rp2040: rtc delayed interrupt

Author: ysoldak

Makefile

@@ -474,6 +474,8 @@ smoketest:
 	@$(MD5SUM) test.hex
 	$(TINYGO) build -size short -o test.hex -target=pca10040            examples/pininterrupt
 	@$(MD5SUM) test.hex
+	$(TINYGO) build -size short -o test.hex -target=nano-rp2040         examples/rtcinterrupt
+	@$(MD5SUM) test.hex
 	$(TINYGO) build -size short -o test.hex -target=pca10040            examples/serial
 	@$(MD5SUM) test.hex
 	$(TINYGO) build -size short -o test.hex -target=pca10040            examples/systick

src/examples/rtcinterrupt/rtcinterrupt.go

@@ -0,0 +1,35 @@
+//go:build rp2040
+
+package main
+
+// This example demonstrates scheduling a delayed interrupt by real time clock.
+//
+// An interrupt may execute user callback function or used for its side effects
+// like waking up from sleep or dormant states.
+//
+// The interrupt can be configured to repeat.
+//
+// There is no separate method to disable interrupt, use 0 delay for that.
+//
+// Unfortunately, it is not possible to use time.Duration to work with RTC directly,
+// that would introduce a circular dependency between "machine" and "time" packages.
+
+import (
+	"fmt"
+	"machine"
+	"time"
+)
+
+func main() {
+
+	// Schedule and enable recurring interrupt.
+	// The callback function is executed in the context of an interrupt handler,
+	// so regular restructions for this sort of code apply: no blocking, no memory allocation, etc.
+	delay := time.Minute + 12*time.Second
+	machine.RTC.SetInterrupt(uint32(delay.Seconds()), true, func() { println("Peekaboo!") })
+
+	for {
+		fmt.Printf("%v\r\n", time.Now().Format(time.RFC3339))
+		time.Sleep(1 * time.Second)
+	}
+}

src/machine/machine_rp2040_rtc.go

@@ -0,0 +1,240 @@
+//go:build rp2040
+
+// Implementation based on code located here:
+// https://github.com/raspberrypi/pico-sdk/blob/master/src/rp2_common/hardware_rtc/rtc.c
+
+package machine
+
+import (
+	"device/rp"
+	"errors"
+	"runtime/interrupt"
+	"unsafe"
+)
+
+type rtcType rp.RTC_Type
+
+type rtcTime struct {
+	Year  int16
+	Month int8
+	Day   int8
+	Dotw  int8
+	Hour  int8
+	Min   int8
+	Sec   int8
+}
+
+var RTC = (*rtcType)(unsafe.Pointer(rp.RTC))
+
+const (
+	second = 1
+	minute = 60 * second
+	hour   = 60 * minute
+	day    = 24 * hour
+)
+
+var (
+	rtcAlarmRepeats bool
+	rtcCallback     func()
+	rtcEpoch        = rtcTime{
+		Year: 1970, Month: 1, Day: 1, Dotw: 4, Hour: 0, Min: 0, Sec: 0,
+	}
+)
+
+var (
+	ErrRtcDelayTooSmall = errors.New("RTC interrupt deplay is too small, shall be at least 1 second")
+	ErrRtcDelayTooLarge = errors.New("RTC interrupt deplay is too large, shall be no more than 1 day")
+)
+
+// SetInterrupt configures delayed and optionally recurring interrupt by real time clock.
+//
+// Delay is specified in whole seconds, allowed range depends on platform.
+// Zero delay disables previously configured interrupt, if any.
+//
+// RP2040 implementation allows delay to be up to 1 day, otherwise a respective error is emitted.
+func (rtc *rtcType) SetInterrupt(delay uint32, repeat bool, callback func()) error {
+
+	// Verify delay range
+	if delay > day {
+		return ErrRtcDelayTooLarge
+	}
+
+	// De-configure delayed interrupt if delay is zero
+	if delay == 0 {
+		rtc.disableInterruptMatch()
+		return nil
+	}
+
+	// Configure delayed interrupt
+	rtc.setDivider()
+
+	rtcAlarmRepeats = repeat
+	rtcCallback = callback
+
+	err := rtc.setTime(rtcEpoch)
+	if err != nil {
+		return err
+	}
+	rtc.setAlarm(toAlarmTime(delay), callback)
+
+	return nil
+}
+
+func toAlarmTime(delay uint32) rtcTime {
+	result := rtcEpoch
+	remainder := delay + 1 // needed "+1", otherwise alarm fires one second too early
+	if remainder >= hour {
+		result.Hour = int8(remainder / hour)
+		remainder %= hour
+	}
+	if remainder >= minute {
+		result.Min = int8(remainder / minute)
+		remainder %= minute
+	}
+	result.Sec = int8(remainder)
+	return result
+}
+
+func (rtc *rtcType) setDivider() {
+	// Get clk_rtc freq and make sure it is running
+	rtcFreq := configuredFreq[clkRTC]
+	if rtcFreq == 0 {
+		panic("can not set RTC divider, clock is not running")
+	}
+
+	// Take rtc out of reset now that we know clk_rtc is running
+	resetBlock(rp.RESETS_RESET_RTC)
+	unresetBlockWait(rp.RESETS_RESET_RTC)
+
+	// Set up the 1 second divider.
+	// If rtc_freq is 400 then clkdiv_m1 should be 399
+	rtcFreq -= 1
+
+	// Check the freq is not too big to divide
+	if rtcFreq > rp.RTC_CLKDIV_M1_CLKDIV_M1_Msk {
+		panic("can not set RTC divider, clock frequency is too big to divide")
+	}
+
+	// Write divide value
+	rtc.CLKDIV_M1.Set(rtcFreq)
+}
+
+// setTime configures RTC with supplied time, initialises and activates it.
+func (rtc *rtcType) setTime(t rtcTime) error {
+
+	// Disable RTC and wait while it is still running
+	rtc.CTRL.Set(0)
+	for rtc.isActive() {
+	}
+
+	rtc.SETUP_0.Set((uint32(t.Year) << rp.RTC_SETUP_0_YEAR_Pos) |
+		(uint32(t.Month) << rp.RTC_SETUP_0_MONTH_Pos) |
+		(uint32(t.Day) << rp.RTC_SETUP_0_DAY_Pos))
+
+	rtc.SETUP_1.Set((uint32(t.Dotw) << rp.RTC_SETUP_1_DOTW_Pos) |
+		(uint32(t.Hour) << rp.RTC_SETUP_1_HOUR_Pos) |
+		(uint32(t.Min) << rp.RTC_SETUP_1_MIN_Pos) |
+		(uint32(t.Sec) << rp.RTC_SETUP_1_SEC_Pos))
+
+	// Load setup values into RTC clock domain
+	rtc.CTRL.SetBits(rp.RTC_CTRL_LOAD)
+
+	// Enable RTC and wait for it to be running
+	rtc.CTRL.SetBits(rp.RTC_CTRL_RTC_ENABLE)
+	for !rtc.isActive() {
+	}
+
+	return nil
+}
+
+func (rtc *rtcType) isActive() bool {
+	return rtc.CTRL.HasBits(rp.RTC_CTRL_RTC_ACTIVE)
+}
+
+// setAlarm configures alarm in RTC and arms it.
+// The callback is executed in the context of an interrupt handler,
+// so regular restructions for this sort of code apply: no blocking, no memory allocation, etc.
+func (rtc *rtcType) setAlarm(t rtcTime, callback func()) {
+
+	rtc.disableInterruptMatch()
+
+	// Clear all match enable bits
+	rtc.IRQ_SETUP_0.ClearBits(rp.RTC_IRQ_SETUP_0_YEAR_ENA | rp.RTC_IRQ_SETUP_0_MONTH_ENA | rp.RTC_IRQ_SETUP_0_DAY_ENA)
+	rtc.IRQ_SETUP_1.ClearBits(rp.RTC_IRQ_SETUP_1_DOTW_ENA | rp.RTC_IRQ_SETUP_1_HOUR_ENA | rp.RTC_IRQ_SETUP_1_MIN_ENA | rp.RTC_IRQ_SETUP_1_SEC_ENA)
+
+	// Only add to setup if it isn't -1 and set the match enable bits for things we care about
+	if t.Year >= 0 {
+		rtc.IRQ_SETUP_0.SetBits(uint32(t.Year) << rp.RTC_SETUP_0_YEAR_Pos)
+		rtc.IRQ_SETUP_0.SetBits(rp.RTC_IRQ_SETUP_0_YEAR_ENA)
+	}
+
+	if t.Month >= 0 {
+		rtc.IRQ_SETUP_0.SetBits(uint32(t.Month) << rp.RTC_SETUP_0_MONTH_Pos)
+		rtc.IRQ_SETUP_0.SetBits(rp.RTC_IRQ_SETUP_0_MONTH_ENA)
+	}
+
+	if t.Day >= 0 {
+		rtc.IRQ_SETUP_0.SetBits(uint32(t.Day) << rp.RTC_SETUP_0_DAY_Pos)
+		rtc.IRQ_SETUP_0.SetBits(rp.RTC_IRQ_SETUP_0_DAY_ENA)
+	}
+
+	if t.Dotw >= 0 {
+		rtc.IRQ_SETUP_1.SetBits(uint32(t.Dotw) << rp.RTC_SETUP_1_DOTW_Pos)
+		rtc.IRQ_SETUP_1.SetBits(rp.RTC_IRQ_SETUP_1_DOTW_ENA)
+	}
+
+	if t.Hour >= 0 {
+		rtc.IRQ_SETUP_1.SetBits(uint32(t.Hour) << rp.RTC_SETUP_1_HOUR_Pos)
+		rtc.IRQ_SETUP_1.SetBits(rp.RTC_IRQ_SETUP_1_HOUR_ENA)
+	}
+
+	if t.Min >= 0 {
+		rtc.IRQ_SETUP_1.SetBits(uint32(t.Min) << rp.RTC_SETUP_1_MIN_Pos)
+		rtc.IRQ_SETUP_1.SetBits(rp.RTC_IRQ_SETUP_1_MIN_ENA)
+	}
+
+	if t.Sec >= 0 {
+		rtc.IRQ_SETUP_1.SetBits(uint32(t.Sec) << rp.RTC_SETUP_1_SEC_Pos)
+		rtc.IRQ_SETUP_1.SetBits(rp.RTC_IRQ_SETUP_1_SEC_ENA)
+	}
+
+	// Enable the IRQ at the proc
+	interrupt.New(rp.IRQ_RTC_IRQ, rtcHandleInterrupt).Enable()
+
+	// Enable the IRQ at the peri
+	rtc.INTE.Set(rp.RTC_INTE_RTC)
+
+	rtc.enableInterruptMatch()
+}
+
+func (rtc *rtcType) enableInterruptMatch() {
+	// Set matching and wait for it to be enabled
+	rtc.IRQ_SETUP_0.SetBits(rp.RTC_IRQ_SETUP_0_MATCH_ENA)
+	for !rtc.IRQ_SETUP_0.HasBits(rp.RTC_IRQ_SETUP_0_MATCH_ACTIVE) {
+	}
+}
+
+func (rtc *rtcType) disableInterruptMatch() {
+	// Disable matching and wait for it to stop being active
+	rtc.IRQ_SETUP_0.ClearBits(rp.RTC_IRQ_SETUP_0_MATCH_ENA)
+	for rtc.IRQ_SETUP_0.HasBits(rp.RTC_IRQ_SETUP_0_MATCH_ACTIVE) {
+	}
+}
+
+func rtcHandleInterrupt(itr interrupt.Interrupt) {
+	// Always disable the alarm to clear the current IRQ.
+	// Even if it is a repeatable alarm, we don't want it to keep firing.
+	// If it matches on a second it can keep firing for that second.
+	RTC.disableInterruptMatch()
+
+	// Call user callback function
+	if rtcCallback != nil {
+		rtcCallback()
+	}
+
+	if rtcAlarmRepeats {
+		// If it is a repeatable alarm, reset time and re-enable the alarm.
+		RTC.setTime(rtcEpoch)
+		RTC.enableInterruptMatch()
+	}
+}