//dacmux.h

namespace HAL {

template<typename dac_write_sequence_t,
    unsigned int chans,
    typename sample_t = uint_fast32_t>
struct dacmux {
private:

    typedef std::array<volatile sample_t, chans> chans_t;
    static chans_t channels;

    static unsigned int nextchan;
...
};

template<typename dac_write_sequence_t,
    unsigned int chans,
    typename sample_t>
   typename dacmux<dac_write_sequence_t, chans, sample_t>::chans_t dacmux<dac_write_sequence_t, chans, sample_t>::channels{0};


template<typename dac_write_sequence_t, unsigned int chans, typename sample_t>
    unsigned int dacmux<dac_write_sequence_t, chans, sample_t>::nextchan = 0;

template<typename dac_t, typename addr_t, typename en_t>
struct muxed_setter {
    ...
};

template<typename dac_t>
struct dac_setter {
    ...
};

}//namespace HAL

//Hardware_types.h
...
//Multiplexer for the internal DAC
typedef HAL::dacmux<HAL::muxed_setter<dac1, mux1_addr, mux1_en>, 8> mux1;

//Sequencer for writing the external DAC values
typedef HAL::dacmux<HAL::dac_setter<extdac1>, 8> extdac_sequencer;
...

20000280 l     O .bss   00000004 _ZN3HAL6dacmuxINS_10dac_setterINS_6ti_dacINS_3SPIINS_5SPI_2EEEN5GPIOs5pin_tINS6_1BELj12EEENS_12_GLOBAL__N_110xx68_frameENSA_12command_xx68ENSA_12channel_xx68EEEEELj8EjE8nextchanE
...
20000254 l     O .bss   00000020 _ZN3HAL6dacmuxINS_10dac_setterINS_6ti_dacINS_3SPIINS_5SPI_2EEEN5GPIOs5pin_tINS6_1BELj12EEENS_12_GLOBAL__N_110xx68_frameENSA_12command_xx68ENSA_12channel_xx68EEEEELj8EjE8channelsE
...
20000288 l     O .bss   00000020 _ZN3HAL6dacmuxINS_10dac_setterINS_6ti_dacINS_3SPIINS_5SPI_2EEEN5GPIOs5pin_tINS6_1BELj12EEENS_12_GLOBAL__N_110xx68_frameENSA_12command_xx68ENSA_12channel_xx68EEEEELj8EjE8channelsE
...
20000234  w    O .bss   00000020 _ZN3HAL6dacmuxINS_12muxed_setterIN4DACs11DAC_channelILj1EN5GPIOs5pin_tINS4_1AELj4EEEEENS4_12bit_stripe_tINS4_1CELj6ELj3EEENS5_ISA_Lj9EEEEELj8EjE8channelsE
...
2000027c  w    O .bss   00000004 _ZN3HAL6dacmuxINS_12muxed_setterIN4DACs11DAC_channelILj1EN5GPIOs5pin_tINS4_1AELj4EEEEENS4_12bit_stripe_tINS4_1CELj6ELj3EEENS5_ISA_Lj9EEEEELj8EjE8nextchanE