diff --git a/src/machine/board_circuitplay_bluefruit.go b/src/machine/board_circuitplay_bluefruit.go
index 38c3995c..0a78ca5e 100644
--- a/src/machine/board_circuitplay_bluefruit.go
+++ b/src/machine/board_circuitplay_bluefruit.go
@@ -58,7 +58,7 @@ const (
 
 // UART0 is the USB device
 var (
-	UART0 = &USB
+	UART0 = USB
 )
 
 // I2C pins
diff --git a/src/machine/board_clue_alpha.go b/src/machine/board_clue_alpha.go
index 0397c476..a6c8807b 100644
--- a/src/machine/board_clue_alpha.go
+++ b/src/machine/board_clue_alpha.go
@@ -105,7 +105,7 @@ const (
 
 // UART0 is the USB device
 var (
-	UART0 = &USB
+	UART0 = USB
 )
 
 // I2C pins
diff --git a/src/machine/board_feather-nrf52840.go b/src/machine/board_feather-nrf52840.go
index ae4b54e0..f353a3b7 100644
--- a/src/machine/board_feather-nrf52840.go
+++ b/src/machine/board_feather-nrf52840.go
@@ -77,7 +77,7 @@ const (
 
 // UART0 is the USB device
 var (
-	UART0 = &USB
+	UART0 = USB
 )
 
 // I2C pins
diff --git a/src/machine/board_itsybitsy-nrf52840.go b/src/machine/board_itsybitsy-nrf52840.go
index 4d98b669..e61be006 100644
--- a/src/machine/board_itsybitsy-nrf52840.go
+++ b/src/machine/board_itsybitsy-nrf52840.go
@@ -72,7 +72,7 @@ const (
 
 // UART0 is the USB device
 var (
-	UART0 = &USB
+	UART0 = USB
 )
 
 // I2C pins
diff --git a/src/machine/board_particle_argon.go b/src/machine/board_particle_argon.go
index 44e5a51b..5401c4ad 100644
--- a/src/machine/board_particle_argon.go
+++ b/src/machine/board_particle_argon.go
@@ -41,7 +41,7 @@ const (
 
 // UART
 var (
-	Serial = &USB
+	Serial = USB
 	UART0  = NRF_UART0
 )
 
diff --git a/src/machine/board_particle_boron.go b/src/machine/board_particle_boron.go
index a50d87eb..cb05e725 100644
--- a/src/machine/board_particle_boron.go
+++ b/src/machine/board_particle_boron.go
@@ -41,7 +41,7 @@ const (
 
 // UART
 var (
-	Serial = &USB
+	Serial = USB
 	UART0  = NRF_UART0
 )
 
diff --git a/src/machine/board_particle_xenon.go b/src/machine/board_particle_xenon.go
index 7a94cf6d..c1614636 100644
--- a/src/machine/board_particle_xenon.go
+++ b/src/machine/board_particle_xenon.go
@@ -41,7 +41,7 @@ const (
 
 // UART
 var (
-	Serial = &USB
+	Serial = USB
 	UART0  = NRF_UART0
 )
 
diff --git a/src/machine/machine_atsamd21.go b/src/machine/machine_atsamd21.go
index 4bacd2aa..058099cd 100644
--- a/src/machine/machine_atsamd21.go
+++ b/src/machine/machine_atsamd21.go
@@ -506,7 +506,7 @@ type UART struct {
 
 var (
 	// UART0 is actually a USB CDC interface.
-	UART0 = USBCDC{Buffer: NewRingBuffer()}
+	UART0 = &USBCDC{Buffer: NewRingBuffer()}
 )
 
 const (
@@ -1788,7 +1788,7 @@ func (usbcdc *USBCDC) Flush() error {
 
 			// send data by setting bank ready
 			setEPSTATUSSET(usb_CDC_ENDPOINT_IN, sam.USB_DEVICE_EPSTATUSSET_BK1RDY)
-			UART0.sent = true
+			usbcdc.sent = true
 		}
 	}
 	return nil
@@ -1802,10 +1802,10 @@ func (usbcdc *USBCDC) WriteByte(c byte) error {
 		for {
 			mask := interrupt.Disable()
 
-			idx := UART0.TxIdx.Get()
+			idx := usbcdc.TxIdx.Get()
 			if (idx & usbcdcTxSizeMask) < usbcdcTxSizeMask {
 				udd_ep_in_cache_buffer[usb_CDC_ENDPOINT_IN][idx] = c
-				UART0.TxIdx.Set(idx + 1)
+				usbcdc.TxIdx.Set(idx + 1)
 				ok = true
 			}
 
@@ -1813,26 +1813,26 @@ func (usbcdc *USBCDC) WriteByte(c byte) error {
 
 			if ok {
 				break
-			} else if usbcdcTxMaxRetriesAllowed < UART0.waitTxcRetryCount {
+			} else if usbcdcTxMaxRetriesAllowed < usbcdc.waitTxcRetryCount {
 				mask := interrupt.Disable()
-				UART0.waitTxc = false
-				UART0.waitTxcRetryCount = 0
-				UART0.TxIdx.Set(0)
+				usbcdc.waitTxc = false
+				usbcdc.waitTxcRetryCount = 0
+				usbcdc.TxIdx.Set(0)
 				usbLineInfo.lineState = 0
 				interrupt.Restore(mask)
 				break
 			} else {
 				mask := interrupt.Disable()
-				if UART0.sent {
-					if UART0.waitTxc {
+				if usbcdc.sent {
+					if usbcdc.waitTxc {
 						if (getEPINTFLAG(usb_CDC_ENDPOINT_IN) & sam.USB_DEVICE_EPINTFLAG_TRCPT1) != 0 {
 							setEPSTATUSCLR(usb_CDC_ENDPOINT_IN, sam.USB_DEVICE_EPSTATUSCLR_BK1RDY)
 							setEPINTFLAG(usb_CDC_ENDPOINT_IN, sam.USB_DEVICE_EPINTFLAG_TRCPT1)
-							UART0.waitTxc = false
-							UART0.Flush()
+							usbcdc.waitTxc = false
+							usbcdc.Flush()
 						}
 					} else {
-						UART0.Flush()
+						usbcdc.Flush()
 					}
 				}
 				interrupt.Restore(mask)
@@ -1843,11 +1843,11 @@ func (usbcdc *USBCDC) WriteByte(c byte) error {
 	return nil
 }
 
-func (usbcdc USBCDC) DTR() bool {
+func (usbcdc *USBCDC) DTR() bool {
 	return (usbLineInfo.lineState & usb_CDC_LINESTATE_DTR) > 0
 }
 
-func (usbcdc USBCDC) RTS() bool {
+func (usbcdc *USBCDC) RTS() bool {
 	return (usbLineInfo.lineState & usb_CDC_LINESTATE_RTS) > 0
 }
 
@@ -1882,7 +1882,7 @@ var (
 )
 
 // Configure the USB CDC interface. The config is here for compatibility with the UART interface.
-func (usbcdc USBCDC) Configure(config UARTConfig) {
+func (usbcdc *USBCDC) Configure(config UARTConfig) {
 	// reset USB interface
 	sam.USB_DEVICE.CTRLA.SetBits(sam.USB_DEVICE_CTRLA_SWRST)
 	for sam.USB_DEVICE.SYNCBUSY.HasBits(sam.USB_DEVICE_SYNCBUSY_SWRST) ||
diff --git a/src/machine/machine_atsamd51.go b/src/machine/machine_atsamd51.go
index f8b0a865..f21d0173 100644
--- a/src/machine/machine_atsamd51.go
+++ b/src/machine/machine_atsamd51.go
@@ -952,7 +952,7 @@ type UART struct {
 
 var (
 	// UART0 is actually a USB CDC interface.
-	UART0 = USBCDC{Buffer: NewRingBuffer()}
+	UART0 = &USBCDC{Buffer: NewRingBuffer()}
 )
 
 const (
@@ -1994,7 +1994,7 @@ func (usbcdc *USBCDC) Flush() error {
 
 			// send data by setting bank ready
 			setEPSTATUSSET(usb_CDC_ENDPOINT_IN, sam.USB_DEVICE_ENDPOINT_EPSTATUSSET_BK1RDY)
-			UART0.sent = true
+			usbcdc.sent = true
 		}
 	}
 	return nil
@@ -2008,10 +2008,10 @@ func (usbcdc *USBCDC) WriteByte(c byte) error {
 		for {
 			mask := interrupt.Disable()
 
-			idx := UART0.TxIdx.Get()
+			idx := usbcdc.TxIdx.Get()
 			if (idx & usbcdcTxSizeMask) < usbcdcTxSizeMask {
 				udd_ep_in_cache_buffer[usb_CDC_ENDPOINT_IN][idx] = c
-				UART0.TxIdx.Set(idx + 1)
+				usbcdc.TxIdx.Set(idx + 1)
 				ok = true
 			}
 
@@ -2019,26 +2019,26 @@ func (usbcdc *USBCDC) WriteByte(c byte) error {
 
 			if ok {
 				break
-			} else if usbcdcTxMaxRetriesAllowed < UART0.waitTxcRetryCount {
+			} else if usbcdcTxMaxRetriesAllowed < usbcdc.waitTxcRetryCount {
 				mask := interrupt.Disable()
-				UART0.waitTxc = false
-				UART0.waitTxcRetryCount = 0
-				UART0.TxIdx.Set(0)
+				usbcdc.waitTxc = false
+				usbcdc.waitTxcRetryCount = 0
+				usbcdc.TxIdx.Set(0)
 				usbLineInfo.lineState = 0
 				interrupt.Restore(mask)
 				break
 			} else {
 				mask := interrupt.Disable()
-				if UART0.sent {
-					if UART0.waitTxc {
+				if usbcdc.sent {
+					if usbcdc.waitTxc {
 						if (getEPINTFLAG(usb_CDC_ENDPOINT_IN) & sam.USB_DEVICE_ENDPOINT_EPINTFLAG_TRCPT1) != 0 {
 							setEPSTATUSCLR(usb_CDC_ENDPOINT_IN, sam.USB_DEVICE_ENDPOINT_EPSTATUSCLR_BK1RDY)
 							setEPINTFLAG(usb_CDC_ENDPOINT_IN, sam.USB_DEVICE_ENDPOINT_EPINTFLAG_TRCPT1)
-							UART0.waitTxc = false
-							UART0.Flush()
+							usbcdc.waitTxc = false
+							usbcdc.Flush()
 						}
 					} else {
-						UART0.Flush()
+						usbcdc.Flush()
 					}
 				}
 				interrupt.Restore(mask)
@@ -2049,11 +2049,11 @@ func (usbcdc *USBCDC) WriteByte(c byte) error {
 	return nil
 }
 
-func (usbcdc USBCDC) DTR() bool {
+func (usbcdc *USBCDC) DTR() bool {
 	return (usbLineInfo.lineState & usb_CDC_LINESTATE_DTR) > 0
 }
 
-func (usbcdc USBCDC) RTS() bool {
+func (usbcdc *USBCDC) RTS() bool {
 	return (usbLineInfo.lineState & usb_CDC_LINESTATE_RTS) > 0
 }
 
@@ -2088,7 +2088,7 @@ var (
 )
 
 // Configure the USB CDC interface. The config is here for compatibility with the UART interface.
-func (usbcdc USBCDC) Configure(config UARTConfig) {
+func (usbcdc *USBCDC) Configure(config UARTConfig) {
 	// reset USB interface
 	sam.USB_DEVICE.CTRLA.SetBits(sam.USB_DEVICE_CTRLA_SWRST)
 	for sam.USB_DEVICE.SYNCBUSY.HasBits(sam.USB_DEVICE_SYNCBUSY_SWRST) ||
diff --git a/src/machine/machine_nrf52840_usb.go b/src/machine/machine_nrf52840_usb.go
index fa117b1c..82a44afe 100644
--- a/src/machine/machine_nrf52840_usb.go
+++ b/src/machine/machine_nrf52840_usb.go
@@ -58,7 +58,7 @@ func (usbcdc *USBCDC) Flush() error {
 				usbcdc.TxIdx.Set(usbcdcTxBank1st)
 			}
 
-			USB.sent = true
+			usbcdc.sent = true
 		}
 	}
 	return nil
@@ -72,10 +72,10 @@ func (usbcdc *USBCDC) WriteByte(c byte) error {
 		for {
 			mask := interrupt.Disable()
 
-			idx := USB.TxIdx.Get()
+			idx := usbcdc.TxIdx.Get()
 			if (idx & usbcdcTxSizeMask) < usbcdcTxSizeMask {
 				udd_ep_in_cache_buffer[usb_CDC_ENDPOINT_IN][idx] = c
-				USB.TxIdx.Set(idx + 1)
+				usbcdc.TxIdx.Set(idx + 1)
 				ok = true
 			}
 
@@ -83,24 +83,24 @@ func (usbcdc *USBCDC) WriteByte(c byte) error {
 
 			if ok {
 				break
-			} else if usbcdcTxMaxRetriesAllowed < USB.waitTxcRetryCount {
+			} else if usbcdcTxMaxRetriesAllowed < usbcdc.waitTxcRetryCount {
 				mask := interrupt.Disable()
-				USB.waitTxc = false
-				USB.waitTxcRetryCount = 0
-				USB.TxIdx.Set(0)
+				usbcdc.waitTxc = false
+				usbcdc.waitTxcRetryCount = 0
+				usbcdc.TxIdx.Set(0)
 				usbLineInfo.lineState = 0
 				interrupt.Restore(mask)
 				break
 			} else {
 				mask := interrupt.Disable()
-				if USB.sent {
-					if USB.waitTxc {
+				if usbcdc.sent {
+					if usbcdc.waitTxc {
 						if !easyDMABusy.HasBits(1) {
-							USB.waitTxc = false
-							USB.Flush()
+							usbcdc.waitTxc = false
+							usbcdc.Flush()
 						}
 					} else {
-						USB.Flush()
+						usbcdc.Flush()
 					}
 				}
 				interrupt.Restore(mask)
@@ -111,16 +111,17 @@ func (usbcdc *USBCDC) WriteByte(c byte) error {
 	return nil
 }
 
-func (usbcdc USBCDC) DTR() bool {
+func (usbcdc *USBCDC) DTR() bool {
 	return (usbLineInfo.lineState & usb_CDC_LINESTATE_DTR) > 0
 }
 
-func (usbcdc USBCDC) RTS() bool {
+func (usbcdc *USBCDC) RTS() bool {
 	return (usbLineInfo.lineState & usb_CDC_LINESTATE_RTS) > 0
 }
 
 var (
-	USB = USBCDC{Buffer: NewRingBuffer()}
+	USB  = &_USB
+	_USB = USBCDC{Buffer: NewRingBuffer()}
 
 	usbEndpointDescriptors [8]usbDeviceDescriptor
 
@@ -174,7 +175,7 @@ func (usbcdc *USBCDC) Configure(config UARTConfig) {
 	// that it is possible to print to the console from a BLE interrupt. You
 	// shouldn't generally do that but it is useful for debugging and panic
 	// logging.
-	usbcdc.interrupt = interrupt.New(nrf.IRQ_USBD, USB.handleInterrupt)
+	usbcdc.interrupt = interrupt.New(nrf.IRQ_USBD, _USB.handleInterrupt)
 	usbcdc.interrupt.SetPriority(0x40) // interrupt priority 2 (lower number means more important)
 	usbcdc.interrupt.Enable()
 
@@ -198,7 +199,7 @@ func (usbcdc *USBCDC) Configure(config UARTConfig) {
 func (usbcdc *USBCDC) handleInterrupt(interrupt.Interrupt) {
 	if nrf.USBD.EVENTS_SOF.Get() == 1 {
 		nrf.USBD.EVENTS_SOF.Set(0)
-		USB.Flush()
+		usbcdc.Flush()
 		// if you want to blink LED showing traffic, this would be the place...
 	}
 
@@ -292,7 +293,7 @@ func (usbcdc *USBCDC) handleInterrupt(interrupt.Interrupt) {
 					}
 				case usb_CDC_ENDPOINT_IN: //, usb_CDC_ENDPOINT_ACM:
 					if inDataDone {
-						USB.waitTxc = false
+						usbcdc.waitTxc = false
 						exitCriticalSection()
 					}
 				}
@@ -496,7 +497,7 @@ func sendUSBPacket(ep uint32, data []byte) {
 	)
 }
 
-func (usbcdc USBCDC) handleEndpoint(ep uint32) {
+func (usbcdc *USBCDC) handleEndpoint(ep uint32) {
 	// get data
 	count := int(nrf.USBD.EPOUT[ep].AMOUNT.Get())
 
diff --git a/src/machine/usb.go b/src/machine/usb.go
index 0b547006..4bea1880 100644
--- a/src/machine/usb.go
+++ b/src/machine/usb.go
@@ -604,7 +604,7 @@ func newUSBSetup(data []byte) usbSetup {
 //
 
 // Read from the RX buffer.
-func (usbcdc USBCDC) Read(data []byte) (n int, err error) {
+func (usbcdc *USBCDC) Read(data []byte) (n int, err error) {
 	// check if RX buffer is empty
 	size := usbcdc.Buffered()
 	if size == 0 {
@@ -626,7 +626,7 @@ func (usbcdc USBCDC) Read(data []byte) (n int, err error) {
 }
 
 // Write data to the USBCDC.
-func (usbcdc USBCDC) Write(data []byte) (n int, err error) {
+func (usbcdc *USBCDC) Write(data []byte) (n int, err error) {
 	for _, v := range data {
 		usbcdc.WriteByte(v)
 	}
@@ -635,7 +635,7 @@ func (usbcdc USBCDC) Write(data []byte) (n int, err error) {
 
 // ReadByte reads a single byte from the RX buffer.
 // If there is no data in the buffer, returns an error.
-func (usbcdc USBCDC) ReadByte() (byte, error) {
+func (usbcdc *USBCDC) ReadByte() (byte, error) {
 	// check if RX buffer is empty
 	buf, ok := usbcdc.Buffer.Get()
 	if !ok {
@@ -645,13 +645,13 @@ func (usbcdc USBCDC) ReadByte() (byte, error) {
 }
 
 // Buffered returns the number of bytes currently stored in the RX buffer.
-func (usbcdc USBCDC) Buffered() int {
+func (usbcdc *USBCDC) Buffered() int {
 	return int(usbcdc.Buffer.Used())
 }
 
 // Receive handles adding data to the UART's data buffer.
 // Usually called by the IRQ handler for a machine.
-func (usbcdc USBCDC) Receive(data byte) {
+func (usbcdc *USBCDC) Receive(data byte) {
 	usbcdc.Buffer.Put(data)
 }