diff --git a/src/atsam/sam3_usb.c b/src/atsam/sam3_usb.c
index d9101478..b990be88 100644
--- a/src/atsam/sam3_usb.c
+++ b/src/atsam/sam3_usb.c
@@ -179,29 +179,6 @@ handle_end_reset(void)
     UOTGHS->UOTGHS_DEVICR = UOTGHS_DEVICR_EORSTC;
 }
 
-void
-usbserial_init(void)
-{
-    // Setup USB clock
-    enable_pclock(ID_UOTGHS);
-    PMC->CKGR_UCKR = CKGR_UCKR_UPLLCOUNT(3) | CKGR_UCKR_UPLLEN;
-    while (!(PMC->PMC_SR & PMC_SR_LOCKU))
-        ;
-    PMC->PMC_USB = PMC_USB_USBS | PMC_USB_USBDIV(0);
-    PMC->PMC_SCER = PMC_SCER_UOTGCLK;
-
-    // Enable USB
-    UOTGHS->UOTGHS_CTRL = (UOTGHS_CTRL_UIMOD | UOTGHS_CTRL_OTGPADE
-                           | UOTGHS_CTRL_USBE);
-    UOTGHS->UOTGHS_DEVCTRL = UOTGHS_DEVCTRL_SPDCONF_FORCED_FS;
-
-    // Enable interrupts
-    NVIC_SetPriority(UOTGHS_IRQn, 1);
-    NVIC_EnableIRQ(UOTGHS_IRQn);
-    UOTGHS->UOTGHS_DEVIER = UOTGHS_DEVIER_EORSTES;
-}
-DECL_INIT(usbserial_init);
-
 void __visible
 UOTGHS_Handler(void)
 {
@@ -227,3 +204,26 @@ UOTGHS_Handler(void)
     if (s & (UOTGHS_DEVISR_PEP_0 << USB_CDC_EP_BULK_IN))
         usb_notify_bulk_in();
 }
+
+void
+usbserial_init(void)
+{
+    // Setup USB clock
+    enable_pclock(ID_UOTGHS);
+    PMC->CKGR_UCKR = CKGR_UCKR_UPLLCOUNT(3) | CKGR_UCKR_UPLLEN;
+    while (!(PMC->PMC_SR & PMC_SR_LOCKU))
+        ;
+    PMC->PMC_USB = PMC_USB_USBS | PMC_USB_USBDIV(0);
+    PMC->PMC_SCER = PMC_SCER_UOTGCLK;
+
+    // Enable USB
+    UOTGHS->UOTGHS_CTRL = (UOTGHS_CTRL_UIMOD | UOTGHS_CTRL_OTGPADE
+                           | UOTGHS_CTRL_USBE);
+    UOTGHS->UOTGHS_DEVCTRL = UOTGHS_DEVCTRL_SPDCONF_FORCED_FS;
+
+    // Enable interrupts
+    NVIC_SetPriority(UOTGHS_IRQn, 1);
+    NVIC_EnableIRQ(UOTGHS_IRQn);
+    UOTGHS->UOTGHS_DEVIER = UOTGHS_DEVIER_EORSTES;
+}
+DECL_INIT(usbserial_init);
diff --git a/src/atsam/sam4_usb.c b/src/atsam/sam4_usb.c
index 0ba85f4b..33e886c5 100644
--- a/src/atsam/sam4_usb.c
+++ b/src/atsam/sam4_usb.c
@@ -160,26 +160,6 @@ usb_set_configure(void)
     UDP->UDP_GLB_STAT |= UDP_GLB_STAT_CONFG;
 }
 
-DECL_CONSTANT_STR("RESERVE_PINS_USB", "PB10,PB11");
-
-void
-usbserial_init(void)
-{
-    // Enable clocks
-    enable_pclock(ID_UDP);
-    PMC->PMC_USB = PMC_USB_USBDIV(5 - 1); // PLLA=240Mhz; divide by 5 for 48Mhz
-    PMC->PMC_SCER = PMC_SCER_UDP;
-
-    // Enable USB pullup
-    UDP->UDP_TXVC = UDP_TXVC_PUON | UDP_TXVC_TXVDIS;
-
-    // Enable interrupts
-    UDP->UDP_ICR = 0xffffffff;
-    NVIC_SetPriority(UDP_IRQn, 1);
-    NVIC_EnableIRQ(UDP_IRQn);
-}
-DECL_INIT(usbserial_init);
-
 // Configure endpoint 0 after usb reset completes
 static void
 handle_end_reset(void)
@@ -216,3 +196,23 @@ UDP_Handler(void)
     if (s & (1<<USB_CDC_EP_BULK_IN))
         usb_notify_bulk_in();
 }
+
+DECL_CONSTANT_STR("RESERVE_PINS_USB", "PB10,PB11");
+
+void
+usbserial_init(void)
+{
+    // Enable clocks
+    enable_pclock(ID_UDP);
+    PMC->PMC_USB = PMC_USB_USBDIV(5 - 1); // PLLA=240Mhz; divide by 5 for 48Mhz
+    PMC->PMC_SCER = PMC_SCER_UDP;
+
+    // Enable USB pullup
+    UDP->UDP_TXVC = UDP_TXVC_PUON | UDP_TXVC_TXVDIS;
+
+    // Enable interrupts
+    UDP->UDP_ICR = 0xffffffff;
+    NVIC_SetPriority(UDP_IRQn, 1);
+    NVIC_EnableIRQ(UDP_IRQn);
+}
+DECL_INIT(usbserial_init);
diff --git a/src/atsam/serial.c b/src/atsam/serial.c
index 051256d4..62c8ac44 100644
--- a/src/atsam/serial.c
+++ b/src/atsam/serial.c
@@ -34,6 +34,28 @@ static const uint32_t tx_pin = GPIO('A', 10);
 DECL_CONSTANT_STR("RESERVE_PINS_serial", "PA9,PA10");
 #endif
 
+void __visible
+Serial_IRQ_Handler(void)
+{
+    uint32_t status = Port->UART_SR;
+    if (status & UART_SR_RXRDY)
+        serial_rx_byte(Port->UART_RHR);
+    if (status & UART_SR_TXRDY) {
+        uint8_t data;
+        int ret = serial_get_tx_byte(&data);
+        if (ret)
+            Port->UART_IDR = UART_IDR_TXRDY;
+        else
+            Port->UART_THR = data;
+    }
+}
+
+void
+serial_enable_tx_irq(void)
+{
+    Port->UART_IER = UART_IDR_TXRDY;
+}
+
 void
 serial_init(void)
 {
@@ -57,25 +79,3 @@ serial_init(void)
     Port->UART_CR = UART_CR_RXEN | UART_CR_TXEN;
 }
 DECL_INIT(serial_init);
-
-void __visible
-Serial_IRQ_Handler(void)
-{
-    uint32_t status = Port->UART_SR;
-    if (status & UART_SR_RXRDY)
-        serial_rx_byte(Port->UART_RHR);
-    if (status & UART_SR_TXRDY) {
-        uint8_t data;
-        int ret = serial_get_tx_byte(&data);
-        if (ret)
-            Port->UART_IDR = UART_IDR_TXRDY;
-        else
-            Port->UART_THR = data;
-    }
-}
-
-void
-serial_enable_tx_irq(void)
-{
-    Port->UART_IER = UART_IDR_TXRDY;
-}