samd21,samd51,nrf52840: refactor usb initialization

src/machine/machine_atsamd21_usb.go

@@ -22,7 +22,6 @@ type USBCDC struct {
 	waitTxc           bool
 	waitTxcRetryCount uint8
 	sent              bool
-	configured        bool
 }
 
 var (
@@ -149,26 +148,8 @@ const (
 	usb_DEVICE_PCKSIZE_MULTI_PACKET_SIZE_Mask = 0x3FFF
 )
 
-var (
-	usbEndpointDescriptors [8]usbDeviceDescriptor
-
-	udd_ep_in_cache_buffer  [7][128]uint8
-	udd_ep_out_cache_buffer [7][128]uint8
-
-	isEndpointHalt        = false
-	isRemoteWakeUpEnabled = false
-	endPoints             = []uint32{usb_ENDPOINT_TYPE_CONTROL,
-		(usb_ENDPOINT_TYPE_INTERRUPT | usbEndpointIn),
-		(usb_ENDPOINT_TYPE_BULK | usbEndpointOut),
-		(usb_ENDPOINT_TYPE_BULK | usbEndpointIn)}
-
-	usbConfiguration uint8
-	usbSetInterface  uint8
-	usbLineInfo      = cdcLineInfo{115200, 0x00, 0x00, 0x08, 0x00}
-)
-
-// Configure the USB CDC interface. The config is here for compatibility with the UART interface.
-func (usbcdc *USBCDC) Configure(config UARTConfig) {
+// Configure the USB peripheral. The config is here for compatibility with the UART interface.
+func (dev *USBDevice) Configure(config UARTConfig) {
 	// reset USB interface
 	sam.USB_DEVICE.CTRLA.SetBits(sam.USB_DEVICE_CTRLA_SWRST)
 	for sam.USB_DEVICE.SYNCBUSY.HasBits(sam.USB_DEVICE_SYNCBUSY_SWRST) ||
@@ -203,15 +184,11 @@ func (usbcdc *USBCDC) Configure(config UARTConfig) {
 	sam.USB_DEVICE.CTRLA.SetBits(sam.USB_DEVICE_CTRLA_ENABLE)
 
 	// enable IRQ
-	intr := interrupt.New(sam.IRQ_USB, handleUSB)
-	intr.Enable()
-
-	usbcdc.configured = true
+	interrupt.New(sam.IRQ_USB, handleUSBIRQ).Enable()
 }
 
-// Configured returns whether usbcdc is configured or not.
-func (usbcdc *USBCDC) Configured() bool {
-	return usbcdc.configured
+func (usbcdc *USBCDC) Configure(config UARTConfig) {
+	// dummy
 }
 
 func handlePadCalibration() {
@@ -257,7 +234,7 @@ func handlePadCalibration() {
 	sam.USB_DEVICE.PADCAL.SetBits(calibTrim << sam.USB_DEVICE_PADCAL_TRIM_Pos)
 }
 
-func handleUSB(intr interrupt.Interrupt) {
+func handleUSBIRQ(intr interrupt.Interrupt) {
 	// reset all interrupt flags
 	flags := sam.USB_DEVICE.INTFLAG.Get()
 	sam.USB_DEVICE.INTFLAG.Set(flags)

src/machine/machine_atsamd51_usb.go

@@ -22,7 +22,6 @@ type USBCDC struct {
 	waitTxc           bool
 	waitTxcRetryCount uint8
 	sent              bool
-	configured        bool
 }
 
 var (
@@ -150,26 +149,8 @@ const (
 	usb_DEVICE_PCKSIZE_MULTI_PACKET_SIZE_Mask = 0x3FFF
 )
 
-var (
-	usbEndpointDescriptors [8]usbDeviceDescriptor
-
-	udd_ep_in_cache_buffer  [7][128]uint8
-	udd_ep_out_cache_buffer [7][128]uint8
-
-	isEndpointHalt        = false
-	isRemoteWakeUpEnabled = false
-	endPoints             = []uint32{usb_ENDPOINT_TYPE_CONTROL,
-		(usb_ENDPOINT_TYPE_INTERRUPT | usbEndpointIn),
-		(usb_ENDPOINT_TYPE_BULK | usbEndpointOut),
-		(usb_ENDPOINT_TYPE_BULK | usbEndpointIn)}
-
-	usbConfiguration uint8
-	usbSetInterface  uint8
-	usbLineInfo      = cdcLineInfo{115200, 0x00, 0x00, 0x08, 0x00}
-)
-
-// Configure the USB CDC interface. The config is here for compatibility with the UART interface.
-func (usbcdc *USBCDC) Configure(config UARTConfig) {
+// Configure the USB peripheral. The config is here for compatibility with the UART interface.
+func (dev *USBDevice) Configure(config UARTConfig) {
 	// reset USB interface
 	sam.USB_DEVICE.CTRLA.SetBits(sam.USB_DEVICE_CTRLA_SWRST)
 	for sam.USB_DEVICE.SYNCBUSY.HasBits(sam.USB_DEVICE_SYNCBUSY_SWRST) ||
@@ -208,13 +189,10 @@ func (usbcdc *USBCDC) Configure(config UARTConfig) {
 	interrupt.New(sam.IRQ_USB_SOF_HSOF, handleUSBIRQ).Enable()
 	interrupt.New(sam.IRQ_USB_TRCPT0, handleUSBIRQ).Enable()
 	interrupt.New(sam.IRQ_USB_TRCPT1, handleUSBIRQ).Enable()
-
-	usbcdc.configured = true
 }
 
-// Configured returns whether usbcdc is configured or not.
-func (usbcdc *USBCDC) Configured() bool {
-	return usbcdc.configured
+func (usbcdc *USBCDC) Configure(config UARTConfig) {
+	// dummy
 }
 
 func handlePadCalibration() {

src/machine/machine_nrf52840_usb.go

@@ -14,8 +14,6 @@ import (
 // USBCDC is the USB CDC aka serial over USB interface on the nRF52840
 type USBCDC struct {
 	Buffer            *RingBuffer
-	interrupt         interrupt.Interrupt
-	initcomplete      bool
 	TxIdx             volatile.Register8
 	waitTxc           bool
 	waitTxcRetryCount uint8
@@ -125,25 +123,11 @@ var (
 	_USB       = USBCDC{Buffer: NewRingBuffer()}
 	waitHidTxc bool
 
-	usbEndpointDescriptors [8]usbDeviceDescriptor
-
-	udd_ep_in_cache_buffer  [7][128]uint8
-	udd_ep_out_cache_buffer [7][128]uint8
-
 	sendOnEP0DATADONE struct {
 		ptr   *byte
 		count int
 	}
-	isEndpointHalt        = false
-	isRemoteWakeUpEnabled = false
-	endPoints             = []uint32{usb_ENDPOINT_TYPE_CONTROL,
-		(usb_ENDPOINT_TYPE_INTERRUPT | usbEndpointIn),
-		(usb_ENDPOINT_TYPE_BULK | usbEndpointOut),
-		(usb_ENDPOINT_TYPE_BULK | usbEndpointIn)}
 
-	usbConfiguration         uint8
-	usbSetInterface          uint8
-	usbLineInfo              = cdcLineInfo{115200, 0x00, 0x00, 0x08, 0x00}
 	epinen                   uint32
 	epouten                  uint32
 	easyDMABusy              volatile.Register8
@@ -167,19 +151,15 @@ func exitCriticalSection() {
 	easyDMABusy.ClearBits(1)
 }
 
-// Configure the USB CDC interface. The config is here for compatibility with the UART interface.
-func (usbcdc *USBCDC) Configure(config UARTConfig) {
-	if usbcdc.initcomplete {
-		return
-	}
-
+// Configure the USB peripheral. The config is here for compatibility with the UART interface.
+func (dev *USBDevice) Configure(config UARTConfig) {
 	// Enable IRQ. Make sure this is higher than the SWI2 interrupt handler so
 	// that it is possible to print to the console from a BLE interrupt. You
 	// shouldn't generally do that but it is useful for debugging and panic
 	// logging.
-	usbcdc.interrupt = interrupt.New(nrf.IRQ_USBD, _USB.handleInterrupt)
-	usbcdc.interrupt.SetPriority(0x40) // interrupt priority 2 (lower number means more important)
-	usbcdc.interrupt.Enable()
+	intr := interrupt.New(nrf.IRQ_USBD, handleUSBIRQ)
+	intr.SetPriority(0x40) // interrupt priority 2 (lower number means more important)
+	intr.Enable()
 
 	// enable USB
 	nrf.USBD.ENABLE.Set(1)
@@ -194,14 +174,16 @@ func (usbcdc *USBCDC) Configure(config UARTConfig) {
 	)
 
 	nrf.USBD.USBPULLUP.Set(0)
-
-	usbcdc.initcomplete = true
 }
 
-func (usbcdc *USBCDC) handleInterrupt(interrupt.Interrupt) {
+func (usbcdc *USBCDC) Configure(config UARTConfig) {
+	// dummy
+}
+
+func handleUSBIRQ(interrupt.Interrupt) {
 	if nrf.USBD.EVENTS_SOF.Get() == 1 {
 		nrf.USBD.EVENTS_SOF.Set(0)
-		usbcdc.Flush()
+		USB.Flush()
 		if hidCallback != nil && !waitHidTxc {
 			hidCallback()
 		}
@@ -301,7 +283,7 @@ func (usbcdc *USBCDC) handleInterrupt(interrupt.Interrupt) {
 					}
 				case usb_CDC_ENDPOINT_IN: //, usb_CDC_ENDPOINT_ACM:
 					if inDataDone {
-						usbcdc.waitTxc = false
+						USB.waitTxc = false
 						exitCriticalSection()
 					}
 				case usb_HID_ENDPOINT_IN:
@@ -327,7 +309,7 @@ func (usbcdc *USBCDC) handleInterrupt(interrupt.Interrupt) {
 				nrf.USBD.TASKS_EP0STATUS.Set(1)
 			}
 			if i == usb_CDC_ENDPOINT_OUT {
-				usbcdc.handleEndpoint(uint32(i))
+				USB.handleEndpoint(uint32(i))
 			}
 			exitCriticalSection()
 		}

src/machine/serial-usb.go

@@ -7,5 +7,4 @@ package machine
 var Serial = USB
 
 func InitSerial() {
-	Serial.Configure(UARTConfig{})
 }

src/machine/usb.go

@@ -8,6 +8,12 @@ import (
 	"runtime/volatile"
 )
 
+type USBDevice struct {
+}
+
+var (
+	USBDev = &USBDevice{}
+)
 var usbDescriptor = descriptorCDC
 
 var (
@@ -47,6 +53,24 @@ var (
 	usb_STRING_LANGUAGE = [2]uint16{(3 << 8) | (2 + 2), 0x0409} // English
 )
 
+var (
+	usbEndpointDescriptors [8]usbDeviceDescriptor
+
+	udd_ep_in_cache_buffer  [7][128]uint8
+	udd_ep_out_cache_buffer [7][128]uint8
+
+	isEndpointHalt        = false
+	isRemoteWakeUpEnabled = false
+	endPoints             = []uint32{usb_ENDPOINT_TYPE_CONTROL,
+		(usb_ENDPOINT_TYPE_INTERRUPT | usbEndpointIn),
+		(usb_ENDPOINT_TYPE_BULK | usbEndpointOut),
+		(usb_ENDPOINT_TYPE_BULK | usbEndpointIn)}
+
+	usbConfiguration uint8
+	usbSetInterface  uint8
+	usbLineInfo      = cdcLineInfo{115200, 0x00, 0x00, 0x08, 0x00}
+)
+
 const (
 	usb_IMANUFACTURER = 1
 	usb_IPRODUCT      = 2

src/runtime/runtime_atsamd21.go

@@ -28,11 +28,8 @@ func init() {
 	initUSBClock()
 	initADCClock()
 
-	// connect to USB CDC interface
+	machine.USBDev.Configure(machine.UARTConfig{})
 	machine.InitSerial()
-	if !machine.USB.Configured() {
-		machine.USB.Configure(machine.UARTConfig{})
-	}
 }
 
 func putchar(c byte) {

src/runtime/runtime_atsamd51.go

@@ -28,11 +28,8 @@ func init() {
 	initUSBClock()
 	initADCClock()
 
-	// connect to USB CDC interface
+	machine.USBDev.Configure(machine.UARTConfig{})
 	machine.InitSerial()
-	if !machine.USB.Configured() {
-		machine.USB.Configure(machine.UARTConfig{})
-	}
 }
 
 func putchar(c byte) {

src/runtime/runtime_nrf.go

@@ -1,5 +1,5 @@
-//go:build nrf
-// +build nrf
+//go:build nrf && !nrf52840
+// +build nrf,!nrf52840
 
 package runtime
 

src/runtime/runtime_nrf52840.go

@@ -0,0 +1,149 @@
+//go:build nrf && nrf52840
+// +build nrf,nrf52840
+
+package runtime
+
+import (
+	"device/arm"
+	"device/nrf"
+	"machine"
+	"runtime/interrupt"
+	"runtime/volatile"
+)
+
+type timeUnit int64
+
+//go:linkname systemInit SystemInit
+func systemInit()
+
+//export Reset_Handler
+func main() {
+	if nrf.FPUPresent {
+		arm.SCB.CPACR.Set(0) // disable FPU if it is enabled
+	}
+	systemInit()
+	preinit()
+	run()
+	exit(0)
+}
+
+func init() {
+	machine.USBDev.Configure(machine.UARTConfig{})
+	machine.InitSerial()
+	initLFCLK()
+	initRTC()
+}
+
+func initLFCLK() {
+	if machine.HasLowFrequencyCrystal {
+		nrf.CLOCK.LFCLKSRC.Set(nrf.CLOCK_LFCLKSTAT_SRC_Xtal)
+	}
+	nrf.CLOCK.TASKS_LFCLKSTART.Set(1)
+	for nrf.CLOCK.EVENTS_LFCLKSTARTED.Get() == 0 {
+	}
+	nrf.CLOCK.EVENTS_LFCLKSTARTED.Set(0)
+}
+
+func initRTC() {
+	nrf.RTC1.TASKS_START.Set(1)
+	intr := interrupt.New(nrf.IRQ_RTC1, func(intr interrupt.Interrupt) {
+		if nrf.RTC1.EVENTS_COMPARE[0].Get() != 0 {
+			nrf.RTC1.EVENTS_COMPARE[0].Set(0)
+			nrf.RTC1.INTENCLR.Set(nrf.RTC_INTENSET_COMPARE0)
+			nrf.RTC1.EVENTS_COMPARE[0].Set(0)
+			rtc_wakeup.Set(1)
+		}
+		if nrf.RTC1.EVENTS_OVRFLW.Get() != 0 {
+			nrf.RTC1.EVENTS_OVRFLW.Set(0)
+			rtcOverflows.Set(rtcOverflows.Get() + 1)
+		}
+	})
+	nrf.RTC1.INTENSET.Set(nrf.RTC_INTENSET_OVRFLW)
+	intr.SetPriority(0xc0) // low priority
+	intr.Enable()
+}
+
+func putchar(c byte) {
+	machine.Serial.WriteByte(c)
+}
+
+func getchar() byte {
+	for machine.Serial.Buffered() == 0 {
+		Gosched()
+	}
+	v, _ := machine.Serial.ReadByte()
+	return v
+}
+
+func buffered() int {
+	return machine.Serial.Buffered()
+}
+
+func sleepTicks(d timeUnit) {
+	for d != 0 {
+		ticks := uint32(d) & 0x7fffff // 23 bits (to be on the safe side)
+		rtc_sleep(ticks)
+		d -= timeUnit(ticks)
+	}
+}
+
+var rtcOverflows volatile.Register32 // number of times the RTC wrapped around
+
+// ticksToNanoseconds converts RTC ticks (at 32768Hz) to nanoseconds.
+func ticksToNanoseconds(ticks timeUnit) int64 {
+	// The following calculation is actually the following, but with both sides
+	// reduced to reduce the risk of overflow:
+	//     ticks * 1e9 / 32768
+	return int64(ticks) * 1953125 / 64
+}
+
+// nanosecondsToTicks converts nanoseconds to RTC ticks (running at 32768Hz).
+func nanosecondsToTicks(ns int64) timeUnit {
+	// The following calculation is actually the following, but with both sides
+	// reduced to reduce the risk of overflow:
+	//     ns * 32768 / 1e9
+	return timeUnit(ns * 64 / 1953125)
+}
+
+// Monotonically increasing numer of ticks since start.
+func ticks() timeUnit {
+	// For some ways of capturing the time atomically, see this thread:
+	// https://www.eevblog.com/forum/microcontrollers/correct-timing-by-timer-overflow-count/msg749617/#msg749617
+	// Here, instead of re-reading the counter register if an overflow has been
+	// detected, we simply try again because that results in (slightly) smaller
+	// code and is perhaps easier to prove correct.
+	for {
+		mask := interrupt.Disable()
+		counter := uint32(nrf.RTC1.COUNTER.Get())
+		overflows := rtcOverflows.Get()
+		hasOverflow := nrf.RTC1.EVENTS_OVRFLW.Get() != 0
+		interrupt.Restore(mask)
+
+		if hasOverflow {
+			// There was an overflow. Try again.
+			continue
+		}
+
+		// The counter is 24 bits in size, so the number of overflows form the
+		// upper 32 bits (together 56 bits, which covers 71493 years at
+		// 32768kHz: I'd argue good enough for most purposes).
+		return timeUnit(overflows)<<24 + timeUnit(counter)
+	}
+}
+
+var rtc_wakeup volatile.Register8
+
+func rtc_sleep(ticks uint32) {
+	nrf.RTC1.INTENSET.Set(nrf.RTC_INTENSET_COMPARE0)
+	rtc_wakeup.Set(0)
+	if ticks == 1 {
+		// Race condition (even in hardware) at ticks == 1.
+		// TODO: fix this in a better way by detecting it, like the manual
+		// describes.
+		ticks = 2
+	}
+	nrf.RTC1.CC[0].Set((nrf.RTC1.COUNTER.Get() + ticks) & 0x00ffffff)
+	for rtc_wakeup.Get() == 0 {
+		waitForEvents()
+	}
+}