Minimal NXP/Teensy support

src/machine/board_teensy36.go

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+// +build nxp,mk66f18,teensy36
+
+package machine
+
+import (
+	"device/nxp"
+)
+
+//go:keep
+//go:section .flashconfig
+var FlashConfig = [16]byte{
+	0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
+	0xFF, 0xFF, 0xFF, 0xFF, 0xDE, 0xF9, 0xFF, 0xFF,
+}
+
+func CPUFrequency() uint32 {
+	return 180000000
+}
+
+// LED on the Teensy
+const LED Pin = 13
+
+var _pinRegisters [64]pinRegisters
+
+func init() {
+	_pinRegisters[13].Bit = 5
+	_pinRegisters[13].PCR = &nxp.PORTC.PCR5
+	_pinRegisters[13].PDOR = nxp.GPIOC.PDOR.Bit(5)
+	_pinRegisters[13].PSOR = nxp.GPIOC.PSOR.Bit(5)
+	_pinRegisters[13].PCOR = nxp.GPIOC.PCOR.Bit(5)
+	_pinRegisters[13].PTOR = nxp.GPIOC.PTOR.Bit(5)
+	_pinRegisters[13].PDIR = nxp.GPIOC.PDIR.Bit(5)
+	_pinRegisters[13].PDDR = nxp.GPIOC.PDDR.Bit(5)
+}
+
+//go:inline
+func (p Pin) registers() pinRegisters {
+	return _pinRegisters[p]
+}

src/machine/machine_nxp.go

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+// +build nxp
+
+package machine
+
+import (
+	"device/arm"
+	"device/nxp"
+)
+
+type PinMode uint8
+
+const (
+	PinInput PinMode = iota
+	PinOutput
+)
+
+// Stop enters STOP (deep sleep) mode
+func Stop() {
+	// set SLEEPDEEP to enable deep sleep
+	nxp.SystemControl.SCR.SetBits(nxp.SystemControl_SCR_SLEEPDEEP)
+
+	// enter STOP mode
+	arm.Asm("wfi")
+}
+
+// Wait enters WAIT (sleep) mode
+func Wait() {
+	// clear SLEEPDEEP bit to disable deep sleep
+	nxp.SystemControl.SCR.ClearBits(nxp.SystemControl_SCR_SLEEPDEEP)
+
+	// enter WAIT mode
+	arm.Asm("wfi")
+}

src/machine/machine_nxpmk66f18.go

@@ -0,0 +1,56 @@
+// +build nxp,mk66f18
+
+package machine
+
+import (
+	"device/nxp"
+	"runtime/volatile"
+)
+
+const (
+	PortControlRegisterSRE = nxp.PORT_PCR0_SRE
+	PortControlRegisterDSE = nxp.PORT_PCR0_DSE
+	PortControlRegisterODE = nxp.PORT_PCR0_ODE
+)
+
+func PortControlRegisterMUX(v uint8) uint32 {
+	return (uint32(v) << nxp.PORT_PCR0_MUX_Pos) & nxp.PORT_PCR0_MUX_Msk
+}
+
+type pinRegisters struct {
+	Bit  uintptr
+	PCR  *volatile.Register32
+	PDOR *volatile.BitRegister
+	PSOR *volatile.BitRegister
+	PCOR *volatile.BitRegister
+	PTOR *volatile.BitRegister
+	PDIR *volatile.BitRegister
+	PDDR *volatile.BitRegister
+}
+
+// Configure this pin with the given configuration.
+func (p Pin) Configure(config PinConfig) {
+	switch config.Mode {
+	case PinInput:
+		panic("todo")
+
+	case PinOutput:
+		p.registers().PDDR.Set()
+		p.registers().PCR.SetBits(PortControlRegisterSRE | PortControlRegisterDSE | PortControlRegisterMUX(1))
+		p.registers().PCR.ClearBits(PortControlRegisterODE)
+	}
+}
+
+// Set changes the value of the GPIO pin. The pin must be configured as output.
+func (p Pin) Set(value bool) {
+	if value {
+		p.registers().PSOR.Set()
+	} else {
+		p.registers().PCOR.Set()
+	}
+}
+
+// Get returns the current value of a GPIO pin.
+func (p Pin) Get() bool {
+	return p.registers().PDIR.Get()
+}