SPI start/end fix for multibyte address. big endian multibyte address…

… fix. Implement signed argument for RWBits

adafruit_register/register_accessor.py

@@ -25,6 +25,8 @@
 
 
 class RegisterAccessor:
+    address_width = None
+
     def _pack_address_into_buffer(self, address, lsb_first, buffer):
         # Pack address into the buffer
         for i in range(self.address_width):
@@ -33,7 +35,9 @@ def _pack_address_into_buffer(self, address, lsb_first, buffer):
                 buffer[i] = (address >> (i * 8)) & 0xFF
             else:
                 # Big-endian: most significant byte first
-                buffer[i] = (address >> ((address - 1 - i) * 8)) & 0xFF
+                big_endian_address = address.to_bytes(self.address_width, byteorder="big")
+                for address_byte_i in range(self.address_width):
+                    buffer[address_byte_i] = big_endian_address[address_byte_i]
 
 
 class SPIRegisterAccessor(RegisterAccessor):
@@ -74,8 +78,8 @@ def read_register(self, address: int, lsb_first: bool, buffer: bytearray):
         self._pack_address_into_buffer(address, lsb_first, buffer)
         self._shift_rw_cmd_bit_into_address_byte(buffer, 1)
         with self.spi_device as spi:
-            spi.write(buffer, end=self.address_width)
-            spi.readinto(buffer, start=self.address_width)
+            spi.write(buffer, end=1)
+            spi.readinto(buffer, start=1)
 
     def write_register(
         self,

adafruit_register/register_bits.py

@@ -27,6 +27,8 @@ class RWBits:
     :param int lowest_bit: The lowest bits index within the byte at ``register_address``
     :param int register_width: The number of bytes in the register. Defaults to 1.
     :param bool lsb_first: Is the first byte we read from the bus the LSB? Defaults to true
+    :param bool signed: If True, the value is a "two's complement" signed value.
+      If False, it is unsigned.
     :param int address_width: The width of the register address in bytes. Defaults to 1.
     """
 
@@ -38,6 +40,7 @@ def __init__(
         lowest_bit: int,
         register_width: int = 1,
         lsb_first: bool = True,
+        signed: bool = False,
         address_width: int = 1,
     ):
         self.bit_mask = ((1 << num_bits) - 1) << lowest_bit
@@ -50,8 +53,8 @@ def __init__(
         self.address = register_address
         self.buffer = bytearray(address_width + register_width)
 
-        # self.buffer[1] = register_width - 1
         self.lsb_first = lsb_first
+        self.sign_bit = (1 << (num_bits - 1)) if signed else 0
 
     def __get__(self, obj, objtype=None):
         # read data from register
@@ -67,6 +70,11 @@ def __get__(self, obj, objtype=None):
 
         # extract integer value from specified bits
         result = (reg & self.bit_mask) >> self.lowest_bit
+
+        # If the value is signed and negative, convert it
+        if result & self.sign_bit:
+            result -= 2 * self.sign_bit
+
         return result
 
     def __set__(self, obj, value):