//go:build stm32 && stm32f103

package runtime

import (
	"device/stm32"
	"machine"
)

func init() {
	initCLK()

	machine.InitSerial()

	initTickTimer(&machine.TIM4)
}

func putchar(c byte) {
	machine.Serial.WriteByte(c)
}

func getchar() byte {
	for machine.Serial.Buffered() == 0 {
		Gosched()
	}
	v, _ := machine.Serial.ReadByte()
	return v
}

func buffered() int {
	return machine.Serial.Buffered()
}

// initCLK sets clock to 72MHz using the board's HSE crystal (defined by the xtalHz) w/ PLL.
func initCLK() {
	pll := machine.PLLParams72MHz()

	stm32.FLASH.ACR.SetBits(stm32.FLASH_ACR_LATENCY_WS2)                            // Two wait states, per datasheet
	stm32.RCC.CFGR.SetBits(stm32.RCC_CFGR_PPRE1_Div2 << stm32.RCC_CFGR_PPRE1_Pos)   // prescale PCLK1 = HCLK/2
	stm32.RCC.CFGR.SetBits(stm32.RCC_CFGR_PPRE2_Div1 << stm32.RCC_CFGR_PPRE2_Pos)   // prescale PCLK2 = HCLK/1
	stm32.RCC.CFGR.SetBits(stm32.RCC_CFGR_ADCPRE_Div6 << stm32.RCC_CFGR_ADCPRE_Pos) // prescale ADCCLK = PCLK2/6
	stm32.RCC.CR.SetBits(stm32.RCC_CR_HSEON)                                        // enable HSE clock

	// wait for the HSEREADY flag
	for !stm32.RCC.CR.HasBits(stm32.RCC_CR_HSERDY) {
	}

	stm32.RCC.CR.SetBits(stm32.RCC_CR_HSION) // enable HSI clock

	// wait for the HSIREADY flag
	for !stm32.RCC.CR.HasBits(stm32.RCC_CR_HSIRDY) {
	}

	stm32.RCC.CFGR.SetBits(stm32.RCC_CFGR_PLLSRC)                     // set PLL source to HSE
	stm32.RCC.CFGR.SetBits(pll.Prediv << stm32.RCC_CFGR_PLLXTPRE_Pos) // optional HSE /2 prescaler
	stm32.RCC.CFGR.SetBits(pll.Mul << stm32.RCC_CFGR_PLLMUL_Pos)      // PLL multiplier
	stm32.RCC.CR.SetBits(stm32.RCC_CR_PLLON)                          // enable the PLL

	// wait for the PLLRDY flag
	for !stm32.RCC.CR.HasBits(stm32.RCC_CR_PLLRDY) {
	}

	stm32.RCC.CFGR.SetBits(stm32.RCC_CFGR_SW_PLL) // set clock source to pll

	// wait for PLL to be CLK
	for !stm32.RCC.CFGR.HasBits(stm32.RCC_CFGR_SWS_PLL << stm32.RCC_CFGR_SWS_Pos) {
	}
}
