template <unsigned char volatile * port, const char bit>
class mypin
{
public:
        inline mypin() {*(port-1)|=(1<<bit);} // смещение -1 - регистр DDR - настраиваем на выход.
        static inline void set()    {*port|=(1<<bit);}
};
int main()
{
    mypin<&PORTA,4> mypinname; // тут мы обьявляем место подключения и инициализируем одновременно
//...
     mypinname.set();
//...
}

    - wrong number of template arguments (1, should be 2) provided for 'template<volatile uint8_t* port, char bit> class mypin'

volatile uint8_t* portC = &PORTC;
*portC &= ~(1<<7);

template <uint8_t volatile & port, const char bit>
class mypin
{
public:
        __inline mypin(){*(&port-1)|=(1<<bit);}
    static __inline void set()    {port|=(1<<bit);}
};

mypin<PORTA,4> mypinname;
mypinname.set();

    - template argument 1 is invalid
    - `*' cannot appear in a constant-expression
    - a cast to a type other than an integral or enumeration type cannot appear in a constant-expression

  mypin< (volatile uint8_t *)0x1B > mypinname;

p.cpp:13: error: a cast to a type other than an integral or enumeration type cannot appear in a constant-expression
p.cpp:13: error: template argument 1 is invalid

template <uint8_t volatile & ctl, uint8_t volatile & port, const char bit>
class mypin
{
public:
        __inline mypin(){ctl|=(1<<bit);}
    static __inline void set()    {port|=(1<<bit);}
};

mypin<DDRA,PORTA, PA4> mypinname;
mypinname.set();

=================
E:\>c:\WinAVR/bin/avr-g++ -Wall -Wextra --version  2>&1
avr-g++ (GCC) 4.4.0 20090323 (experimental)
Copyright (C) 2009 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.


E:\>c:\WinAVR/bin/avr-gcc -Wall -Wextra -Os -S -mmcu=atmega64 p.cpp  2>&1
p.cpp: In function 'void foo()':
p.cpp:14: error: a cast to a type other than an integral or enumeration type cannot appear in a constant-expression
p.cpp:14: error: '*' cannot appear in a constant-expression
p.cpp:14: error: a cast to a type other than an integral or enumeration type cannot appear in a constant-expression
p.cpp:14: error: '*' cannot appear in a constant-expression
p.cpp:14: error: template argument 1 is invalid
p.cpp:14: error: template argument 2 is invalid
p.cpp:14: error: invalid type in declaration before ';' token
p.cpp:15: error: request for member 'set' in 'mypinname', which is of non-class type 'int'

===================

avr-gcc.exe (WinAVR 20090313) 4.3.2
Copyright (C) 2008 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

p.cpp: In function 'void foo()':
p.cpp:14: error: a cast to a type other than an integral or enumeration type cannot appear in a constant-expression
p.cpp:14: error: `*' cannot appear in a constant-expression
p.cpp:14: error: a cast to a type other than an integral or enumeration type cannot appear in a constant-expression
p.cpp:14: error: `*' cannot appear in a constant-expression
p.cpp:14: error: template argument 1 is invalid
p.cpp:14: error: template argument 2 is invalid
p.cpp:14: error: invalid type in declaration before ';' token
p.cpp:15: error: request for member 'set' in 'mypinname', which is of non-class type 'int'

===================

avr-gcc.exe (GCC) 4.2.2 (WinAVR 20071221)
Copyright (C) 2007 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

p.cpp: In function 'void foo()':
p.cpp:14: error: a cast to a type other than an integral or enumeration type cannot appear in a constant-expression
p.cpp:14: error: `*' cannot appear in a constant-expression
p.cpp:14: error: a cast to a type other than an integral or enumeration type cannot appear in a constant-expression
p.cpp:14: error: `*' cannot appear in a constant-expression
p.cpp:14: error: template argument 1 is invalid
p.cpp:14: error: template argument 2 is invalid
p.cpp:14: error: invalid type in declaration before ';' token
p.cpp:15: error: request for member 'set' in 'mypinname', which is of non-class type 'int'

enum __bits {__bit_0=0, __bit_1=1, __bit_2=2, __bit_3=3, __bit_4=4, __bit_5=5, __bit_6=6, __bit_7=7};
enum __ports{__port_A,__port_B,__port_C,__port_D,__port_E,__port_F,__port_G};
enum __ports_reg {__reg_PORT, __reg_DDR, __reg_PIN};

// Шаблон функции, определяющей требуемые адреса в пространстве В/В
template <__ports port, __ports_reg reg> volatile uint8_t& __ports_ref();

#define AVRLIB_SPECIALIZE_PORT_REF(_port_) \
template <> inline volatile uint8_t& __ports_ref<__port_##_port_, __reg_PORT>() { return PORT##_port_; } \
template <> inline volatile uint8_t& __ports_ref<__port_##_port_, __reg_DDR >() { return DDR##_port_; } \
template <> inline volatile uint8_t& __ports_ref<__port_##_port_, __reg_PIN >() { return PIN##_port_; }

#if defined (PORTA)
AVRLIB_SPECIALIZE_PORT_REF(A)
#endif
#if defined (PORTB)
AVRLIB_SPECIALIZE_PORT_REF(B)
#endif
.....
template <__ports port, __bits bit>
class __pin
{
public:
    static inline void set(void)
    {
        __ports_ref<port, __reg_PORT>()|=bit_mask(bit);
    }
};
__pin<__port_C,__bit_4> out4;
out4.set();

// In .h file
extern volatile uint8_t PORTA;

// In .ld file
_PORTA = 0x3B

template<GPIO_mode_t mode, char port, int bit, char activestate>
class Pin{
    inline volatile uint8_t & PORTx()
            {
        #if defined (PORTA)
                                 if (port == 'A') return PORTA;
         #endif
        #if defined (PORTB)
                                 if (port == 'B') return PORTB;
        #endif
      //..................такая конструкция для буков С..F и все вместе для DDRх и PINх}
    inline void On()
    {
        if ( mode==BIDIR || mode==OUTPUT ) {activestate == 'L' ? PORTx()&=~mask : PORTx()|=mask;}
        if ( mode==OUTPUT_OK ) {activestate == 'L' ? DDRx()|=mask : DDRx()&=~mask;}
    }
// и тп
}

template<char port> class Base_Pin;

template<>  // такой шаблон для всех буков - можно сделать макрос
    class Base_Pin<'A'>
    {
    public:
        inline volatile uint8_t & PORTx(){return PORTA;}
                        inline volatile uint8_t & DDRx(){return DDRA;}
                        inline volatile uint8_t & PINx(){return PINA;}
    };

template<GPIO_mode_t mode, char port, int bit, char activestate>
class Pin2 : public Base_Pin<port>
{    inline void On(){Base_Pin<port>::PORTx()|=(1<<bit);} };

// объявление шаблона регистров порта:
template<char port>struct port_regs_t;

// специализация для каждого порта:
template <> struct port_regs_t<'A'>
{
     inline volatile uint8_t & PORTx(){return PORTA;}
     ...
};
...
// и наконец, собственно шаблон ноги:
template<GPIO_mode_t mode, char port, int bit, char activestate>
class Pin2
{
private:
     typedef port_regs_t<port> regs_t;
public:
     typename regs_t::PORTx PORTx;
     typename pins_t::DDRx DDRx;
     typename pins_t::PINx PINx;
...
};