avr: pin change interrupt - yet more cleanup

Author: Tyler Bell

src/machine/machine.go

@@ -9,6 +9,7 @@ var (
 	ErrInvalidClockPin    = errors.New("machine: invalid clock pin")
 	ErrInvalidDataPin     = errors.New("machine: invalid data pin")
 	ErrNoPinChangeChannel = errors.New("machine: no channel available for pin interrupt")
+	ErrNotImplemented     = errors.New("machine: not implemented")
 )
 
 // Device is the running program's chip name, such as "ATSAMD51J19A" or

src/machine/machine_atmega328p.go

@@ -10,6 +10,10 @@ import (
 	"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.
@@ -501,63 +505,60 @@ func handlePCINT2Interrupts(intr interrupt.Interrupt) {
 func SetInterrupt(pin Pin, callback func(Pin)) (err error) {
 	if callback == nil {
 		// Disable this pin interrupt
-		return errors.New("Not implemented")
-	} else {
-		var PCMSK_REG *volatile.Register8
-		var PCIE uint8
-		var PCINT uint8
-		var IRQ uint8
-		var PIN0 Pin
-		//var PIN *volatile.Register8
-		switch {
-		case pin >= PB0 && pin <= PB7:
-			// PCMSK0 - PCINT0-7
-			PCMSK_REG = avr.PCMSK0
-			PCIE = avr.PCICR_PCIE0
-			PIN0 = PD0
-			PCINT = 1 << (pin - PIN0)
-			IRQ = avr.IRQ_PCINT0
-			if interrupts[IRQ-avr.IRQ_PCINT0] == nil {
-				intr := interrupt.New(avr.IRQ_PCINT0, handlePCINT0Interrupts)
-				interrupts[IRQ-avr.IRQ_PCINT0] = &intr
-			} else {
-			}
-		case pin >= PC0 && pin <= PC7:
-			// PCMSK1 - PCINT8-14
-			PCMSK_REG = avr.PCMSK1
-			PCIE = avr.PCICR_PCIE1
-			PIN0 = PC0
-			PCINT = 1 << (pin - PIN0)
-			IRQ = avr.IRQ_PCINT1
-			if interrupts[IRQ-avr.IRQ_PCINT0] == nil {
-				intr := interrupt.New(avr.IRQ_PCINT1, handlePCINT1Interrupts)
-				interrupts[IRQ-avr.IRQ_PCINT0] = &intr
-			} else {
-			}
-		case pin >= PD0 && pin <= PD7:
-			// PCMSK2 - PCINT16-23
-			PCMSK_REG = avr.PCMSK2
-			PCIE = avr.PCICR_PCIE2
-			PIN0 = PD0
-			PCINT = 1 << (pin - PIN0)
-			IRQ = avr.IRQ_PCINT2
-			if interrupts[IRQ-avr.IRQ_PCINT0] == nil {
-				intr := interrupt.New(avr.IRQ_PCINT2, handlePCINT2Interrupts)
-				interrupts[IRQ-avr.IRQ_PCINT0] = &intr
-			}
-		default:
-			return errors.New("Unsupported pin")
-		}
+		return ErrNotImplemented
+	}
+	var PCMSK_REG *volatile.Register8
+	var PCIE uint8
+	var PCINT uint8
+	var IRQ uint8
+	var PIN0 Pin
 
-		if pinCallbacks[IRQ-avr.IRQ_PCINT0][pin-PIN0] == nil {
-			pinCallbacks[IRQ-avr.IRQ_PCINT0][pin-PIN0] = callback
-		} else {
-			return errors.New("callback already defined")
+	switch {
+	case pin >= PB0 && pin <= PB7:
+		// PCMSK0 - PCINT0-7
+		PCMSK_REG = avr.PCMSK0
+		PCIE = avr.PCICR_PCIE0
+		PIN0 = PD0
+		PCINT = 1 << (pin - PIN0)
+		IRQ = avr.IRQ_PCINT0
+		if interrupts[IRQ-avr.IRQ_PCINT0] == nil {
+			intr := interrupt.New(avr.IRQ_PCINT0, handlePCINT0Interrupts)
+			interrupts[IRQ-avr.IRQ_PCINT0] = &intr
 		}
+	case pin >= PC0 && pin <= PC7:
+		// PCMSK1 - PCINT8-14
+		PCMSK_REG = avr.PCMSK1
+		PCIE = avr.PCICR_PCIE1
+		PIN0 = PC0
+		PCINT = 1 << (pin - PIN0)
+		IRQ = avr.IRQ_PCINT1
+		if interrupts[IRQ-avr.IRQ_PCINT0] == nil {
+			intr := interrupt.New(avr.IRQ_PCINT1, handlePCINT1Interrupts)
+			interrupts[IRQ-avr.IRQ_PCINT0] = &intr
+		}
+	case pin >= PD0 && pin <= PD7:
+		// PCMSK2 - PCINT16-23
+		PCMSK_REG = avr.PCMSK2
+		PCIE = avr.PCICR_PCIE2
+		PIN0 = PD0
+		PCINT = 1 << (pin - PIN0)
+		IRQ = avr.IRQ_PCINT2
+		if interrupts[IRQ-avr.IRQ_PCINT0] == nil {
+			intr := interrupt.New(avr.IRQ_PCINT2, handlePCINT2Interrupts)
+			interrupts[IRQ-avr.IRQ_PCINT0] = &intr
+		}
+	default:
+		return ErrInvalidInputPin
+	}
 
-		PCMSK_REG.SetBits(PCINT)
-		avr.PCICR.SetBits(PCIE)
-
-		return nil
+	if pinCallbacks[IRQ-avr.IRQ_PCINT0][pin-PIN0] != nil {
+		return ErrCallbackAlreadyDefined
 	}
+
+	pinCallbacks[IRQ-avr.IRQ_PCINT0][pin-PIN0] = callback
+
+	PCMSK_REG.SetBits(PCINT)
+	avr.PCICR.SetBits(PCIE)
+
+	return nil
 }