diff --git a/keyboards/pierce/config.h b/keyboards/pierce/config.h
index 82c4b4b2642..3b89c38603c 100644
--- a/keyboards/pierce/config.h
+++ b/keyboards/pierce/config.h
@@ -23,3 +23,40 @@
 
 /* COL2ROW or ROW2COL */
 #define DIODE_DIRECTION COL2ROW
+
+#ifdef PS2_DRIVER_USART
+#define PS2_CLOCK_PIN   D5
+#define PS2_DATA_PIN    D2
+
+/* synchronous, odd parity, 1-bit stop, 8-bit data, sample at falling edge */
+/* set DDR of CLOCK as input to be slave */
+#define PS2_USART_INIT() do {   \
+    PS2_CLOCK_DDR &= ~(1<<PS2_CLOCK_BIT);   \
+    PS2_DATA_DDR &= ~(1<<PS2_DATA_BIT);     \
+    UCSR1C = ((1 << UMSEL10) |  \
+              (3 << UPM10)   |  \
+              (0 << USBS1)   |  \
+              (3 << UCSZ10)  |  \
+              (0 << UCPOL1));   \
+    UCSR1A = 0;                 \
+    UBRR1H = 0;                 \
+    UBRR1L = 0;                 \
+} while (0)
+#define PS2_USART_RX_INT_ON() do {  \
+    UCSR1B = ((1 << RXCIE1) |       \
+              (1 << RXEN1));        \
+} while (0)
+#define PS2_USART_RX_POLL_ON() do { \
+    UCSR1B = (1 << RXEN1);          \
+} while (0)
+#define PS2_USART_OFF() do {    \
+    UCSR1C = 0;                 \
+    UCSR1B &= ~((1 << RXEN1) |  \
+                (1 << TXEN1));  \
+} while (0)
+#define PS2_USART_RX_READY      (UCSR1A & (1<<RXC1))
+#define PS2_USART_RX_DATA       UDR1
+#define PS2_USART_ERROR         (UCSR1A & ((1<<FE1) | (1<<DOR1) | (1<<UPE1)))
+#define PS2_USART_RX_VECT       USART1_RX_vect
+#define PS2_MOUSE_ROTATE 270 /* Compensate for East-facing device orientation. */
+#endif
diff --git a/platforms/chibios/config.h b/platforms/chibios/config.h
index 006415a5dc5..a58479bb974 100644
--- a/platforms/chibios/config.h
+++ b/platforms/chibios/config.h
@@ -5,3 +5,7 @@
 #ifndef CORTEX_ENABLE_WFI_IDLE
 #    define CORTEX_ENABLE_WFI_IDLE TRUE
 #endif // CORTEX_ENABLE_WFI_IDLE
+
+#ifndef SERIAL_NUMBER_USE_HARDWARE_ID
+#    define SERIAL_NUMBER_USE_HARDWARE_ID TRUE
+#endif // SERIAL_NUMBER_USE_HARDWARE_ID
diff --git a/tmk_core/protocol/usb_descriptor.c b/tmk_core/protocol/usb_descriptor.c
index 6078984e42f..4c6ce46dd4c 100644
--- a/tmk_core/protocol/usb_descriptor.c
+++ b/tmk_core/protocol/usb_descriptor.c
@@ -49,6 +49,16 @@
 #    include "os_detection.h"
 #endif
 
+#if defined(SERIAL_NUMBER) || (defined(SERIAL_NUMBER_USE_HARDWARE_ID) && SERIAL_NUMBER_USE_HARDWARE_ID == TRUE)
+
+#    define HAS_SERIAL_NUMBER
+
+#    if defined(SERIAL_NUMBER_USE_HARDWARE_ID) && SERIAL_NUMBER_USE_HARDWARE_ID == TRUE
+#        include "hardware_id.h"
+#    endif
+
+#endif // defined(SERIAL_NUMBER) || (defined(SERIAL_NUMBER_USE_HARDWARE_ID) && SERIAL_NUMBER_USE_HARDWARE_ID == TRUE)
+
 // clang-format off
 
 /*
@@ -475,11 +485,11 @@ const USB_Descriptor_Device_t PROGMEM DeviceDescriptor = {
     .ReleaseNumber              = DEVICE_VER,
     .ManufacturerStrIndex       = 0x01,
     .ProductStrIndex            = 0x02,
-#if defined(SERIAL_NUMBER)
+#ifdef HAS_SERIAL_NUMBER
     .SerialNumStrIndex          = 0x03,
-#else
+#else // HAS_SERIAL_NUMBER
     .SerialNumStrIndex          = 0x00,
-#endif
+#endif // HAS_SERIAL_NUMBER
     .NumberOfConfigurations     = FIXED_NUM_CONFIGURATIONS
 };
 
@@ -1111,9 +1121,13 @@ const USB_Descriptor_Configuration_t PROGMEM ConfigurationDescriptor = {
 /*
  * String descriptors
  */
+
+#define USB_DESCRIPTOR_SIZE_LITERAL_U16STRING(str) \
+    (sizeof(USB_Descriptor_Header_t) + sizeof(str) - sizeof(wchar_t)) // include header, don't count null terminator
+
 const USB_Descriptor_String_t PROGMEM LanguageString = {
     .Header = {
-        .Size                   = 4,
+        .Size                   = sizeof(USB_Descriptor_Header_t) + sizeof(uint16_t),
         .Type                   = DTYPE_String
     },
     .UnicodeString              = {LANGUAGE_ID_ENG}
@@ -1121,7 +1135,7 @@ const USB_Descriptor_String_t PROGMEM LanguageString = {
 
 const USB_Descriptor_String_t PROGMEM ManufacturerString = {
     .Header = {
-        .Size                   = sizeof(USBSTR(MANUFACTURER)),
+        .Size                   = USB_DESCRIPTOR_SIZE_LITERAL_U16STRING(USBSTR(MANUFACTURER)),
         .Type                   = DTYPE_String
     },
     .UnicodeString              = USBSTR(MANUFACTURER)
@@ -1129,24 +1143,70 @@ const USB_Descriptor_String_t PROGMEM ManufacturerString = {
 
 const USB_Descriptor_String_t PROGMEM ProductString = {
     .Header = {
-        .Size                   = sizeof(USBSTR(PRODUCT)),
+        .Size                   = USB_DESCRIPTOR_SIZE_LITERAL_U16STRING(USBSTR(PRODUCT)),
         .Type                   = DTYPE_String
     },
     .UnicodeString              = USBSTR(PRODUCT)
 };
 
+// clang-format on
+
 #if defined(SERIAL_NUMBER)
+// clang-format off
 const USB_Descriptor_String_t PROGMEM SerialNumberString = {
     .Header = {
-        .Size                   = sizeof(USBSTR(SERIAL_NUMBER)),
+        .Size                   = USB_DESCRIPTOR_SIZE_LITERAL_U16STRING(USBSTR(SERIAL_NUMBER)),
         .Type                   = DTYPE_String
     },
     .UnicodeString              = USBSTR(SERIAL_NUMBER)
 };
-#endif
-
 // clang-format on
 
+#else // defined(SERIAL_NUMBER)
+
+#    if defined(SERIAL_NUMBER_USE_HARDWARE_ID) && SERIAL_NUMBER_USE_HARDWARE_ID == TRUE
+
+#        if defined(__AVR__)
+#            error Dynamically setting the serial number on AVR is unsupported as LUFA requires the string to be in PROGMEM.
+#        endif // defined(__AVR__)
+
+#        ifndef SERIAL_NUMBER_LENGTH
+#            define SERIAL_NUMBER_LENGTH (sizeof(hardware_id_t) * 2)
+#        endif
+
+#        define SERIAL_NUMBER_DESCRIPTOR_SIZE                                            \
+            (sizeof(USB_Descriptor_Header_t)                     /* Descriptor header */ \
+             + (((SERIAL_NUMBER_LENGTH) + 1) * sizeof(wchar_t))) /* Length of serial number, with potential extra character as we're converting 2 nibbles at a time */
+
+uint8_t SerialNumberString[SERIAL_NUMBER_DESCRIPTOR_SIZE] = {0};
+
+void set_serial_number_descriptor(void) {
+    static bool is_set = false;
+    if (is_set) {
+        return;
+    }
+    is_set = true;
+
+    static const char        hex_str[] = "0123456789ABCDEF";
+    hardware_id_t            id        = get_hardware_id();
+    USB_Descriptor_String_t* desc      = (USB_Descriptor_String_t*)SerialNumberString;
+
+    // Copy across nibbles from the hardware ID as unicode hex characters
+    int      length = MIN(sizeof(id) * 2, SERIAL_NUMBER_LENGTH);
+    uint8_t* p      = (uint8_t*)&id;
+    for (int i = 0; i < length; i += 2) {
+        desc->UnicodeString[i + 0] = hex_str[p[i / 2] >> 4];
+        desc->UnicodeString[i + 1] = hex_str[p[i / 2] & 0xF];
+    }
+
+    desc->Header.Size = sizeof(USB_Descriptor_Header_t) + (length * sizeof(wchar_t)); // includes header, don't count null terminator
+    desc->Header.Type = DTYPE_String;
+}
+
+#    endif // defined(SERIAL_NUMBER_USE_HARDWARE_ID) && SERIAL_NUMBER_USE_HARDWARE_ID == TRUE
+
+#endif // defined(SERIAL_NUMBER)
+
 /**
  * This function is called by the library when in device mode, and must be overridden (see library "USB Descriptors"
  * documentation) by the application code so that the address and size of a requested descriptor can be given
@@ -1188,13 +1248,18 @@ uint16_t get_usb_descriptor(const uint16_t wValue, const uint16_t wIndex, const
                     Size    = pgm_read_byte(&ProductString.Header.Size);
 
                     break;
-#if defined(SERIAL_NUMBER)
+#ifdef HAS_SERIAL_NUMBER
                 case 0x03:
-                    Address = &SerialNumberString;
-                    Size    = pgm_read_byte(&SerialNumberString.Header.Size);
+                    Address = (const USB_Descriptor_String_t*)&SerialNumberString;
+#    if defined(SERIAL_NUMBER)
+                    Size = pgm_read_byte(&SerialNumberString.Header.Size);
+#    else
+                    set_serial_number_descriptor();
+                    Size = ((const USB_Descriptor_String_t*)SerialNumberString)->Header.Size;
+#    endif
 
                     break;
-#endif
+#endif // HAS_SERIAL_NUMBER
             }
 #ifdef OS_DETECTION_ENABLE
             process_wlength(wLength);