diff --git a/Makefile b/Makefile
index e5e72d0f..bbb00fb6 100644
--- a/Makefile
+++ b/Makefile
@@ -349,6 +349,8 @@ smoketest:
 	@$(MD5SUM) test.hex
 	$(TINYGO) build -size short -o test.hex -target=feather-m4-can      examples/caninterrupt
 	@$(MD5SUM) test.hex
+	$(TINYGO) build -size short -o test.hex -target=arduino-nano33      examples/blinky1
+	@$(MD5SUM) test.hex
 	# test pwm
 	$(TINYGO) build -size short -o test.hex -target=itsybitsy-m0        examples/pwm
 	@$(MD5SUM) test.hex
diff --git a/src/examples/echo/echo.go b/src/examples/echo/echo.go
index 97a5dc4c..be129dd0 100644
--- a/src/examples/echo/echo.go
+++ b/src/examples/echo/echo.go
@@ -9,7 +9,7 @@ import (
 
 // change these to test a different UART or pins if available
 var (
-	uart = machine.UART0
+	uart = machine.Serial
 	tx   = machine.UART_TX_PIN
 	rx   = machine.UART_RX_PIN
 )
diff --git a/src/machine/board_arduino_mkr1000.go b/src/machine/board_arduino_mkr1000.go
index e4605942..863faeeb 100644
--- a/src/machine/board_arduino_mkr1000.go
+++ b/src/machine/board_arduino_mkr1000.go
@@ -47,7 +47,9 @@ const (
 	LED = D6
 )
 
-// UART0 aka USBCDC pins
+var Serial = USB
+
+// USBCDC pins
 const (
 	USBCDC_DM_PIN Pin = PA24
 	USBCDC_DP_PIN Pin = PA25
diff --git a/src/machine/board_arduino_nano33.go b/src/machine/board_arduino_nano33.go
index 81aa815c..606f5e63 100644
--- a/src/machine/board_arduino_nano33.go
+++ b/src/machine/board_arduino_nano33.go
@@ -46,7 +46,7 @@ const (
 	LED = D13
 )
 
-// UART0 aka USBCDC pins
+// USBCDC pins
 const (
 	USBCDC_DM_PIN Pin = PA24
 	USBCDC_DP_PIN Pin = PA25
diff --git a/src/machine/board_arduino_zero.go b/src/machine/board_arduino_zero.go
index 651eea82..773515c9 100644
--- a/src/machine/board_arduino_zero.go
+++ b/src/machine/board_arduino_zero.go
@@ -35,6 +35,8 @@ const (
 	LED3 Pin = PB03 // RX LED
 )
 
+var Serial = USB
+
 // ADC pins
 const (
 	AREF Pin = PA03
diff --git a/src/machine/board_atsamd21.go b/src/machine/board_atsamd21.go
index 3b11b452..800c4cb3 100644
--- a/src/machine/board_atsamd21.go
+++ b/src/machine/board_atsamd21.go
@@ -74,3 +74,5 @@ const (
 	PB30 Pin = 62
 	PB31 Pin = 63
 )
+
+var Serial = USB
diff --git a/src/machine/board_atsame54-xpro.go b/src/machine/board_atsame54-xpro.go
index a70ab7b0..01ae282c 100644
--- a/src/machine/board_atsame54-xpro.go
+++ b/src/machine/board_atsame54-xpro.go
@@ -15,6 +15,8 @@ const (
 	BUTTON = PB31
 )
 
+var Serial = USB
+
 const (
 	// https://ww1.microchip.com/downloads/en/DeviceDoc/70005321A.pdf
 
@@ -152,7 +154,7 @@ const (
 	PIN_USB_ID      = PC19
 )
 
-// UART0 aka USBCDC pins
+// USBCDC pins
 const (
 	USBCDC_DM_PIN = PA24
 	USBCDC_DP_PIN = PA25
diff --git a/src/machine/board_bluepill.go b/src/machine/board_bluepill.go
index 4aece086..480aa19e 100644
--- a/src/machine/board_bluepill.go
+++ b/src/machine/board_bluepill.go
@@ -50,6 +50,8 @@ const (
 	LED = PC13
 )
 
+var Serial = UART1
+
 // UART pins
 const (
 	UART_TX_PIN     = PA9
@@ -60,22 +62,21 @@ const (
 
 var (
 	// USART1 is the first hardware serial port on the STM32.
-	// Both UART0 and UART1 refer to USART1.
-	UART0  = &_UART0
-	_UART0 = UART{
+	UART1  = &_UART1
+	_UART1 = UART{
 		Buffer: NewRingBuffer(),
 		Bus:    stm32.USART1,
 	}
-	UART1  = &_UART1
-	_UART1 = UART{
+	UART2  = &_UART2
+	_UART2 = UART{
 		Buffer: NewRingBuffer(),
 		Bus:    stm32.USART2,
 	}
 )
 
 func init() {
-	UART0.Interrupt = interrupt.New(stm32.IRQ_USART1, _UART0.handleInterrupt)
-	UART1.Interrupt = interrupt.New(stm32.IRQ_USART2, _UART1.handleInterrupt)
+	UART1.Interrupt = interrupt.New(stm32.IRQ_USART1, _UART1.handleInterrupt)
+	UART2.Interrupt = interrupt.New(stm32.IRQ_USART2, _UART2.handleInterrupt)
 }
 
 // SPI pins
diff --git a/src/machine/board_circuitplay_bluefruit.go b/src/machine/board_circuitplay_bluefruit.go
index 0a78ca5e..ccb2e3c1 100644
--- a/src/machine/board_circuitplay_bluefruit.go
+++ b/src/machine/board_circuitplay_bluefruit.go
@@ -56,10 +56,7 @@ const (
 	UART_RX_PIN = P0_30 // PORTB
 )
 
-// UART0 is the USB device
-var (
-	UART0 = USB
-)
+var Serial = USB
 
 // I2C pins
 const (
diff --git a/src/machine/board_clue_alpha.go b/src/machine/board_clue_alpha.go
index a6c8807b..89f82056 100644
--- a/src/machine/board_clue_alpha.go
+++ b/src/machine/board_clue_alpha.go
@@ -103,9 +103,9 @@ const (
 	UART_TX_PIN = D1
 )
 
-// UART0 is the USB device
+// Serial is the USB device
 var (
-	UART0 = USB
+	Serial = USB
 )
 
 // I2C pins
diff --git a/src/machine/board_esp32-coreboard-v2.go b/src/machine/board_esp32-coreboard-v2.go
index 0145fe4e..b1d61d87 100644
--- a/src/machine/board_esp32-coreboard-v2.go
+++ b/src/machine/board_esp32-coreboard-v2.go
@@ -68,6 +68,8 @@ const (
 	ADC3 Pin = IO39
 )
 
+var Serial = UART0
+
 // UART0 pins
 const (
 	UART_TX_PIN = IO1
diff --git a/src/machine/board_feather-m0.go b/src/machine/board_feather-m0.go
index f0f72ea7..b09c4371 100644
--- a/src/machine/board_feather-m0.go
+++ b/src/machine/board_feather-m0.go
@@ -42,7 +42,7 @@ const (
 	LED = D13
 )
 
-// UART0 aka USBCDC pins
+// USBCDC pins
 const (
 	USBCDC_DM_PIN = PA24
 	USBCDC_DP_PIN = PA25
diff --git a/src/machine/board_feather-m4-can.go b/src/machine/board_feather-m4-can.go
index 5ad3cd15..d5750f96 100644
--- a/src/machine/board_feather-m4-can.go
+++ b/src/machine/board_feather-m4-can.go
@@ -46,7 +46,9 @@ const (
 	NEOPIXELS = D8
 )
 
-// UART0 aka USBCDC pins
+var Serial = USB
+
+// USBCDC pins
 const (
 	USBCDC_DM_PIN = PA24
 	USBCDC_DP_PIN = PA25
diff --git a/src/machine/board_feather-m4.go b/src/machine/board_feather-m4.go
index bec23fc8..251da721 100644
--- a/src/machine/board_feather-m4.go
+++ b/src/machine/board_feather-m4.go
@@ -39,7 +39,9 @@ const (
 	LED = D13
 )
 
-// UART0 aka USBCDC pins
+var Serial = USB
+
+// USBCDC pins
 const (
 	USBCDC_DM_PIN = PA24
 	USBCDC_DP_PIN = PA25
diff --git a/src/machine/board_feather-nrf52840.go b/src/machine/board_feather-nrf52840.go
index f353a3b7..2c6e8465 100644
--- a/src/machine/board_feather-nrf52840.go
+++ b/src/machine/board_feather-nrf52840.go
@@ -75,9 +75,9 @@ const (
 	UART_TX_PIN = D1
 )
 
-// UART0 is the USB device
+// Serial is the USB device
 var (
-	UART0 = USB
+	Serial = USB
 )
 
 // I2C pins
diff --git a/src/machine/board_feather-stm32f405.go b/src/machine/board_feather-stm32f405.go
index f55572ff..e5e8d4b7 100644
--- a/src/machine/board_feather-stm32f405.go
+++ b/src/machine/board_feather-stm32f405.go
@@ -140,7 +140,7 @@ var (
 		TxAltFuncSelector: AF7_USART1_2_3,
 		RxAltFuncSelector: AF7_USART1_2_3,
 	}
-	UART0 = UART1
+	Serial = UART1
 )
 
 func initUART() {
diff --git a/src/machine/board_grandcentral-m4.go b/src/machine/board_grandcentral-m4.go
index fdd09ecd..6d42034d 100644
--- a/src/machine/board_grandcentral-m4.go
+++ b/src/machine/board_grandcentral-m4.go
@@ -141,6 +141,8 @@ const (
 	NEOPIXEL = NEOPIXEL_PIN
 )
 
+var Serial = USB
+
 // UART pins
 const (
 	UART1_RX_PIN = D0 // (PB25)
diff --git a/src/machine/board_hifive1b.go b/src/machine/board_hifive1b.go
index 10fd4a9f..7ce225cc 100644
--- a/src/machine/board_hifive1b.go
+++ b/src/machine/board_hifive1b.go
@@ -35,6 +35,8 @@ const (
 	LED_BLUE  = P21
 )
 
+var Serial = UART0
+
 const (
 	// TODO: figure out the pin numbers for these.
 	UART_TX_PIN = D1
diff --git a/src/machine/board_itsybitsy-m0.go b/src/machine/board_itsybitsy-m0.go
index a4161429..bd0272d4 100644
--- a/src/machine/board_itsybitsy-m0.go
+++ b/src/machine/board_itsybitsy-m0.go
@@ -42,7 +42,7 @@ const (
 	LED = D13
 )
 
-// UART0 aka USBCDC pins
+// USBCDC pins
 const (
 	USBCDC_DM_PIN = PA24
 	USBCDC_DP_PIN = PA25
diff --git a/src/machine/board_itsybitsy-m4.go b/src/machine/board_itsybitsy-m4.go
index 5fef841c..282f9087 100644
--- a/src/machine/board_itsybitsy-m4.go
+++ b/src/machine/board_itsybitsy-m4.go
@@ -37,7 +37,9 @@ const (
 	LED = D13
 )
 
-// UART0 aka USBCDC pins
+var Serial = USB
+
+// USBCDC pins
 const (
 	USBCDC_DM_PIN = PA24
 	USBCDC_DP_PIN = PA25
diff --git a/src/machine/board_itsybitsy-nrf52840.go b/src/machine/board_itsybitsy-nrf52840.go
index e61be006..64aeed50 100644
--- a/src/machine/board_itsybitsy-nrf52840.go
+++ b/src/machine/board_itsybitsy-nrf52840.go
@@ -70,9 +70,9 @@ const (
 	UART_TX_PIN = D1
 )
 
-// UART0 is the USB device
+// Serial is the USB device
 var (
-	UART0 = USB
+	Serial = USB
 )
 
 // I2C pins
diff --git a/src/machine/board_lgt92.go b/src/machine/board_lgt92.go
index 81fe2220..97e1fa2a 100644
--- a/src/machine/board_lgt92.go
+++ b/src/machine/board_lgt92.go
@@ -54,6 +54,8 @@ const (
 	I2C0_SDA_PIN = PA10
 )
 
+var Serial = UART0
+
 var (
 
 	// Console UART (LPUSART1)
diff --git a/src/machine/board_maixbit.go b/src/machine/board_maixbit.go
index 718a46e4..766054d0 100644
--- a/src/machine/board_maixbit.go
+++ b/src/machine/board_maixbit.go
@@ -52,6 +52,8 @@ const (
 	LED_BLUE  = D14
 )
 
+var Serial = UART0
+
 // Default pins for UARTHS.
 const (
 	UART_TX_PIN = D5
diff --git a/src/machine/board_metro-m4-airlift.go b/src/machine/board_metro-m4-airlift.go
index 5d12dd73..5665a081 100644
--- a/src/machine/board_metro-m4-airlift.go
+++ b/src/machine/board_metro-m4-airlift.go
@@ -40,7 +40,9 @@ const (
 	LED = D13
 )
 
-// UART0 aka USBCDC pins
+var Serial = USB
+
+// USBCDC pins
 const (
 	USBCDC_DM_PIN = PA24
 	USBCDC_DP_PIN = PA25
diff --git a/src/machine/board_microbit-v2.go b/src/machine/board_microbit-v2.go
index 9d42bd49..a034e2ef 100644
--- a/src/machine/board_microbit-v2.go
+++ b/src/machine/board_microbit-v2.go
@@ -12,6 +12,8 @@ const (
 	BUTTONB Pin = P11
 )
 
+var Serial = UART0
+
 // UART pins
 const (
 	UART_TX_PIN Pin = P34
diff --git a/src/machine/board_microbit.go b/src/machine/board_microbit.go
index a606ad86..5b0ac2bf 100644
--- a/src/machine/board_microbit.go
+++ b/src/machine/board_microbit.go
@@ -12,6 +12,8 @@ const (
 	BUTTONB Pin = 26
 )
 
+var Serial = UART0
+
 // UART pins
 const (
 	UART_TX_PIN Pin = 24
diff --git a/src/machine/board_nicenano.go b/src/machine/board_nicenano.go
index 0a79fad3..213fdb33 100644
--- a/src/machine/board_nicenano.go
+++ b/src/machine/board_nicenano.go
@@ -54,9 +54,9 @@ const (
 	UART_TX_PIN = P0_08
 )
 
-// UART0 is the USB device
+// Serial is the USB device
 var (
-	UART0 = USB
+	Serial = USB
 )
 
 // I2C pins
diff --git a/src/machine/board_nodemcu.go b/src/machine/board_nodemcu.go
index f9f1af4f..4177f80c 100644
--- a/src/machine/board_nodemcu.go
+++ b/src/machine/board_nodemcu.go
@@ -20,6 +20,8 @@ const (
 // Onboard blue LED (on the AI-Thinker module).
 const LED = D4
 
+var Serial = UART0
+
 // SPI pins
 const (
 	SPI0_SCK_PIN = D5
diff --git a/src/machine/board_nrf52840-mdk-usb-dongle.go b/src/machine/board_nrf52840-mdk-usb-dongle.go
index 45d175ff..e4923f4e 100644
--- a/src/machine/board_nrf52840-mdk-usb-dongle.go
+++ b/src/machine/board_nrf52840-mdk-usb-dongle.go
@@ -23,10 +23,8 @@ const (
 	UART_RX_PIN Pin = NoPin
 )
 
-// UART0 is the USB device
-var (
-	UART0 = USB
-)
+// Serial is the USB device
+var Serial = USB
 
 // I2C pins (unused)
 const (
diff --git a/src/machine/board_nrf52840-mdk.go b/src/machine/board_nrf52840-mdk.go
index 19c6cbfd..d9dc4130 100644
--- a/src/machine/board_nrf52840-mdk.go
+++ b/src/machine/board_nrf52840-mdk.go
@@ -18,10 +18,8 @@ const (
 	UART_RX_PIN Pin = 19
 )
 
-// UART0 is the USB device
-var (
-	UART0 = USB
-)
+// Serial is the USB device
+var Serial = USB
 
 // I2C pins (unused)
 const (
diff --git a/src/machine/board_nucleof103rb.go b/src/machine/board_nucleof103rb.go
index 0efdd5d8..89ce8449 100644
--- a/src/machine/board_nucleof103rb.go
+++ b/src/machine/board_nucleof103rb.go
@@ -99,17 +99,16 @@ const (
 var (
 	// USART2 is the hardware serial port connected to the onboard ST-LINK
 	// debugger to be exposed as virtual COM port over USB on Nucleo boards.
-	// Both UART0 and UART1 refer to USART2.
-	UART0  = &_UART0
-	_UART0 = UART{
+	UART2  = &_UART2
+	_UART2 = UART{
 		Buffer: NewRingBuffer(),
 		Bus:    stm32.USART2,
 	}
-	UART2 = UART0
+	Serial = UART2
 )
 
 func init() {
-	UART0.Interrupt = interrupt.New(stm32.IRQ_USART2, _UART0.handleInterrupt)
+	UART2.Interrupt = interrupt.New(stm32.IRQ_USART2, _UART2.handleInterrupt)
 }
 
 // SPI pins
diff --git a/src/machine/board_nucleof722ze.go b/src/machine/board_nucleof722ze.go
index 4c1a2cd2..003e8fc7 100644
--- a/src/machine/board_nucleof722ze.go
+++ b/src/machine/board_nucleof722ze.go
@@ -31,19 +31,18 @@ const (
 var (
 	// USART3 is the hardware serial port connected to the onboard ST-LINK
 	// debugger to be exposed as virtual COM port over USB on Nucleo boards.
-	// Both UART0 and UART1 refer to USART2.
-	UART0  = &_UART0
-	_UART0 = UART{
+	UART1  = &_UART1
+	_UART1 = UART{
 		Buffer:            NewRingBuffer(),
 		Bus:               stm32.USART3,
 		TxAltFuncSelector: UART_ALT_FN,
 		RxAltFuncSelector: UART_ALT_FN,
 	}
-	UART1 = UART0
+	Serial = UART1
 )
 
 func init() {
-	UART0.Interrupt = interrupt.New(stm32.IRQ_USART3, _UART0.handleInterrupt)
+	UART1.Interrupt = interrupt.New(stm32.IRQ_USART3, _UART1.handleInterrupt)
 }
 
 // SPI pins
diff --git a/src/machine/board_nucleol031k6.go b/src/machine/board_nucleol031k6.go
index dc80b50d..695dd8b0 100644
--- a/src/machine/board_nucleol031k6.go
+++ b/src/machine/board_nucleol031k6.go
@@ -63,15 +63,14 @@ const (
 var (
 	// USART2 is the hardware serial port connected to the onboard ST-LINK
 	// debugger to be exposed as virtual COM port over USB on Nucleo boards.
-	// Both UART0 and UART1 refer to USART2.
-	UART0  = &_UART0
-	_UART0 = UART{
+	UART1  = &_UART1
+	_UART1 = UART{
 		Buffer:            NewRingBuffer(),
 		Bus:               stm32.USART2,
 		TxAltFuncSelector: 4,
 		RxAltFuncSelector: 4,
 	}
-	UART1 = UART0
+	Serial = UART1
 
 	// I2C1 is documented, alias to I2C0 as well
 	I2C1 = &I2C{
@@ -89,5 +88,5 @@ var (
 )
 
 func init() {
-	UART0.Interrupt = interrupt.New(stm32.IRQ_USART2, _UART0.handleInterrupt)
+	UART1.Interrupt = interrupt.New(stm32.IRQ_USART2, _UART1.handleInterrupt)
 }
diff --git a/src/machine/board_nucleol432kc.go b/src/machine/board_nucleol432kc.go
index bb5133d2..8f32c46a 100644
--- a/src/machine/board_nucleol432kc.go
+++ b/src/machine/board_nucleol432kc.go
@@ -65,15 +65,14 @@ const (
 var (
 	// USART2 is the hardware serial port connected to the onboard ST-LINK
 	// debugger to be exposed as virtual COM port over USB on Nucleo boards.
-	// Both UART0 and UART1 refer to USART2.
-	UART0  = &_UART0
-	_UART0 = UART{
+	UART1  = &_UART1
+	_UART1 = UART{
 		Buffer:            NewRingBuffer(),
 		Bus:               stm32.USART2,
 		TxAltFuncSelector: 7,
 		RxAltFuncSelector: 3,
 	}
-	UART1 = UART0
+	Serial = UART1
 
 	// I2C1 is documented, alias to I2C0 as well
 	I2C1 = &I2C{
@@ -91,5 +90,5 @@ var (
 )
 
 func init() {
-	UART0.Interrupt = interrupt.New(stm32.IRQ_USART2, _UART0.handleInterrupt)
+	UART1.Interrupt = interrupt.New(stm32.IRQ_USART2, _UART1.handleInterrupt)
 }
diff --git a/src/machine/board_nucleol552ze.go b/src/machine/board_nucleol552ze.go
index a20285c4..98e2d5c1 100644
--- a/src/machine/board_nucleol552ze.go
+++ b/src/machine/board_nucleol552ze.go
@@ -31,15 +31,14 @@ const (
 var (
 	// LPUART1 is the hardware serial port connected to the onboard ST-LINK
 	// debugger to be exposed as virtual COM port over USB on Nucleo boards.
-	// Both UART0 and UART1 refer to LPUART1.
-	UART0  = &_UART0
-	_UART0 = UART{
+	UART1  = &_UART1
+	_UART1 = UART{
 		Buffer:            NewRingBuffer(),
 		Bus:               stm32.LPUART1,
 		TxAltFuncSelector: UART_ALT_FN,
 		RxAltFuncSelector: UART_ALT_FN,
 	}
-	UART1 = UART0
+	Serial = UART1
 )
 
 const (
@@ -57,5 +56,5 @@ var (
 )
 
 func init() {
-	UART0.Interrupt = interrupt.New(stm32.IRQ_LPUART1, _UART0.handleInterrupt)
+	UART1.Interrupt = interrupt.New(stm32.IRQ_LPUART1, _UART1.handleInterrupt)
 }
diff --git a/src/machine/board_p1am-100.go b/src/machine/board_p1am-100.go
index 1f492fe5..46964e4e 100644
--- a/src/machine/board_p1am-100.go
+++ b/src/machine/board_p1am-100.go
@@ -66,7 +66,7 @@ const (
 	BASE_ENABLE_PIN       Pin = PB09
 )
 
-// UART0 aka USBCDC pins
+// USBCDC pins
 const (
 	USBCDC_DM_PIN          Pin = PA24
 	USBCDC_DP_PIN          Pin = PA25
diff --git a/src/machine/board_particle_argon.go b/src/machine/board_particle_argon.go
index 5401c4ad..1130eaf8 100644
--- a/src/machine/board_particle_argon.go
+++ b/src/machine/board_particle_argon.go
@@ -41,8 +41,7 @@ const (
 
 // UART
 var (
-	Serial = USB
-	UART0  = NRF_UART0
+	Serial = UART0
 )
 
 const (
diff --git a/src/machine/board_particle_boron.go b/src/machine/board_particle_boron.go
index cb05e725..6c2f70a8 100644
--- a/src/machine/board_particle_boron.go
+++ b/src/machine/board_particle_boron.go
@@ -41,8 +41,7 @@ const (
 
 // UART
 var (
-	Serial = USB
-	UART0  = NRF_UART0
+	Serial = UART0
 )
 
 const (
diff --git a/src/machine/board_particle_xenon.go b/src/machine/board_particle_xenon.go
index c1614636..a6e48ae0 100644
--- a/src/machine/board_particle_xenon.go
+++ b/src/machine/board_particle_xenon.go
@@ -41,8 +41,7 @@ const (
 
 // UART
 var (
-	Serial = USB
-	UART0  = NRF_UART0
+	Serial = UART0
 )
 
 const (
diff --git a/src/machine/board_pca10031.go b/src/machine/board_pca10031.go
index a4798814..fbddfb23 100644
--- a/src/machine/board_pca10031.go
+++ b/src/machine/board_pca10031.go
@@ -19,6 +19,8 @@ const (
 	LED_BLUE  Pin = 23
 )
 
+var Serial = UART0
+
 // UART pins
 const (
 	UART_TX_PIN Pin = 9
diff --git a/src/machine/board_pca10040.go b/src/machine/board_pca10040.go
index 8d73e655..10e2ab2e 100644
--- a/src/machine/board_pca10040.go
+++ b/src/machine/board_pca10040.go
@@ -23,6 +23,8 @@ const (
 	BUTTON4 Pin = 16
 )
 
+var Serial = UART0
+
 // UART pins for NRF52840-DK
 const (
 	UART_TX_PIN Pin = 6
diff --git a/src/machine/board_pca10056.go b/src/machine/board_pca10056.go
index 5a9bcd5f..824bd3f0 100644
--- a/src/machine/board_pca10056.go
+++ b/src/machine/board_pca10056.go
@@ -22,6 +22,8 @@ const (
 	BUTTON4 Pin = 25
 )
 
+var Serial = UART0
+
 // UART pins
 const (
 	UART_TX_PIN Pin = 6
diff --git a/src/machine/board_pca10056_baremetal.go b/src/machine/board_pca10056_baremetal.go
deleted file mode 100644
index 75fcdee0..00000000
--- a/src/machine/board_pca10056_baremetal.go
+++ /dev/null
@@ -1,8 +0,0 @@
-// +build nrf52840,pca10056
-
-package machine
-
-// UART0 is the NRF UART
-var (
-	UART0 = NRF_UART0
-)
diff --git a/src/machine/board_pca10059.go b/src/machine/board_pca10059.go
index fd70cd3b..5079534a 100644
--- a/src/machine/board_pca10059.go
+++ b/src/machine/board_pca10059.go
@@ -34,9 +34,9 @@ const (
 	UART_RX_PIN Pin = NoPin
 )
 
-// UART0 is the USB device
+// Serial is the USB device
 var (
-	UART0 = USB
+	Serial = USB
 )
 
 // I2C pins (unused)
diff --git a/src/machine/board_pinetime-devkit0.go b/src/machine/board_pinetime-devkit0.go
index 3526769c..5222010b 100644
--- a/src/machine/board_pinetime-devkit0.go
+++ b/src/machine/board_pinetime-devkit0.go
@@ -17,6 +17,8 @@ const (
 	LED3 = LCD_BACKLIGHT_LOW
 )
 
+var Serial = UART0
+
 // UART pins for PineTime. Note that RX is set to NoPin as RXD is not listed in
 // the PineTime schematic 1.0:
 // http://files.pine64.org/doc/PineTime/PineTime%20Port%20Assignment%20rev1.0.pdf
diff --git a/src/machine/board_pybadge.go b/src/machine/board_pybadge.go
index 35e446b3..687d933b 100644
--- a/src/machine/board_pybadge.go
+++ b/src/machine/board_pybadge.go
@@ -66,7 +66,9 @@ const (
 	BUTTON_B_MASK      = 128
 )
 
-// UART0 aka USBCDC pins
+var Serial = USB
+
+// USBCDC pins
 const (
 	USBCDC_DM_PIN = PA24
 	USBCDC_DP_PIN = PA25
diff --git a/src/machine/board_pygamer.go b/src/machine/board_pygamer.go
index 7e5c08e7..e12eed9e 100644
--- a/src/machine/board_pygamer.go
+++ b/src/machine/board_pygamer.go
@@ -69,7 +69,9 @@ const (
 	BUTTON_B_MASK      = 128
 )
 
-// UART0 aka USBCDC pins
+var Serial = USB
+
+// USBCDC pins
 const (
 	USBCDC_DM_PIN = PA24
 	USBCDC_DP_PIN = PA25
diff --git a/src/machine/board_pyportal.go b/src/machine/board_pyportal.go
index ff3ad1a1..c2ffb386 100644
--- a/src/machine/board_pyportal.go
+++ b/src/machine/board_pyportal.go
@@ -94,7 +94,9 @@ const (
 	LED = D13
 )
 
-// UART0 aka USBCDC pins
+var Serial = USB
+
+// USBCDC pins
 const (
 	USBCDC_DM_PIN = PA24
 	USBCDC_DP_PIN = PA25
diff --git a/src/machine/board_qtpy.go b/src/machine/board_qtpy.go
index 883a32ba..23c7beca 100644
--- a/src/machine/board_qtpy.go
+++ b/src/machine/board_qtpy.go
@@ -45,7 +45,7 @@ const (
 	LED = D13
 )
 
-// UART0 aka USBCDC pins
+// USBCDC pins
 const (
 	USBCDC_DM_PIN = PA24
 	USBCDC_DP_PIN = PA25
diff --git a/src/machine/board_reelboard.go b/src/machine/board_reelboard.go
index 400ad421..70eb7053 100644
--- a/src/machine/board_reelboard.go
+++ b/src/machine/board_reelboard.go
@@ -29,6 +29,8 @@ const (
 	BUTTON Pin = 7
 )
 
+var Serial = UART0
+
 // UART pins
 const (
 	UART_TX_PIN Pin = 6
diff --git a/src/machine/board_reelboard_baremetal.go b/src/machine/board_reelboard_baremetal.go
deleted file mode 100644
index 3ae65074..00000000
--- a/src/machine/board_reelboard_baremetal.go
+++ /dev/null
@@ -1,8 +0,0 @@
-// +build nrf52840,reelboard
-
-package machine
-
-// UART0 is the NRF UART
-var (
-	UART0 = NRF_UART0
-)
diff --git a/src/machine/board_stm32f4disco.go b/src/machine/board_stm32f4disco.go
index 8c3976ab..7a061607 100644
--- a/src/machine/board_stm32f4disco.go
+++ b/src/machine/board_stm32f4disco.go
@@ -27,19 +27,19 @@ const (
 )
 
 var (
-	UART0  = &_UART0
-	_UART0 = UART{
+	UART1  = &_UART1
+	_UART1 = UART{
 		Buffer:            NewRingBuffer(),
 		Bus:               stm32.USART2,
 		TxAltFuncSelector: AF7_USART1_2_3,
 		RxAltFuncSelector: AF7_USART1_2_3,
 	}
-	UART1 = UART0
+	Serial = UART1
 )
 
 // set up RX IRQ handler. Follow similar pattern for other UARTx instances
 func init() {
-	UART0.Interrupt = interrupt.New(stm32.IRQ_USART2, _UART0.handleInterrupt)
+	UART1.Interrupt = interrupt.New(stm32.IRQ_USART2, _UART1.handleInterrupt)
 }
 
 // SPI pins
diff --git a/src/machine/board_teensy40.go b/src/machine/board_teensy40.go
index 7f0781f0..54ae4e6b 100644
--- a/src/machine/board_teensy40.go
+++ b/src/machine/board_teensy40.go
@@ -136,7 +136,7 @@ const (
 )
 
 var (
-	UART0  = UART1 // alias UART0 to UART1
+	Serial = UART1
 	UART1  = &_UART1
 	_UART1 = UART{
 		Bus:      nxp.LPUART6,
diff --git a/src/machine/board_trinket.go b/src/machine/board_trinket.go
index 6305cb70..068fa0d7 100644
--- a/src/machine/board_trinket.go
+++ b/src/machine/board_trinket.go
@@ -33,7 +33,7 @@ const (
 	LED = D13
 )
 
-// UART0 aka USBCDC pins
+// USBCDC pins
 const (
 	USBCDC_DM_PIN = PA24
 	USBCDC_DP_PIN = PA25
diff --git a/src/machine/board_wioterminal.go b/src/machine/board_wioterminal.go
index 7fde5c72..abbe5550 100644
--- a/src/machine/board_wioterminal.go
+++ b/src/machine/board_wioterminal.go
@@ -325,7 +325,9 @@ const (
 	OUTPUT_CTR_3V3 = PC15
 )
 
-// UART0 aka USBCDC pins
+var Serial = USB
+
+// USBCDC pins
 const (
 	USBCDC_DM_PIN = PIN_USB_DM
 	USBCDC_DP_PIN = PIN_USB_DP
diff --git a/src/machine/board_x9pro.go b/src/machine/board_x9pro.go
index d615b598..63d7257a 100644
--- a/src/machine/board_x9pro.go
+++ b/src/machine/board_x9pro.go
@@ -26,3 +26,5 @@ const (
 )
 
 const HasLowFrequencyCrystal = true
+
+var Serial = UART0
diff --git a/src/machine/board_xiao.go b/src/machine/board_xiao.go
index b18a44e3..ac5ffbda 100644
--- a/src/machine/board_xiao.go
+++ b/src/machine/board_xiao.go
@@ -48,7 +48,7 @@ const (
 	LED3    = LED_TXL
 )
 
-// UART0 aka USBCDC pins
+// USBCDC pins
 const (
 	USBCDC_DM_PIN = PA24
 	USBCDC_DP_PIN = PA25
diff --git a/src/machine/machine_atmega.go b/src/machine/machine_atmega.go
index 6d9a5eda..fe6536e7 100644
--- a/src/machine/machine_atmega.go
+++ b/src/machine/machine_atmega.go
@@ -121,6 +121,9 @@ func (i2c *I2C) readByte() byte {
 	return byte(avr.TWDR.Get())
 }
 
+// Always use UART0 as the serial output.
+var Serial = UART0
+
 // UART
 var (
 	// UART0 is the hardware serial port on the AVR.
diff --git a/src/machine/machine_atsamd21.go b/src/machine/machine_atsamd21.go
index a9a02437..97704584 100644
--- a/src/machine/machine_atsamd21.go
+++ b/src/machine/machine_atsamd21.go
@@ -505,8 +505,7 @@ type UART struct {
 }
 
 var (
-	// UART0 is actually a USB CDC interface.
-	UART0 = &USBCDC{Buffer: NewRingBuffer()}
+	USB = &USBCDC{Buffer: NewRingBuffer()}
 )
 
 const (
@@ -1985,7 +1984,7 @@ func handleUSB(intr interrupt.Interrupt) {
 
 	// Start of frame
 	if (flags & sam.USB_DEVICE_INTFLAG_SOF) > 0 {
-		UART0.Flush()
+		USB.Flush()
 		// if you want to blink LED showing traffic, this would be the place...
 	}
 
@@ -2045,7 +2044,7 @@ func handleUSB(intr interrupt.Interrupt) {
 				setEPINTFLAG(i, sam.USB_DEVICE_EPINTFLAG_TRCPT1)
 
 				if i == usb_CDC_ENDPOINT_IN {
-					UART0.waitTxc = false
+					USB.waitTxc = false
 				}
 			}
 		}
@@ -2359,7 +2358,7 @@ func handleEndpoint(ep uint32) {
 
 	// move to ring buffer
 	for i := 0; i < count; i++ {
-		UART0.Receive(byte((udd_ep_out_cache_buffer[ep][i] & 0xFF)))
+		USB.Receive(byte((udd_ep_out_cache_buffer[ep][i] & 0xFF)))
 	}
 
 	// set byte count to zero
diff --git a/src/machine/machine_atsamd51.go b/src/machine/machine_atsamd51.go
index 4b633389..2e7a6700 100644
--- a/src/machine/machine_atsamd51.go
+++ b/src/machine/machine_atsamd51.go
@@ -951,8 +951,8 @@ type UART struct {
 }
 
 var (
-	// UART0 is actually a USB CDC interface.
-	UART0 = &USBCDC{Buffer: NewRingBuffer()}
+	// USB is a USB CDC interface.
+	USB = &USBCDC{Buffer: NewRingBuffer()}
 )
 
 const (
@@ -2193,7 +2193,7 @@ func handleUSBIRQ(interrupt.Interrupt) {
 
 	// Start of frame
 	if (flags & sam.USB_DEVICE_INTFLAG_SOF) > 0 {
-		UART0.Flush()
+		USB.Flush()
 		// if you want to blink LED showing traffic, this would be the place...
 	}
 
@@ -2253,7 +2253,7 @@ func handleUSBIRQ(interrupt.Interrupt) {
 				setEPINTFLAG(i, sam.USB_DEVICE_ENDPOINT_EPINTFLAG_TRCPT1)
 
 				if i == usb_CDC_ENDPOINT_IN {
-					UART0.waitTxc = false
+					USB.waitTxc = false
 				}
 			}
 		}
@@ -2567,7 +2567,7 @@ func handleEndpoint(ep uint32) {
 
 	// move to ring buffer
 	for i := 0; i < count; i++ {
-		UART0.Receive(byte((udd_ep_out_cache_buffer[ep][i] & 0xFF)))
+		USB.Receive(byte((udd_ep_out_cache_buffer[ep][i] & 0xFF)))
 	}
 
 	// set byte count to zero
diff --git a/src/machine/machine_generic.go b/src/machine/machine_generic.go
index 697af241..98dca2df 100644
--- a/src/machine/machine_generic.go
+++ b/src/machine/machine_generic.go
@@ -8,6 +8,7 @@ var (
 	SPI0  = SPI{0}
 	I2C0  = &I2C{0}
 	UART0 = &UART{0}
+	USB   = &UART{100}
 )
 
 const (
diff --git a/src/machine/machine_nrf.go b/src/machine/machine_nrf.go
index ee883ccc..7af22000 100644
--- a/src/machine/machine_nrf.go
+++ b/src/machine/machine_nrf.go
@@ -138,8 +138,8 @@ type UART struct {
 // UART
 var (
 	// UART0 is the hardware UART on the NRF SoC.
-	_NRF_UART0 = UART{Buffer: NewRingBuffer()}
-	NRF_UART0  = &_NRF_UART0
+	_UART0 = UART{Buffer: NewRingBuffer()}
+	UART0  = &_UART0
 )
 
 // Configure the UART.
@@ -165,7 +165,7 @@ func (uart *UART) Configure(config UARTConfig) {
 	nrf.UART0.INTENSET.Set(nrf.UART_INTENSET_RXDRDY_Msk)
 
 	// Enable RX IRQ.
-	intr := interrupt.New(nrf.IRQ_UART0, _NRF_UART0.handleInterrupt)
+	intr := interrupt.New(nrf.IRQ_UART0, _UART0.handleInterrupt)
 	intr.SetPriority(0xc0) // low priority
 	intr.Enable()
 }
diff --git a/src/machine/machine_nrf51.go b/src/machine/machine_nrf51.go
index 4615a549..d60dc5f1 100644
--- a/src/machine/machine_nrf51.go
+++ b/src/machine/machine_nrf51.go
@@ -6,10 +6,6 @@ import (
 	"device/nrf"
 )
 
-var (
-	UART0 = NRF_UART0
-)
-
 func CPUFrequency() uint32 {
 	return 16000000
 }
diff --git a/src/machine/machine_nrf52.go b/src/machine/machine_nrf52.go
index 44120028..45e48159 100644
--- a/src/machine/machine_nrf52.go
+++ b/src/machine/machine_nrf52.go
@@ -42,10 +42,6 @@ const (
 	P0_31 Pin = 31
 )
 
-var (
-	UART0 = NRF_UART0
-)
-
 // Get peripheral and pin number for this GPIO pin.
 func (p Pin) getPortPin() (*nrf.GPIO_Type, uint32) {
 	return nrf.P0, uint32(p)
diff --git a/src/machine/machine_nrf52833.go b/src/machine/machine_nrf52833.go
index 1920b4e6..73f86f15 100644
--- a/src/machine/machine_nrf52833.go
+++ b/src/machine/machine_nrf52833.go
@@ -58,10 +58,6 @@ const (
 	P1_15 Pin = 47
 )
 
-var (
-	UART0 = NRF_UART0
-)
-
 // Get peripheral and pin number for this GPIO pin.
 func (p Pin) getPortPin() (*nrf.GPIO_Type, uint32) {
 	if p >= 32 {
diff --git a/src/runtime/runtime_atmega.go b/src/runtime/runtime_atmega.go
index 6d02e071..3c3d57bc 100644
--- a/src/runtime/runtime_atmega.go
+++ b/src/runtime/runtime_atmega.go
@@ -8,11 +8,11 @@ import (
 )
 
 func initUART() {
-	machine.UART0.Configure(machine.UARTConfig{})
+	machine.Serial.Configure(machine.UARTConfig{})
 }
 
 func putchar(c byte) {
-	machine.UART0.WriteByte(c)
+	machine.Serial.WriteByte(c)
 }
 
 // Sleep for a given period. The period is defined by the WDT peripheral, and is
diff --git a/src/runtime/runtime_atsamd21.go b/src/runtime/runtime_atsamd21.go
index 117f5a6d..5ae58121 100644
--- a/src/runtime/runtime_atsamd21.go
+++ b/src/runtime/runtime_atsamd21.go
@@ -30,11 +30,11 @@ func init() {
 	initADCClock()
 
 	// connect to USB CDC interface
-	machine.UART0.Configure(machine.UARTConfig{})
+	machine.Serial.Configure(machine.UARTConfig{})
 }
 
 func putchar(c byte) {
-	machine.UART0.WriteByte(c)
+	machine.Serial.WriteByte(c)
 }
 
 func initClocks() {
diff --git a/src/runtime/runtime_atsamd51.go b/src/runtime/runtime_atsamd51.go
index f59c82f2..54034445 100644
--- a/src/runtime/runtime_atsamd51.go
+++ b/src/runtime/runtime_atsamd51.go
@@ -30,11 +30,11 @@ func init() {
 	initADCClock()
 
 	// connect to USB CDC interface
-	machine.UART0.Configure(machine.UARTConfig{})
+	machine.Serial.Configure(machine.UARTConfig{})
 }
 
 func putchar(c byte) {
-	machine.UART0.WriteByte(c)
+	machine.Serial.WriteByte(c)
 }
 
 func initClocks() {
diff --git a/src/runtime/runtime_esp32.go b/src/runtime/runtime_esp32.go
index ca7d7c14..2fdeab90 100644
--- a/src/runtime/runtime_esp32.go
+++ b/src/runtime/runtime_esp32.go
@@ -14,7 +14,7 @@ type timeUnit int64
 var currentTime timeUnit
 
 func putchar(c byte) {
-	machine.UART0.WriteByte(c)
+	machine.Serial.WriteByte(c)
 }
 
 func postinit() {}
@@ -53,7 +53,7 @@ func main() {
 	preinit()
 
 	// Initialize UART.
-	machine.UART0.Configure(machine.UARTConfig{})
+	machine.Serial.Configure(machine.UARTConfig{})
 
 	// Configure timer 0 in timer group 0, for timekeeping.
 	//   EN:       Enable the timer.
diff --git a/src/runtime/runtime_esp8266.go b/src/runtime/runtime_esp8266.go
index 28af3c55..290d51c7 100644
--- a/src/runtime/runtime_esp8266.go
+++ b/src/runtime/runtime_esp8266.go
@@ -14,7 +14,7 @@ type timeUnit int64
 var currentTime timeUnit = 0
 
 func putchar(c byte) {
-	machine.UART0.WriteByte(c)
+	machine.Serial.WriteByte(c)
 }
 
 // Write to the internal control bus (using I2C?).
@@ -37,7 +37,7 @@ func main() {
 	rom_i2c_writeReg(103, 4, 2, 145)
 
 	// Initialize UART.
-	machine.UART0.Configure(machine.UARTConfig{})
+	machine.Serial.Configure(machine.UARTConfig{})
 
 	// Initialize timer. Bits:
 	//  ENABLE:   timer enable
diff --git a/src/runtime/runtime_fe310.go b/src/runtime/runtime_fe310.go
index d2e0d91e..fbc97199 100644
--- a/src/runtime/runtime_fe310.go
+++ b/src/runtime/runtime_fe310.go
@@ -93,11 +93,11 @@ func initPeripherals() {
 	sifive.RTC.RTCCFG.Set(sifive.RTC_RTCCFG_ENALWAYS)
 
 	// Configure the UART.
-	machine.UART0.Configure(machine.UARTConfig{})
+	machine.Serial.Configure(machine.UARTConfig{})
 }
 
 func putchar(c byte) {
-	machine.UART0.WriteByte(c)
+	machine.Serial.WriteByte(c)
 }
 
 var timerWakeup volatile.Register8
diff --git a/src/runtime/runtime_k210.go b/src/runtime/runtime_k210.go
index 93236181..8648f11c 100644
--- a/src/runtime/runtime_k210.go
+++ b/src/runtime/runtime_k210.go
@@ -105,11 +105,11 @@ func initPeripherals() {
 	// Enable FPIOA peripheral.
 	kendryte.SYSCTL.CLK_EN_PERI.SetBits(kendryte.SYSCTL_CLK_EN_PERI_FPIOA_CLK_EN)
 
-	machine.UART0.Configure(machine.UARTConfig{})
+	machine.Serial.Configure(machine.UARTConfig{})
 }
 
 func putchar(c byte) {
-	machine.UART0.WriteByte(c)
+	machine.Serial.WriteByte(c)
 }
 
 var timerWakeup volatile.Register8
diff --git a/src/runtime/runtime_nrf.go b/src/runtime/runtime_nrf.go
index 2e7765b6..60d20bdf 100644
--- a/src/runtime/runtime_nrf.go
+++ b/src/runtime/runtime_nrf.go
@@ -29,7 +29,7 @@ func main() {
 }
 
 func init() {
-	machine.UART0.Configure(machine.UARTConfig{})
+	machine.Serial.Configure(machine.UARTConfig{})
 	initLFCLK()
 	initRTC()
 }
@@ -64,7 +64,7 @@ func initRTC() {
 }
 
 func putchar(c byte) {
-	machine.UART0.WriteByte(c)
+	machine.Serial.WriteByte(c)
 }
 
 func sleepTicks(d timeUnit) {
diff --git a/src/runtime/runtime_stm32f103.go b/src/runtime/runtime_stm32f103.go
index 50d2b968..9af5cea1 100644
--- a/src/runtime/runtime_stm32f103.go
+++ b/src/runtime/runtime_stm32f103.go
@@ -33,7 +33,7 @@ func init() {
 		Device:         stm32.TIM3,
 	})
 
-	machine.UART0.Configure(machine.UARTConfig{})
+	machine.Serial.Configure(machine.UARTConfig{})
 
 	initTickTimer(&timerInfo{
 		EnableRegister: &stm32.RCC.APB1ENR,
@@ -43,7 +43,7 @@ func init() {
 }
 
 func putchar(c byte) {
-	machine.UART0.WriteByte(c)
+	machine.Serial.WriteByte(c)
 }
 
 // initCLK sets clock to 72MHz using HSE 8MHz crystal w/ PLL X 9 (8MHz x 9 = 72MHz).
diff --git a/src/runtime/runtime_stm32f405.go b/src/runtime/runtime_stm32f405.go
index 799e4eac..7944fe12 100644
--- a/src/runtime/runtime_stm32f405.go
+++ b/src/runtime/runtime_stm32f405.go
@@ -181,10 +181,10 @@ func initCLK() {
 
 func initCOM() {
 	if machine.NUM_UART_INTERFACES > 0 {
-		machine.UART0.Configure(machine.UARTConfig{})
+		machine.Serial.Configure(machine.UARTConfig{})
 	}
 }
 
 func putchar(c byte) {
-	machine.UART0.WriteByte(c)
+	machine.Serial.WriteByte(c)
 }
diff --git a/src/runtime/runtime_stm32f407.go b/src/runtime/runtime_stm32f407.go
index a1af7bbf..17a79eb7 100644
--- a/src/runtime/runtime_stm32f407.go
+++ b/src/runtime/runtime_stm32f407.go
@@ -51,7 +51,7 @@ func init() {
 		Device:         stm32.TIM3,
 	})
 
-	machine.UART0.Configure(machine.UARTConfig{})
+	machine.Serial.Configure(machine.UARTConfig{})
 
 	initTickTimer(&timerInfo{
 		EnableRegister: &stm32.RCC.APB1ENR,
@@ -61,7 +61,7 @@ func init() {
 }
 
 func putchar(c byte) {
-	machine.UART0.WriteByte(c)
+	machine.Serial.WriteByte(c)
 }
 
 func initCLK() {
diff --git a/src/runtime/runtime_stm32f7x2.go b/src/runtime/runtime_stm32f7x2.go
index 034986b3..9e76694f 100644
--- a/src/runtime/runtime_stm32f7x2.go
+++ b/src/runtime/runtime_stm32f7x2.go
@@ -50,7 +50,7 @@ func init() {
 		Device:         stm32.TIM3,
 	})
 
-	machine.UART0.Configure(machine.UARTConfig{})
+	machine.Serial.Configure(machine.UARTConfig{})
 
 	initTickTimer(&timerInfo{
 		EnableRegister: &stm32.RCC.APB1ENR,
@@ -60,7 +60,7 @@ func init() {
 }
 
 func putchar(c byte) {
-	machine.UART0.WriteByte(c)
+	machine.Serial.WriteByte(c)
 }
 
 func initCLK() {
diff --git a/src/runtime/runtime_stm32l0.go b/src/runtime/runtime_stm32l0.go
index be61749e..ef1be16d 100644
--- a/src/runtime/runtime_stm32l0.go
+++ b/src/runtime/runtime_stm32l0.go
@@ -14,7 +14,7 @@ const (
 type arrtype = uint16
 
 func putchar(c byte) {
-	machine.UART0.WriteByte(c)
+	machine.Serial.WriteByte(c)
 }
 
 func initCLK() {
diff --git a/src/runtime/runtime_stm32l0x1.go b/src/runtime/runtime_stm32l0x1.go
index 1d48388e..264efaf0 100644
--- a/src/runtime/runtime_stm32l0x1.go
+++ b/src/runtime/runtime_stm32l0x1.go
@@ -34,7 +34,7 @@ func init() {
 		Device:         stm32.TIM22,
 	})
 
-	machine.UART0.Configure(machine.UARTConfig{})
+	machine.Serial.Configure(machine.UARTConfig{})
 
 	initTickTimer(&timerInfo{
 		EnableRegister: &stm32.RCC.APB2ENR,
diff --git a/src/runtime/runtime_stm32l0x2.go b/src/runtime/runtime_stm32l0x2.go
index 6eccf0eb..2412d7e5 100644
--- a/src/runtime/runtime_stm32l0x2.go
+++ b/src/runtime/runtime_stm32l0x2.go
@@ -34,7 +34,7 @@ func init() {
 		Device:         stm32.TIM3,
 	})
 
-	machine.UART0.Configure(machine.UARTConfig{})
+	machine.Serial.Configure(machine.UARTConfig{})
 
 	initTickTimer(&timerInfo{
 		EnableRegister: &stm32.RCC.APB1ENR,
diff --git a/src/runtime/runtime_stm32l4x2.go b/src/runtime/runtime_stm32l4x2.go
index 9aad880c..7bdf39bf 100644
--- a/src/runtime/runtime_stm32l4x2.go
+++ b/src/runtime/runtime_stm32l4x2.go
@@ -75,7 +75,7 @@ func init() {
 		Device:         stm32.TIM15,
 	})
 
-	machine.UART0.Configure(machine.UARTConfig{})
+	machine.Serial.Configure(machine.UARTConfig{})
 
 	initTickTimer(&timerInfo{
 		EnableRegister: &stm32.RCC.APB2ENR,
@@ -85,7 +85,7 @@ func init() {
 }
 
 func putchar(c byte) {
-	machine.UART0.WriteByte(c)
+	machine.Serial.WriteByte(c)
 }
 
 func initCLK() {
diff --git a/src/runtime/runtime_stm32l5x2.go b/src/runtime/runtime_stm32l5x2.go
index 1ecc662b..e4445080 100644
--- a/src/runtime/runtime_stm32l5x2.go
+++ b/src/runtime/runtime_stm32l5x2.go
@@ -51,7 +51,7 @@ func init() {
 		Device:         stm32.TIM15,
 	})
 
-	machine.UART0.Configure(machine.UARTConfig{})
+	machine.Serial.Configure(machine.UARTConfig{})
 
 	initTickTimer(&timerInfo{
 		EnableRegister: &stm32.RCC.APB2ENR,
@@ -61,7 +61,7 @@ func init() {
 }
 
 func putchar(c byte) {
-	machine.UART0.WriteByte(c)
+	machine.Serial.WriteByte(c)
 }
 
 func initCLK() {