text: #include <string.h>
  
  #include "py/runtime.h"
  #include "py/mperrno.h"
  #include "py/mphal.h"
  #include "extmod/misc.h"
  #include "usb.h"
  #include "uart.h"
  
  // this table converts from HAL_StatusTypeDef to POSIX errno
  const byte mp_hal_status_to_errno_table[4] = {
      [HAL_OK] = 0,
      [HAL_ERROR] = MP_EIO,
      [HAL_BUSY] = MP_EBUSY,
      [HAL_TIMEOUT] = MP_ETIMEDOUT,
  };
  
  NORETURN void mp_hal_raise(HAL_StatusTypeDef status) {
      mp_raise_OSError(mp_hal_status_to_errno_table[status]);
  }
  
  int mp_hal_stdin_rx_chr(void) {
      for (;;) {
  #if 0
  #ifdef USE_HOST_MODE
          pyb_usb_host_process();
          int c = pyb_usb_host_get_keyboard();
          if (c != 0) {
              return c;
          }
  #endif
  #endif
  
          #if MICROPY_HW_ENABLE_USB
          byte c;
          if (usb_vcp_recv_byte(&c) != 0) {
              return c;
          }
          #endif
          if (MP_STATE_PORT(pyb_stdio_uart) != NULL && uart_rx_any(MP_STATE_PORT(pyb_stdio_uart))) {
              return uart_rx_char(MP_STATE_PORT(pyb_stdio_uart));
          }
          int dupterm_c = mp_uos_dupterm_rx_chr();
          if (dupterm_c >= 0) {
              return dupterm_c;
          }
          MICROPY_EVENT_POLL_HOOK
      }
  }
  
  void mp_hal_stdout_tx_str(const char *str) {
      mp_hal_stdout_tx_strn(str, strlen(str));
  }
  
  void mp_hal_stdout_tx_strn(const char *str, size_t len) {
      if (MP_STATE_PORT(pyb_stdio_uart) != NULL) {
          uart_tx_strn(MP_STATE_PORT(pyb_stdio_uart), str, len);
      }
  #if 0 && defined(USE_HOST_MODE) && MICROPY_HW_HAS_LCD
      lcd_print_strn(str, len);
  #endif
      #if MICROPY_HW_ENABLE_USB
      if (usb_vcp_is_enabled()) {
          usb_vcp_send_strn(str, len);
      }
      #endif
      mp_uos_dupterm_tx_strn(str, len);
  }
  
  // Efficiently convert "\n" to "\r\n"
  void mp_hal_stdout_tx_strn_cooked(const char *str, size_t len) {
      const char *last = str;
      while (len--) {
          if (*str == '\n') {
              if (str > last) {
                  mp_hal_stdout_tx_strn(last, str - last);
              }
              mp_hal_stdout_tx_strn("\r\n", 2);
              ++str;
              last = str;
          } else {
              ++str;
          }
      }
      if (str > last) {
          mp_hal_stdout_tx_strn(last, str - last);
      }
  }
  
  void mp_hal_ticks_cpu_enable(void) {
      if (!(DWT->CTRL & DWT_CTRL_CYCCNTENA_Msk)) {
          CoreDebug->DEMCR |= CoreDebug_DEMCR_TRCENA_Msk;
          #if defined(__CORTEX_M) && __CORTEX_M == 7
          // on Cortex-M7 we must unlock the DWT before writing to its registers
          DWT->LAR = 0xc5acce55;
          #endif
          DWT->CYCCNT = 0;
          DWT->CTRL |= DWT_CTRL_CYCCNTENA_Msk;
      }
  }
  
  void mp_hal_gpio_clock_enable(GPIO_TypeDef *gpio) {
      #if defined(STM32L476xx) || defined(STM32L496xx)
      if (gpio == GPIOG) {
          // Port G pins 2 thru 15 are powered using VddIO2 on these MCUs.
          HAL_PWREx_EnableVddIO2();
      }
      #endif
  
      // This logic assumes that all the GPIOx_EN bits are adjacent and ordered in one register
  
      #if defined(STM32F4) || defined(STM32F7)
      #define AHBxENR AHB1ENR
      #define AHBxENR_GPIOAEN_Pos RCC_AHB1ENR_GPIOAEN_Pos
      #elif defined(STM32H7)
      #define AHBxENR AHB4ENR
      #define AHBxENR_GPIOAEN_Pos RCC_AHB4ENR_GPIOAEN_Pos
      #elif defined(STM32L4)
      #define AHBxENR AHB2ENR
      #define AHBxENR_GPIOAEN_Pos RCC_AHB2ENR_GPIOAEN_Pos
      #endif
  
      uint32_t gpio_idx = ((uint32_t)gpio - GPIOA_BASE) / (GPIOB_BASE - GPIOA_BASE);
      RCC->AHBxENR |= 1 << (AHBxENR_GPIOAEN_Pos + gpio_idx);
      volatile uint32_t tmp = RCC->AHBxENR; // Delay after enabling clock
      (void)tmp;
  }
  
  void mp_hal_pin_config(mp_hal_pin_obj_t pin_obj, uint32_t mode, uint32_t pull, uint32_t alt) {
      GPIO_TypeDef *gpio = pin_obj->gpio;
      uint32_t pin = pin_obj->pin;
      mp_hal_gpio_clock_enable(gpio);
      gpio->MODER = (gpio->MODER & ~(3 << (2 * pin))) | ((mode & 3) << (2 * pin));
      #if defined(GPIO_ASCR_ASC0)
      // The L4 has a special analog switch to connect the GPIO to the ADC
      gpio->OTYPER = (gpio->OTYPER & ~(1 << pin)) | (((mode >> 2) & 1) << pin);
      gpio->ASCR = (gpio->ASCR & ~(1 << pin)) | ((mode >> 3) & 1) << pin;
      #else
      gpio->OTYPER = (gpio->OTYPER & ~(1 << pin)) | ((mode >> 2) << pin);
      #endif
      gpio->OSPEEDR = (gpio->OSPEEDR & ~(3 << (2 * pin))) | (2 << (2 * pin)); // full speed
      gpio->PUPDR = (gpio->PUPDR & ~(3 << (2 * pin))) | (pull << (2 * pin));
      gpio->AFR[pin >> 3] = (gpio->AFR[pin >> 3] & ~(15 << (4 * (pin & 7)))) | (alt << (4 * (pin & 7)));
  }
  
  bool mp_hal_pin_config_alt(mp_hal_pin_obj_t pin, uint32_t mode, uint32_t pull, uint8_t fn, uint8_t unit) {
      const pin_af_obj_t *af = pin_find_af(pin, fn, unit);
      if (af == NULL) {
          return false;
      }
      mp_hal_pin_config(pin, mode, pull, af->idx);
      return true;
  }
  
  void mp_hal_pin_config_speed(mp_hal_pin_obj_t pin_obj, uint32_t speed) {
      GPIO_TypeDef *gpio = pin_obj->gpio;
      uint32_t pin = pin_obj->pin;
      gpio->OSPEEDR = (gpio->OSPEEDR & ~(3 << (2 * pin))) | (speed << (2 * pin));
  }
  