3ee47a9c1b
This is only very minimal support. More support (such as tinygo flash, or peripheral access) should be added in later commits, to keep this one focused. Importantly, this commit changes the LLVM repo from llvm/llvm-project to tinygo-org/llvm-project. This provides a little bit of versioning in case something changes in the Espressif fork. If we want to upgrade to LLVM 11 it's easy to switch back to llvm/llvm-project until Espressif has updated their fork.
126 строки
3,7 КиБ
Go
126 строки
3,7 КиБ
Go
// +build esp32
|
|
|
|
package runtime
|
|
|
|
import (
|
|
"device"
|
|
"device/esp"
|
|
"machine"
|
|
"unsafe"
|
|
)
|
|
|
|
type timeUnit int64
|
|
|
|
var currentTime timeUnit
|
|
|
|
func putchar(c byte) {
|
|
machine.UART0.WriteByte(c)
|
|
}
|
|
|
|
func postinit() {}
|
|
|
|
// This is the function called on startup right after the stack pointer has been
|
|
// set.
|
|
//export main
|
|
func main() {
|
|
// Disable both watchdog timers that are enabled by default on startup.
|
|
// Note that these watchdogs can be protected, but the ROM bootloader
|
|
// doesn't seem to protect them.
|
|
esp.RTCCNTL.WDTCONFIG0.Set(0)
|
|
esp.TIMG0.WDTCONFIG0.Set(0)
|
|
|
|
// Switch SoC clock source to PLL (instead of the default which is XTAL).
|
|
// This switches the CPU (and APB) clock from 40MHz to 80MHz.
|
|
// Options:
|
|
// RTCCNTL_CLK_CONF_SOC_CLK_SEL: PLL (default XTAL)
|
|
// RTCCNTL_CLK_CONF_CK8M_DIV_SEL: 2 (default)
|
|
// RTCCNTL_CLK_CONF_DIG_CLK8M_D256_EN: Enable (default)
|
|
// RTCCNTL_CLK_CONF_CK8M_DIV: DIV256 (default)
|
|
// The only real change made here is modifying RTCCNTL_CLK_CONF_SOC_CLK_SEL,
|
|
// but setting a fixed value produces smaller code.
|
|
esp.RTCCNTL.CLK_CONF.Set((esp.RTCCNTL_CLK_CONF_SOC_CLK_SEL_PLL << esp.RTCCNTL_CLK_CONF_SOC_CLK_SEL_Pos) |
|
|
(2 << esp.RTCCNTL_CLK_CONF_CK8M_DIV_SEL_Pos) |
|
|
(esp.RTCCNTL_CLK_CONF_DIG_CLK8M_D256_EN_Enable << esp.RTCCNTL_CLK_CONF_DIG_CLK8M_D256_EN_Pos) |
|
|
(esp.RTCCNTL_CLK_CONF_CK8M_DIV_DIV256 << esp.RTCCNTL_CLK_CONF_CK8M_DIV_Pos))
|
|
|
|
// Switch CPU from 80MHz to 160MHz. This doesn't affect the APB clock,
|
|
// which is still running at 80MHz.
|
|
esp.DPORT.CPU_PER_CONF.Set(esp.DPORT_CPU_PER_CONF_CPUPERIOD_SEL_SEL_160)
|
|
|
|
// Clear .bss section. .data has already been loaded by the ROM bootloader.
|
|
// Do this after increasing the CPU clock to possibly make startup slightly
|
|
// faster.
|
|
preinit()
|
|
|
|
// Initialize UART.
|
|
machine.UART0.Configure(machine.UARTConfig{})
|
|
|
|
// Configure timer 0 in timer group 0, for timekeeping.
|
|
// EN: Enable the timer.
|
|
// INCREASE: Count up every tick (as opposed to counting down).
|
|
// DIVIDER: 16-bit prescaler, set to 2 for dividing the APB clock by two
|
|
// (40MHz).
|
|
esp.TIMG0.T0CONFIG.Set(esp.TIMG_T0CONFIG_T0_EN | esp.TIMG_T0CONFIG_T0_INCREASE | 2<<esp.TIMG_T0CONFIG_T0_DIVIDER_Pos)
|
|
|
|
// Set the timer counter value to 0.
|
|
esp.TIMG0.T0LOADLO.Set(0)
|
|
esp.TIMG0.T0LOADHI.Set(0)
|
|
esp.TIMG0.T0LOAD.Set(0) // value doesn't matter.
|
|
|
|
run()
|
|
|
|
// Fallback: if main ever returns, hang the CPU.
|
|
abort()
|
|
}
|
|
|
|
//go:extern _sbss
|
|
var _sbss [0]byte
|
|
|
|
//go:extern _ebss
|
|
var _ebss [0]byte
|
|
|
|
func preinit() {
|
|
// Initialize .bss: zero-initialized global variables.
|
|
// The .data section has already been loaded by the ROM bootloader.
|
|
ptr := unsafe.Pointer(&_sbss)
|
|
for ptr != unsafe.Pointer(&_ebss) {
|
|
*(*uint32)(ptr) = 0
|
|
ptr = unsafe.Pointer(uintptr(ptr) + 4)
|
|
}
|
|
}
|
|
|
|
func ticks() timeUnit {
|
|
// First, update the LO and HI register pair by writing any value to the
|
|
// register. This allows reading the pair atomically.
|
|
esp.TIMG0.T0UPDATE.Set(0)
|
|
// Then read the two 32-bit parts of the timer.
|
|
return timeUnit(uint64(esp.TIMG0.T0LO.Get()) | uint64(esp.TIMG0.T0HI.Get())<<32)
|
|
}
|
|
|
|
const asyncScheduler = false
|
|
|
|
func nanosecondsToTicks(ns int64) timeUnit {
|
|
// Calculate the number of ticks from the number of nanoseconds. At a 80MHz
|
|
// APB clock, that's 25 nanoseconds per tick with a timer prescaler of 2:
|
|
// 25 = 1e9 / (80MHz / 2)
|
|
return timeUnit(ns / 25)
|
|
}
|
|
|
|
func ticksToNanoseconds(ticks timeUnit) int64 {
|
|
// See nanosecondsToTicks.
|
|
return int64(ticks) * 25
|
|
}
|
|
|
|
// sleepTicks busy-waits until the given number of ticks have passed.
|
|
func sleepTicks(d timeUnit) {
|
|
sleepUntil := ticks() + d
|
|
for ticks() < sleepUntil {
|
|
// TODO: suspend the CPU to not burn power here unnecessarily.
|
|
}
|
|
}
|
|
|
|
func abort() {
|
|
for {
|
|
device.Asm("waiti 0")
|
|
}
|
|
}
|