avr: adding pin change interrupt handling to atmega328p

src/machine/machine.go

@@ -3,12 +3,13 @@ package machine
 import "errors"
 
 var (
-	ErrTimeoutRNG         = errors.New("machine: RNG Timeout")
-	ErrInvalidInputPin    = errors.New("machine: invalid input pin")
-	ErrInvalidOutputPin   = errors.New("machine: invalid output pin")
-	ErrInvalidClockPin    = errors.New("machine: invalid clock pin")
-	ErrInvalidDataPin     = errors.New("machine: invalid data pin")
-	ErrNoPinChangeChannel = errors.New("machine: no channel available for pin interrupt")
+	ErrTimeoutRNG            = errors.New("machine: RNG Timeout")
+	ErrInvalidInputPin       = errors.New("machine: invalid input pin")
+	ErrInvalidOutputPin      = errors.New("machine: invalid output pin")
+	ErrInvalidClockPin       = errors.New("machine: invalid clock pin")
+	ErrInvalidDataPin        = errors.New("machine: invalid data pin")
+	ErrNoPinChangeChannel    = errors.New("machine: no channel available for pin interrupt")
+	ErrFeatureNotImplemented = errors.New("machine: this feature is not yet implemented")
 )
 
 // Device is the running program's chip name, such as "ATSAMD51J19A" or

src/machine/machine_atmega328p.go

@@ -5,10 +5,15 @@ package machine
 
 import (
 	"device/avr"
+	"errors"
 	"runtime/interrupt"
 	"runtime/volatile"
 )
 
+var (
+	ErrCallbackAlreadyDefined = errors.New("machine: callback already defined")
+)
+
 const irq_USART0_RX = avr.IRQ_USART_RX
 
 // getPortMask returns the PORTx register and mask for the pin.
@@ -467,3 +472,71 @@ var SPI0 = SPI{
 	sdo:  PB3,
 	sdi:  PB4,
 	cs:   PB2}
+
+// Pin Change Interrupts
+var (
+	pinCallbacks [3][8]func(Pin)
+)
+
+func handlePCINTInterrupts(intr uint8, port *volatile.Register8) {
+	current := port.Get()
+	for i := uint8(0); i < 8; i++ {
+		if (current>>i)&0x01 == 0x01 && pinCallbacks[intr][i] != nil {
+			pinCallbacks[intr][i](Pin(i * (intr + 1)))
+		}
+	}
+}
+
+func handlePCINT0Interrupts(intr interrupt.Interrupt) {
+	handlePCINTInterrupts(avr.IRQ_PCINT0-avr.IRQ_PCINT0, avr.PINB)
+}
+
+func handlePCINT1Interrupts(intr interrupt.Interrupt) {
+	handlePCINTInterrupts(avr.IRQ_PCINT1-avr.IRQ_PCINT0, avr.PINC)
+}
+
+func handlePCINT2Interrupts(intr interrupt.Interrupt) {
+	handlePCINTInterrupts(avr.IRQ_PCINT2-avr.IRQ_PCINT0, avr.PIND)
+}
+
+type PinChange uint8
+
+// Pin change interrupt constants for SetInterrupt.
+const (
+	PinToggle PinChange = 1
+)
+
+func (pin Pin) SetInterrupt(pinChange PinChange, callback func(Pin)) (err error) {
+	if callback == nil {
+		// Disable this pin interrupt
+		return ErrFeatureNotImplemented
+	}
+
+	switch {
+	case pin >= PB0 && pin <= PB7:
+		// PCMSK0 - PCINT0-7
+		pinIndex := pin - PD0
+		pinCallbacks[0][pinIndex] = callback
+		avr.PCMSK0.SetBits(1 << pinIndex)
+		avr.PCICR.SetBits(avr.PCICR_PCIE0)
+		interrupt.New(avr.IRQ_PCINT0, handlePCINT0Interrupts)
+	case pin >= PC0 && pin <= PC7:
+		// PCMSK1 - PCINT8-14
+		pinIndex := pin - PC0
+		pinCallbacks[1][pinIndex] = callback
+		avr.PCMSK1.SetBits(1 << pinIndex)
+		avr.PCICR.SetBits(avr.PCICR_PCIE1)
+		interrupt.New(avr.IRQ_PCINT1, handlePCINT1Interrupts)
+	case pin >= PD0 && pin <= PD7:
+		// PCMSK2 - PCINT16-23
+		pinIndex := pin - PD0
+		pinCallbacks[2][pinIndex] = callback
+		avr.PCMSK2.SetBits(1 << pinIndex)
+		avr.PCICR.SetBits(avr.PCICR_PCIE2)
+		interrupt.New(avr.IRQ_PCINT2, handlePCINT2Interrupts)
+	default:
+		return ErrInvalidInputPin
+	}
+
+	return nil
+}