Here is the register and bit map for the MCP23017 and the chip pinout...
Supply Voltage 1.8v - 5.5v Supply current typ 1mA Standby cur. 1-3uA Input Lo 0.15 x Vdd Input Hi 0.8 x Vdd Output Lo 0.6v Output Hi Vdd - 0.7v Max src/sink I 25mA
IODIR 1 = Input Pin 0 = Output Pin IPOL 1 = Input is inverted GPINTEN 1 = Interrupt enabled on that Pin GPIO read gets vlaue on port / write changes OLAT reg GPPU 1 = Pull-Up resistor enabled OLAT read gets value on o/p latches write sets latches which sets those pins set to output IOCON BANK 1 adds are porta 0x00 - 0x0A, portb 0x10 - 0x1A BANK 0 A/B addresses interleved (default) SEQOP = 0 for byte mode
Jim Jackson <email@example.com> Wed May 15 17:55:59 BST 2013
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