f7f7d4cbbc
This is the last critical part of the C runtime. Code size is reduced by 4 bytes for examples/blinky2 (probably due to inlining) and is unchanged for examples/test.
114 строки
2,4 КиБ
Go
114 строки
2,4 КиБ
Go
// +build nrf
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package runtime
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import (
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"device/arm"
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"device/nrf"
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)
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const Microsecond = 1
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//go:export _start
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func _start() {
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main()
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}
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func init() {
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initUART()
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initLFCLK()
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initRTC()
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}
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func initUART() {
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nrf.UART0.ENABLE = nrf.UART0_ENABLE_ENABLE_Enabled
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nrf.UART0.BAUDRATE = nrf.UART0_BAUDRATE_BAUDRATE_Baud115200
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nrf.UART0.TASKS_STARTTX = 1
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nrf.UART0.PSELTXD = 6 // pin 6 for NRF52840-DK
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}
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func initLFCLK() {
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nrf.CLOCK.LFCLKSRC = nrf.CLOCK_LFCLKSTAT_SRC_Xtal
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nrf.CLOCK.TASKS_LFCLKSTART = 1
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for nrf.CLOCK.EVENTS_LFCLKSTARTED == 0 {
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}
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nrf.CLOCK.EVENTS_LFCLKSTARTED = 0
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}
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func initRTC() {
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nrf.RTC0.TASKS_START = 1
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// TODO: set priority
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arm.EnableIRQ(nrf.IRQ_RTC0)
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}
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func putchar(c byte) {
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nrf.UART0.TXD = nrf.RegValue(c)
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for nrf.UART0.EVENTS_TXDRDY == 0 {
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}
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nrf.UART0.EVENTS_TXDRDY = 0
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}
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func sleep(d Duration) {
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ticks64 := d / 32
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for ticks64 != 0 {
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monotime() // update timestamp
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ticks := uint32(ticks64) & 0x7fffff // 23 bits (to be on the safe side)
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rtc_sleep(ticks) // TODO: not accurate (must be d / 30.5175...)
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ticks64 -= Duration(ticks)
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}
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}
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var (
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timestamp uint64 // microseconds since boottime
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rtcLastCounter uint32 // 24 bits ticks
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)
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// Monotonically increasing numer of microseconds since start.
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//
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// Note: very long pauses between measurements (more than 8 minutes) may
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// overflow the counter, leading to incorrect results. This might be fixed by
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// handling the overflow event.
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func monotime() uint64 {
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rtcCounter := uint32(nrf.RTC0.COUNTER)
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offset := (rtcCounter - rtcLastCounter) % 0xffffff // change since last measurement
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rtcLastCounter = rtcCounter
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timestamp += uint64(offset * 32) // TODO: not precise
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return timestamp
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}
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func abort() {
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for {
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arm.Asm("wfi")
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}
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}
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// Align on word boundary.
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func align(ptr uintptr) uintptr {
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return (ptr + 3) &^ 3
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}
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type __volatile bool
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var rtc_wakeup __volatile
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func rtc_sleep(ticks uint32) {
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nrf.RTC0.INTENSET = nrf.RTC0_INTENSET_COMPARE0_Msk
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rtc_wakeup = false
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if ticks == 1 {
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// Race condition (even in hardware) at ticks == 1.
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// TODO: fix this in a better way by detecting it, like the manual
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// describes.
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ticks = 2
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}
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nrf.RTC0.CC[0] = (nrf.RTC0.COUNTER + nrf.RegValue(ticks)) & 0x00ffffff
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for !rtc_wakeup {
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arm.Asm("wfi")
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}
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}
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//go:export RTC0_IRQHandler
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func RTC0_IRQHandler() {
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nrf.RTC0.INTENCLR = nrf.RTC0_INTENSET_COMPARE0_Msk
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nrf.RTC0.EVENTS_COMPARE[0] = 0
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rtc_wakeup = true
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}
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