Add basic atmega32u support (#3337)

machine/atmega32u: add support for arduino leonardo

src/machine/machine_atmega32u4.go

@@ -0,0 +1,76 @@
+//go:build avr && atmega32u4
+
+package machine
+
+import (
+	"device/avr"
+	"runtime/volatile"
+)
+
+const (
+	// Note: start at port B because there is no port A.
+	portB Pin = iota * 8
+	portC
+	portD
+	portE
+	portF
+)
+
+const (
+	PB0 = portB + 0
+	PB1 = portB + 1 // peripherals: Timer1 channel A
+	PB2 = portB + 2 // peripherals: Timer1 channel B
+	PB3 = portB + 3 // peripherals: Timer2 channel A
+	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
+	PE0 = portE + 0
+	PE1 = portE + 1
+	PE2 = portE + 2
+	PE3 = portE + 3
+	PE4 = portE + 4
+	PE5 = portE + 5
+	PE6 = portE + 6
+	PE7 = portE + 7
+	PF0 = portF + 0
+	PF1 = portF + 1
+	PF2 = portF + 2
+	PF3 = portF + 3
+	PF4 = portF + 4
+	PF5 = portF + 5
+	PF6 = portF + 6
+	PF7 = portF + 7
+)
+
+// getPortMask returns the PORTx register and mask for the pin.
+func (p Pin) getPortMask() (*volatile.Register8, uint8) {
+	switch {
+	case p >= PB0 && p <= PB7: // port B
+		return avr.PORTB, 1 << uint8(p-portB)
+	case p >= PC0 && p <= PC7: // port C
+		return avr.PORTC, 1 << uint8(p-portC)
+	case p >= PD0 && p <= PD7: // port D
+		return avr.PORTD, 1 << uint8(p-portD)
+	case p >= PE0 && p <= PE7: // port E
+		return avr.PORTE, 1 << uint8(p-portE)
+	default: // port F
+		return avr.PORTF, 1 << uint8(p-portF)
+	}
+}