diff --git a/src/machine/board_arduino_nano33.go b/src/machine/board_arduino_nano33.go
index 475a1d1e..067098aa 100644
--- a/src/machine/board_arduino_nano33.go
+++ b/src/machine/board_arduino_nano33.go
@@ -1,4 +1,4 @@
-// +build sam,atsamd21,arduino_nano33
+// +build arduino_nano33
 
 // This contains the pin mappings for the Arduino Nano33 IoT board.
 //
@@ -6,8 +6,6 @@
 //
 package machine
 
-import "device/sam"
-
 // used to reset into bootloader
 const RESET_MAGIC_VALUE = 0x07738135
 
@@ -54,56 +52,18 @@ const (
 	USBCDC_DP_PIN Pin = PA25
 )
 
-// UART1 on the Arduino Nano 33 connects to the onboard NINA-W102 WiFi chip.
-var (
-	UART1 = UART{
-		Buffer: NewRingBuffer(),
-		Bus:    sam.SERCOM5_USART,
-		SERCOM: 5,
-	}
-)
-
 // UART1 pins
 const (
 	UART_TX_PIN Pin = PA22
 	UART_RX_PIN Pin = PA23
 )
 
-//go:export SERCOM5_IRQHandler
-func handleUART1() {
-	defaultUART1Handler()
-}
-
-// UART2 on the Arduino Nano 33 connects to the normal TX/RX pins.
-var (
-	UART2 = UART{
-		Buffer: NewRingBuffer(),
-		Bus:    sam.SERCOM3_USART,
-		SERCOM: 3,
-	}
-)
-
-//go:export SERCOM3_IRQHandler
-func handleUART2() {
-	// should reset IRQ
-	UART2.Receive(byte((UART2.Bus.DATA.Get() & 0xFF)))
-	UART2.Bus.INTFLAG.SetBits(sam.SERCOM_USART_INTFLAG_RXC)
-}
-
 // I2C pins
 const (
 	SDA_PIN Pin = A4 // SDA: SERCOM4/PAD[1]
 	SCL_PIN Pin = A5 // SCL: SERCOM4/PAD[1]
 )
 
-// I2C on the Arduino Nano 33.
-var (
-	I2C0 = I2C{
-		Bus:    sam.SERCOM4_I2CM,
-		SERCOM: 4,
-	}
-)
-
 // SPI pins
 const (
 	SPI0_SCK_PIN  Pin = A2 // SCK: SERCOM0/PAD[3]
@@ -111,14 +71,6 @@ const (
 	SPI0_MISO_PIN Pin = A6 // MISO: SERCOM0/PAD[1]
 )
 
-// SPI on the Arduino Nano 33.
-var (
-	SPI0 = SPI{
-		Bus:    sam.SERCOM0_SPI,
-		SERCOM: 0,
-	}
-)
-
 // NINA-W102 Pins
 const (
 	NINA_MOSI   Pin = PA12
@@ -132,23 +84,9 @@ const (
 	NINA_RX     Pin = PA23
 )
 
-// SPI1 is connected to the NINA-W102 chip on the Arduino Nano 33.
-var (
-	SPI1 = SPI{
-		Bus:    sam.SERCOM2_SPI,
-		SERCOM: 2,
-	}
-	NINA_SPI = SPI1
-)
-
 // I2S pins
 const (
 	I2S_SCK_PIN Pin = PA10
 	I2S_SD_PIN  Pin = PA08
 	I2S_WS_PIN      = NoPin // TODO: figure out what this is on Arduino Nano 33.
 )
-
-// I2S on the Arduino Nano 33.
-var (
-	I2S0 = I2S{Bus: sam.I2S}
-)
diff --git a/src/machine/board_arduino_nano33_baremetal.go b/src/machine/board_arduino_nano33_baremetal.go
new file mode 100644
index 00000000..cd1055e0
--- /dev/null
+++ b/src/machine/board_arduino_nano33_baremetal.go
@@ -0,0 +1,65 @@
+// +build sam,atsamd21,arduino_nano33
+
+package machine
+
+import "device/sam"
+
+// UART1 on the Arduino Nano 33 connects to the onboard NINA-W102 WiFi chip.
+var (
+	UART1 = UART{
+		Buffer: NewRingBuffer(),
+		Bus:    sam.SERCOM5_USART,
+		SERCOM: 5,
+	}
+)
+
+//go:export SERCOM5_IRQHandler
+func handleUART1() {
+	defaultUART1Handler()
+}
+
+// UART2 on the Arduino Nano 33 connects to the normal TX/RX pins.
+var (
+	UART2 = UART{
+		Buffer: NewRingBuffer(),
+		Bus:    sam.SERCOM3_USART,
+		SERCOM: 3,
+	}
+)
+
+//go:export SERCOM3_IRQHandler
+func handleUART2() {
+	// should reset IRQ
+	UART2.Receive(byte((UART2.Bus.DATA.Get() & 0xFF)))
+	UART2.Bus.INTFLAG.SetBits(sam.SERCOM_USART_INTFLAG_RXC)
+}
+
+// I2C on the Arduino Nano 33.
+var (
+	I2C0 = I2C{
+		Bus:    sam.SERCOM4_I2CM,
+		SERCOM: 4,
+	}
+)
+
+// SPI on the Arduino Nano 33.
+var (
+	SPI0 = SPI{
+		Bus:    sam.SERCOM0_SPI,
+		SERCOM: 0,
+	}
+)
+
+// SPI1 is connected to the NINA-W102 chip on the Arduino Nano 33.
+var (
+	SPI1 = SPI{
+		Bus:    sam.SERCOM2_SPI,
+		SERCOM: 2,
+	}
+	NINA_SPI = SPI1
+)
+
+// I2S on the Arduino Nano 33.
+var (
+	I2S0 = I2S{Bus: sam.I2S}
+)
diff --git a/src/machine/board_atsamd21.go b/src/machine/board_atsamd21.go
index 8c3a44df..5867cebd 100644
--- a/src/machine/board_atsamd21.go
+++ b/src/machine/board_atsamd21.go
@@ -1,4 +1,4 @@
-// +build sam,atsamd21 circuitplay_express
+// +build sam,atsamd21 arduino_nano33 circuitplay_express
 
 package machine