prototyping MCP3002 class

prototyping only. need to check datasheet and test this

adafruit_mcp3xxx/mcp3002.py

@@ -0,0 +1,47 @@
+# The MIT License (MIT)
+#
+# Copyright (c) 2018 Brent Rubell for Adafruit
+#
+# Permission is hereby granted, free of charge, to any person obtaining a copy
+# of this software and associated documentation files (the "Software"), to deal
+# in the Software without restriction, including without limitation the rights
+# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+# copies of the Software, and to permit persons to whom the Software is
+# furnished to do so, subject to the following conditions:
+#
+# The above copyright notice and this permission notice shall be included in
+# all copies or substantial portions of the Software.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+# THE SOFTWARE.
+"""
+:py:class:`~adafruit_mcp3xxx.MCP3002.MCP3002`
+================================================
+MCP3002 2-channel, 10-bit, analog-to-digital
+converter instance.
+
+* Author(s): Brent Rubell
+"""
+
+from .mcp3xxx import MCP3xxx
+
+# MCP3002 Pin Mapping
+P0 = 0
+P1 = 1
+
+class MCP3002(MCP3xxx):
+
+    """
+    MCP3002 Differential channel mapping.
+        - 0: CH0 = IN+, CH1 = IN-
+        - 1: CH1 = IN+, CH0 = IN-
+    """
+    MCP3002_DIFF_PINS = {
+        (0, 1) : P0,
+        (1, 0) : P1
+    }