1// +build stm32,stm32f103xx 2 3package runtime 4 5import ( 6 "device/arm" 7 "device/stm32" 8 "machine" 9 "runtime/interrupt" 10 "runtime/volatile" 11) 12 13func init() { 14 initCLK() 15 initRTC() 16 initTIM() 17 machine.UART0.Configure(machine.UARTConfig{}) 18} 19 20func putchar(c byte) { 21 machine.UART0.WriteByte(c) 22} 23 24// initCLK sets clock to 72MHz using HSE 8MHz crystal w/ PLL X 9 (8MHz x 9 = 72MHz). 25func initCLK() { 26 stm32.FLASH.ACR.SetBits(stm32.FLASH_ACR_LATENCY_2) // Two wait states, per datasheet 27 stm32.RCC.CFGR.SetBits(stm32.RCC_CFGR_PPRE1_DIV_2) // prescale PCLK1 = HCLK/2 28 stm32.RCC.CFGR.SetBits(stm32.RCC_CFGR_PPRE2_DIV_NONE) // prescale PCLK2 = HCLK/1 29 stm32.RCC.CR.SetBits(stm32.RCC_CR_HSEON) // enable HSE clock 30 31 // wait for the HSEREADY flag 32 for !stm32.RCC.CR.HasBits(stm32.RCC_CR_HSERDY) { 33 } 34 35 stm32.RCC.CR.SetBits(stm32.RCC_CR_HSION) // enable HSI clock 36 37 // wait for the HSIREADY flag 38 for !stm32.RCC.CR.HasBits(stm32.RCC_CR_HSIRDY) { 39 } 40 41 stm32.RCC.CFGR.SetBits(stm32.RCC_CFGR_PLLSRC) // set PLL source to HSE 42 stm32.RCC.CFGR.SetBits(stm32.RCC_CFGR_PLLMUL_9) // multiply by 9 43 stm32.RCC.CR.SetBits(stm32.RCC_CR_PLLON) // enable the PLL 44 45 // wait for the PLLRDY flag 46 for !stm32.RCC.CR.HasBits(stm32.RCC_CR_PLLRDY) { 47 } 48 49 stm32.RCC.CFGR.SetBits(stm32.RCC_CFGR_SW_PLL) // set clock source to pll 50 51 // wait for PLL to be CLK 52 for !stm32.RCC.CFGR.HasBits(stm32.RCC_CFGR_SWS_PLL) { 53 } 54} 55 56var ( 57 timestamp timeUnit // microseconds since boottime 58 timerLastCounter uint64 59) 60 61var timerWakeup volatile.Register8 62 63func initRTC() { 64 // Enable the PWR and BKP. 65 stm32.RCC.APB1ENR.SetBits(stm32.RCC_APB1ENR_PWREN | stm32.RCC_APB1ENR_BKPEN) 66 67 // access to backup register 68 stm32.PWR.CR.SetBits(stm32.PWR_CR_DBP) 69 70 // Enable LSE 71 stm32.RCC.BDCR.SetBits(stm32.RCC_BDCR_LSEON) 72 73 // wait until LSE is ready 74 for !stm32.RCC.BDCR.HasBits(stm32.RCC_BDCR_LSERDY) { 75 } 76 77 // Select LSE 78 stm32.RCC.BDCR.SetBits(stm32.RCC_RTCCLKSource_LSE) 79 80 // set prescaler to "max" per datasheet 81 stm32.RTC.PRLH.Set(stm32.RTC_PRLH_PRLH_Msk) 82 stm32.RTC.PRLL.Set(stm32.RTC_PRLL_PRLL_Msk) 83 84 // set count to zero 85 stm32.RTC.CNTH.Set(0x0) 86 stm32.RTC.CNTL.Set(0x0) 87 88 // Enable RTC 89 stm32.RCC.BDCR.SetBits(stm32.RCC_BDCR_RTCEN) 90 91 // Clear RSF 92 stm32.RTC.CRL.ClearBits(stm32.RTC_CRL_RSF) 93 94 // Wait till flag is set 95 for !stm32.RTC.CRL.HasBits(stm32.RTC_CRL_RSF) { 96 } 97} 98 99// Enable the TIM3 clock. 100func initTIM() { 101 stm32.RCC.APB1ENR.SetBits(stm32.RCC_APB1ENR_TIM3EN) 102 103 intr := interrupt.New(stm32.IRQ_TIM3, handleTIM3) 104 intr.SetPriority(0xc3) 105 intr.Enable() 106} 107 108const asyncScheduler = false 109 110func ticksToNanoseconds(ticks timeUnit) int64 { 111 return int64(ticks) * 1000 112} 113 114func nanosecondsToTicks(ns int64) timeUnit { 115 return timeUnit(ns / 1000) 116} 117 118// sleepTicks should sleep for specific number of microseconds. 119func sleepTicks(d timeUnit) { 120 for d != 0 { 121 ticks() // update timestamp 122 ticks := uint32(d) // current scaling only supports 100 usec to 6553 msec 123 timerSleep(ticks) 124 d -= timeUnit(ticks) 125 } 126} 127 128// number of ticks (microseconds) since start. 129func ticks() timeUnit { 130 // convert RTC counter from seconds to microseconds 131 timerCounter := uint64(stm32.RTC.CNTH.Get()<<16|stm32.RTC.CNTL.Get()) * 1000 * 1000 132 133 // add the fractional part of current time using DIV register 134 timerCounter += uint64(0x8000-stm32.RTC.DIVL.Get()) * 31 135 136 // change since last measurement 137 offset := (timerCounter - timerLastCounter) 138 timerLastCounter = timerCounter 139 timestamp += timeUnit(offset) 140 return timestamp 141} 142 143// ticks are in microseconds 144func timerSleep(ticks uint32) { 145 timerWakeup.Set(0) 146 147 // STM32 timer update event period is calculated as follows: 148 // 149 // Update_event = TIM_CLK/((PSC + 1)*(ARR + 1)*(RCR + 1)) 150 // 151 // Where: 152 // 153 // TIM_CLK = timer clock input 154 // PSC = 16-bit prescaler register 155 // ARR = 16/32-bit Autoreload register 156 // RCR = 16-bit repetition counter 157 // 158 // Example: 159 // 160 // TIM_CLK = 72 MHz 161 // Prescaler = 1 162 // Auto reload = 65535 163 // No repetition counter RCR = 0 164 // Update_event = 72*(10^6)/((1 + 1)*(65535 + 1)*(1)) 165 // Update_event = 549.3 Hz 166 // 167 // Set the timer prescaler/autoreload timing registers. 168 169 // TODO: support smaller or larger scales (autoscaling) based 170 // on the length of sleep time requested. 171 // The current scaling only supports a range of 200 usec to 6553 msec. 172 173 // prescale counter down from 72mhz to 10khz aka 0.1 ms frequency. 174 stm32.TIM3.PSC.Set(machine.CPUFrequency()/10000 - 1) // 7199 175 176 // Set duty aka duration. 177 // STM32 dividers use n-1, i.e. n counts from 0 to n-1. 178 // As a result, with these prescaler settings, 179 // the minimum allowed duration is 200 microseconds. 180 if ticks < 200 { 181 ticks = 200 182 } 183 stm32.TIM3.ARR.Set(ticks/100 - 1) // convert from microseconds to 0.1 ms 184 185 // Enable the hardware interrupt. 186 stm32.TIM3.DIER.SetBits(stm32.TIM_DIER_UIE) 187 188 // Enable the timer. 189 stm32.TIM3.CR1.SetBits(stm32.TIM_CR1_CEN) 190 191 // wait till timer wakes up 192 for timerWakeup.Get() == 0 { 193 arm.Asm("wfi") 194 } 195} 196 197func handleTIM3(interrupt.Interrupt) { 198 if stm32.TIM3.SR.HasBits(stm32.TIM_SR_UIF) { 199 // Disable the timer. 200 stm32.TIM3.CR1.ClearBits(stm32.TIM_CR1_CEN) 201 202 // clear the update flag 203 stm32.TIM3.SR.ClearBits(stm32.TIM_SR_UIF) 204 205 // timer was triggered 206 timerWakeup.Set(1) 207 } 208} 209