Update Adafruit_CharLCDPlate.py

Setting read/write on wrong bit in GPIOB. 
Bit 7 from display is in bit 1 of GPIOB.
Need to set/clear correct bit in IODIRB.

Author: kenrbell

Adafruit_CharLCDPlate/Adafruit_CharLCDPlate.py

@@ -82,7 +82,7 @@ def __init__(self, busnum=-1, addr=0x20, debug=False):
 
         # I2C is relatively slow.  MCP output port states are cached
         # so we don't need to constantly poll-and-change bit states.
-        self.porta, self.portb, self.ddrb = 0, 0, 0b00010000
+        self.porta, self.portb, self.ddrb = 0, 0, 0b00000010
 
         # Set MCP23017 IOCON register to Bank 0 with sequential operation.
         # If chip is already set for Bank 0, this will just write to OLATB,
@@ -187,7 +187,7 @@ def write(self, value, char_mode=False):
         """ Send command/data to LCD """
 
         # If pin D7 is in input state, poll LCD busy flag until clear.
-        if self.ddrb & 0b00010000:
+        if self.ddrb & 0b00000010:
             lo = (self.portb & 0b00000001) | 0b01000000
             hi = lo | 0b00100000 # E=1 (strobe)
             self.i2c.bus.write_byte_data(
@@ -204,7 +204,7 @@ def write(self, value, char_mode=False):
             self.portb = lo
 
             # Polling complete, change D7 pin to output
-            self.ddrb &= 0b11101111
+            self.ddrb &= 0b11111101
             self.i2c.bus.write_byte_data(self.i2c.address,
               self.MCP23017_IODIRB, self.ddrb)
 
@@ -249,7 +249,7 @@ def write(self, value, char_mode=False):
         # If a poll-worthy instruction was issued, reconfigure D7
         # pin as input to indicate need for polling on next call.
         if (not char_mode) and (value in self.pollables):
-            self.ddrb |= 0b00010000
+            self.ddrb |= 0b00000010
             self.i2c.bus.write_byte_data(self.i2c.address,
               self.MCP23017_IODIRB, self.ddrb)