mirror of
https://github.com/tinygo-org/tinygo.git
synced 2026-08-03 02:27:48 +00:00
Ayke van Laethem
41e501aaf4
The timeUnit is now the same type everywhere. Move it to a single place and add some documentation to it.
85 lines
2.2 KiB
Go
85 lines
2.2 KiB
Go
//go:build esp32 || esp32c3
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package runtime
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import (
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"device/esp"
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"machine"
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"unsafe"
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)
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// Initialize .bss: zero-initialized global variables.
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// The .data section has already been loaded by the ROM bootloader.
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func clearbss() {
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ptr := unsafe.Pointer(&_sbss)
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for ptr != unsafe.Pointer(&_ebss) {
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*(*uint32)(ptr) = 0
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ptr = unsafe.Add(ptr, 4)
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}
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}
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func initTimer() {
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// Configure timer 0 in timer group 0, for timekeeping.
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// EN: Enable the timer.
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// INCREASE: Count up every tick (as opposed to counting down).
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// DIVIDER: 16-bit prescaler, set to 2 for dividing the APB clock by two
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// (40MHz).
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// esp.TIMG0.T0CONFIG.Set(0 << esp.TIMG_T0CONFIG_T0_EN_Pos)
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esp.TIMG0.T0CONFIG.Set(esp.TIMG_T0CONFIG_EN | esp.TIMG_T0CONFIG_INCREASE | 2<<esp.TIMG_T0CONFIG_DIVIDER_Pos)
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// esp.TIMG0.T0CONFIG.Set(1 << esp.TIMG_T0CONFIG_T0_DIVCNT_RST_Pos)
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// esp.TIMG0.T0CONFIG.Set(esp.TIMG_T0CONFIG_T0_EN)
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// Set the timer counter value to 0.
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esp.TIMG0.T0LOADLO.Set(0)
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esp.TIMG0.T0LOADHI.Set(0)
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esp.TIMG0.T0LOAD.Set(0) // value doesn't matter.
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}
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func ticks() timeUnit {
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// First, update the LO and HI register pair by writing any value to the
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// register. This allows reading the pair atomically.
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esp.TIMG0.T0UPDATE.Set(0)
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// Then read the two 32-bit parts of the timer.
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return timeUnit(uint64(esp.TIMG0.T0LO.Get()) | uint64(esp.TIMG0.T0HI.Get())<<32)
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}
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func nanosecondsToTicks(ns int64) timeUnit {
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// Calculate the number of ticks from the number of nanoseconds. At a 80MHz
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// APB clock, that's 25 nanoseconds per tick with a timer prescaler of 2:
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// 25 = 1e9 / (80MHz / 2)
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return timeUnit(ns / 25)
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}
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func ticksToNanoseconds(ticks timeUnit) int64 {
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// See nanosecondsToTicks.
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return int64(ticks) * 25
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}
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// sleepTicks busy-waits until the given number of ticks have passed.
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func sleepTicks(d timeUnit) {
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sleepUntil := ticks() + d
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for ticks() < sleepUntil {
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// TODO: suspend the CPU to not burn power here unnecessarily.
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}
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}
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func exit(code int) {
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abort()
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}
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func putchar(c byte) {
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machine.Serial.WriteByte(c)
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}
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func getchar() byte {
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for machine.Serial.Buffered() == 0 {
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Gosched()
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}
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v, _ := machine.Serial.ReadByte()
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return v
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}
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func buffered() int {
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return machine.Serial.Buffered()
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}
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