Add event handling methods

src/devices/Mcp23xxx/Mcp23x1x.cs

@@ -54,5 +54,27 @@ protected Mcp23x1x(BusAdapter device, int reset, int interruptA, int interruptB,
         /// Reads the interrupt pin for the given port if configured.
         /// </summary>
         public PinValue ReadInterrupt(Port port) => InternalReadInterrupt(port);
+
+        /// <summary>
+        /// Reads all bits of port A in a single operation.
+        /// </summary>
+        /// <returns>In the low byte: A bit field of the value of the first 8 GPIO ports
+        /// (Bit 0: GPIO 0, Bit 1: GPIO 1 etc.). Only the bits of input ports are defined.</returns>
+        public int ReadPortA()
+        {
+            int value = ReadByte(Register.GPIO, Port.PortA);
+            return value;
+        }
+
+        /// <summary>
+        /// Reads all bits of port B in a single operation.
+        /// </summary>
+        /// <returns>In the low byte: A bit field of the value of the second 8 GPIO ports
+        /// (Bit 0: GPIO 8, Bit 1: GPIO 9 etc.). Only the bits of input ports are defined.</returns>
+        public int ReadPortB()
+        {
+            int value = ReadByte(Register.GPIO, Port.PortB);
+            return value;
+        }
     }
 }