Lee Richmond

template<unsigned int P, unsigned char N, bool = N >= 8>
struct GpioMode
{
  inline static void mode(Mode::Mode_ m)
  {
    reinterpret_cast<GPIO_TypeDef*>(P)->CRH &= ~(0xf<<((N-8)*4));
    reinterpret_cast<GPIO_TypeDef*>(P)->CRH |= m<<((N-8)*4);
  }
};

template<unsigned int P, unsigned char N>
struct GpioMode<P, N, false>
{
  inline static void mode(Mode::Mode_ m)
  {
    reinterpret_cast<GPIO_TypeDef*>(P)->CRL &= ~(0xf<<(N*4));
    reinterpret_cast<GPIO_TypeDef*>(P)->CRL |= m<<(N*4);
  }
};

template<unsigned int P, unsigned char N>
class Gpio
{
public:
  static void mode(Mode::Mode_ m)
  {
    GpioMode<P, N>::mode(m);
  }
};