File content as of revision 2:b34e91b54373:

#pragma once
#pragma pack(push, 1)

namespace TMC2209_n {
  struct IOIN_t {
    constexpr static uint8_t address = 0x06;
    union {
      uint32_t sr;
      struct {
        bool  enn : 1,
                  : 1,
              ms1 : 1,
              ms2 : 1,
              diag : 1,
                   : 1,
              pdn_uart : 1,
              step : 1,
              spread_en : 1,
              dir : 1;
        uint16_t : 14;
        uint8_t version : 8;
      };
    };
  };

  struct SGTHRS_t {
    constexpr static uint8_t address = 0x40;
    uint8_t sr : 8;
  };

  struct SG_RESULT_t {
    constexpr static uint8_t address = 0x41;
    uint16_t sr : 10;
  };

  struct COOLCONF_t {
    constexpr static uint8_t address = 0x42;
    union {
      uint16_t sr;
      struct {
        uint8_t semin : 4,
                      : 1,
                seup : 2,
                      : 1,
                semax : 4,
                      : 1,
                sedn : 2;
        bool    seimin : 1;
      };
    };
  };

} //namespace 
//////////////////////////////////////////////////////
struct SLAVECONF_t {
  constexpr static uint8_t address = 0x03;
  union {
    uint16_t sr : 12;
    struct {
      uint8_t slaveaddr : 8;
      uint8_t senddelay : 4;
    };
  };
};

struct PWM_AUTO_t {
  constexpr static uint8_t address = 0x72;
  union {
    uint32_t sr : 24;
    struct {
      uint8_t pwm_ofs_auto : 8,
                           : 8,
              pwm_grad_auto : 8;
    };
  };
};

struct GCONF_t {
  constexpr static uint8_t address = 0x00;
  union {
    uint32_t sr : 18;
    struct {
      bool  i_scale_analog : 1, // 2130, 5130
            internal_rsense : 1, // 2130, 5130
            en_pwm_mode : 1,
            enc_commutation : 1, // 2130, 5130
            shaft : 1,
            diag0_error : 1,
            diag0_otpw : 1,
            diag0_stall : 1,
            diag1_stall : 1,
            diag1_index : 1,
            diag1_onstate : 1,
            diag1_steps_skipped : 1,
            diag0_int_pushpull : 1,
            diag1_pushpull : 1,
            small_hysteresis : 1,
            stop_enable : 1,
            direct_mode : 1;
    };
    struct { // TMC5160
      bool recalibrate : 1,
           faststandstill : 1,
                          : 1,
           multistep_filt : 1,
                    : 3,
           diag0_step : 1,
           diag1_dir : 1,
                 : 4,
           diag1_poscomp_pushpull : 1;
    };
  };
};

struct IHOLD_IRUN_t {
  constexpr static uint8_t address = 0x10;
  union {
    uint32_t sr : 20;
    struct {
      uint8_t ihold : 5,
                    : 3,
              irun : 5,
                   : 3,
              iholddelay : 4;
    };
  };
};

struct GSTAT_t {
  constexpr static uint8_t address = 0x01;
  union {
    uint8_t sr : 3;
    struct {
      bool  reset : 1,
            drv_err : 1,
            uv_cp : 1;
    };
  };
};

struct TPOWERDOWN_t {
  constexpr static uint8_t address = 0x11;
  uint8_t sr : 8;
};

struct TPWMTHRS_t {
  constexpr static uint8_t address = 0x13;
  uint32_t sr : 20;
};

struct TCOOLTHRS_t {
  constexpr static uint8_t address = 0x14;
  uint32_t sr : 20;
};

struct THIGH_t {
  constexpr static uint8_t address = 0x15;
  uint32_t sr : 20;
};

struct XDIRECT_t {
  constexpr static uint8_t address = 0x2D;
  union {
    uint32_t sr : 25;
    struct {
      int16_t coil_A : 9;
      int8_t         : 7;
      int16_t coil_B : 9;
    };
  };
};

struct VDCMIN_t {
  constexpr static uint8_t address = 0x33;
  uint32_t sr : 23;
};

struct CHOPCONF_t {
  constexpr static uint8_t address = 0x6C;
  union {
    uint32_t sr : 32;
    struct {
      uint8_t toff : 4,
              hstrt : 3,
              hend : 4,
                   : 1;
      bool    disfdcc : 1,
              rndtf : 1,
              chm : 1;
      uint8_t tbl : 2;
      bool    vsense : 1,
              vhighfs : 1,
              vhighchm : 1;
      uint8_t sync : 4, // 2130, 5130
              mres : 4;
      bool    intpol : 1,
              dedge : 1,
              diss2g : 1;
    };
    struct { // TMC5160
      uint32_t     : 20;
      uint8_t tpfd : 4; // 5160
      uint16_t     : 7;
      bool diss2vs : 1; // TMC5160 only
    };
  };
};

struct DCCTRL_t {
    constexpr static uint8_t address = 0x6E;
    union {
        uint32_t sr : 24;
        struct {
            uint16_t dc_time : 10,
                : 6;
            uint8_t dc_sg : 8;
        };
    };
};

struct PWMCONF_t {
  constexpr static uint8_t address = 0x70;
  union {
    uint32_t sr : 22;
    struct {
      uint8_t pwm_ampl : 8,
              pwm_grad : 8,
              pwm_freq : 2;
      bool pwm_autoscale : 1,
           pwm_symmetric : 1;
      uint8_t freewheel : 2;
    };
  };
};

struct ENCM_CTRL_t {
  constexpr static uint8_t address = 0x72;
  union {
    uint8_t sr : 2;
    struct {
      bool  inv : 1,
            maxspeed : 1;
    };
  };
};  
  
#pragma pack(pop)