPortNo = 1;
+		}
+		else if(strcmp(*argv, "-2") == 0)
+		{
+			targetPortNo = 2;
+		}
+		else if(strcmp(*argv, "-3") == 0)
+		{
+			targetPortNo = 3;
+		}
+		else if(strcmp(*argv, "-4") == 0)
+		{
+			targetPortNo = 4;
+		}
+		else if(strcmp(*argv, "-5") == 0)
+		{
+			targetPortNo = 5;
+		}
+		else if(strcmp(*argv, "-6") == 0)
+		{
+			targetPortNo = 6;
+		}
 		else
 		{
 			usage(1);