115 строки
2,7 КиБ
Go
115 строки
2,7 КиБ
Go
// +build esp8266
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package runtime
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import (
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"device"
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"device/esp"
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"machine"
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"unsafe"
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)
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type timeUnit int64
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var currentTime timeUnit = 0
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func putchar(c byte) {
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machine.UART0.WriteByte(c)
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}
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// Write to the internal control bus (using I2C?).
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// Signature found here:
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// https://github.com/espressif/ESP8266_RTOS_SDK/blob/14171de0/components/esp8266/include/esp8266/rom_functions.h#L54
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//export rom_i2c_writeReg
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func rom_i2c_writeReg(block, host_id, reg_add, data uint8)
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func postinit() {}
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//export main
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func main() {
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// Clear .bss section. .data has already been loaded by the ROM bootloader.
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preinit()
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// Initialize PLL.
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// I'm not quite sure what this magic incantation means, but it does set the
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// esp8266 to the right clock speed. Without this, it is running too slow.
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rom_i2c_writeReg(103, 4, 1, 136)
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rom_i2c_writeReg(103, 4, 2, 145)
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// Initialize UART.
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machine.UART0.Configure(machine.UARTConfig{})
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// Initialize timer. Bits:
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// ENABLE: timer enable
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// ROLLOVER: automatically reload when hitting 0
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// PRESCALE: divide by 256
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esp.TIMER.FRC1_CTRL.Set(
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esp.TIMER_FRC1_CTRL_TIMER_ENABLE | esp.TIMER_FRC1_CTRL_ROLLOVER | esp.TIMER_FRC1_CTRL_PRESCALE_DIVIDER_DEVIDED_BY_256<<esp.TIMER_FRC1_CTRL_PRESCALE_DIVIDER_Pos)
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esp.TIMER.FRC1_LOAD.Set(0x3fffff) // set all 22 bits to 1
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esp.TIMER.FRC1_COUNT.Set(0x3fffff) // set all 22 bits to 1
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run()
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// Fallback: if main ever returns, hang the CPU.
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abort()
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}
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//go:extern _sbss
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var _sbss [0]byte
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//go:extern _ebss
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var _ebss [0]byte
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func preinit() {
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// Initialize .bss: zero-initialized global variables.
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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.Pointer(uintptr(ptr) + 4)
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}
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}
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func ticks() timeUnit {
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// Get the counter value of the timer. It is 22 bits and starts with all
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// ones (0x3fffff). To make it easier to work with, let it count upwards.
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count := 0x3fffff - esp.TIMER.FRC1_COUNT.Get()
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// Replace the lowest 22 bits of the current time with the counter.
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newTime := (currentTime &^ 0x3fffff) | timeUnit(count)
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// If there was an overflow, the new time will be lower than the current
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// time, so will need to add (1<<22).
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if newTime < currentTime {
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newTime += 0x400000
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}
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// Update the timestamp for the next call to ticks().
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currentTime = newTime
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return currentTime
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}
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const asyncScheduler = false
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const tickNanos = 3200 // time.Second / (80MHz / 256)
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func ticksToNanoseconds(ticks timeUnit) int64 {
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return int64(ticks) * tickNanos
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}
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func nanosecondsToTicks(ns int64) timeUnit {
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return timeUnit(ns / tickNanos)
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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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}
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}
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func abort() {
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for {
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device.Asm("waiti 0")
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}
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}
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