diff --git a/platform/samd11/main.c b/platform/samd11/main.c
index 47e0d42..fe7cd07 100644
--- a/platform/samd11/main.c
+++ b/platform/samd11/main.c
@@ -62,8 +62,9 @@
 #endif
 
 /*- Variables ---------------------------------------------------------------*/
-alignas(4) uint8_t app_request_buffer[DAP_CONFIG_PACKET_SIZE];
-alignas(4) uint8_t app_response_buffer[DAP_CONFIG_PACKET_SIZE];
+static alignas(4) uint8_t app_request_buffer[DAP_CONFIG_PACKET_SIZE];
+static alignas(4) uint8_t app_response_buffer[DAP_CONFIG_PACKET_SIZE];
+extern char usb_serial_number[16];
 
 /*- Implementations ---------------------------------------------------------*/
 
@@ -71,6 +72,7 @@ alignas(4) uint8_t app_response_buffer[DAP_CONFIG_PACKET_SIZE];
 static void sys_init(void)
 {
   uint32_t coarse, fine;
+  uint32_t sn = 0;
 
   SYSCTRL->OSC8M.bit.PRESC = 0;
 
@@ -97,6 +99,16 @@ static void sys_init(void)
   GCLK->GENCTRL.reg = GCLK_GENCTRL_ID(0) | GCLK_GENCTRL_SRC(GCLK_SOURCE_DFLL48M) |
       GCLK_GENCTRL_RUNSTDBY | GCLK_GENCTRL_GENEN;
   while (GCLK->STATUS.reg & GCLK_STATUS_SYNCBUSY);
+
+  sn ^= *(volatile uint32_t *)0x0080a00c;
+  sn ^= *(volatile uint32_t *)0x0080a040;
+  sn ^= *(volatile uint32_t *)0x0080a044;
+  sn ^= *(volatile uint32_t *)0x0080a048;
+
+  for (int i = 0; i < 8; i++)
+    usb_serial_number[i] = "0123456789ABCDEF"[(sn >> (i * 4)) & 0xf];
+
+  usb_serial_number[9] = 0;
 }
 
 //-----------------------------------------------------------------------------
diff --git a/platform/samd11/usb_descriptors.c b/platform/samd11/usb_descriptors.c
index 5aaa925..c534e1b 100644
--- a/platform/samd11/usb_descriptors.c
+++ b/platform/samd11/usb_descriptors.c
@@ -137,11 +137,13 @@ const alignas(4) usb_string_descriptor_zero_t usb_string_descriptor_zero =
   .wLANGID               = 0x0409, // English (United States)
 };
 
+char usb_serial_number[16];
+
 char *usb_strings[] =
 {
   [USB_STR_MANUFACTURER]  = "Alex Taradov",
   [USB_STR_PRODUCT]       = "Generic CMSIS-DAP Adapter",
-  [USB_STR_SERIAL_NUMBER] = "123456",
+  [USB_STR_SERIAL_NUMBER] = usb_serial_number,
   [USB_STR_CONFIGURATION] = "Main Configuration",
   [USB_STR_INTERFACE]     = "Main Interface",
 };