PS2 keyboard chip, more inputs?

Author	Message
BobD Guru Joined: 07/12/2011 Location: Australia Posts: 935	Posted: 09:11pm 13 Mar 2012       Another approach if you want more signal lines is to use the Remote 8-bit I/O expander for I2C bus - PCF8574. You can put 8 of these on an I2C bus and each has 8 "quasi-directional I/O ports". To run them you also need a digital input for the chip(s) to notify the processor there is inbound data. 2012-03-14_070625_PCF8574_data_sheet.pdf There is also version called PCF8574A which can have 16 chips on the bus but it seems to use an extra address bit which, I think, will prevent its use with the MM.