diff --git a/Makefile b/Makefile
index bacd9b5d..b027d9c0 100644
--- a/Makefile
+++ b/Makefile
@@ -182,7 +182,7 @@ tinygo-test:
 .PHONY: smoketest
 smoketest:
 	$(TINYGO) version
-	# test all examples
+	# test all examples (except pwm)
 	$(TINYGO) build -size short -o test.hex -target=pca10040            examples/blinky1
 	@$(MD5SUM) test.hex
 	$(TINYGO) build -size short -o test.hex -target=pca10040            examples/adc
@@ -203,8 +203,6 @@ smoketest:
 	@$(MD5SUM) test.hex
 	$(TINYGO) build -size short -o test.hex -target=microbit            examples/microbit-blink
 	@$(MD5SUM) test.hex
-	$(TINYGO) build -size short -o test.hex -target=pca10040            examples/pwm
-	@$(MD5SUM) test.hex
 	$(TINYGO) build -size short -o test.hex -target=pca10040            examples/serial
 	@$(MD5SUM) test.hex
 	$(TINYGO) build -size short -o test.hex -target=pca10040            examples/systick
@@ -296,6 +294,8 @@ ifneq ($(AVR), 0)
 	@$(MD5SUM) test.hex
 	$(TINYGO) build -size short -o test.hex -target=arduino             examples/blinky1
 	@$(MD5SUM) test.hex
+	$(TINYGO) build -size short -o test.hex -target=arduino             examples/pwm
+	@$(MD5SUM) test.hex
 	$(TINYGO) build -size short -o test.hex -target=arduino -scheduler=tasks  examples/blinky1
 	@$(MD5SUM) test.hex
 	$(TINYGO) build -size short -o test.hex -target=arduino-nano        examples/blinky1
diff --git a/src/examples/button/button.go b/src/examples/button/button.go
index 8c245cda..ad028ea0 100644
--- a/src/examples/button/button.go
+++ b/src/examples/button/button.go
@@ -5,11 +5,9 @@ import (
 	"time"
 )
 
-// This example assumes that the button is connected to pin 8. Change the value
-// below to use a different pin.
 const (
 	led    = machine.LED
-	button = machine.Pin(8)
+	button = machine.BUTTON
 )
 
 func main() {
diff --git a/src/examples/pwm/pwm.go b/src/examples/pwm/pwm.go
index 104934e5..96220ee5 100644
--- a/src/examples/pwm/pwm.go
+++ b/src/examples/pwm/pwm.go
@@ -8,9 +8,9 @@ import (
 // This example assumes that an RGB LED is connected to pins 3, 5 and 6 on an Arduino.
 // Change the values below to use different pins.
 const (
-	redPin   = 3
-	greenPin = 5
-	bluePin  = 6
+	redPin   = machine.D3
+	greenPin = machine.D5
+	bluePin  = machine.D6
 )
 
 // cycleColor is just a placeholder until math/rand or some equivalent is working.
diff --git a/src/machine/board_arduino.go b/src/machine/board_arduino.go
index 92f17dac..001ba9c7 100644
--- a/src/machine/board_arduino.go
+++ b/src/machine/board_arduino.go
@@ -7,21 +7,39 @@ func CPUFrequency() uint32 {
 	return 16000000
 }
 
+// Digital pins, marked as plain numbers on the board.
+const (
+	D0  = PD0 // RX
+	D1  = PD1 // TX
+	D2  = PD2
+	D3  = PD3
+	D4  = PD4
+	D5  = PD5
+	D6  = PD6
+	D7  = PD7
+	D8  = PB0
+	D9  = PB1
+	D10 = PB2
+	D11 = PB3
+	D12 = PB4
+	D13 = PB5
+)
+
 // LED on the Arduino
-const LED Pin = 13
+const LED Pin = D13
 
 // ADC on the Arduino
 const (
-	ADC0 Pin = 0
-	ADC1 Pin = 1
-	ADC2 Pin = 2
-	ADC3 Pin = 3
-	ADC4 Pin = 4 // Used by TWI for SDA
-	ADC5 Pin = 5 // Used by TWI for SCL
+	ADC0 Pin = PC0
+	ADC1 Pin = PC1
+	ADC2 Pin = PC2
+	ADC3 Pin = PC3
+	ADC4 Pin = PC4 // Used by TWI for SDA
+	ADC5 Pin = PC5 // Used by TWI for SCL
 )
 
 // UART pins
 const (
-	UART_TX_PIN Pin = 1
-	UART_RX_PIN Pin = 0
+	UART_TX_PIN Pin = PD1
+	UART_RX_PIN Pin = PD0
 )
diff --git a/src/machine/board_arduino_nano.go b/src/machine/board_arduino_nano.go
index 1e96c95f..d84b23f3 100644
--- a/src/machine/board_arduino_nano.go
+++ b/src/machine/board_arduino_nano.go
@@ -7,21 +7,39 @@ func CPUFrequency() uint32 {
 	return 16000000
 }
 
+// Digital pins.
+const (
+	D0  = PD0 // RX0
+	D1  = PD1 // TX1
+	D2  = PD2
+	D3  = PD3
+	D4  = PD4
+	D5  = PD5
+	D6  = PD6
+	D7  = PD7
+	D8  = PB0
+	D9  = PB1
+	D10 = PB2
+	D11 = PB3
+	D12 = PB4
+	D13 = PB5
+)
+
 // LED on the Arduino
-const LED Pin = 13
+const LED Pin = D13
 
 // ADC on the Arduino
 const (
-	ADC0 Pin = 0
-	ADC1 Pin = 1
-	ADC2 Pin = 2
-	ADC3 Pin = 3
-	ADC4 Pin = 4 // Used by TWI for SDA
-	ADC5 Pin = 5 // Used by TWI for SCL
+	ADC0 Pin = PC0
+	ADC1 Pin = PC1
+	ADC2 Pin = PC2
+	ADC3 Pin = PC3
+	ADC4 Pin = PC4 // Used by TWI for SDA
+	ADC5 Pin = PC5 // Used by TWI for SCL
 )
 
 // UART pins
 const (
-	UART_TX_PIN Pin = 1
-	UART_RX_PIN Pin = 0
+	UART_TX_PIN Pin = PD1
+	UART_RX_PIN Pin = PD0
 )
diff --git a/src/machine/board_atmega328p.go b/src/machine/board_atmega328p.go
new file mode 100644
index 00000000..030c78fe
--- /dev/null
+++ b/src/machine/board_atmega328p.go
@@ -0,0 +1,37 @@
+// +build avr,atmega328p arduino arduino_nano
+
+package machine
+
+const (
+	// Note: start at port B because there is no port A.
+	portB Pin = iota * 8
+	portC
+	portD
+)
+
+const (
+	PB0 = portB + 0
+	PB1 = portB + 1
+	PB2 = portB + 2
+	PB3 = portB + 3
+	PB4 = portB + 4
+	PB5 = portB + 5
+	PB6 = portB + 6
+	PB7 = portB + 7
+	PC0 = portC + 0
+	PC1 = portC + 1
+	PC2 = portC + 2
+	PC3 = portC + 3
+	PC4 = portC + 4
+	PC5 = portC + 5
+	PC6 = portC + 6
+	PC7 = portC + 7
+	PD0 = portD + 0
+	PD1 = portD + 1
+	PD2 = portD + 2
+	PD3 = portD + 3
+	PD4 = portD + 4
+	PD5 = portD + 5
+	PD6 = portD + 6
+	PD7 = portD + 7
+)
diff --git a/src/machine/machine_atmega.go b/src/machine/machine_atmega.go
index cac2ce6e..147d80ff 100644
--- a/src/machine/machine_atmega.go
+++ b/src/machine/machine_atmega.go
@@ -7,72 +7,6 @@ import (
 	"runtime/interrupt"
 )
 
-// InitPWM initializes the registers needed for PWM.
-func InitPWM() {
-	// use waveform generation
-	avr.TCCR0A.SetBits(avr.TCCR0A_WGM00)
-
-	// set timer 0 prescale factor to 64
-	avr.TCCR0B.SetBits(avr.TCCR0B_CS01 | avr.TCCR0B_CS00)
-
-	// set timer 1 prescale factor to 64
-	avr.TCCR1B.SetBits(avr.TCCR1B_CS11)
-
-	// put timer 1 in 8-bit phase correct pwm mode
-	avr.TCCR1A.SetBits(avr.TCCR1A_WGM10)
-
-	// set timer 2 prescale factor to 64
-	avr.TCCR2B.SetBits(avr.TCCR2B_CS22)
-
-	// configure timer 2 for phase correct pwm (8-bit)
-	avr.TCCR2A.SetBits(avr.TCCR2A_WGM20)
-}
-
-// Configure configures a PWM pin for output.
-func (pwm PWM) Configure() {
-	if pwm.Pin < 8 {
-		avr.DDRD.SetBits(1 << uint8(pwm.Pin))
-	} else {
-		avr.DDRB.SetBits(1 << uint8(pwm.Pin-8))
-	}
-}
-
-// Set turns on the duty cycle for a PWM pin using the provided value. On the AVR this is normally a
-// 8-bit value ranging from 0 to 255.
-func (pwm PWM) Set(value uint16) {
-	value8 := uint8(value >> 8)
-	switch pwm.Pin {
-	case 3:
-		// connect pwm to pin on timer 2, channel B
-		avr.TCCR2A.SetBits(avr.TCCR2A_COM2B1)
-		avr.OCR2B.Set(value8) // set pwm duty
-	case 5:
-		// connect pwm to pin on timer 0, channel B
-		avr.TCCR0A.SetBits(avr.TCCR0A_COM0B1)
-		avr.OCR0B.Set(value8) // set pwm duty
-	case 6:
-		// connect pwm to pin on timer 0, channel A
-		avr.TCCR0A.SetBits(avr.TCCR0A_COM0A1)
-		avr.OCR0A.Set(value8) // set pwm duty
-	case 9:
-		// connect pwm to pin on timer 1, channel A
-		avr.TCCR1A.SetBits(avr.TCCR1A_COM1A1)
-		// this is a 16-bit value, but we only currently allow the low order bits to be set
-		avr.OCR1AL.Set(value8) // set pwm duty
-	case 10:
-		// connect pwm to pin on timer 1, channel B
-		avr.TCCR1A.SetBits(avr.TCCR1A_COM1B1)
-		// this is a 16-bit value, but we only currently allow the low order bits to be set
-		avr.OCR1BL.Set(value8) // set pwm duty
-	case 11:
-		// connect pwm to pin on timer 2, channel A
-		avr.TCCR2A.SetBits(avr.TCCR2A_COM2A1)
-		avr.OCR2A.Set(value8) // set pwm duty
-	default:
-		panic("Invalid PWM pin")
-	}
-}
-
 // I2CConfig is used to store config info for I2C.
 type I2CConfig struct {
 	Frequency uint32
diff --git a/src/machine/machine_atmega328p.go b/src/machine/machine_atmega328p.go
index 60c36a37..2e7926a9 100644
--- a/src/machine/machine_atmega328p.go
+++ b/src/machine/machine_atmega328p.go
@@ -12,44 +12,114 @@ const irq_USART0_RX = avr.IRQ_USART_RX
 // Configure sets the pin to input or output.
 func (p Pin) Configure(config PinConfig) {
 	if config.Mode == PinOutput { // set output bit
-		if p < 8 {
-			avr.DDRD.SetBits(1 << uint8(p))
-		} else if p < 14 {
-			avr.DDRB.SetBits(1 << uint8(p-8))
-		} else {
-			avr.DDRC.SetBits(1 << uint8(p-14))
+		switch p / 8 {
+		case 0: // port B
+			avr.DDRB.SetBits(1 << uint8(p))
+		case 1: // port C
+			avr.DDRC.SetBits(1 << uint8(p-8))
+		case 2: // port D
+			avr.DDRD.SetBits(1 << uint8(p-16))
 		}
 	} else { // configure input: clear output bit
-		if p < 8 {
-			avr.DDRD.ClearBits(1 << uint8(p))
-		} else if p < 14 {
-			avr.DDRB.ClearBits(1 << uint8(p-8))
-		} else {
-			avr.DDRC.ClearBits(1 << uint8(p-14))
+		switch p / 8 {
+		case 0: // port B
+			avr.DDRB.ClearBits(1 << uint8(p))
+		case 1: // port C
+			avr.DDRC.ClearBits(1 << uint8(p-8))
+		case 2: // port D
+			avr.DDRD.ClearBits(1 << uint8(p-16))
 		}
 	}
 }
 
 // Get returns the current value of a GPIO pin.
 func (p Pin) Get() bool {
-	if p < 8 {
-		val := avr.PIND.Get() & (1 << uint8(p))
-		return (val > 0)
-	} else if p < 14 {
-		val := avr.PINB.Get() & (1 << uint8(p-8))
-		return (val > 0)
-	} else {
-		val := avr.PINC.Get() & (1 << uint8(p-14))
-		return (val > 0)
+	var val uint8
+	switch p / 8 {
+	case 0: // port B
+		val = avr.PINB.Get() & (1 << uint8(p))
+	case 1: // port C
+		val = avr.PINC.Get() & (1 << uint8(p-8))
+	case 2: // port D
+		val = avr.PIND.Get() & (1 << uint8(p-16))
 	}
+	return val != 0
 }
 
 func (p Pin) getPortMask() (*volatile.Register8, uint8) {
-	if p < 8 {
-		return avr.PORTD, 1 << uint8(p)
-	} else if p < 14 {
-		return avr.PORTB, 1 << uint8(p-8)
-	} else {
-		return avr.PORTC, 1 << uint8(p-14)
+	switch p / 8 {
+	case 0: // port B
+		return avr.PORTB, 1 << uint8(p)
+	case 1:
+		return avr.PORTC, 1 << uint8(p-8)
+	default:
+		return avr.PORTD, 1 << uint8(p-16)
+	}
+}
+
+// InitPWM initializes the registers needed for PWM.
+func InitPWM() {
+	// use waveform generation
+	avr.TCCR0A.SetBits(avr.TCCR0A_WGM00)
+
+	// set timer 0 prescale factor to 64
+	avr.TCCR0B.SetBits(avr.TCCR0B_CS01 | avr.TCCR0B_CS00)
+
+	// set timer 1 prescale factor to 64
+	avr.TCCR1B.SetBits(avr.TCCR1B_CS11)
+
+	// put timer 1 in 8-bit phase correct pwm mode
+	avr.TCCR1A.SetBits(avr.TCCR1A_WGM10)
+
+	// set timer 2 prescale factor to 64
+	avr.TCCR2B.SetBits(avr.TCCR2B_CS22)
+
+	// configure timer 2 for phase correct pwm (8-bit)
+	avr.TCCR2A.SetBits(avr.TCCR2A_WGM20)
+}
+
+// Configure configures a PWM pin for output.
+func (pwm PWM) Configure() {
+	switch pwm.Pin / 8 {
+	case 0: // port B
+		avr.DDRB.SetBits(1 << uint8(pwm.Pin))
+	case 2: // port D
+		avr.DDRD.SetBits(1 << uint8(pwm.Pin-16))
+	}
+}
+
+// Set turns on the duty cycle for a PWM pin using the provided value. On the AVR this is normally a
+// 8-bit value ranging from 0 to 255.
+func (pwm PWM) Set(value uint16) {
+	value8 := uint8(value >> 8)
+	switch pwm.Pin {
+	case PD3:
+		// connect pwm to pin on timer 2, channel B
+		avr.TCCR2A.SetBits(avr.TCCR2A_COM2B1)
+		avr.OCR2B.Set(value8) // set pwm duty
+	case PD5:
+		// connect pwm to pin on timer 0, channel B
+		avr.TCCR0A.SetBits(avr.TCCR0A_COM0B1)
+		avr.OCR0B.Set(value8) // set pwm duty
+	case PD6:
+		// connect pwm to pin on timer 0, channel A
+		avr.TCCR0A.SetBits(avr.TCCR0A_COM0A1)
+		avr.OCR0A.Set(value8) // set pwm duty
+	case PB1:
+		// connect pwm to pin on timer 1, channel A
+		avr.TCCR1A.SetBits(avr.TCCR1A_COM1A1)
+		// this is a 16-bit value, but we only currently allow the low order bits to be set
+		avr.OCR1AL.Set(value8) // set pwm duty
+	case PB2:
+		// connect pwm to pin on timer 1, channel B
+		avr.TCCR1A.SetBits(avr.TCCR1A_COM1B1)
+		// this is a 16-bit value, but we only currently allow the low order bits to be set
+		avr.OCR1BL.Set(value8) // set pwm duty
+	case PB3:
+		// connect pwm to pin on timer 2, channel A
+		avr.TCCR2A.SetBits(avr.TCCR2A_COM2A1)
+		avr.OCR2A.Set(value8) // set pwm duty
+	default:
+		panic("Invalid PWM pin")
 	}
 }