add rp2040, pico

adds preliminary support (just enough to run blinky1) for the Raspberry Pi Pico board along with the rp2040 mcu.

src/machine/machine_rp2040_gpio.go

@@ -0,0 +1,131 @@
+// +build rp2040
+
+package machine
+
+import (
+	"device/rp"
+	"runtime/volatile"
+	"unsafe"
+)
+
+type io struct {
+	status volatile.Register32
+	ctrl   volatile.Register32
+}
+
+type irqCtrl struct {
+	intE [4]volatile.Register32
+	intS [4]volatile.Register32
+	intF [4]volatile.Register32
+}
+
+type ioBank0Type struct {
+	io                 [30]io
+	intR               [4]volatile.Register32
+	proc0IRQctrl       irqCtrl
+	proc1IRQctrl       irqCtrl
+	dormantWakeIRQctrl irqCtrl
+}
+
+var ioBank0 = (*ioBank0Type)(unsafe.Pointer(rp.IO_BANK0))
+
+type padsBank0Type struct {
+	voltageSelect volatile.Register32
+	io            [30]volatile.Register32
+}
+
+var padsBank0 = (*padsBank0Type)(unsafe.Pointer(rp.PADS_BANK0))
+
+// pinFunc represents a GPIO function.
+//
+// Each GPIO can have one function selected at a time.
+// Likewise, each peripheral input (e.g. UART0 RX) should only be  selected
+// on one GPIO at a time. If the same peripheral input is connected to multiple GPIOs,
+// the peripheral sees the logical OR of these GPIO inputs.
+type pinFunc uint8
+
+// GPIO function selectors
+const (
+	fnJTAG pinFunc = 0
+	fnSPI  pinFunc = 1
+	fnUART pinFunc = 2
+	fnI2C  pinFunc = 3
+	fnPWM  pinFunc = 4
+	fnSIO  pinFunc = 5
+	fnPIO0 pinFunc = 6
+	fnPIO1 pinFunc = 7
+	fnGPCK pinFunc = 8
+	fnUSB  pinFunc = 9
+	fnNULL pinFunc = 0x1f
+
+	fnXIP pinFunc = 0
+)
+
+const (
+	PinOutput PinMode = iota
+)
+
+// set drives the pin high
+func (p Pin) set() {
+	mask := uint32(1) << p
+	rp.SIO.GPIO_OUT_SET.Set(mask)
+}
+
+// clr drives the pin low
+func (p Pin) clr() {
+	mask := uint32(1) << p
+	rp.SIO.GPIO_OUT_CLR.Set(mask)
+}
+
+// xor toggles the pin
+func (p Pin) xor() {
+	mask := uint32(1) << p
+	rp.SIO.GPIO_OUT_XOR.Set(mask)
+}
+
+func (p Pin) ioCtrl() *volatile.Register32 {
+	return &ioBank0.io[p].ctrl
+}
+
+func (p Pin) padCtrl() *volatile.Register32 {
+	return &padsBank0.io[p]
+}
+
+// setFunc will set pin function to fn.
+func (p Pin) setFunc(fn pinFunc) {
+	// Set input enable, Clear output disable
+	p.padCtrl().ReplaceBits(rp.PADS_BANK0_GPIO0_IE,
+		rp.PADS_BANK0_GPIO0_IE_Msk|rp.PADS_BANK0_GPIO0_OD_Msk, 0)
+
+	// Zero all fields apart from fsel; we want this IO to do what the peripheral tells it.
+	// This doesn't affect e.g. pullup/pulldown, as these are in pad controls.
+	p.ioCtrl().Set(uint32(fn) << rp.IO_BANK0_GPIO0_CTRL_FUNCSEL_Pos)
+}
+
+// init initializes the gpio pin
+func (p Pin) init() {
+	mask := uint32(1) << p
+	rp.SIO.GPIO_OE_CLR.Set(mask)
+	p.clr()
+	p.setFunc(fnSIO)
+
+}
+
+// Configure configures the gpio pin as per mode.
+func (p Pin) Configure(config PinConfig) {
+	p.init()
+	mask := uint32(1) << p
+	switch config.Mode {
+	case PinOutput:
+		rp.SIO.GPIO_OE_SET.Set(mask)
+	}
+}
+
+// Set drives the pin high if value is true else drives it low.
+func (p Pin) Set(value bool) {
+	if value {
+		p.set()
+	} else {
+		p.clr()
+	}
+}