add target stm32f051

ch32v003/adcdma.cpp

@@ -1,8 +1,8 @@
 #include "system.h"
 #include "oneway.h"
-#include "adcclass.h"
+#include "adcdma.h"
 
-static AdcClass * pInstance = nullptr;
+static AdcDma * pInstance = nullptr;
 
 extern "C" void DMA1_Channel1_IRQHandler( void ) __attribute__((interrupt));
 void DMA1_Channel1_IRQHandler( void ) {
@@ -90,7 +90,7 @@ static inline void AdcPostInit (void) noexcept {
   });
 }
 ////////////////////////////////////////////////////////////////////////////////////
-AdcClass::AdcClass() noexcept : pL (buffer), pH (buffer + HALF_LEN), dst (nullptr) {
+AdcDma::AdcDma() noexcept : pL (buffer), pH (buffer + HALF_LEN), dst (nullptr) {
   pInstance = this;
   EnableClock ();
   Timer2Init  (1000u);
@@ -101,7 +101,7 @@ AdcClass::AdcClass() noexcept : pL (buffer), pH (buffer + HALF_LEN), dst (nullpt
   // start timer
   TIM2.CTLR1.B.CEN = SET;
 }
-inline void AdcClass::send(const bool b) {
+inline void AdcDma::send(const bool b) {
   if (!dst) return;
   if (b) dst->Send (pH, HALF_LEN);
   else   dst->Send (pL, HALF_LEN);

ch32v003/config.h

@@ -0,0 +1,10 @@
+#ifndef CONFIG_H
+#define CONFIG_H
+
+#define LED_CFG GPIOD,2
+#define REL_CFG GPIOD,4
+
+#define SW__ON false
+#define SW_OFF true
+
+#endif // CONFIG_H

ch32v003/usart.cpp

@@ -0,0 +1,80 @@
+#include "system.h"
+#include "usart.h"
+static Usart * pInstance  = nullptr;
+static constexpr unsigned HCLK = 48'000'000u;
+
+extern "C" void USART1_IRQHandler (void) __attribute__((interrupt));
+void USART1_IRQHandler (void) {
+  if (pInstance) pInstance->irq();
+};
+
+Usart::Usart(const uint32_t _baud) noexcept : BaseLayer (), tx_ring () {
+  pInstance = this;
+  // 1. Clock Enable
+  RCC.APB2PCENR.modify([](RCC_Type::APB2PCENR_DEF & r) -> auto {
+    r.B.USART1EN = SET;
+    r.B.IOPDEN   = SET;
+    return r.R;
+  });
+  // 2. GPIO Alternate Config - default TX/PD5, RX/PD6
+  GPIOD.CFGLR.modify([](GPIOA_Type::CFGLR_DEF & r) -> auto {
+    r.B.MODE5 = 1u; 
+    r.B.CNF5  = 2u;  // or 3u for open drain
+    r.B.MODE6 = 0u;
+    r.B.CNF6  = 1u;  // floating input
+    return r.R;
+  });
+  // 4. NVIC
+  NVIC.EnableIRQ (USART1_IRQn);
+  // 5. USART registry 8.bit bez parity
+  USART1.CTLR1.modify([] (USART1_Type::CTLR1_DEF & r) -> auto {
+    r.B.RE      = SET;
+    r.B.TE      = SET;
+    r.B.RXNEIE  = SET;
+    return r.R;
+  });
+  USART1.CTLR2.R = 0;
+  //USART1.CTLR3.B.OVRDIS = SET;
+  const uint32_t tmp = HCLK / _baud;
+  USART1.BRR.R = tmp;
+  USART1.CTLR1.B.UE = SET;        // nakonec povolit globálně
+}
+void Usart::irq () {
+  volatile USART1_Type::STATR_DEF status (USART1.STATR);   // načti status přerušení
+  char rdata, tdata;
+  
+  if (status.B.TXE) {                         // od vysílače
+    if (tx_ring.Read (tdata)) {               // pokud máme data
+      USART1.DATAR.B.DR = (uint8_t) tdata;    // zapíšeme do výstupu
+    } else {                                  // pokud ne
+      // Předpoklad je half-duplex i.e. RS485, jinak jen zakázat TXEIE
+      rdata = (USART1.DATAR.B.DR);            // dummy read
+      USART1.CTLR1.modify([](USART1_Type::CTLR1_DEF & r) -> auto {
+        r.B.RE    = SET;                      // povol prijem
+        r.B.TXEIE = RESET;                    // je nutné zakázat přerušení od vysílače
+        return r.R;
+      });
+    }
+  }
+  if (status.B.RXNE) {                        // od přijímače
+    rdata = (USART1.DATAR.B.DR);              // načteme data
+    Up (&rdata, 1u);                          // a pošleme dál
+  }
+}
+uint32_t Usart::Down(const char * data, const uint32_t len) {
+  unsigned n = 0u;
+  for (n=0u; n<len; n++) {
+    if (!tx_ring.Write(data[n])) break;
+  }
+  USART1.CTLR1.modify([](USART1_Type::CTLR1_DEF & r) -> auto {
+    r.B.RE    = RESET;
+    r.B.TXEIE = SET;    // po povolení přerušení okamžitě přeruší
+    return r.R;
+  });
+  return n;
+}
+void Usart::SetRS485  (const bool polarity) const {
+}
+void Usart::SetHalfDuplex  (const bool on) const {
+}
+

common/adcdma.h

@@ -1,21 +1,21 @@
-#ifndef ADCCLASS_H
-#define ADCCLASS_H
+#ifndef ADCDMA_H
+#define ADCDMA_H
 #include <stdint.h>
 
 class OneWay;
 static constexpr unsigned HALF_LEN = 120u;
 static constexpr unsigned FULL_LEN = HALF_LEN * 2u;
 
-class AdcClass {
+class AdcDma {
   uint16_t * pL;
   uint16_t * pH;
   uint16_t buffer [FULL_LEN];
   OneWay   * dst;
   public:
-    explicit AdcClass () noexcept;
+    explicit AdcDma () noexcept;
     void attach (OneWay & d) { dst = & d; }
     void send (const bool b);
     
 };
 
-#endif // ADCCLASS_H
+#endif // ADCDMA_H

common/usart.h

@@ -0,0 +1,21 @@
+#ifndef USART_H
+#define USART_H
+#include "fifo.h"
+#include "baselayer.h"
+/** @class Usart
+ * @brief Sériový port.
+ * 
+ * Zde RS485, jen výstup.
+ */
+class Usart : public BaseLayer {
+  FIFO<char, 64> tx_ring;
+  public:
+    explicit Usart (const uint32_t baud = 9600) noexcept;
+    uint32_t Down  (const char * data, const uint32_t len) override;
+    void SetRS485  (const bool polarity) const;
+    
+    void irq            (void);
+    void SetHalfDuplex  (const bool on) const;
+};
+
+#endif // USART_H

hdo/Makefile

@@ -1,6 +1,9 @@
-# ch32v003
+# ch32v003 | stm32f051
 TARGET?= ch32v003
+#TARGET?= stm32f051
 TOOL  ?= gcc
+# do not use for ch32v003
+#TOOL  ?= clang
 
 PRJ    = example
 
@@ -16,8 +19,8 @@ CFLAGS+= -I. -I./common -I./$(TARGET) -I/usr/include/newlib -DUSE_HSE=1
 DEL    = rm -f
 
 # zdrojaky
-OBJS   = main.o adcclass.o hdo.o
-OBJS  += usartclass.o print.o
+OBJS   = main.o adcdma.o hdo.o
+OBJS  += usart.o print.o
 
 include $(TARGET)/$(TOOL).mk
 BOBJS = $(addprefix $(BLD),$(OBJS))
@@ -44,9 +47,9 @@ $(BLD)%.o: %.cpp
 	@$(CXX) -std=c++17 -fno-rtti -c $(CFLAGS) $< -o $@
 $(BLD):
 	mkdir $(BLD)
-flash: $(PRJ).elf
+flash: $(BLD) $(PRJ).elf
 	minichlink -w $(PRJ).bin flash -b
 # vycisti
 clean:
 	$(DEL) $(BLD)* *.lst *.bin *.elf *.map sin.c *~
-.PHONY: all clean
+.PHONY: all clean flash

hdo/hdo.cpp

@@ -37,8 +37,8 @@ void Hdo::pass () {
   cout << value << "      \r";
   value -= trigger;
   
-  if (value > 0) led << false;  // LED je zapojená proti VCC
-  else           led << true;
+  if (value > 0) led << SW__ON;  // LED je zapojená proti VCC
+  else           led << SW_OFF;
   // Konečné vyhodnocení.
   if (Decode (value, buf1)) {   // Telegram OK.
     HumanRead (buf1, buf2);     // Převeď ho do čitelné podoby

hdo/hdo.h

@@ -1,9 +1,10 @@
 #ifndef HDO_H
 #define HDO_H
 #include "gpio.h"
-#include "usartclass.h"
+#include "usart.h"
 #include "print.h"
 #include "oneway.h"
+#include "config.h"
 
 static constexpr int ISHIFT = 12;
 /* Tady je ten výpočet proveden externě.
@@ -28,7 +29,7 @@ static constexpr int TBUFLEN =  64;
 
 class Hdo : public OneWay {
   GpioClass     led, relay;
-  UsartClass    serial;
+  Usart         serial;
   Print         cout;
   FIFO<int, 8>  data;
   const int     coeff;
@@ -44,7 +45,7 @@ class Hdo : public OneWay {
   
   public:
     explicit Hdo (const char * command) noexcept : OneWay (),
-      led (GPIOD, 2), relay (GPIOD, 4), serial (115200u), cout (DEC), data(), coeff (1706), trigger (0x4000),
+      led (LED_CFG), relay (REL_CFG), serial (115200u), cout (DEC), data(), coeff (1706), trigger (0x4000),
       cmd (command), suma (0), bits (0), counter (0), status (WAIT_FOR_BEGIN) {
         /* trigger musí být nastaven tak do 1/3 až do 1/2 maximální vyhodnocené hodnoty (viz výpis)
          * Je nutné použít HSE, tj. krystal 24 HHz. Bez toho to fakt nechodí a to i na procesorech i.e. STM.

hdo/main.cpp

@@ -1,4 +1,4 @@
-#include "adcclass.h"
+#include "adcdma.h"
 #include "hdo.h"
 ///////////////////////////////////////////////////////////////
 /* Tohle je trochu komplexnější příklad.
@@ -27,7 +27,7 @@
  * !!! Krystal 24 MHz nutný !!!
  * */
 ///////////////////////////////////////////////////////////////
-static AdcClass adc;
+static AdcDma adc;
 static Hdo    hdo ("A1B8DP1");
 int main () {
   adc.attach(hdo);

hdo/stm32f051

@@ -0,0 +1 @@
+../stm32f051/

stm32f051/CortexM0.h

@@ -0,0 +1,139 @@
+#ifndef ARMCM0_HDEF
+#define ARMCM0_HDEF
+
+/** @brief SYSTICK for Cortex-M0
+ * Není to moc domyšlené, před tt. hlavičkou je nutné mít definován NVIC a IRQn,
+ * což je v STM generované hlavičce většinou uděláno. NVIC_EnableIRQ je zjednodušen
+ * jen pro CM0, jinak se tam čaruje s PRIO_BITS, tady to není potřeba.
+ */
+
+// tohle je jediné, co je potřeba z core_cm0.h
+static inline void NVIC_EnableIRQ (IRQn irq) {
+  NVIC.ISER.R = ((1 << (static_cast<uint32_t>(irq) & 0x1F)));
+}
+static constexpr uint32_t SysTick_LOAD_RELOAD_Msk = (0xFFFFFFUL);        /*!< SysTick LOAD: RELOAD Mask */
+// ////////////////////+++ SysTick +-+//////////////////// //
+struct SysTick_DEF { /*!< 24Bit System Tick Timer for use in RTOS */
+  union CSR_DEF   {  //!< [0000](04)[0x00000004] SysTick Control and Status Register
+    enum ENABLE_ENUM /*: uint32_t */ {
+      ENABLE_0 = 0,  //!< disabled
+      ENABLE_1 = 1,  //!< enabled
+    };
+    enum TICKINT_ENUM /*: uint32_t */ {
+      TICKINT_0 = 0,  //!< Enable SysTick Exception
+      TICKINT_1 = 1,  //!< Disable SysTick Exception
+    };
+    enum CLKSOURCE_ENUM /*: uint32_t */ {
+      CLKSOURCE_0 = 0,  //!< External Clock
+      CLKSOURCE_1 = 1,  //!< CPU Clock
+    };
+    struct {
+      __IO ENABLE_ENUM     ENABLE    :  1; //!<[00] Enable SysTick Timer
+      __IO TICKINT_ENUM    TICKINT   :  1; //!<[01] Generate Tick Interrupt
+      __IO CLKSOURCE_ENUM  CLKSOURCE :  1; //!<[02] Source to count from
+           uint32_t        UNUSED0   : 13; //!<[03] 
+      __IO ONE_BIT         COUNTFLAG :  1; //!<[16] SysTick counted to zero
+    } B;
+    __IO uint32_t  R;
+
+    explicit CSR_DEF () noexcept { R = 0x00000004u; }
+    template<typename F> void setbit (F f) volatile {
+      CSR_DEF r;
+      R = f (r);
+    }
+
+    template<typename F> void modify (F f) volatile {
+      CSR_DEF r; r.R = R;
+      R = f (r);
+    }
+  };
+  __IO CSR_DEF CSR ;  //!< register definition
+
+  union RVR_DEF   {  //!< [0004](04)[0x00000000] SysTick Reload Value Register
+    struct {
+      __IO uint32_t   RELOAD : 24; //!<[00] Value to auto reload SysTick after reaching zero
+    } B;
+    __IO uint32_t  R;
+
+    explicit RVR_DEF () noexcept { R = 0x00000000u; }
+    template<typename F> void setbit (F f) volatile {
+      RVR_DEF r;
+      R = f (r);
+    }
+
+    template<typename F> void modify (F f) volatile {
+      RVR_DEF r; r.R = R;
+      R = f (r);
+    }
+  };
+  __IO RVR_DEF RVR ;  //!< register definition
+
+  union CVR_DEF   {  //!< [0008](04)[0x00000000] SysTick Current Value Register
+    struct {
+      __IO uint32_t   CURRENT : 24; //!<[00] Current value
+    } B;
+    __IO uint32_t  R;
+
+    explicit CVR_DEF () noexcept { R = 0x00000000u; }
+    template<typename F> void setbit (F f) volatile {
+      CVR_DEF r;
+      R = f (r);
+    }
+
+    template<typename F> void modify (F f) volatile {
+      CVR_DEF r; r.R = R;
+      R = f (r);
+    }
+  };
+  __IO CVR_DEF CVR ;  //!< register definition
+
+  union CALIB_DEF {  //!< [000c](04)[0x00000000] SysTick Calibration Value Register
+    enum SKEW_ENUM /*: uint32_t */ {
+      SKEW_0 = 0,  //!< 10ms calibration value is exact
+      SKEW_1 = 1,  //!< 10ms calibration value is inexact, because of the clock frequency
+    };
+    enum NOREF_ENUM /*: uint32_t */ {
+      NOREF_0 = 0,  //!< Ref Clk available
+      NOREF_1 = 1,  //!< Ref Clk not available
+    };
+    struct {
+      __I  uint32_t    TENMS   : 24; //!<[00] Reload value to use for 10ms timing
+           uint32_t    UNUSED0 :  6; //!<[24] 
+      __I  SKEW_ENUM   SKEW    :  1; //!<[30] Clock Skew
+      __I  NOREF_ENUM  NOREF   :  1; //!<[31] No Ref
+    } B;
+    __IO uint32_t  R;
+
+    explicit CALIB_DEF () noexcept { R = 0x00000000u; }
+    template<typename F> void setbit (F f) volatile {
+      CALIB_DEF r;
+      R = f (r);
+    }
+
+    template<typename F> void modify (F f) volatile {
+      CALIB_DEF r; r.R = R;
+      R = f (r);
+    }
+  };
+  __IO CALIB_DEF CALIB ;  //!< register definition
+  // methods :
+  bool Config (const uint32_t ticks) {
+    if (ticks > SysTick_LOAD_RELOAD_Msk)  return false;         // Reload value impossible
+    RVR.B.RELOAD    = ticks  - 1u;                              // set reload register
+    NVIC_EnableIRQ    (SysTick_IRQn);                           // Enable Interrupt
+    CVR.B.CURRENT   = 0;                                        // Load the SysTick Counter Value
+    CSR.modify([](CSR_DEF & r) -> auto {                        // Enable SysTick IRQ and SysTick Timer
+      r.B.CLKSOURCE = CSR_DEF::CLKSOURCE_ENUM::CLKSOURCE_1;
+      r.B.TICKINT   = CSR_DEF::TICKINT_ENUM  ::TICKINT_1;
+      r.B.ENABLE    = CSR_DEF::ENABLE_ENUM   ::ENABLE_1;
+      return r.R;
+    });
+    return true;                                                 // Function successful
+  }
+
+}; /* total size = 0x0010, struct size = 0x0010 */
+static SysTick_DEF & SysTick = * reinterpret_cast<SysTick_DEF *> (0xe000e010);
+
+static_assert (sizeof(struct SysTick_DEF) == 16, "size error SysTick");
+
+#endif

stm32f051/adcdma.cpp

@@ -0,0 +1,119 @@
+#include "STM32F0x1.h"
+#include "CortexM0.h"
+#include "gpio.h"
+#include "adcdma.h"
+#include "oneway.h"
+
+static constexpr uint32_t AdcChanel = 2u;
+static constexpr uint32_t AdcPin    = 2u;
+
+static inline void EnableClock (void) {
+  RCC.APB2ENR.B.ADCEN  = SET;
+  RCC.AHBENR.B.DMA1EN  = SET;
+  RCC.APB1ENR.B.TIM3EN = SET;
+}
+static inline void Timer3Init (uint32_t us) {
+  TIM3.PSC.R  = 47u;
+  TIM3.ARR.R  = us - 1u;
+  // Preload, enable
+  TIM3.CR1.B.ARPE = SET;
+  // TRGO update for ADC
+  TIM3.CR2.B.MMS  = 2;
+}
+typedef __SIZE_TYPE__ size_t;
+static inline void Dma1Ch1Init (void * ptr) {
+  // Enable DMA transfer on ADC and circular mode
+  ADC.CFGR1.B.DMAEN  = SET;
+  ADC.CFGR1.B.DMACFG = SET;
+  // Configure the peripheral data register address
+  DMA1.CPAR1.R = reinterpret_cast<size_t> (&(ADC.DR));
+  // Configure the memory address
+  DMA1.CMAR1.R = reinterpret_cast<size_t> (ptr);
+  // Configure the number of DMA tranfer to be performs on DMA channel 1
+  DMA1.CNDTR1.R = FULL_LEN;
+  // Configure increment, size, interrupts and circular mode
+  DMA1.CCR1.modify([] (auto & r) -> auto {
+    r.B.MINC  = SET;
+    r.B.MSIZE = 1u;
+    r.B.PSIZE = 1u;
+    r.B.HTIE  = SET;
+    r.B.TCIE  = SET;
+    r.B.CIRC  = SET;
+    return r.R;
+  });
+  // Enable DMA Channel 1
+  DMA1.CCR1.B.EN = SET;
+
+}
+static inline void AdcCalibrate (void) {
+  // Ensure that ADEN = 0
+  // Clear ADEN
+  if (ADC.CR.B.ADEN != RESET) {
+    ADC.CR.B.ADEN = RESET;
+  }
+  // Launch the calibration by setting ADCAL
+  ADC.CR.B.ADCAL = SET;
+  // Wait until ADCAL=0
+  while (ADC.CR.B.ADCAL != RESET);
+  //__NOP();
+  //__NOP();   // This 2 NOPs are to ensure 2 ADC Cycles  before setting ADEN bit
+}
+static inline void AdcInit (void) {
+  // PCLK / 2 - jitter
+  ADC.CFGR2.B.JITOFF_D2 = SET;
+  // Select TRG TIM3
+  ADC.CFGR1.modify([] (auto & r) -> auto {
+    r.B.EXTEN  = 1u;
+    r.B.EXTSEL = 3u;
+    return r.R;
+  });
+  // Select CHSELx
+  ADC.CHSELR.R = (1 << AdcChanel);
+  // Select a sampling mode of 000
+  ADC.SMPR.R   = 1u;
+}
+static inline void AdcStart (void) {
+  ADC.CR.B.ADEN    = SET;
+  TIM3.CR1.B.CEN   = SET;
+  ADC.CR.B.ADSTART = SET;
+}
+static AdcDma * Instance = nullptr;
+
+AdcDma::AdcDma() noexcept : pL (buffer), pH (buffer + HALF_LEN), dst (nullptr) {
+  Instance = this;
+  EnableClock ();
+  AdcCalibrate();
+  GpioClass in   (GpioPortA, AdcPin, GPIO_Mode_AN);
+  Timer3Init     (1000);
+  NVIC_EnableIRQ (DMA1_CH1_IRQn);
+  Dma1Ch1Init (buffer);
+  AdcInit     ();
+  AdcStart    ();
+}
+/*
+void AdcDma::dmaIrq (void) {
+  volatile DMA_ISR_s  status (DMA1.ISR);
+  current = nullptr;
+  if (status.B.HTIF1) current = ptr_l;
+  if (status.B.TCIF1) current = ptr_h;
+  // znuluj příznaky
+  DMA1.IFCR.R = status.R;
+  if (!current) return;
+  // zpracuj data, pokud je potřeba
+  send (current, PERIOD);
+  ~led;
+}
+*/
+extern "C" void DMA1_Channel1_IRQHandler (void) {
+  volatile DMA1_Type::ISR_DEF status (DMA1.ISR);
+  // znuluj příznaky
+  DMA1.IFCR.R = status.R;
+  if (!Instance) return;
+  if      (status.B.HTIF1 != RESET) Instance->send (false);
+  else if (status.B.TCIF1 != RESET) Instance->send (true);
+}
+inline void AdcDma::send(const bool b) {
+  if (!dst) return;
+  if (b) dst->Send (pH, HALF_LEN);
+  else   dst->Send (pL, HALF_LEN);
+}

stm32f051/clang.mk

@@ -0,0 +1,30 @@
+# Use clang / llvm toolchain
+CC = clang
+CXX = clang++
+# linker je vlastně ld.lld
+LD   = clang++
+# Zde kvůli jednoduchosti použijeme arm-none-eabi-g++ jako linker.
+# Clang nemá některé ABI funkce, toolchain je v zásadě kompatibilní,
+# takže než to hledat někde po webu, raději použijeme rovnou libc.
+# Bez složité matematiky jde použít ld.lld nebo přidat libaeabi-cortexm0.a
+# LD = arm-none-eabi-g++
+SIZE = llvm-size
+DUMP = llvm-objdump
+COPY = llvm-objcopy
+
+CCPU   = -mcpu=cortex-m0
+MCPU   = -mthumb $(CCPU)
+TRIP   = thumbv6-none-eabi
+CFLAGS+= -Oz -flto
+#CFLAGS+= -Wno-deprecated-volatile
+CFLAGS+= --target=$(TRIP) $(MCPU)
+LFLAGS+= --target=$(TRIP)
+#LFLAGS+= $(MCPU)
+#LFLAGS+= -nostartfiles
+LFLAGS+= -nostdlib -lto-O3
+LFLAGS+= -Wl,--Map=$(@:%.elf=%.map),--gc-sections
+LDLIBS+= -L./stm32f051 -T script.ld
+LDLIBS+= -L/usr/lib/gcc/arm-none-eabi/9.2.1/thumb/v6-m/nofp -lgcc
+DFLAGS+= --triple=$(TRIP) $(CCPU)
+OBJS  += startup.o system.o gpio.o
+

stm32f051/config.h

@@ -0,0 +1,10 @@
+#ifndef CONFIG_H
+#define CONFIG_H
+
+#define LED_CFG GpioPortA,0
+#define REL_CFG GpioPortA,1
+
+#define SW__ON true
+#define SW_OFF false
+
+#endif // CONFIG_H

stm32f051/gcc.mk

@@ -0,0 +1,21 @@
+# Use gcc / binutils toolchain
+PREFIX = arm-none-eabi-
+CC  = $(PREFIX)gcc
+CXX = $(PREFIX)g++
+# linker je ld
+LD   = $(PREFIX)g++
+SIZE = $(PREFIX)size
+DUMP = $(PREFIX)objdump
+COPY = $(PREFIX)objcopy
+CFLAGS+= -Os -flto
+
+CCPU   = -mcpu=cortex-m0
+MCPU   = -mthumb $(CCPU)
+CFLAGS+= $(MCPU)
+LFLAGS+= $(MCPU)
+LFLAGS+= -Wl,--Map=$(@:%.elf=%.map),--gc-sections
+LFLAGS+= -nostartfiles -flto -O3
+LDLIBS+= -L./stm32f051 -T script.ld
+OBJS  += startup.o system.o gpio.o
+
+

stm32f051/gpio.cpp

@@ -0,0 +1,26 @@
+#include "gpio.h"
+
+static constexpr uint32_t RCC_AHBENR_GPIOAEN = 1u << 17;        /*!< GPIOA clock enable */
+static constexpr uint32_t RCC_AHBENR_GPIOBEN = 1u << 18;        /*!< GPIOB clock enable */
+static constexpr uint32_t RCC_AHBENR_GPIOCEN = 1u << 19;        /*!< GPIOC clock enable */
+static constexpr uint32_t RCC_AHBENR_GPIODEN = 1u << 20;        /*!< GPIOD clock enable */
+static constexpr uint32_t RCC_AHBENR_GPIOFEN = 1u << 22;        /*!< GPIOF clock enable */
+
+static const GpioAssocPort cPortTab[] = {
+  {&GPIOA, RCC_AHBENR_GPIOAEN},
+  {&GPIOB, RCC_AHBENR_GPIOBEN},
+  {&GPIOC, RCC_AHBENR_GPIOCEN},
+  {&GPIOD, RCC_AHBENR_GPIODEN},
+  {&GPIOF, RCC_AHBENR_GPIOFEN},
+};
+GpioClass::GpioClass (GpioPortNum const port, const uint32_t no, const GPIOMode_TypeDef type) noexcept :
+  io(cPortTab[port].portAdr), pos(1UL << no), num(no) {
+  // Povol hodiny
+  RCC.AHBENR.R |= cPortTab[port].clkMask;
+  // A nastav pin (pořadí dle ST knihovny).
+  setSpeed (GPIO_Speed_Level_3);
+  setOType (GPIO_OType_PP);
+  setMode  (type);
+  setPuPd  (GPIO_PuPd_NOPULL);
+}
+

stm32f051/gpio.h

@@ -0,0 +1,142 @@
+#ifndef GPIO_H
+#define GPIO_H
+
+#include "STM32F0x1.h"
+
+/** 
+  * @brief General Purpose IO
+  */
+
+typedef enum {
+  GPIO_Mode_IN   = 0x00, /*!< GPIO Input Mode              */
+  GPIO_Mode_OUT  = 0x01, /*!< GPIO Output Mode             */
+  GPIO_Mode_AF   = 0x02, /*!< GPIO Alternate function Mode */
+  GPIO_Mode_AN   = 0x03  /*!< GPIO Analog In/Out Mode      */
+} GPIOMode_TypeDef;
+
+typedef enum {
+  GPIO_OType_PP = 0x00,
+  GPIO_OType_OD = 0x01
+} GPIOOType_TypeDef;
+
+typedef enum {
+  GPIO_Speed_Level_1  = 0x01, /*!< Medium Speed */
+  GPIO_Speed_Level_2  = 0x02, /*!< Fast Speed   */
+  GPIO_Speed_Level_3  = 0x03  /*!< High Speed   */
+} GPIOSpeed_TypeDef;
+
+typedef enum {
+  GPIO_PuPd_NOPULL = 0x00,
+  GPIO_PuPd_UP     = 0x01,
+  GPIO_PuPd_DOWN   = 0x02
+} GPIOPuPd_TypeDef;
+/// Enum pro PortNumber
+typedef enum {
+  GpioPortA,
+  GpioPortB,
+  GpioPortC,
+  GpioPortD,
+  GpioPortF
+} GpioPortNum;
+/// Asociace port Adress a RCC clock
+struct GpioAssocPort {
+  GPIOF_Type * const portAdr;
+  const uint32_t    clkMask;
+};
+/** @file
+  * @brief Obecný GPIO pin.
+  * 
+  * @class GpioClass
+  * @brief Obecný GPIO pin.
+  * 
+  *  Ukázka přetížení operátorů. Návratové hodnoty jsou v tomto případě celkem zbytečné,
+  * ale umožňují řetězení, takže je možné napsat např.
+    @code
+    +-+-+-led;
+    @endcode
+  * a máme na led 3 pulsy. Je to sice blbost, ale funguje.
+  * Všechny metody jsou konstantní, protože nemění data uvnitř třídy.
+  * Vlastně ani nemohou, protože data jsou konstantní.
+*/
+class GpioClass {
+  public:
+    /** Konstruktor
+    @param port GpioPortA | GpioPortB | GpioPortC | GpioPortD | GpioPortF
+    @param no   číslo pinu na portu
+    @param type IN, OUT, AF, AN default OUT 
+    */
+    explicit GpioClass (GpioPortNum const port, const uint32_t no, const GPIOMode_TypeDef type = GPIO_Mode_OUT) noexcept;
+    /// Nastav pin @param b na tuto hodnotu
+    const GpioClass& operator<< (const bool b) const {
+      if (b) io->BSRR.R = pos;
+      else   io->BRR.R  = pos;
+      return *this;
+    }
+//![Gpio example]
+    /// Nastav pin na log. H
+    const GpioClass& operator+ (void) const {
+      io->BSRR.R = (uint32_t) pos;
+      return *this;
+    }
+    /// Nastav pin na log. L
+    const GpioClass& operator- (void) const {
+      io->BRR.R  = pos;
+      return *this;
+    }
+    /// Změň hodnotu pinu
+    const GpioClass& operator~ (void) const {
+      io->ODR.R ^= pos;
+      return *this;
+    };
+    /// Načti logickou hodnotu na pinu
+    const bool get (void) const {
+      if (io->IDR.R & pos) return true;
+      else               return false;
+    };
+    /// A to samé jako operátor
+    const GpioClass& operator>> (bool& b) const {
+      b = get();
+      return *this;
+    }
+//![Gpio example]
+    void setMode (GPIOMode_TypeDef p) {
+      uint32_t dno = num * 2;
+      io->MODER.R   &= ~(3UL << dno);
+      io->MODER.R   |=  (p   << dno);
+    }
+    void setOType (GPIOOType_TypeDef p) {
+      io->OTYPER.R  &= (uint16_t)~(1UL << num);
+      io->OTYPER.R  |= (uint16_t) (p   << num);
+    }
+    void setSpeed (GPIOSpeed_TypeDef p) {
+      uint32_t dno = num * 2;
+      io->OSPEEDR.R &= ~(3UL << dno);
+      io->OSPEEDR.R |=  (p   << dno);
+    }
+    void setPuPd (GPIOPuPd_TypeDef p) {
+      uint32_t dno = num * 2;
+      io->PUPDR.R   &= ~(3UL << dno);
+      io->PUPDR.R   |=  (p   << dno);
+    }
+    void setAF (unsigned af) {
+      unsigned int pd,pn = num;
+      pd = (pn & 7) << 2; pn >>= 3;
+      if (pn) {
+        io->AFRH.R &= ~(0xFU << pd);
+        io->AFRH.R |=  (  af << pd);
+      } else {
+        io->AFRL.R &= ~(0xFU << pd);
+        io->AFRL.R |=  (  af << pd);
+      }
+    }
+  private:
+    /// Port.
+    GPIOF_Type * const io;
+    /// A pozice pinu na něm, stačí 16.bit
+    const uint16_t   pos;
+    /// pro funkce setXXX necháme i číslo pinu
+    const uint16_t   num;
+  
+};
+
+#endif // GPIO_H

stm32f051/script.ld

@@ -0,0 +1,94 @@
+/*
+*/
+
+/* Entry Point */
+ENTRY(Vectors)
+
+/* Generate a link error if heap and stack don't fit into RAM */
+_Min_Heap_Size  = 0; /* required amount of heap  */
+_Min_Stack_Size = 0; /* required amount of stack */
+
+/* Specify the memory areas */
+MEMORY {
+  FLASH (rx)      : ORIGIN = 0x08000000, LENGTH = 64K
+  RAM (xrw)       : ORIGIN = 0x20000000, LENGTH = 8K
+}
+
+/* Highest address of the user mode stack */
+_estack = ORIGIN(RAM) + LENGTH(RAM);
+
+/* Define output sections */
+SECTIONS {
+  /* The startup code goes first into FLASH */
+  /* The program code and other data goes into FLASH */
+  .text :
+  {
+    . = ALIGN(4);
+    KEEP(*(.isr_vector)) /* Startup code */
+    . = ALIGN(4);
+    *(.text)           /* .text sections (code) */
+    *(.text*)          /* .text* sections (code) */
+    *(.rodata)         /* .rodata sections (constants, strings, etc.) */
+    *(.rodata*)        /* .rodata* sections (constants, strings, etc.) */
+    *(.glue_7)         /* glue arm to thumb code */
+    *(.glue_7t)        /* glue thumb to arm code */
+    *(.eh_frame)
+
+    *(.init)
+    *(.fini)
+    /* Pro použití statických konstruktorů v C++, KEEP musí být použit při gc */
+    . = ALIGN(4);
+    PROVIDE_HIDDEN (__init_array_start = .);
+    KEEP (*(.ctors))		/* for clang */
+    KEEP (*(.init_array*))
+    PROVIDE_HIDDEN (__init_array_end   = .);
+    
+    . = ALIGN(4);
+    _etext = .;        /* define a global symbols at end of code */
+  } >FLASH
+
+  /* used by the startup to initialize data */
+  _sidata = .;
+
+  /* Initialized data sections goes into RAM, load LMA copy after code */
+  .data : AT ( _sidata )
+  {
+    . = ALIGN(4);
+    _sdata = .;        /* create a global symbol at data start */
+    *(.data)           /* .data sections */
+    *(.data*)          /* .data* sections */
+
+    . = ALIGN(4);
+    _edata = .;        /* define a global symbol at data end */
+  } >RAM
+
+  /* Uninitialized data section */
+  . = ALIGN(4);
+  .bss :
+  {
+    /* This is used by the startup in order to initialize the .bss secion */
+    _sbss = .;         /* define a global symbol at bss start */
+    __bss_start__ = _sbss;
+    *(.bss)
+    *(.bss*)
+    *(COMMON)
+    _ebss = .;
+    __bss_end__ = _ebss;
+  } >RAM
+
+  _end = .;
+  /* Remove information from the standard libraries */
+  /DISCARD/ :
+  {
+    /*
+    libc.a ( * )
+    libm.a ( * )
+    libgcc.a ( * )
+    *(.debug*)
+    */
+    *(.comment*)
+    *(.ARM.*)
+  }
+
+  .ARM.attributes 0 : { *(.ARM.attributes) }
+}

stm32f051/startup.c

@@ -0,0 +1,163 @@
+#include <stdint.h>
+
+#if defined (__cplusplus)
+extern "C" {
+#endif
+//! [InitStaticConstructors]
+extern void (*__init_array_start)(); // definováno v linker skriptu
+extern void (*__init_array_end)  (); // definováno v linker skriptu
+void static_init() {
+  void (**p)();
+  for (p = &__init_array_start; p < &__init_array_end; p++) (*p)();
+}
+//! [InitStaticConstructors]
+#define WEAK     __attribute__ ((weak))
+#define ALIAS(f) __attribute__ ((weak, alias (#f)))
+
+extern unsigned int _estack;
+extern unsigned int _sidata;
+extern unsigned int _sdata;
+extern unsigned int _edata;
+extern unsigned int _sbss;
+extern unsigned int _ebss;
+
+WEAK void Reset_Handler     (void);
+WEAK void DefaultHandler    (void);
+void NonMaskableInt_Handler                 (void) ALIAS(Default_Handler);
+void HardFault_Handler                      (void) ALIAS(Default_Handler);
+void MemoryManagement_Handler               (void) ALIAS(Default_Handler);
+void BusFault_Handler                       (void) ALIAS(Default_Handler);
+void UsageFault_Handler                     (void) ALIAS(Default_Handler);
+void SVCall_Handler                         (void) ALIAS(Default_Handler);
+void DebugMonitor_Handler                   (void) ALIAS(Default_Handler);
+void PendSV_Handler                         (void) ALIAS(Default_Handler);
+void SysTick_Handler                        (void) ALIAS(Default_Handler);
+
+void WWDG_IRQHandler                        (void) ALIAS(Default_Handler);
+void PVD_IRQHandler                         (void) ALIAS(Default_Handler);
+void RTC_IRQHandler                         (void) ALIAS(Default_Handler);
+void FLASH_IRQHandler                       (void) ALIAS(Default_Handler);
+void RCC_CRS_IRQHandler                     (void) ALIAS(Default_Handler);
+void EXTI0_1_IRQHandler                     (void) ALIAS(Default_Handler);
+void EXTI2_3_IRQHandler                     (void) ALIAS(Default_Handler);
+void EXTI4_15_IRQHandler                    (void) ALIAS(Default_Handler);
+void TSC_IRQHandler                         (void) ALIAS(Default_Handler);
+void DMA1_CH1_IRQHandler                    (void) ALIAS(Default_Handler);
+void DMA1_CH2_3_DMA2_CH1_2_IRQHandler       (void) ALIAS(Default_Handler);
+void DMA1_CH4_5_6_7_DMA2_CH3_4_5_IRQHandler (void) ALIAS(Default_Handler);
+void ADC_COMP_IRQHandler                    (void) ALIAS(Default_Handler);
+void TIM1_BRK_UP_TRG_COM_IRQHandler         (void) ALIAS(Default_Handler);
+void TIM1_CC_IRQHandler                     (void) ALIAS(Default_Handler);
+void TIM2_IRQHandler                        (void) ALIAS(Default_Handler);
+void TIM3_IRQHandler                        (void) ALIAS(Default_Handler);
+void TIM6_DAC_IRQHandler                    (void) ALIAS(Default_Handler);
+void TIM7_IRQHandler                        (void) ALIAS(Default_Handler);
+void TIM14_IRQHandler                       (void) ALIAS(Default_Handler);
+void TIM15_IRQHandler                       (void) ALIAS(Default_Handler);
+void TIM16_IRQHandler                       (void) ALIAS(Default_Handler);
+void TIM17_IRQHandler                       (void) ALIAS(Default_Handler);
+void I2C1_IRQHandler                        (void) ALIAS(Default_Handler);
+void I2C2_IRQHandler                        (void) ALIAS(Default_Handler);
+void SPI1_IRQHandler                        (void) ALIAS(Default_Handler);
+void SPI2_IRQHandler                        (void) ALIAS(Default_Handler);
+void USART1_IRQHandler                      (void) ALIAS(Default_Handler);
+void USART2_IRQHandler                      (void) ALIAS(Default_Handler);
+void USART3_4_5_6_7_8_IRQHandler            (void) ALIAS(Default_Handler);
+void CEC_CAN_IRQHandler                     (void) ALIAS(Default_Handler);
+void USB_IRQHandler                         (void) ALIAS(Default_Handler);
+
+extern int  main (void);
+extern void SystemInit (void);
+extern void SystemCoreClockUpdate (void);
+
+#if defined (__cplusplus)
+}; // extern "C"
+#endif
+typedef void (*handler) (void);
+__attribute__ ((section(".isr_vector")))
+handler Vectors[] = {
+  (handler) &_estack,
+  Reset_Handler,
+  NonMaskableInt_Handler,
+  HardFault_Handler,
+  MemoryManagement_Handler,
+  BusFault_Handler,
+  UsageFault_Handler,
+  0,
+  0,
+  0,
+  0,
+  SVCall_Handler,
+  DebugMonitor_Handler,
+  0,
+  PendSV_Handler,
+  SysTick_Handler,
+
+  WWDG_IRQHandler,
+  PVD_IRQHandler,
+  RTC_IRQHandler,
+  FLASH_IRQHandler,
+  RCC_CRS_IRQHandler,
+  EXTI0_1_IRQHandler,
+  EXTI2_3_IRQHandler,
+  EXTI4_15_IRQHandler,
+  TSC_IRQHandler,
+  DMA1_CH1_IRQHandler,
+  DMA1_CH2_3_DMA2_CH1_2_IRQHandler,
+  DMA1_CH4_5_6_7_DMA2_CH3_4_5_IRQHandler,
+  ADC_COMP_IRQHandler,
+  TIM1_BRK_UP_TRG_COM_IRQHandler,
+  TIM1_CC_IRQHandler,
+  TIM2_IRQHandler,
+  TIM3_IRQHandler,
+  TIM6_DAC_IRQHandler,
+  TIM7_IRQHandler,
+  TIM14_IRQHandler,
+  TIM15_IRQHandler,
+  TIM16_IRQHandler,
+  TIM17_IRQHandler,
+  I2C1_IRQHandler,
+  I2C2_IRQHandler,
+  SPI1_IRQHandler,
+  SPI2_IRQHandler,
+  USART1_IRQHandler,
+  USART2_IRQHandler,
+  USART3_4_5_6_7_8_IRQHandler,
+  CEC_CAN_IRQHandler,
+  USB_IRQHandler,
+
+};
+static inline void fillStack (void) {
+  register unsigned int *dst, *end;
+  dst = &_ebss;
+  end = &_estack;
+  while (dst < end) *dst++ = 0xDEADBEEFU;
+}
+void Reset_Handler(void) {
+  
+  fillStack();
+  
+  register unsigned int *src, *dst, *end;
+  /* Zero fill the bss section */
+  dst = &_sbss;
+  end = &_ebss;
+  while (dst < end)  *dst++ = 0U;
+
+  /* Copy data section from flash to RAM */
+  src = &_sidata;
+  dst = &_sdata;
+  end = &_edata;
+  while (dst < end) *dst++ = *src++;
+
+  SystemInit();
+  SystemCoreClockUpdate();          // Potřebné pro USART
+  static_init();                    // Zde zavolám globální konstruktory
+
+  main();
+
+  for (;;);
+}
+
+void Default_Handler (void) {
+  asm volatile ("bkpt 1");
+}

stm32f051/system.cpp

@@ -0,0 +1,232 @@
+#include "STM32F0x1.h"
+#include "system.h"
+
+#if !defined  (HSE_VALUE)     
+#define HSE_VALUE        ((uint32_t)8000000)           /*!< Value of the External oscillator in Hz */
+#endif /* HSE_VALUE */
+#if !defined  (HSI_VALUE) 
+#define HSI_VALUE        ((uint32_t)8000000)           /*!< Value of the Internal High Speed oscillator in Hz. */
+#endif /* HSI_VALUE */
+
+#define HSE_STARTUP_TIMEOUT   ((uint16_t)0x5000)       /*!< Time out for HSE start up */
+//! [EnumExampleSW_EN_Def]
+typedef enum {
+  USEHSI = 0, USEHSE, USEPLL
+} SW_EN;
+//! [EnumExampleSW_EN_Def]
+typedef enum {
+  RCC_CFGR_PLLMUL2 = 0,
+  RCC_CFGR_PLLMUL3, 
+  RCC_CFGR_PLLMUL4, 
+  RCC_CFGR_PLLMUL5, 
+  RCC_CFGR_PLLMUL6, 
+  RCC_CFGR_PLLMUL7, 
+  RCC_CFGR_PLLMUL8, 
+  RCC_CFGR_PLLMUL9, 
+  RCC_CFGR_PLLMUL10,
+  RCC_CFGR_PLLMUL11,
+  RCC_CFGR_PLLMUL12,
+  RCC_CFGR_PLLMUL13,
+  RCC_CFGR_PLLMUL14,
+  RCC_CFGR_PLLMUL15,
+  RCC_CFGR_PLLMUL16,
+} PLLML_EN;
+
+/* Select the PLL clock source */
+//#define PLL_SOURCE_HSI        // HSI (~8MHz) used to clock the PLL, and the PLL is used as system clock source
+  #define PLL_SOURCE_HSE        // HSE (8MHz) used to clock the PLL, and the PLL is used as system clock source
+//#define PLL_SOURCE_HSE_BYPASS // HSE bypassed with an external clock (8MHz, coming from ST-Link) used to clock
+// the PLL, and the PLL is used as system clock source
+
+uint32_t SystemCoreClock    = 48000000;
+const uint8_t AHBPrescTable[16] = {0, 0, 0, 0, 0, 0, 0, 0, 1, 2, 3, 4, 6, 7, 8, 9};
+
+
+static void SetSysClock (void);
+
+/**
+  * @brief  Setup the microcontroller system.
+  *         Initialize the Embedded Flash Interface, the PLL and update the
+  *         SystemCoreClock variable.
+  * @param  None
+  * @retval None
+  */
+extern "C"
+void SystemInit (void) {
+  /* Set HSION bit */
+  RCC.CR.R    |= (uint32_t) 0x00000001;
+  /* Reset SW[1:0], HPRE[3:0], PPRE[2:0], ADCPRE and MCOSEL[2:0] bits */
+  RCC.CFGR.R  &= (uint32_t) 0xF8FFB80C;
+  /* Reset HSEON, CSSON and PLLON bits */
+  RCC.CR.R    &= (uint32_t) 0xFEF6FFFF;
+  /* Reset HSEBYP bit */
+  RCC.CR.R    &= (uint32_t) 0xFFFBFFFF;
+  /* Reset PLLSRC, PLLXTPRE and PLLMUL[3:0] bits */
+  RCC.CFGR.R  &= (uint32_t) 0xFFC0FFFF;
+  /* Reset PREDIV1[3:0] bits */
+  RCC.CFGR2.R &= (uint32_t) 0xFFFFFFF0;
+  /* Reset USARTSW[1:0], I2CSW, CECSW and ADCSW bits */
+  RCC.CFGR3.R &= (uint32_t) 0xFFFFFEAC;
+  /* Reset HSI14 bit */
+  RCC.CR2.R   &= (uint32_t) 0xFFFFFFFE;
+  /* Disable all interrupts */
+  RCC.CIR.R = 0x00000000u;
+  /* Configure the System clock frequency, AHB/APBx prescalers and Flash settings */
+  SetSysClock();
+}
+
+/**
+  * @brief  Update SystemCoreClock according to Clock Register Values
+  *         The SystemCoreClock variable contains the core clock (HCLK), it can
+  *         be used by the user application to setup the SysTick timer or configure
+  *         other parameters.
+  *
+  * @note   Each time the core clock (HCLK) changes, this function must be called
+  *         to update SystemCoreClock variable value. Otherwise, any configuration
+  *         based on this variable will be incorrect.
+  *
+  * @note   - The system frequency computed by this function is not the real
+  *           frequency in the chip. It is calculated based on the predefined
+  *           constant and the selected clock source:
+  *
+  *           - If SYSCLK source is HSI, SystemCoreClock will contain the HSI_VALUE(*)
+  *
+  *           - If SYSCLK source is HSE, SystemCoreClock will contain the HSE_VALUE(**)
+  *
+  *           - If SYSCLK source is PLL, SystemCoreClock will contain the HSE_VALUE(**)
+  *             or HSI_VALUE(*) multiplied/divided by the PLL factors.
+  *
+  *         (*) HSI_VALUE is a constant defined in stm32f0xx.h file (default value
+  *             8 MHz) but the real value may vary depending on the variations
+  *             in voltage and temperature.
+  *
+  *         (**) HSE_VALUE is a constant defined in stm32f0xx.h file (default value
+  *              8 MHz), user has to ensure that HSE_VALUE is same as the real
+  *              frequency of the crystal used. Otherwise, this function may
+  *              have wrong result.
+  *
+  *         - The result of this function could be not correct when using fractional
+  *           value for HSE crystal.
+  * @param  None
+  * @retval None
+  */
+extern "C"
+void SystemCoreClockUpdate (void) {
+  uint32_t prediv1factor, pllmull;
+
+//! [EnumExampleSW_EN_Use]
+  switch (RCC.CFGR.B.SWS) {
+    case USEHSI:  /* HSI used as system clock */
+      SystemCoreClock = HSI_VALUE;
+      break;
+    case USEHSE:  /* HSE used as system clock */
+      SystemCoreClock = HSE_VALUE;
+      break;
+    case USEPLL:  /* PLL used as system clock */
+      /* Get PLL clock source and multiplication factor */
+      pllmull = RCC.CFGR.B.PLLMUL + 2u;
+      // ...
+//! [EnumExampleSW_EN_Use]
+      if (RCC.CFGR.B.PLLSRC == RESET) {
+        /* HSI oscillator clock divided by 2 selected as PLL clock entry */
+        SystemCoreClock = (HSI_VALUE >> 1) * pllmull;
+      } else {
+        prediv1factor = RCC.CFGR2.B.PREDIV + 1;
+        /* HSE oscillator clock selected as PREDIV1 clock entry */
+        SystemCoreClock = (HSE_VALUE / prediv1factor) * pllmull;
+      }
+      break;
+    default: /* HSI used as system clock */
+      SystemCoreClock = HSI_VALUE;
+      break;
+  }
+  /* Compute HCLK clock frequency */
+  /* Get HCLK prescaler */
+  pllmull = AHBPrescTable[RCC.CFGR.B.HPRE];
+  /* HCLK clock frequency */
+  SystemCoreClock >>= pllmull;
+}
+
+/**
+  * @brief  Configures the System clock frequency, AHB/APBx prescalers and Flash
+  *         settings.
+  * @note   This function should be called only once the RCC clock configuration
+  *         is reset to the default reset state (done in SystemInit() function).
+  * @param  None
+  * @retval None
+  */
+
+static void SetSysClock (void) {
+  /* SYSCLK, HCLK, PCLK configuration */
+#if defined (PLL_SOURCE_HSI)
+  /* At this stage the HSI is already enabled */
+  /* Enable Prefetch Buffer and set Flash Latency */
+  Flash.ACR.setbit([] (auto & r) -> auto { // C++14
+    r.B.PRFTBE  = SET;
+    r.B.LATENCY = SET;
+    return r.R;
+  });
+  RCC.CFGR.modify([] (auto & r) -> auto {
+    r.B.HPRE     = 0;
+    r.B.PPRE     = 0;
+    r.B.PLLSRC   = RESET;
+    r.B.PLLXTPRE = RESET;
+    r.B.PLLMUL   = RCC_CFGR_PLLMUL12;
+    return r.R;
+  });
+  /* Enable PLL */
+  RCC.CR.B.PLLON = SET;
+  /* Wait till PLL is ready */
+  while ((RCC.CR.B.PLLRDY) == RESET);
+  /* Select PLL as system clock source */
+  RCC.CFGR.B.SW = USEPLL;
+  /* Wait till PLL is used as system clock source */
+  while (RCC.CFGR.B.SWS != USEPLL);
+#else
+#if defined (PLL_SOURCE_HSE)
+  /* Enable HSE */
+  RCC.CR.B.HSEON = SET;
+#elif defined (PLL_SOURCE_HSE_BYPASS)
+  /* HSE oscillator bypassed with external clock */
+  RCC.CR.B.HSEON  = SET;
+  RCC.CR.B.HSEBYP = SET;
+#endif /* PLL_SOURCE_HSE */
+  __IO uint32_t StartUpCounter = 0;
+  __IO uint32_t HSEStatus;
+  /* Wait till HSE is ready and if Time out is reached exit */
+  do {
+    HSEStatus = RCC.CR.B.HSERDY;
+    StartUpCounter++;
+  } while ((HSEStatus == RESET) && (StartUpCounter != HSE_STARTUP_TIMEOUT));
+
+  HSEStatus = RCC.CR.B.HSERDY;
+
+  if (HSEStatus == SET) {
+    /* Enable Prefetch Buffer and set Flash Latency */
+    Flash.ACR.setbit([] (auto & r) -> uint32_t {
+      r.B.PRFTBE  = SET;
+      r.B.LATENCY = SET;
+      return r.R;
+    });
+    RCC.CFGR.modify([] (auto & r) -> uint32_t {
+      r.B.HPRE     = 0;
+      r.B.PPRE     = 0;
+      r.B.PLLSRC   = SET;
+      r.B.PLLXTPRE = RESET;
+      r.B.PLLMUL   = RCC_CFGR_PLLMUL12;
+      return r.R;
+    });
+    /* Enable PLL */
+    RCC.CR.B.PLLON = SET;
+    /* Wait till PLL is ready */
+    while ((RCC.CR.B.PLLRDY) == RESET);
+    /* Select PLL as system clock source */
+    RCC.CFGR.B.SW = USEPLL;
+    /* Wait till PLL is used as system clock source */
+    while (RCC.CFGR.B.SWS != USEPLL);
+  } else {
+    /* If HSE fails to start-up, the application will have wrong clock
+         configuration. User can add here some code to deal with this error */
+  }
+#endif /* PLL_SOURCE_HSI */
+}

stm32f051/system.h

@@ -0,0 +1,17 @@
+#ifndef __SYSTEM_STM32F0XX_H
+#define __SYSTEM_STM32F0XX_H
+
+#ifdef __cplusplus
+ extern "C" {
+#endif 
+
+extern uint32_t SystemCoreClock;          /*!< System Clock Frequency (Core Clock) */
+extern void SystemInit(void);
+extern void SystemCoreClockUpdate(void);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /*__SYSTEM_STM32F0XX_H */
+

stm32f051/usart.cpp

@@ -0,0 +1,110 @@
+#include "STM32F0x1.h"
+#include "CortexM0.h"   // NVIC_EnableIRQ
+#include "gpio.h"
+#include "usart.h"
+
+extern "C" uint32_t SystemCoreClock;
+static Usart * Instance = nullptr;
+
+void Usart::irq (void) {
+  volatile USART1_Type::ISR_DEF status (USART1.ISR);    // načti status přerušení
+  char tdata;
+  volatile char rdata;
+  if (status.B.TC) {                         // od vysílače
+    if (tx_ring.Read (tdata)) {               // pokud máme data
+      USART1.TDR.R = (uint32_t) tdata & 0xFFu;// zapíšeme do výstupu
+    } else {                                  // pokud ne
+    //USART1.CR1.B.RE   = SET;                // povol prijem
+      USART1.CR1.B.TCIE = RESET;              // je nutné zakázat přerušení od vysílače
+    }
+  }
+  if (status.B.RXNE) {                       // od přijímače
+    rdata = (USART1.RDR.R) & 0xFFu;           // načteme data
+    (void) rdata;           // zahodime
+  }
+}
+/// Voláno z čistého C - startup.c
+extern "C" void USART1_IRQHandler (void) {
+  if (Instance) Instance->irq();
+};
+//! [MembersConstructorExample]
+Usart::Usart(const uint32_t baud) noexcept : BaseLayer(), tx_ring() {
+//! [MembersConstructorExample]
+  if (Instance) return;     // Chyba - jedina instance
+  Instance = this;
+  // 1. Clock Enable
+  RCC.APB2ENR.B.USART1EN = SET;
+  // 2. GPIO Alternate Config
+  GpioClass txp (GpioPortA,  9, GPIO_Mode_AF);
+  GpioClass rxp (GpioPortA, 10, GPIO_Mode_AF);
+  txp.setAF (1);
+  rxp.setAF (1);
+  // 4. NVIC
+  NVIC_EnableIRQ (USART1_IRQn);
+  uint32_t tmp = 0;
+  // 5. USART registry 8.bit bez parity
+  USART1.CR1.modify([] (USART1_Type::CR1_DEF & r) -> uint32_t { // pro ilustraci, co by bylo auto
+    r.B.TE      = SET;
+  //r.B.RE      = SET;  // příjem je zde zbytečný
+  //r.B.RXNEIE  = SET;
+    return r.R;
+  });
+  USART1.CR2.R = 0;
+  USART1.CR3.B.OVRDIS = SET;
+  // Tuhle část už vezmeme přímo z knihovny, jen ty hodiny zjednodušíme na SystemCoreClock
+  uint32_t apbclock = SystemCoreClock;
+  uint32_t integerdivider, fractionaldivider;
+  /* Determine the integer part */
+  if (USART1.CR1.B.OVER8 != RESET) {
+    /* Integer part computing in case Oversampling mode is 8 Samples */
+    integerdivider = ((25u * apbclock) / (2u * (baud)));    
+  } else  {
+    /* Integer part computing in case Oversampling mode is 16 Samples */
+    integerdivider = ((25u * apbclock) / (4u * (baud)));    
+  }
+  tmp = (integerdivider / 100u) << 4;
+  /* Determine the fractional part */
+  fractionaldivider = integerdivider - (100u * (tmp >> 4));
+  /* Implement the fractional part in the register */
+  if (USART1.CR1.B.OVER8 != RESET) {
+    tmp |= ((((fractionaldivider * 8u ) + 50u) / 100u)) & ((uint8_t)0x07u);
+  } else {
+    tmp |= ((((fractionaldivider * 16u) + 50u) / 100u)) & ((uint8_t)0x0Fu);
+  } 
+  /* Write to USART BRR */
+  USART1.BRR.R = (uint16_t)tmp;
+  USART1.CR1.B.UE = SET;        // nakonec povolit globálně
+}
+//! [VirtualMethodBottom]
+uint32_t Usart::Down (const char * data, const uint32_t len) {
+  uint32_t res;                 // výsledek, musí žít i po ukončení smyčky
+  for (res=0; res<len; res++) if (!tx_ring.Write(data[res])) break;
+  USART1.CR1.B.TCIE = SET;      // po povolení přerušení okamžitě přeruší
+  return res;
+}
+//! [VirtualMethodBottom]
+void Usart::SetHalfDuplex (const bool on) const {
+  USART1.CR1.B.UE = RESET;       // zakázat, jinak nelze nastavovat
+  if (on)  USART1.CR3.B.HDSEL = SET;    // poloduplex on
+  else     USART1.CR3.B.HDSEL = RESET;  // poloduplex off
+  USART1.CR1.B.UE = SET;         // nakonec povolit globálně
+}
+void Usart::SetRS485 (const bool polarity) const {
+  USART1.CR1.B.UE = RESET;       // zakázat, jinak nelze nastavovat
+  // Nastavit pin DE (RTS)
+  GpioClass de (GpioPortA,  12u, GPIO_Mode_AF);
+  de.setAF (1u);
+  // Nastavení driveru
+  USART1.CR3.B.DEM  = SET;       // povolit DE v USARTu
+  if (polarity) USART1.CR3.B.DEP = SET;
+  else          USART1.CR3.B.DEP = RESET;
+  // A nakonec doby vybavení (přesah) - to je hodně užitečné
+//! [LambdaExampleUsage]
+  USART1.CR1.modify([] (auto & r) -> auto {
+    r.B.DEAT   = 1u;       // doba vybavení před start bitem - 16 ~= 1 bit, 0..31
+    r.B.DEDT   = 1u;       // doba vybavení po stop bitu     - 16 ~= 1 bit, 0..31
+    return r.R;
+  });
+//! [LambdaExampleUsage]
+  USART1.CR1.B.UE = SET;
+}