App sync code, handles button presses from mixer and syncs changes from VM. Included python code from the mixer. Some other PCB changes, but still needs improvements

ControlMixerPython/key_interface.py

@@ -0,0 +1,40 @@
+import board
+import busio
+import digitalio
+from adafruit_mcp230xx.mcp23017 import MCP23017
+
+class KeyInterface:
+    _MCP23017_OLATA = 0x14
+    _MCP23017_OLATB = 0x15
+    
+    def set_olata(self, val: int):
+        self.mcp._write_u8(self._MCP23017_OLATA, val)
+    
+    def set_olatb(self, val: int):
+        self.mcp._write_u8(self._MCP23017_OLATB, val)
+    
+    def __init__(self, i2c):
+        self._i2c = i2c
+        
+        # Turn on MCP
+        self._mcp_reset_pin = digitalio.DigitalInOut(board.D4)
+        self._mcp_reset_pin.direction = digitalio.Direction.OUTPUT
+        self._mcp_reset_pin.value = True
+        
+        # Initialize MCP
+        self.mcp = MCP23017(self._i2c)
+        
+        # Set up MCP pins
+        self.mcp.iodirb = 255  # GPIO B (rows) all input
+        self.mcp.ipolb = 255   # GPIO B inverted polarity
+        self.mcp.gppub = 255   # GPIO B all pulled up
+        self.set_olata(0) # GPIO A all output low
+        
+    def scan(self):
+        result = []
+        for i in range(0, 6):
+            self.mcp.iodira = 0xFF ^ (0x01 << i)
+            result.append(self.mcp.gpiob)
+        self.mcp.iodira = 0xFF
+        return result
+