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// Derivative work of Teensyduino Core Library
// http://www.pjrc.com/teensy/
// Copyright (c) 2017 PJRC.COM, LLC.
//
// Permission is hereby granted, free of charge, to any person obtaining
// a copy of this software and associated documentation files (the
// "Software"), to deal in the Software without restriction, including
// without limitation the rights to use, copy, modify, merge, publish,
// distribute, sublicense, and/or sell copies of the Software, and to
// permit persons to whom the Software is furnished to do so, subject to
// the following conditions:
//
// 1. The above copyright notice and this permission notice shall be
// included in all copies or substantial portions of the Software.
//
// 2. If the Software is incorporated into a build system that allows
// selection among a list of target devices, then similar target
// devices manufactured by PJRC.COM must be included in the list of
// target devices and selectable in the same manner.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
// BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
// ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
// CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.
//go:build nxp && mk66f18
package runtime
import (
"device/arm"
"device/nxp"
"machine"
"runtime/interrupt"
"runtime/volatile"
)
type timeUnit int64
func ticksToNanoseconds(ticks timeUnit) int64 {
return int64(ticks) * 1000
}
func nanosecondsToTicks(ns int64) timeUnit {
return timeUnit(ns / 1000)
}
// cyclesPerMilli-1 is used for the systick reset value.
// The systick current value will be decremented on every clock cycle.
// An interrupt is generated when the current value reaches 0.
// A value of freq/1000 generates a tick (irq) every millisecond (1/1000 s).
var cyclesPerMilli = machine.CPUFrequency() / 1000
// number of systick irqs (milliseconds) since boot
var systickCount volatile.Register64
func millisSinceBoot() uint64 {
return systickCount.Get()
}
func initSysTick() {
nxp.SysTick.RVR.Set(cyclesPerMilli - 1)
nxp.SysTick.CVR.Set(0)
nxp.SysTick.CSR.Set(nxp.SysTick_CSR_CLKSOURCE | nxp.SysTick_CSR_TICKINT | nxp.SysTick_CSR_ENABLE)
nxp.SystemControl.SHPR3.Set((32 << nxp.SystemControl_SHPR3_PRI_15_Pos) | (32 << nxp.SystemControl_SHPR3_PRI_14_Pos)) // set systick and pendsv priority to 32
}
func initSleepTimer() {
nxp.SIM.SCGC5.SetBits(nxp.SIM_SCGC5_LPTMR)
nxp.LPTMR0.CSR.Set(nxp.LPTMR0_CSR_TIE)
timerInterrupt = interrupt.New(nxp.IRQ_LPTMR0, timerWake)
timerInterrupt.Enable()
}
//go:export SysTick_Handler
func tick() {
systickCount.Set(systickCount.Get() + 1)
}
// ticks are in microseconds
func ticks() timeUnit {
mask := arm.DisableInterrupts()
current := nxp.SysTick.CVR.Get() // current value of the systick counter
count := millisSinceBoot() // number of milliseconds since boot
istatus := nxp.SystemControl.ICSR.Get() // interrupt status register
arm.EnableInterrupts(mask)
micros := timeUnit(count * 1000) // a tick (1ms) = 1000 us
// if the systick counter was about to reset and ICSR indicates a pending systick irq, increment count
if istatus&nxp.SystemControl_ICSR_PENDSTSET != 0 && current > 50 {
micros += 1000
} else {
cycles := cyclesPerMilli - 1 - current // number of cycles since last 1ms tick
cyclesPerMicro := machine.CPUFrequency() / 1000000
micros += timeUnit(cycles / cyclesPerMicro)
}
return micros
}
// sleepTicks spins for a number of microseconds
func sleepTicks(duration timeUnit) {
now := ticks()
end := duration + now
cyclesPerMicro := machine.ClockFrequency() / 1000000
if duration <= 0 {
return
}
nxp.LPTMR0.PSR.Set((3 << nxp.LPTMR0_PSR_PCS_Pos) | nxp.LPTMR0_PSR_PBYP) // use 16MHz clock, undivided
for now < end {
count := uint32(end-now) / cyclesPerMicro
if count > 65535 {
count = 65535
}
if !timerSleep(count) {
// return early due to interrupt
return
}
now = ticks()
}
}
var timerInterrupt interrupt.Interrupt
var timerActive volatile.Register32
func timerSleep(count uint32) bool {
timerActive.Set(1)
nxp.LPTMR0.CMR.Set(count) // set count
nxp.LPTMR0.CSR.SetBits(nxp.LPTMR0_CSR_TEN) // enable
for {
arm.Asm("wfi")
if timerActive.Get() == 0 {
return true
}
if hasScheduler {
// bail out, as the interrupt may have awoken a goroutine
break
}
// if there is no scheduler, block for the entire count
}
timerWake(timerInterrupt)
return false
}
func timerWake(interrupt.Interrupt) {
timerActive.Set(0)
nxp.LPTMR0.CSR.Set(nxp.LPTMR0.CSR.Get()&^nxp.LPTMR0_CSR_TEN | nxp.LPTMR0_CSR_TCF) // clear flag and disable
}
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