diff --git a/Makefile b/Makefile
index 4fd67a1..f207c37 100644
--- a/Makefile
+++ b/Makefile
@@ -14,6 +14,12 @@ ifeq ($(UNAME),Linux)
     OBJS        += hid-libusb.o
 endif
 
+# Mac OS X
+ifeq ($(UNAME),Darwin)
+    OBJS        += hid-macos.o
+    LIBS        += -framework IOKit -framework CoreFoundation
+endif
+
 all:		dmrconfig
 
 dmrconfig:	$(OBJS)
diff --git a/hid-libusb.c b/hid-libusb.c
index accc510..994bb36 100644
--- a/hid-libusb.c
+++ b/hid-libusb.c
@@ -204,7 +204,7 @@ void hid_send_recv(const unsigned char *data, unsigned nbytes, unsigned char *rd
 // Initiate the programming session.
 // Query and return the device identification string.
 //
-const char *hid_init(unsigned vid, unsigned pid)
+const char *hid_init(int vid, int pid)
 {
     int error = libusb_init(&ctx);
     if (error < 0) {
@@ -312,7 +312,6 @@ void hid_read_block(int bno, uint8_t *data, int nbytes)
     }
 }
 
-
 void hid_write_block(int bno, uint8_t *data, int nbytes)
 {
     unsigned addr = bno * nbytes;
diff --git a/hid-macos.c b/hid-macos.c
new file mode 100644
index 0000000..4cc8af0
--- /dev/null
+++ b/hid-macos.c
@@ -0,0 +1,351 @@
+/*
+ * HID routines for Mac OS X.
+ *
+ * Copyright (C) 2018 Serge Vakulenko, KK6ABQ
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ *   1. Redistributions of source code must retain the above copyright notice,
+ *      this list of conditions and the following disclaimer.
+ *   2. Redistributions in binary form must reproduce the above copyright
+ *      notice, this list of conditions and the following disclaimer in the
+ *      documentation and/or other materials provided with the distribution.
+ *   3. The name of the author may not be used to endorse or promote products
+ *      derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
+ * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO
+ * EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+ * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
+ * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
+ * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
+ * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
+ * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <IOKit/hid/IOHIDManager.h>
+#include "util.h"
+
+static const unsigned char CMD_PRG[]   = "\2PROGRA";
+static const unsigned char CMD_PRG2[]  = "M\2";
+static const unsigned char CMD_ACK[]   = "A";
+static const unsigned char CMD_READ[]  = "Raan";
+static const unsigned char CMD_WRITE[] = "Waan...";
+static const unsigned char CMD_ENDR[]  = "ENDR";
+static const unsigned char CMD_ENDW[]  = "ENDW";
+static const unsigned char CMD_CWB0[]  = "CWB\4\0\0\0\0";
+static const unsigned char CMD_CWB1[]  = "CWB\4\0\1\0\0";
+
+static volatile IOHIDDeviceRef dev;         // device handle
+static unsigned char transfer_buf[42];      // device buffer
+static unsigned char receive_buf[42];       // receive buffer
+static volatile int nbytes_received = 0;    // receive result
+static unsigned offset = 0;                 // CWD offset
+
+//
+// Send a request to the device.
+// Store the reply into the rdata[] array.
+// Terminate in case of errors.
+//
+void hid_send_recv(const unsigned char *data, unsigned nbytes, unsigned char *rdata, unsigned rlength)
+{
+    unsigned char buf[42];
+    unsigned k;
+
+    memset(buf, 0, sizeof(buf));
+    buf[0] = 1;
+    buf[1] = 0;
+    buf[2] = nbytes;
+    buf[3] = nbytes >> 8;
+    if (nbytes > 0)
+        memcpy(buf+4, data, nbytes);
+    nbytes += 4;
+
+    if (trace_flag > 0) {
+        fprintf(stderr, "---Send");
+        for (k=0; k<nbytes; ++k) {
+            if (k != 0 && (k & 15) == 0)
+                fprintf(stderr, "\n       ");
+            fprintf(stderr, " %02x", buf[k]);
+        }
+        fprintf(stderr, "\n");
+    }
+    nbytes_received = 0;
+    memset(receive_buf, 0, sizeof(receive_buf));
+
+    // Write to HID device.
+    IOReturn result = IOHIDDeviceSetReport(dev, kIOHIDReportTypeOutput, 0, buf, sizeof(buf));
+    if (result != kIOReturnSuccess) {
+        fprintf(stderr, "HID output error: %d!\n", result);
+        exit(-1);
+    }
+
+    // Run main application loop until reply received.
+    while (nbytes_received == 0) {
+        //TODO: timeout
+        CFRunLoopRunInMode(kCFRunLoopDefaultMode, 0, 0);
+    }
+
+    if (nbytes_received != sizeof(receive_buf)) {
+        fprintf(stderr, "Short read: %d bytes instead of %d!\n",
+            nbytes_received, (int)sizeof(receive_buf));
+        exit(-1);
+    }
+    if (trace_flag > 0) {
+        fprintf(stderr, "---Recv");
+        for (k=0; k<nbytes_received; ++k) {
+            if (k != 0 && (k & 15) == 0)
+                fprintf(stderr, "\n       ");
+            fprintf(stderr, " %02x", receive_buf[k]);
+        }
+        fprintf(stderr, "\n");
+    }
+    if (receive_buf[0] != 3 || receive_buf[1] != 0 || receive_buf[3] != 0) {
+        fprintf(stderr, "incorrect reply\n");
+        exit(-1);
+    }
+    if (receive_buf[2] != rlength) {
+        fprintf(stderr, "incorrect reply length %d, expected %d\n",
+            receive_buf[2], rlength);
+        exit(-1);
+    }
+    memcpy(rdata, receive_buf+4, rlength);
+}
+
+//
+// Callback: data is received from the HID device
+//
+static void callback_input(void *context,
+    IOReturn result, void *sender, IOHIDReportType type,
+    uint32_t reportID, uint8_t *data, CFIndex nbytes)
+{
+    if (result != kIOReturnSuccess) {
+        fprintf(stderr, "HID input error: %d!\n", result);
+        exit(-1);
+    }
+
+    if (nbytes > sizeof(receive_buf)) {
+        fprintf(stderr, "Too large HID input: %d bytes!\n", (int)nbytes);
+        exit(-1);
+    }
+
+    nbytes_received = nbytes;
+    if (nbytes > 0)
+        memcpy(receive_buf, data, nbytes);
+}
+
+//
+// Callback: device specified in the matching dictionary has been added
+//
+static void callback_open(void *context,
+    IOReturn result, void *sender, IOHIDDeviceRef deviceRef)
+{
+    IOReturn o = IOHIDDeviceOpen(deviceRef, kIOHIDOptionsTypeSeizeDevice);
+    if (o != kIOReturnSuccess) {
+        fprintf(stderr, "Cannot open HID device!\n");
+        exit(-1);
+    }
+
+    // Register input callback.
+    IOHIDDeviceRegisterInputReportCallback(deviceRef,
+        transfer_buf, sizeof(transfer_buf), callback_input, 0);
+
+    dev = deviceRef;
+}
+
+//
+// Callback: device specified in the matching dictionary has been removed
+//
+static void callback_close(void *ontext,
+    IOReturn result, void *sender, IOHIDDeviceRef deviceRef)
+{
+    // De-register input callback.
+    IOHIDDeviceRegisterInputReportCallback(deviceRef, transfer_buf, sizeof(transfer_buf), NULL, NULL);
+}
+
+//
+// Launch the IOHIDManager.
+//
+const char *hid_init(int vid, int pid)
+{
+    // Create the USB HID Manager.
+    IOHIDManagerRef HIDManager = IOHIDManagerCreate(kCFAllocatorDefault,
+                                                    kIOHIDOptionsTypeNone);
+
+    // Create an empty matching dictionary for filtering USB devices in our HID manager.
+    CFMutableDictionaryRef matchDict = CFDictionaryCreateMutable(kCFAllocatorDefault,
+        2, &kCFTypeDictionaryKeyCallBacks, &kCFTypeDictionaryValueCallBacks);
+
+    // Specify the USB device manufacturer and product in our matching dictionary.
+    CFDictionarySetValue(matchDict, CFSTR(kIOHIDVendorIDKey), CFNumberCreate(kCFAllocatorDefault, kCFNumberIntType, &vid));
+    CFDictionarySetValue(matchDict, CFSTR(kIOHIDProductIDKey), CFNumberCreate(kCFAllocatorDefault, kCFNumberIntType, &pid));
+
+    // Apply the matching to our HID manager.
+    IOHIDManagerSetDeviceMatching(HIDManager, matchDict);
+    CFRelease(matchDict);
+
+    // The HID manager will use callbacks when specified USB devices are connected/disconnected.
+    IOHIDManagerRegisterDeviceMatchingCallback(HIDManager, &callback_open, NULL);
+    IOHIDManagerRegisterDeviceRemovalCallback(HIDManager, &callback_close, NULL);
+
+    // Add the HID manager to the main run loop
+    IOHIDManagerScheduleWithRunLoop(HIDManager, CFRunLoopGetMain(), kCFRunLoopDefaultMode);
+
+    // Open the HID mangager
+    IOReturn IOReturn = IOHIDManagerOpen(HIDManager, kIOHIDOptionsTypeNone);
+    if (IOReturn != kIOReturnSuccess) {
+        if (trace_flag) {
+            fprintf(stderr, "Cannot find USB device %04x:%04x\n",
+                vid, pid);
+        }
+        return 0;
+    }
+
+    // Run main application loop until device found.
+    while (!dev) {
+        //TODO: timeout
+        CFRunLoopRunInMode(kCFRunLoopDefaultMode, 0, 0);
+    }
+
+    static unsigned char reply[38];
+    unsigned char ack;
+
+    hid_send_recv(CMD_PRG, 7, &ack, 1);
+    if (ack != CMD_ACK[0]) {
+        fprintf(stderr, "%s: Wrong PRD acknowledge %#x, expected %#x\n",
+            __func__, ack, CMD_ACK[0]);
+        return 0;
+    }
+
+    hid_send_recv(CMD_PRG2, 2, reply, 16);
+
+    hid_send_recv(CMD_ACK, 1, &ack, 1);
+    if (ack != CMD_ACK[0]) {
+        fprintf(stderr, "%s: Wrong PRG2 acknowledge %#x, expected %#x\n",
+            __func__, ack, CMD_ACK[0]);
+        return 0;
+    }
+
+    // Reply:
+    // 42 46 2d 35 52 ff ff ff 56 32 31 30 00 04 80 04
+    //  B  F  -  5  R           V  2  1  0
+
+    // Terminate the string.
+    char *p = memchr(reply, 0xff, sizeof(reply));
+    if (p)
+        *p = 0;
+    return (char*)reply;
+}
+
+//
+// Close HID device.
+//
+void hid_close()
+{
+    if (!dev)
+        return;
+
+    IOHIDDeviceClose(dev, kIOHIDOptionsTypeNone);
+    dev = 0;
+}
+
+void hid_read_block(int bno, uint8_t *data, int nbytes)
+{
+    unsigned addr = bno * nbytes;
+    unsigned char ack, cmd[4], reply[32+4];
+    int n;
+
+    if (addr < 0x10000 && offset != 0) {
+        offset = 0;
+        hid_send_recv(CMD_CWB0, 8, &ack, 1);
+        if (ack != CMD_ACK[0]) {
+            fprintf(stderr, "%s: Wrong acknowledge %#x, expected %#x\n",
+                __func__, ack, CMD_ACK[0]);
+            exit(-1);
+        }
+    } else if (addr >= 0x10000 && offset == 0) {
+        offset = 0x00010000;
+        hid_send_recv(CMD_CWB1, 8, &ack, 1);
+        if (ack != CMD_ACK[0]) {
+            fprintf(stderr, "%s: Wrong acknowledge %#x, expected %#x\n",
+                __func__, ack, CMD_ACK[0]);
+            exit(-1);
+        }
+    }
+
+    for (n=0; n<nbytes; n+=32) {
+        cmd[0] = CMD_READ[0];
+        cmd[1] = (addr + n) >> 8;
+        cmd[2] = addr + n;
+        cmd[3] = 32;
+        hid_send_recv(cmd, 4, reply, sizeof(reply));
+        memcpy(data + n, reply + 4, 32);
+    }
+}
+
+void hid_write_block(int bno, uint8_t *data, int nbytes)
+{
+    unsigned addr = bno * nbytes;
+    unsigned char ack, cmd[4+32];
+    int n;
+
+    if (addr < 0x10000 && offset != 0) {
+        offset = 0;
+        hid_send_recv(CMD_CWB0, 8, &ack, 1);
+        if (ack != CMD_ACK[0]) {
+            fprintf(stderr, "%s: Wrong acknowledge %#x, expected %#x\n",
+                __func__, ack, CMD_ACK[0]);
+            exit(-1);
+        }
+    } else if (addr >= 0x10000 && offset == 0) {
+        offset = 0x00010000;
+        hid_send_recv(CMD_CWB1, 8, &ack, 1);
+        if (ack != CMD_ACK[0]) {
+            fprintf(stderr, "%s: Wrong acknowledge %#x, expected %#x\n",
+                __func__, ack, CMD_ACK[0]);
+            exit(-1);
+        }
+    }
+
+    for (n=0; n<nbytes; n+=32) {
+        cmd[0] = CMD_WRITE[0];
+        cmd[1] = (addr + n) >> 8;
+        cmd[2] = addr + n;
+        cmd[3] = 32;
+        memcpy(cmd + 4, data + n, 32);
+        hid_send_recv(cmd, 4+32, &ack, 1);
+        if (ack != CMD_ACK[0]) {
+            fprintf(stderr, "%s: Wrong acknowledge %#x, expected %#x\n",
+                __func__, ack, CMD_ACK[0]);
+            exit(-1);
+        }
+    }
+}
+
+void hid_read_finish()
+{
+    unsigned char ack;
+
+    hid_send_recv(CMD_ENDR, 4, &ack, 1);
+    if (ack != CMD_ACK[0]) {
+        fprintf(stderr, "%s: Wrong acknowledge %#x, expected %#x\n",
+            __func__, ack, CMD_ACK[0]);
+    }
+}
+
+void hid_write_finish()
+{
+    unsigned char ack;
+
+    hid_send_recv(CMD_ENDW, 4, &ack, 1);
+    if (ack != CMD_ACK[0]) {
+        fprintf(stderr, "%s: Wrong acknowledge %#x, expected %#x\n",
+            __func__, ack, CMD_ACK[0]);
+    }
+}
diff --git a/rd5r.c b/rd5r.c
index 0078dc1..a0d4895 100644
--- a/rd5r.c
+++ b/rd5r.c
@@ -279,7 +279,7 @@ typedef struct {
     uint8_t radio_name[8];
 
     // Bytes e8-eb
-    uint8_t  radio_id[3];
+    uint8_t  radio_id[4];
 } general_settings_t;
 
 //
diff --git a/util.h b/util.h
index 26dda3d..c4bf349 100644
--- a/util.h
+++ b/util.h
@@ -68,7 +68,7 @@ void dfu_reboot(void);
 //
 // HID functions.
 //
-const char *hid_init(unsigned vid, unsigned pid);
+const char *hid_init(int vid, int pid);
 void hid_close(void);
 int hid_write_read(const unsigned char *data, unsigned length, unsigned char *reply, unsigned rlength);
 void hid_read_block(int bno, unsigned char *data, int nbytes);