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// +build nrf
package runtime
import (
"device/arm"
"device/nrf"
"machine"
)
type timeUnit int64
const tickMicros = 1024 * 32
//go:linkname systemInit SystemInit
func systemInit()
//go:export Reset_Handler
func main() {
systemInit()
preinit()
initAll()
callMain()
abort()
}
func init() {
machine.UART0.Configure(machine.UARTConfig{})
initLFCLK()
initRTC()
}
func initLFCLK() {
if machine.HasLowFrequencyCrystal {
nrf.CLOCK.LFCLKSRC = nrf.CLOCK_LFCLKSTAT_SRC_Xtal
}
nrf.CLOCK.TASKS_LFCLKSTART = 1
for nrf.CLOCK.EVENTS_LFCLKSTARTED == 0 {
}
nrf.CLOCK.EVENTS_LFCLKSTARTED = 0
}
func initRTC() {
nrf.RTC1.TASKS_START = 1
arm.SetPriority(nrf.IRQ_RTC1, 0xc0) // low priority
arm.EnableIRQ(nrf.IRQ_RTC1)
}
func putchar(c byte) {
machine.UART0.WriteByte(c)
}
const asyncScheduler = false
func sleepTicks(d timeUnit) {
for d != 0 {
ticks() // update timestamp
ticks := uint32(d) & 0x7fffff // 23 bits (to be on the safe side)
rtc_sleep(ticks) // TODO: not accurate (must be d / 30.5175...)
d -= timeUnit(ticks)
}
}
var (
timestamp timeUnit // nanoseconds since boottime
rtcLastCounter uint32 // 24 bits ticks
)
// Monotonically increasing numer of ticks since start.
//
// Note: very long pauses between measurements (more than 8 minutes) may
// overflow the counter, leading to incorrect results. This might be fixed by
// handling the overflow event.
func ticks() timeUnit {
rtcCounter := uint32(nrf.RTC1.COUNTER)
offset := (rtcCounter - rtcLastCounter) & 0xffffff // change since last measurement
rtcLastCounter = rtcCounter
timestamp += timeUnit(offset) // TODO: not precise
return timestamp
}
//go:volatile
type isrFlag bool
var rtc_wakeup isrFlag
func rtc_sleep(ticks uint32) {
nrf.RTC1.INTENSET = nrf.RTC_INTENSET_COMPARE0
rtc_wakeup = false
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] = (nrf.RTC1.COUNTER + nrf.RegValue(ticks)) & 0x00ffffff
for !rtc_wakeup {
arm.Asm("wfi")
}
}
//go:export RTC1_IRQHandler
func handleRTC1() {
nrf.RTC1.INTENCLR = nrf.RTC_INTENSET_COMPARE0
nrf.RTC1.EVENTS_COMPARE[0] = 0
rtc_wakeup = true
}
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