micropython-lib/micropython/register/i2c_register.py

"""
    * Author(s): SquirtleSquadLeader
    
    * License: MIT
        
    * Purpose:
        * The purpose of this module is to provide easy I2C Register
        * access.  It is inspired by the CircuitPython Register
        * module maintained by Adafruit.
        
            * RORegBit - Single bit Read Only 
            * RWRegBit - Single bit Read/Write
            
            * RORegBits - Multi-bit Read Only
            * RWRegBits - Multi-bit Read/Write
            
            * ROReg - Single/Multi Read Only
            * RWReg - Single/Multi Read/Write
            
        
    * Notes:
        1) Reference format strings below:                   
             Format          C Type          Standard size    
                c         char                    1
                b         signed char             1
                B         unsigned char           1
                h         short                   2
                H         unsigned short          2
                i         integer                 4
                I         unsigned int            4
                l         long                    4
                L         unsigned long           4
                q         long long               8
                Q         unsigned long long      8
                f         float                   4
                d         double                  8
   

"""

from machine import I2C
from struct import pack, unpack


class RORegBit:
    def __init__(self, i2c, dev_addr, reg_addr, num_bytes, bit_location, endian="", fmt="B"):
        """
        Creates an :class:`RORegBit` object which allows read only access to a single bit within a register.


        :param i2c: I2C bus which connects the host system to the peripheral device
        :type kind: machine.I2C()
        :param dev_addr: I2C address of the device which
        :type dev_addr: int()
        :param reg_addr: Physical register address which contains the bit of interest
        :type reg_addr: int()
        :param num_bytes: Number of bytes to read
        :type num_bytes: int()
        :param bit_location: Location of bit within bitfield
        :type bit_locatin: int()
        :param endian: Endian-ness of system for which the code is intended to run on. str('') uses native Endian-ness.
        :type endian: str()
        :param fmt: Format code which is used to unpack data from bytes().  Defaults to 'B' which is good for a single 8-bit register
        :type fmt: int()

        :return: An initialized RORegBit object
        :rtype: RORegBit()


         **Quickstart: Importing and using the device**

        Here is an example of using the :class:`RORegBit` class.
        First you will need to import the following libraries:

        .. code-block:: python

            from machine import I2C
            from register.register import RORegBit

        Once this is done you must define a :class:`machine.I2C` object and then pass that
        to the :class:`RORegBit` object to instantiate it.

        .. code-block:: python

            i2c = I2C(0)  # I2C details are project specific

            my_reg = RORegBit(i2c, 68, 5, 1, 5)

        'my_reg' can now provide access to the :method:`__get__().  Using this method
        will return the value of the bit found at :param bit_location:.

        .. code-block:: python

            value = my_reg.__get__() # 0 or 1

        Alternatively, a :class:`RORegBit` object(s) can be placed within another class.

        .. code-block:: python
            # import
            from machine import I2C
            from register.register import RORegBit

            # define I2C
            i2c = I2C(0)

            # create class with desired functionality
            class FooDevice:

                def __init__(self, i2c_bus):
                    self._my_reg_1 = RORegBit(i2c_bus, 68, 5, 1, 5)
                    self._my_reg_2 = RORegBit(i2c_bus, 68, 6, 1, 5)

                def get_my_reg1(self):
                    return self._my_reg_1.__get__()

                def get_my_reg2(self):
                    return self._my_reg_1.__get__()

            # invoke class object
            device = FooDevice(i2c)

        """
        self._i2c = i2c
        self._dev_addr = dev_addr
        self._reg_addr = reg_addr
        self._num_bytes = num_bytes
        self._bit_location = bit_location
        self._endian = endian
        self._fmt = fmt

        __check_reg(self)

        del (i2c, dev_addr, reg_addr, num_bytes, bit_location, fmt)

    def __get__(self):
        """
        :return: Returns the value of the bit located at :param bit_location:
        :rtype: int()
        """
        return __getbit(self)


class RWRegBit:
    def __init__(self, i2c, dev_addr, reg_addr, num_bytes, bit_location, endian="", fmt="B"):
        """
        Creates an :class:`RORegBit` object which allows read and write access to a single bit within a register.

        :param i2c: I2C bus which connects the host system to the peripheral device
        :type kind: machine.I2C()
        :param dev_addr: I2C address of the device which
        :type dev_addr: int()
        :param reg_addr: Physical register address which contains the bit of interest
        :type reg_addr: int()
        :param num_bytes: Number of bytes to read
        :type num_bytes: int()
        :param bit_location: Location of bit within bitfield
        :type bit_locatin: int()
        :param endian: Endian-ness of system for which the code is intended to run on. str('') uses native Endian-ness.
        :type endian: str()
        :param fmt: Format code which is used to unpack data from bytes().  Defaults to 'B' which is good for a single 8-bit register
        :type fmt: int()

        :return: An initialized RWRegBit object
        :rtype: RWRegBit()


         **Quickstart: Importing and using the device**

        Here is an example of using the :class:`RWRegBit` class.
        First you will need to import the following libraries:

        .. code-block:: python

            from machine import I2C
            from register.register import RWRegBit

        Once this is done you must define a :class:`machine.I2C` object and then pass that
        to the :class:`RWRegBit` object to instantiate it.

        .. code-block:: python

            i2c = I2C(0)  # I2C details are project specific

            my_reg = RWRegBit(i2c, 68, 5, 1, 5)

        'my_reg' can now provide access to the :method:`__get__() and :method:`__set__().
        Using these methods will get/set the value of the bit found at :param bit_location:.

        .. code-block:: python
            my_reg.__set__(1)

            print(my_reg.__get__()) # prints 1

        Alternatively, a :class:`RWRegBit` object(s) can be placed within another class.

        .. code-block:: python
            # import
            from machine import I2C
            from register.register import RWRegBit

            # define I2C
            i2c = I2C(0)

            # create class with desired functionality
            class FooDevice:

                def __init__(self, i2c_bus):
                    self._my_reg = RORegBit(i2c_bus, 68, 5, 1, 5)

                def get_my_reg(self):
                    return self._my_reg.__get__()

                def get_my_reg2(self, n):
                    return self._my_reg.__set__(n)

            # invoke class object
            device = FooDevice(i2c)

        """
        self._i2c = i2c
        self._dev_addr = dev_addr
        self._reg_addr = reg_addr
        self._num_bytes = num_bytes
        self._bit_location = bit_location
        self._endian = endian
        self._fmt = fmt

        __check_reg(self)

        self._premask, self._postmask = __calc_mask(bit_location, bit_location, num_bytes)

        del (i2c, dev_addr, reg_addr, num_bytes, bit_location, endian, fmt)

    def __get__(self):
        """
        :return: Returns the value of the bit located at :param bit_location:
        :rtype: int()
        """
        return __getbit(self)

    def __set__(self, setting):
        """
        :return: Returns 'True' if operation successful
        :rtype: bool()
        """
        return __setbit(self, setting)


class RORegBits:
    def __init__(self, i2c, dev_addr, reg_addr, num_bytes, lsb, msb, endian="", fmt="B"):
        """
        Creates an :class:`RORegBits` object which allows read only access to a sequential set of bits within a bitfield.

        :param i2c: I2C bus which connects the host system to the peripheral device
        :type kind: machine.I2C()
        :param dev_addr: I2C address of the device which
        :type dev_addr: int()
        :param reg_addr: Physical register address which contains the bit of interest
        :type reg_addr: int()
        :param num_bytes: Number of bytes to read
        :type num_bytes: int()
        :param lsb: Location of least significant bit within bitfield
        :type lsb: int()
        :param msb: Location of most significant bit within bitfield
        :type msb: int()
        :param endian: Endian-ness of system for which the code is intended to run on. str('') uses native Endian-ness.
        :type endian: str()
        :param fmt: Format code which is used to unpack data from bytes().  Defaults to 'B' which is good for a single 8-bit register
        :type fmt: int()

        :return: An initialized RORegBits object
        :rtype: RORegBits()


         **Quickstart: Importing and using the device**

        Here is an example of using the :class:`RORegBits` class.
        First you will need to import the following libraries:

        .. code-block:: python

            from machine import I2C
            from register.register import RORegBits

        Once this is done you must define a :class:`machine.I2C` object and then pass that
        to the :class:`RORegBits` object to instantiate it.

        .. code-block:: python

            i2c = I2C(0)  # I2C details are project specific

            my_reg = RORegBits(i2c_bus, 68, 5, 1, 0, 2)

        'my_reg' can now provide access to the :method:`__get__().  Using this method
        will return the value of the bit found at :param bit_location:.

        .. code-block:: python

            value = my_reg.__get__() # Returns some value from 0b000 to 0b111

        Alternatively, a :class:`RORegBits` object(s) can be placed within another class.

        .. code-block:: python
            # import
            from machine import I2C
            from register.register import RORegBits

            # define I2C
            i2c = I2C(0)

            # create class with desired functionality
            class FooDevice:

                def __init__(self, i2c_bus):
                    self._my_reg_1 = RORegBits(i2c_bus, 68, 5, 1, 0, 2)
                    self._my_reg_2 = RORegBits(i2c_bus, 68, 6, 1, 3, 6)

                def get_my_reg1(self):
                    return self._my_reg_1.__get__()

                @property
                def my_reg2(self):
                    return self._my_reg_2.__get__()

            # invoke class object
            device = FooDevice(i2c)

            n1 = device.get_my_reg()
            n2 = device.my_reg2

        """
        self._i2c = i2c
        self._dev_addr = dev_addr
        self._reg_addr = reg_addr
        self._num_bytes = num_bytes
        self._endian = endian
        self._fmt = fmt

        __check_reg(self)

        self._premask, self._mask, self._postmask = __calc_mask(lsb, msb, num_bytes)

        del (i2c, dev_addr, reg_addr, num_bytes, lsb, msb, endian, fmt)

    def __get__(self):
        """
        :return: Returns the value of the bitfield located between :param lsb: and :param msb:
        :rtype: int()
        """
        return __getbits(self)


class RWRegBits:
    def __init__(self, i2c, dev_addr, reg_addr, num_bytes, lsb, msb, endian="", fmt="B"):
        """
        Creates an :class:`RWRegBits` object which allows read and write access to a sequential set of bits within a bitfield.

        :param i2c: I2C bus which connects the host system to the peripheral device
        :type kind: machine.I2C()
        :param dev_addr: I2C address of the device which
        :type dev_addr: int()
        :param reg_addr: Physical register address which contains the bit of interest
        :type reg_addr: int()
        :param num_bytes: Number of bytes to read
        :type num_bytes: int()
        :param lsb: Location of least significant bit within bitfield
        :type lsb: int()
        :param msb: Location of most significant bit within bitfield
        :type msb: int()
        :param endian: Endian-ness of system for which the code is intended to run on. str('') uses native Endian-ness.
        :type endian: str()
        :param fmt: Format code which is used to unpack data from bytes().  Defaults to 'B' which is good for a single 8-bit register
        :type fmt: int()

        :return: An initialized RWRegBits object
        :rtype: RWRegBits()


         **Quickstart: Importing and using the device**

        Here is an example of using the :class:`RWRegBits` class.
        First you will need to import the following libraries:

        .. code-block:: python

            from machine import I2C
            from register.register import RWRegBits

        Once this is done you must define a :class:`machine.I2C` object and then pass that
        to the :class:`RWRegBits` object to instantiate it.

        .. code-block:: python

            i2c = I2C(0)  # I2C details are project specific

            my_reg = RWRegBits(i2c_bus, 68, 5, 1, 0, 2)

        'my_reg' can now provide access to :method:`__get__() and :method:`__set__().

        .. code-block:: python

            my_reg.__set__(0b110) # Returns some value from 0b000 to 0b111
            value = my_reg.__get__() # Returns 0b110, assuming nothing changes

        Alternatively, a :class:`RWRegBits` object(s) can be placed within another class.

        .. code-block:: python
            # import
            from machine import I2C
            from register.register import RWRegBits

            # define I2C
            i2c = I2C(0)

            # create class with desired functionality
            class FooDevice:

                def __init__(self, i2c_bus):
                    self._my_reg_1 = RWRegBits(i2c_bus, 68, 5, 1, 0, 2)
                    self._my_reg_2 = RWRegBits(i2c_bus, 68, 6, 1, 3, 6)

                def get_my_reg1(self):
                    return self._my_reg_1.__get__()

                def set_my_reg1(self, n):
                    return self._my_reg_1.__set__(n)

                @property
                def my_reg2(self):
                    return self._my_reg_2.__get__()

                @my_reg2.setter
                def my_reg2(self, n):
                    return self._my_reg_2.__set__(n)

            # invoke class object
            device = FooDevice(i2c)

            device.set_my_reg(0b110)
            print(device.get_my_reg()) # prints 6

           device.my_reg2 = 0b110
           print(device.my_reg2) # prints 6

        """
        self._i2c = i2c
        self._dev_addr = dev_addr
        self._reg_addr = reg_addr
        self._num_bytes = num_bytes
        self._endian = endian
        self._fmt = fmt

        __check_reg(self)

        self._premask, self._mask, self._postmask = __calc_mask(lsb, msb, num_bytes)

        del (i2c, dev_addr, reg_addr, num_bytes, lsb, msb, fmt, endian)

    def __get__(self):
        """
        :return: Returns the value of the bitfield located between :param lsb: and :param msb:
        :rtype: int()
        """
        return __getbits(self)

    def __set__(self, setting):
        """
        :return: True if successful
        :rtype: bool()
        """
        return __setbits(self, setting)


class ROReg:
    def __init__(self, i2c, dev_addr, reg_addr, num_bytes=1, endian="", fmt="B"):
        """
        Creates a :class:`ROReg` object which allows read only access to n number of sequential registers,
        where n is specified by :param num_bytes:.


        :param i2c: I2C bus which connects the host system to the peripheral device
        :type kind: machine.I2C()
        :param dev_addr: I2C address of the device which
        :type dev_addr: int()
        :param reg_addr: Physical register address which contains the bit of interest
        :type reg_addr: int()
        :param num_bytes: Number of bytes to read. Defaults to 1.
        :type num_bytes: int()
        :param fmt: Format code which is used to unpack data from bytes().  Defaults to 'B'.
        :type fmt: int()

        :return: An initialized ROReg object
        :rtype: ROReg()


         **Quickstart: Importing and using the device**

        Here is an example of using the :class:`ROReg` class.
        First you will need to import the following libraries:

        .. code-block:: python

            from machine import I2C
            from register.register import ROReg

        Once this is done you must define a :class:`machine.I2C` object and then pass that
        to the :class:`ROReg` object to instantiate it.

        .. code-block:: python

            i2c = I2C(0)  # I2C details are project specific

            my_reg = ROReg(i2c, 68, 5)

        'my_reg' can now provide access to the :method:`__get__().  Using this method
        will return the value of the bit found at :param bit_location:.

        .. code-block:: python

            value = my_reg.__get__() # some value between 0b0 and 0b1111_1111

        Alternatively, a :class:`ROReg` object(s) can be placed within another class.

        .. code-block:: python
            # import
            from machine import I2C
            from register.register import ROReg

            # define I2C
            i2c = I2C(0)

            # create class with desired functionality
            class FooDevice:

                def __init__(self, i2c_bus):
                    self._my_reg_1 = ROReg(i2c_bus, 68, 5)
                    self._my_reg_2 = ROReg(i2c_bus, 68, 6)

                def get_my_reg1(self):
                    return self._my_reg_1.__get__()

                @property
                def my_reg2(self):
                    return self._my_reg_1.__get__()

            # invoke class object
            device = FooDevice(i2c)

            print(device.get_my_reg1())
            print(device.my_reg2)

        """
        self._i2c = i2c
        self._dev_addr = dev_addr
        self._reg_addr = reg_addr
        self._num_bytes = num_bytes
        self._fmt = fmt
        self._endian = endian

        __check_reg(self)

        del (i2c, dev_addr, reg_addr, num_bytes, fmt, endian)

    def __get__(self):
        """
        :return: Returns tuple containing n number of elements, where n is the number of characters in :param fmt:
        :rtype: tuple()
        """
        return __getreg(self)


class RWReg:
    def __init__(self, i2c, dev_addr, reg_addr, num_bytes, endian="", fmt="B"):
        """
        Creates a :class:`RWReg` object which allows read and write access to n number of sequential registers,
        where n is specified by :param num_bytes:.

        :param i2c: I2C bus which connects the host system to the peripheral device
        :type kind: machine.I2C()
        :param dev_addr: I2C address of the device which
        :type dev_addr: int()
        :param reg_addr: Physical register address which contains the bit of interest
        :type reg_addr: int()
        :param num_bytes: Number of bytes to read. Defaults to 1.
        :type num_bytes: int()
        :param fmt: Format code which is used to unpack data from bytes().  Defaults to 'B'.
        :type fmt: int()

        :return: An initialized RWReg object
        :rtype: RWReg()


         **Quickstart: Importing and using the device**

        Here is an example of using the :class:`RWReg` class.
        First you will need to import the following libraries:

        .. code-block:: python

            from machine import I2C
            from register.register import RWReg

        Once this is done you must define a :class:`machine.I2C` object and then pass that
        to the :class:`RWReg` object to instantiate it.

        .. code-block:: python

            i2c = I2C(0)  # I2C details are project specific

            my_reg = RWReg(i2c, 68, 5)

        'my_reg' can now provide access to the :method:`__get__() and __set__().

        .. code-block:: python
            my_reg.__set__(0b0)
            value = my_reg.__get__() # 0b0 if nothing changed

        Alternatively, a :class:`RWReg` object(s) can be placed within another class.

        .. code-block:: python
            # import
            from machine import I2C
            from register.register import RWReg

            # define I2C
            i2c = I2C(0)

            # create class with desired functionality
            class FooDevice:

                def __init__(self, i2c_bus):
                    self._my_reg_1 = RWReg(i2c_bus, 68, 5)
                    self._my_reg_2 = RWReg(i2c_bus, 68, 6)

                def get_my_reg1(self):
                    return self._my_reg_1.__get__()

                def set_my_reg1(self, n):
                    return self._my_reg_1.__set__(n)

                @property
                def my_reg2(self):
                    return self._my_reg_1.__get__()

                @my_reg2.setter
                def my_reg2(self, n):
                    return self._my_reg_1.__set__(n)


            # invoke class object
            device = FooDevice(i2c)

            device.set_my_reg1(0b110)
            print(device.get_my_reg1()) # prints 6, assuming nothing changed

            device.my_reg2 = 0b1111_0000
            print(device.my_reg2) # prints 240

        """
        self._i2c = i2c
        self._dev_addr = dev_addr
        self._reg_addr = reg_addr
        self._num_bytes = num_bytes
        self._fmt = fmt
        self._endian = endian

        __check_reg(self)

        del (i2c, dev_addr, reg_addr, num_bytes, fmt, endian)

    def __get__(self):
        """
        :return: Returns tuple containing n number of elements, where n is the number of characters in :param fmt:
        :rtype: tuple()
        """
        return __getreg(self)

    def __set__(self, setting):
        """
        :param setting: Value(s) to be written to register(s).  Order must match :param fmt:.
        :type setting: int(), bytes(), bytearray(), or list/tuple containing those values in order
        :return: Returns True if operation successful
        :rtype: tuple()
        """
        return __setreg(self, setting)


"""
*
* GLOBAL HELPER FUNCTIONS
*
*
"""


def __getbit(reg_object):
    if isinstance(reg_object, (RORegBit, RWRegBit)):
        # Retrieve register value and unpack to int
        value = reg_object._i2c.readfrom_mem(
            reg_object._dev_addr, reg_object._reg_addr, reg_object._num_bytes
        )

        # Unpack byte
        value = unpack(reg_object._endian + reg_object._fmt, value)[0]

        # Perform shift followed by _AND_ operation to determine bit state
        return (value >> reg_object._bit_location) & 0b1

    else:
        raise TypeError("incorrect object type - must be RORegBit, RWRegBit")


def __setbit(reg_object, setting):
    if isinstance(reg_object, RWRegBit):
        if setting in (0, 1):
            # Retrieve register value and unpack to int
            value = reg_object._i2c.readfrom_mem(
                reg_object._dev_addr, reg_object._reg_addr, reg_object._num_bytes
            )

            # Unpack byte
            value = unpack(reg_object._endian + reg_object._fmt, value)[0]

            # Assemble byte
            value = (
                (value & reg_object._postmask)
                + (setting << reg_object._bit_location)
                + (value & reg_object._premask)
            )

            # Pack to bytes
            value = pack(reg_object._endian + reg_object._fmt, value)

            # Write to I2C
            reg_object._i2c.writeto_mem(reg_object._dev_addr, reg_object._reg_addr, value)

            # Return True for success
            return True

        else:
            raise ValueError("setting must be int(0) or int(1)")
    else:
        raise TypeError("incorrect object type - must be RWRegBit")


def __getbits(reg_object):
    if isinstance(reg_object, (RORegBits, RWRegBits)):
        # Retrieve register value and unpack to int
        value = reg_object._i2c.readfrom_mem(
            reg_object._dev_addr, reg_object._reg_addr, reg_object._num_bytes
        )

        # Unpack bytes
        value = unpack(reg_object._endian + reg_object._fmt, value)[0]

        # Return value of bit field
        return (value & reg_object._mask) >> reg_object._lsb

    else:
        raise TypeError("incorrect object type - must be RORegBits, RWRegBits")


def __setbits(reg_object, setting):
    if isinstance(reg_object, RWRegBits):
        if isinstance(setting, int) and setting <= reg_object._mask:
            # Retrieve register value and unpack to int
            value = reg_object._i2c.readfrom_mem(
                reg_object._dev_addr, reg_object._reg_addr, reg_object._num_bytes
            )

            # Unpack bytes
            value = unpack(reg_object._endian + reg_object._fmt, value)[0]

            # Assemble
            value = (
                (value & reg_object._postmask)
                + (setting << reg_object._lsb)
                + (value & reg_object._premask)
            )

            # Pack to bytes object
            value = struct.pack(reg_object._endian + reg_object._fmt, value)

            # Write to device
            reg_object._i2c.writeto_mem(reg_object._dev_addr, reg_object._reg_addr, value)

            return True

        else:
            raise ValueError(f"value of setting exceeds max value of bitfield: {reg_object._mask}")
    else:
        raise TypeError("incorrect object type - must be RWRegBits")


def __getreg(reg_object):
    if isinstance(reg_object, (ROReg, RWReg)):
        # Retrieve register value and unpack to int
        values = reg_object._i2c.readfrom_mem(
            reg_object._dev_addr, reg_object._reg_addr, reg_object._num_bytes
        )

        # Return Tuple of values
        return unpack(reg_object._endian + reg_object._fmt, values)

    else:
        raise TypeError("incorrect object type - must be ROReg, RWReg")


def __setreg(reg_object, settings):
    if isinstance(reg_object, RWReg):
        if isinstance(settings, (bytes, bytearray)):
            # Write to device
            reg_object._i2c.writeto_mem(reg_object._dev_addr, reg_object._reg_addr, settings)

        elif isinstance(settings, (tuple, list)):
            # Where our data will go
            d = bytearray()

            # Pack and append to d
            for n in range(0, len(settings)):
                d.extend(pack(reg_object._endian + reg_object._fmt[n], settings[n]))

            # Write to device
            reg_object._i2c.writeto_mem(reg_object._dev_addr, reg_object._reg_addr, d)

        # Assumed single int() for single reg-op
        elif isinstance(settings, int):
            d = pack(reg_object._endian + reg_object._fmt, settings)
            reg_object._i2c.writeto_mem(reg_object._dev_addr, reg_object._reg_addr, d)

        else:
            raise TypeError(
                "unsupported object type, settings must be int(), bytes(), bytearray(), tuple(), or list()"
            )
    else:
        raise TypeError("incorrect object type - must be ROReg, RWReg")


def __calc_mask(lsb, msb, numbytes):
    """
    Takes in full description of bitfield that needs masking

    returns ints() pre, mask, post
    """

    # Check input types
    if lsb.__class__() == int() and lsb >= 0:
        if msb.__class__() == int() and msb >= 0:
            if numbytes.__class__() == int() and numbytes >= 0:
                # Check for detectable errors
                if msb >= lsb:
                    # Single bit mask
                    if msb == lsb:
                        pre, post = 0b0, 0b0

                        # Calc post masking
                        for bit in range(msb + 1, numbytes * 8):
                            post = (post << 1) + 0b1

                        # Calc pre masking
                        for bit in range(0, lsb):
                            pre = (pre << 1) + 0b1

                        return pre, post

                    # Multibit mask
                    else:
                        # Values to return
                        pre, mask, post = 0b0, 0b0, 0b0

                        # Calc post masking
                        for bit in range(msb + 1, numbytes * 8):
                            post = (post << 1) + 0b1

                        # Calc bitfield masking
                        for bit in range(lsb, msb + 1):
                            mask = (mask << 1) + 0b1

                        # No bits lower than 0
                        if lsb == 0:
                            return 0b0, mask, post

                        else:
                            for bit in range(0, lsb):
                                pre = (pre << 1) + 0b1

                            return pre, mask, post
                else:
                    raise ValueError("msb must be greater than or equal to lsb")
            else:
                raise ValueError("numbytes must be of type int() and 0 or greater")
        else:
            raise ValueError("msb must be of type int() and 0 or greater")
    else:
        raise ValueError("lsb must be of type int() and 0 or greater")


def __check_reg(reg_object):
    # Alowable struct.pack/unpack formats to check for
    fmts = {
        "b": 1,
        "B": 1,
        "h": 2,
        "H": 2,
        "f": 4,
        "i": 4,
        "I": 4,
        "l": 4,
        "L": 4,
        "q": 8,
        "Q": 8,
    }
    endians = "@><"
    byte_count = 0

    # Take in only register objects
    if isinstance(reg_object, (RORegBit, RWRegBit, RORegBits, RWRegBits, ROReg, RWReg)):
        # Make sure they are strings
        if type(reg_object._fmt) == str and type(reg_object._endian) == str:
            # Check each letter in format string, To see if allowable
            for n in range(0, len(reg_object._fmt)):
                if reg_object._fmt[n] in fmts:
                    # Add corresonding byte length to verify _num_bytes and format string agree
                    byte_count = byte_count + fmts[reg_object._fmt[n]]

                else:
                    raise ValueError(f"unsupported format code of '{reg_object._fmt[n]}'")

            if byte_count != reg_object._num_bytes:
                raise ValueError(
                    f"format string accounts for {byte_count} bytes, _num_bytes value of {reg_object._num_bytes} does not match"
                )

        else:
            raise TypeError("format and endian must be of type str()")
    else:
        raise TypeError(
            "incorrect object type - must be ROReg, RWReg, ROBits, RWBits, ROReg, RWReg"
        )