stm32: support pin input interrupts

16 files changed, 527 insertions, 0 deletions

diff --git a/src/examples/pininterrupt/stm32.go b/src/examples/pininterrupt/stm32.go
new file mode 100644
index 000000000..30a86313b
--- /dev/null
+++ b/src/examples/pininterrupt/stm32.go
@@ -0,0 +1,10 @@
+// +build stm32
+
+package main
+
+import "machine"
+
+const (
+	buttonMode      = machine.PinInputPulldown
+	buttonPinChange = machine.PinRising | machine.PinFalling
+)
diff --git a/src/machine/board_bluepill.go b/src/machine/board_bluepill.go
index 6d0e4dd91..ce925025f 100644
--- a/src/machine/board_bluepill.go
+++ b/src/machine/board_bluepill.go
@@ -11,6 +11,12 @@ const (
 	LED = PC13
 )
 
+const (
+	// This board does not have a user button, so
+	// use first GPIO pin by default
+	BUTTON = PA0
+)
+
 var Serial = UART1
 
 // UART pins
diff --git a/src/machine/board_nucleol031k6.go b/src/machine/board_nucleol031k6.go
index 695dd8b0e..a758ba932 100644
--- a/src/machine/board_nucleol031k6.go
+++ b/src/machine/board_nucleol031k6.go
@@ -14,6 +14,12 @@ const (
 )
 
 const (
+	// This board does not have a user button, so
+	// use first GPIO pin by default
+	BUTTON = PA0
+)
+
+const (
 	// Arduino Pins
 	A0 = PA0 // ADC_IN0
 	A1 = PA1 // ADC_IN1
diff --git a/src/machine/board_nucleol432kc.go b/src/machine/board_nucleol432kc.go
index 8f32c46a1..d44e0f4fd 100644
--- a/src/machine/board_nucleol432kc.go
+++ b/src/machine/board_nucleol432kc.go
@@ -14,6 +14,12 @@ const (
 )
 
 const (
+	// This board does not have a user button, so
+	// use first GPIO pin by default
+	BUTTON = PA0
+)
+
+const (
 	// Arduino Pins
 	A0 = PA0
 	A1 = PA1
diff --git a/src/machine/board_stm32f4disco.go b/src/machine/board_stm32f4disco.go
index 7a0616079..49f5650fd 100644
--- a/src/machine/board_stm32f4disco.go
+++ b/src/machine/board_stm32f4disco.go
@@ -20,6 +20,10 @@ const (
 	LED_BLUE    = PD15
 )
 
+const (
+	BUTTON = PA0
+)
+
 // UART pins
 const (
 	UART_TX_PIN = PA2
diff --git a/src/machine/machine_stm32.go b/src/machine/machine_stm32.go
index 363036ca2..0ba9ef8d6 100644
--- a/src/machine/machine_stm32.go
+++ b/src/machine/machine_stm32.go
@@ -31,6 +31,13 @@ const (
 // Also, the stm32f1xx series handles things differently from the stm32f0/2/3/4
 
 // ---------- General pin operations ----------
+type PinChange uint8
+
+const (
+	PinRising PinChange = 1 << iota
+	PinFalling
+	PinToggle = PinRising | PinFalling
+)
 
 // Set the pin to high or low.
 // Warning: only use this on an output pin!
diff --git a/src/machine/machine_stm32_exti_afio.go b/src/machine/machine_stm32_exti_afio.go
new file mode 100644
index 000000000..aee4936ac
--- /dev/null
+++ b/src/machine/machine_stm32_exti_afio.go
@@ -0,0 +1,27 @@
+// +build stm32f1
+
+package machine
+
+import (
+	"device/stm32"
+	"runtime/volatile"
+)
+
+func getEXTIConfigRegister(pin uint8) *volatile.Register32 {
+	switch (pin & 0xf) / 4 {
+	case 0:
+		return &stm32.AFIO.EXTICR1
+	case 1:
+		return &stm32.AFIO.EXTICR2
+	case 2:
+		return &stm32.AFIO.EXTICR3
+	case 3:
+		return &stm32.AFIO.EXTICR4
+	}
+	return nil
+}
+
+func enableEXTIConfigRegisters() {
+	// Enable AFIO
+	stm32.RCC.APB2ENR.SetBits(stm32.RCC_APB2ENR_AFIOEN)
+}
diff --git a/src/machine/machine_stm32_exti_exti.go b/src/machine/machine_stm32_exti_exti.go
new file mode 100644
index 000000000..73db5e1e4
--- /dev/null
+++ b/src/machine/machine_stm32_exti_exti.go
@@ -0,0 +1,26 @@
+// +build stm32l5
+
+package machine
+
+import (
+	"device/stm32"
+	"runtime/volatile"
+)
+
+func getEXTIConfigRegister(pin uint8) *volatile.Register32 {
+	switch (pin & 0xf) / 4 {
+	case 0:
+		return &stm32.EXTI.EXTICR1
+	case 1:
+		return &stm32.EXTI.EXTICR2
+	case 2:
+		return &stm32.EXTI.EXTICR3
+	case 3:
+		return &stm32.EXTI.EXTICR4
+	}
+	return nil
+}
+
+func enableEXTIConfigRegisters() {
+	// No-op
+}
diff --git a/src/machine/machine_stm32_exti_syscfg.go b/src/machine/machine_stm32_exti_syscfg.go
new file mode 100644
index 000000000..34d111fbe
--- /dev/null
+++ b/src/machine/machine_stm32_exti_syscfg.go
@@ -0,0 +1,27 @@
+// +build stm32,!stm32f1,!stm32l5
+
+package machine
+
+import (
+	"device/stm32"
+	"runtime/volatile"
+)
+
+func getEXTIConfigRegister(pin uint8) *volatile.Register32 {
+	switch (pin & 0xf) / 4 {
+	case 0:
+		return &stm32.SYSCFG.EXTICR1
+	case 1:
+		return &stm32.SYSCFG.EXTICR2
+	case 2:
+		return &stm32.SYSCFG.EXTICR3
+	case 3:
+		return &stm32.SYSCFG.EXTICR4
+	}
+	return nil
+}
+
+func enableEXTIConfigRegisters() {
+	// Enable SYSCFG
+	stm32.RCC.APB2ENR.SetBits(stm32.RCC_APB2ENR_SYSCFGEN)
+}
diff --git a/src/machine/machine_stm32_gpio_reva.go b/src/machine/machine_stm32_gpio_reva.go
new file mode 100644
index 000000000..3c0d4fe02
--- /dev/null
+++ b/src/machine/machine_stm32_gpio_reva.go
@@ -0,0 +1,92 @@
+// +build stm32,!stm32l4,!stm32l5
+
+package machine
+
+import (
+	"device/stm32"
+)
+
+// This variant of the GPIO input interrupt logic is for
+// chips with a smaller number of interrupt channels
+// (that fits in a single register).
+
+//
+// STM32 allows one interrupt source per pin number, with
+// the same pin number in different ports sharing a single
+// interrupt source (so PA0, PB0, PC0 all share).  Only a
+// single physical pin can be connected to each interrupt
+// line.
+//
+// To call interrupt callbacks, we record here for each
+// pin number the callback and the actual associated pin.
+//
+
+// Callbacks for pin interrupt events
+var pinCallbacks [16]func(Pin)
+
+// The pin currently associated with interrupt callback
+// for a given slot.
+var interruptPins [16]Pin
+
+// SetInterrupt sets an interrupt to be executed when a particular pin changes
+// state. The pin should already be configured as an input, including a pull up
+// or down if no external pull is provided.
+//
+// This call will replace a previously set callback on this pin. You can pass a
+// nil func to unset the pin change interrupt. If you do so, the change
+// parameter is ignored and can be set to any value (such as 0).
+func (p Pin) SetInterrupt(change PinChange, callback func(Pin)) error {
+	port := uint32(uint8(p) / 16)
+	pin := uint8(p) % 16
+
+	enableEXTIConfigRegisters()
+
+	if callback == nil {
+		stm32.EXTI.IMR.ClearBits(1 << pin)
+		pinCallbacks[pin] = nil
+		return nil
+	}
+
+	if pinCallbacks[pin] != nil {
+		// The pin was already configured.
+		// To properly re-configure a pin, unset it first and set a new
+		// configuration.
+		return ErrNoPinChangeChannel
+	}
+
+	// Set the callback now (before the interrupt is enabled) to avoid
+	// possible race condition
+	pinCallbacks[pin] = callback
+	interruptPins[pin] = p
+
+	crReg := getEXTIConfigRegister(pin)
+	shift := (pin & 0x3) * 4
+	crReg.ReplaceBits(port, 0xf, shift)
+
+	if (change & PinRising) != 0 {
+		stm32.EXTI.RTSR.SetBits(1 << pin)
+	}
+	if (change & PinFalling) != 0 {
+		stm32.EXTI.FTSR.SetBits(1 << pin)
+	}
+	stm32.EXTI.IMR.SetBits(1 << pin)
+
+	intr := p.registerInterrupt()
+	intr.SetPriority(0)
+	intr.Enable()
+
+	return nil
+}
+
+func handlePinInterrupt(pin uint8) {
+	if stm32.EXTI.PR.HasBits(1 << pin) {
+		// Writing 1 to the pending register clears the
+		// pending flag for that bit
+		stm32.EXTI.PR.Set(1 << pin)
+
+		callback := pinCallbacks[pin]
+		if callback != nil {
+			callback(interruptPins[pin])
+		}
+	}
+}
diff --git a/src/machine/machine_stm32_gpio_revb.go b/src/machine/machine_stm32_gpio_revb.go
new file mode 100644
index 000000000..1a0e35378
--- /dev/null
+++ b/src/machine/machine_stm32_gpio_revb.go
@@ -0,0 +1,79 @@
+// +build stm32l4 stm32l5
+
+package machine
+
+import (
+	"device/stm32"
+)
+
+// This variant of the GPIO input interrupt logic is for
+// chips with a larger number of interrupt channels (more
+// than fits in a single register).
+
+//
+// STM32 allows one interrupt source per pin number, with
+// the same pin number in different ports sharing a single
+// interrupt source (so PA0, PB0, PC0 all share).  Only a
+// single physical pin can be connected to each interrupt
+// line.
+//
+// To call interrupt callbacks, we record here for each
+// pin number the callback and the actual associated pin.
+//
+
+// Callbacks for pin interrupt events
+var pinCallbacks [16]func(Pin)
+
+// The pin currently associated with interrupt callback
+// for a given slot.
+var interruptPins [16]Pin
+
+// SetInterrupt sets an interrupt to be executed when a particular pin changes
+// state. The pin should already be configured as an input, including a pull up
+// or down if no external pull is provided.
+//
+// This call will replace a previously set callback on this pin. You can pass a
+// nil func to unset the pin change interrupt. If you do so, the change
+// parameter is ignored and can be set to any value (such as 0).
+func (p Pin) SetInterrupt(change PinChange, callback func(Pin)) error {
+	port := uint32(uint8(p) / 16)
+	pin := uint8(p) % 16
+
+	enableEXTIConfigRegisters()
+
+	if callback == nil {
+		stm32.EXTI.IMR1.ClearBits(1 << pin)
+		pinCallbacks[pin] = nil
+		return nil
+	}
+
+	if pinCallbacks[pin] != nil {
+		// The pin was already configured.
+		// To properly re-configure a pin, unset it first and set a new
+		// configuration.
+		return ErrNoPinChangeChannel
+	}
+
+	// Set the callback now (before the interrupt is enabled) to avoid
+	// possible race condition
+	pinCallbacks[pin] = callback
+	interruptPins[pin] = p
+
+	crReg := getEXTIConfigRegister(pin)
+	shift := (pin & 0x3) * 4
+	crReg.ReplaceBits(port, 0xf, shift)
+
+	if (change & PinRising) != 0 {
+		stm32.EXTI.RTSR1.SetBits(1 << pin)
+	}
+	if (change & PinFalling) != 0 {
+		stm32.EXTI.FTSR1.SetBits(1 << pin)
+	}
+	stm32.EXTI.IMR1.SetBits(1 << pin)
+
+	intr := p.registerInterrupt()
+	intr.SetPriority(0)
+	intr.Enable()
+
+	return nil
+}
diff --git a/src/machine/machine_stm32f4.go b/src/machine/machine_stm32f4.go
index 3e6156606..652757a3b 100644
--- a/src/machine/machine_stm32f4.go
+++ b/src/machine/machine_stm32f4.go
@@ -200,6 +200,47 @@ func (p Pin) enableClock() {
 	}
 }
 
+func (p Pin) registerInterrupt() interrupt.Interrupt {
+	pin := uint8(p) % 16
+
+	switch pin {
+	case 0:
+		return interrupt.New(stm32.IRQ_EXTI0, func(interrupt.Interrupt) { handlePinInterrupt(0) })
+	case 1:
+		return interrupt.New(stm32.IRQ_EXTI1, func(interrupt.Interrupt) { handlePinInterrupt(1) })
+	case 2:
+		return interrupt.New(stm32.IRQ_EXTI2, func(interrupt.Interrupt) { handlePinInterrupt(2) })
+	case 3:
+		return interrupt.New(stm32.IRQ_EXTI3, func(interrupt.Interrupt) { handlePinInterrupt(3) })
+	case 4:
+		return interrupt.New(stm32.IRQ_EXTI4, func(interrupt.Interrupt) { handlePinInterrupt(4) })
+	case 5:
+		return interrupt.New(stm32.IRQ_EXTI9_5, func(interrupt.Interrupt) { handlePinInterrupt(5) })
+	case 6:
+		return interrupt.New(stm32.IRQ_EXTI9_5, func(interrupt.Interrupt) { handlePinInterrupt(6) })
+	case 7:
+		return interrupt.New(stm32.IRQ_EXTI9_5, func(interrupt.Interrupt) { handlePinInterrupt(7) })
+	case 8:
+		return interrupt.New(stm32.IRQ_EXTI9_5, func(interrupt.Interrupt) { handlePinInterrupt(8) })
+	case 9:
+		return interrupt.New(stm32.IRQ_EXTI9_5, func(interrupt.Interrupt) { handlePinInterrupt(9) })
+	case 10:
+		return interrupt.New(stm32.IRQ_EXTI15_10, func(interrupt.Interrupt) { handlePinInterrupt(10) })
+	case 11:
+		return interrupt.New(stm32.IRQ_EXTI15_10, func(interrupt.Interrupt) { handlePinInterrupt(11) })
+	case 12:
+		return interrupt.New(stm32.IRQ_EXTI15_10, func(interrupt.Interrupt) { handlePinInterrupt(12) })
+	case 13:
+		return interrupt.New(stm32.IRQ_EXTI15_10, func(interrupt.Interrupt) { handlePinInterrupt(13) })
+	case 14:
+		return interrupt.New(stm32.IRQ_EXTI15_10, func(interrupt.Interrupt) { handlePinInterrupt(14) })
+	case 15:
+		return interrupt.New(stm32.IRQ_EXTI15_10, func(interrupt.Interrupt) { handlePinInterrupt(15) })
+	}
+
+	return interrupt.Interrupt{}
+}
+
 // Enable peripheral clock
 func enableAltFuncClock(bus unsafe.Pointer) {
 	switch bus {
diff --git a/src/machine/machine_stm32f7.go b/src/machine/machine_stm32f7.go
index 51235709e..76f1007ac 100644
--- a/src/machine/machine_stm32f7.go
+++ b/src/machine/machine_stm32f7.go
@@ -309,6 +309,47 @@ func enableAltFuncClock(bus unsafe.Pointer) {
 	}
 }
 
+func (p Pin) registerInterrupt() interrupt.Interrupt {
+	pin := uint8(p) % 16
+
+	switch pin {
+	case 0:
+		return interrupt.New(stm32.IRQ_EXTI0, func(interrupt.Interrupt) { handlePinInterrupt(0) })
+	case 1:
+		return interrupt.New(stm32.IRQ_EXTI1, func(interrupt.Interrupt) { handlePinInterrupt(1) })
+	case 2:
+		return interrupt.New(stm32.IRQ_EXTI2, func(interrupt.Interrupt) { handlePinInterrupt(2) })
+	case 3:
+		return interrupt.New(stm32.IRQ_EXTI3, func(interrupt.Interrupt) { handlePinInterrupt(3) })
+	case 4:
+		return interrupt.New(stm32.IRQ_EXTI4, func(interrupt.Interrupt) { handlePinInterrupt(4) })
+	case 5:
+		return interrupt.New(stm32.IRQ_EXTI9_5, func(interrupt.Interrupt) { handlePinInterrupt(5) })
+	case 6:
+		return interrupt.New(stm32.IRQ_EXTI9_5, func(interrupt.Interrupt) { handlePinInterrupt(6) })
+	case 7:
+		return interrupt.New(stm32.IRQ_EXTI9_5, func(interrupt.Interrupt) { handlePinInterrupt(7) })
+	case 8:
+		return interrupt.New(stm32.IRQ_EXTI9_5, func(interrupt.Interrupt) { handlePinInterrupt(8) })
+	case 9:
+		return interrupt.New(stm32.IRQ_EXTI9_5, func(interrupt.Interrupt) { handlePinInterrupt(9) })
+	case 10:
+		return interrupt.New(stm32.IRQ_EXTI15_10, func(interrupt.Interrupt) { handlePinInterrupt(10) })
+	case 11:
+		return interrupt.New(stm32.IRQ_EXTI15_10, func(interrupt.Interrupt) { handlePinInterrupt(11) })
+	case 12:
+		return interrupt.New(stm32.IRQ_EXTI15_10, func(interrupt.Interrupt) { handlePinInterrupt(12) })
+	case 13:
+		return interrupt.New(stm32.IRQ_EXTI15_10, func(interrupt.Interrupt) { handlePinInterrupt(13) })
+	case 14:
+		return interrupt.New(stm32.IRQ_EXTI15_10, func(interrupt.Interrupt) { handlePinInterrupt(14) })
+	case 15:
+		return interrupt.New(stm32.IRQ_EXTI15_10, func(interrupt.Interrupt) { handlePinInterrupt(15) })
+	}
+
+	return interrupt.Interrupt{}
+}
+
 //---------- Timer related code
 
 var (
diff --git a/src/machine/machine_stm32l0.go b/src/machine/machine_stm32l0.go
index a25d6c9f2..f2a95e8d3 100644
--- a/src/machine/machine_stm32l0.go
+++ b/src/machine/machine_stm32l0.go
@@ -6,6 +6,7 @@ package machine
 
 import (
 	"device/stm32"
+	"runtime/interrupt"
 )
 
 func CPUFrequency() uint32 {
@@ -147,6 +148,47 @@ func (p Pin) enableClock() {
 	}
 }
 
+func (p Pin) registerInterrupt() interrupt.Interrupt {
+	pin := uint8(p) % 16
+
+	switch pin {
+	case 0:
+		return interrupt.New(stm32.IRQ_EXTI0_1, func(interrupt.Interrupt) { handlePinInterrupt(0) })
+	case 1:
+		return interrupt.New(stm32.IRQ_EXTI0_1, func(interrupt.Interrupt) { handlePinInterrupt(1) })
+	case 2:
+		return interrupt.New(stm32.IRQ_EXTI2_3, func(interrupt.Interrupt) { handlePinInterrupt(2) })
+	case 3:
+		return interrupt.New(stm32.IRQ_EXTI2_3, func(interrupt.Interrupt) { handlePinInterrupt(3) })
+	case 4:
+		return interrupt.New(stm32.IRQ_EXTI4_15, func(interrupt.Interrupt) { handlePinInterrupt(4) })
+	case 5:
+		return interrupt.New(stm32.IRQ_EXTI4_15, func(interrupt.Interrupt) { handlePinInterrupt(5) })
+	case 6:
+		return interrupt.New(stm32.IRQ_EXTI4_15, func(interrupt.Interrupt) { handlePinInterrupt(6) })
+	case 7:
+		return interrupt.New(stm32.IRQ_EXTI4_15, func(interrupt.Interrupt) { handlePinInterrupt(7) })
+	case 8:
+		return interrupt.New(stm32.IRQ_EXTI4_15, func(interrupt.Interrupt) { handlePinInterrupt(8) })
+	case 9:
+		return interrupt.New(stm32.IRQ_EXTI4_15, func(interrupt.Interrupt) { handlePinInterrupt(9) })
+	case 10:
+		return interrupt.New(stm32.IRQ_EXTI4_15, func(interrupt.Interrupt) { handlePinInterrupt(10) })
+	case 11:
+		return interrupt.New(stm32.IRQ_EXTI4_15, func(interrupt.Interrupt) { handlePinInterrupt(11) })
+	case 12:
+		return interrupt.New(stm32.IRQ_EXTI4_15, func(interrupt.Interrupt) { handlePinInterrupt(12) })
+	case 13:
+		return interrupt.New(stm32.IRQ_EXTI4_15, func(interrupt.Interrupt) { handlePinInterrupt(13) })
+	case 14:
+		return interrupt.New(stm32.IRQ_EXTI4_15, func(interrupt.Interrupt) { handlePinInterrupt(14) })
+	case 15:
+		return interrupt.New(stm32.IRQ_EXTI4_15, func(interrupt.Interrupt) { handlePinInterrupt(15) })
+	}
+
+	return interrupt.Interrupt{}
+}
+
 //---------- UART related types and code
 
 // Configure the UART.
diff --git a/src/machine/machine_stm32l4.go b/src/machine/machine_stm32l4.go
index c464fa702..be58e9b5f 100644
--- a/src/machine/machine_stm32l4.go
+++ b/src/machine/machine_stm32l4.go
@@ -203,6 +203,60 @@ func enableAltFuncClock(bus unsafe.Pointer) {
 	}
 }
 
+func handlePinInterrupt(pin uint8) {
+	if stm32.EXTI.PR1.HasBits(1 << pin) {
+		// Writing 1 to the pending register clears the
+		// pending flag for that bit
+		stm32.EXTI.PR1.Set(1 << pin)
+
+		callback := pinCallbacks[pin]
+		if callback != nil {
+			callback(interruptPins[pin])
+		}
+	}
+}
+
+func (p Pin) registerInterrupt() interrupt.Interrupt {
+	pin := uint8(p) % 16
+
+	switch pin {
+	case 0:
+		return interrupt.New(stm32.IRQ_EXTI0, func(interrupt.Interrupt) { handlePinInterrupt(0) })
+	case 1:
+		return interrupt.New(stm32.IRQ_EXTI1, func(interrupt.Interrupt) { handlePinInterrupt(1) })
+	case 2:
+		return interrupt.New(stm32.IRQ_EXTI2, func(interrupt.Interrupt) { handlePinInterrupt(2) })
+	case 3:
+		return interrupt.New(stm32.IRQ_EXTI3, func(interrupt.Interrupt) { handlePinInterrupt(3) })
+	case 4:
+		return interrupt.New(stm32.IRQ_EXTI4, func(interrupt.Interrupt) { handlePinInterrupt(4) })
+	case 5:
+		return interrupt.New(stm32.IRQ_EXTI9_5, func(interrupt.Interrupt) { handlePinInterrupt(5) })
+	case 6:
+		return interrupt.New(stm32.IRQ_EXTI9_5, func(interrupt.Interrupt) { handlePinInterrupt(6) })
+	case 7:
+		return interrupt.New(stm32.IRQ_EXTI9_5, func(interrupt.Interrupt) { handlePinInterrupt(7) })
+	case 8:
+		return interrupt.New(stm32.IRQ_EXTI9_5, func(interrupt.Interrupt) { handlePinInterrupt(8) })
+	case 9:
+		return interrupt.New(stm32.IRQ_EXTI9_5, func(interrupt.Interrupt) { handlePinInterrupt(9) })
+	case 10:
+		return interrupt.New(stm32.IRQ_EXTI15_10, func(interrupt.Interrupt) { handlePinInterrupt(10) })
+	case 11:
+		return interrupt.New(stm32.IRQ_EXTI15_10, func(interrupt.Interrupt) { handlePinInterrupt(11) })
+	case 12:
+		return interrupt.New(stm32.IRQ_EXTI15_10, func(interrupt.Interrupt) { handlePinInterrupt(12) })
+	case 13:
+		return interrupt.New(stm32.IRQ_EXTI15_10, func(interrupt.Interrupt) { handlePinInterrupt(13) })
+	case 14:
+		return interrupt.New(stm32.IRQ_EXTI15_10, func(interrupt.Interrupt) { handlePinInterrupt(14) })
+	case 15:
+		return interrupt.New(stm32.IRQ_EXTI15_10, func(interrupt.Interrupt) { handlePinInterrupt(15) })
+	}
+
+	return interrupt.Interrupt{}
+}
+
 //---------- SPI related types and code
 
 // SPI on the STM32Fxxx using MODER / alternate function pins
diff --git a/src/machine/machine_stm32l5.go b/src/machine/machine_stm32l5.go
index 23aba7a07..3f2935cc2 100644
--- a/src/machine/machine_stm32l5.go
+++ b/src/machine/machine_stm32l5.go
@@ -271,6 +271,65 @@ func enableAltFuncClock(bus unsafe.Pointer) {
 	}
 }
 
+func (p Pin) registerInterrupt() interrupt.Interrupt {
+	pin := uint8(p) % 16
+
+	switch pin {
+	case 0:
+		return interrupt.New(stm32.IRQ_EXTI0, func(interrupt.Interrupt) { handlePinInterrupt(0) })
+	case 1:
+		return interrupt.New(stm32.IRQ_EXTI1, func(interrupt.Interrupt) { handlePinInterrupt(1) })
+	case 2:
+		return interrupt.New(stm32.IRQ_EXTI2, func(interrupt.Interrupt) { handlePinInterrupt(2) })
+	case 3:
+		return interrupt.New(stm32.IRQ_EXTI3, func(interrupt.Interrupt) { handlePinInterrupt(3) })
+	case 4:
+		return interrupt.New(stm32.IRQ_EXTI4, func(interrupt.Interrupt) { handlePinInterrupt(4) })
+	case 5:
+		return interrupt.New(stm32.IRQ_EXTI5, func(interrupt.Interrupt) { handlePinInterrupt(5) })
+	case 6:
+		return interrupt.New(stm32.IRQ_EXTI6, func(interrupt.Interrupt) { handlePinInterrupt(6) })
+	case 7:
+		return interrupt.New(stm32.IRQ_EXTI7, func(interrupt.Interrupt) { handlePinInterrupt(7) })
+	case 8:
+		return interrupt.New(stm32.IRQ_EXTI8, func(interrupt.Interrupt) { handlePinInterrupt(8) })
+	case 9:
+		return interrupt.New(stm32.IRQ_EXTI9, func(interrupt.Interrupt) { handlePinInterrupt(9) })
+	case 10:
+		return interrupt.New(stm32.IRQ_EXTI10, func(interrupt.Interrupt) { handlePinInterrupt(10) })
+	case 11:
+		return interrupt.New(stm32.IRQ_EXTI11, func(interrupt.Interrupt) { handlePinInterrupt(11) })
+	case 12:
+		return interrupt.New(stm32.IRQ_EXTI12, func(interrupt.Interrupt) { handlePinInterrupt(12) })
+	case 13:
+		return interrupt.New(stm32.IRQ_EXTI13, func(interrupt.Interrupt) { handlePinInterrupt(13) })
+	case 14:
+		return interrupt.New(stm32.IRQ_EXTI14, func(interrupt.Interrupt) { handlePinInterrupt(14) })
+	case 15:
+		return interrupt.New(stm32.IRQ_EXTI15, func(interrupt.Interrupt) { handlePinInterrupt(15) })
+	}
+
+	return interrupt.Interrupt{}
+}
+
+func handlePinInterrupt(pin uint8) {
+	// The pin abstraction doesn't differentiate pull-up
+	// events from pull-down events, so combine them to
+	// a single call here.
+
+	if stm32.EXTI.RPR1.HasBits(1<<pin) || stm32.EXTI.FPR1.HasBits(1<<pin) {
+		// Writing 1 to the pending register clears the
+		// pending flag for that bit
+		stm32.EXTI.RPR1.Set(1 << pin)
+		stm32.EXTI.FPR1.Set(1 << pin)
+
+		callback := pinCallbacks[pin]
+		if callback != nil {
+			callback(interruptPins[pin])
+		}
+	}
+}
+
 //---------- Timer related code
 
 var (