Driving an LCD with a PCF8574 over I2C

Page last updated 09 Aug 2010, by Romilly Cocking. 1 reply I2C, LCD, PCF8574

I'm mean with pins, even on the mbed, so I prefer to drive LCDs with an I2C bus rather than use six special-purpose pins for each LCD.

I've now hacked Simon Ford's LCD driver to drive an LCD via a PCF8574 Port expander using I2C. The program is here.

I'm hoping that someone better at C++ than me will merge Simon's code and mine into a common base class from which our concrete classes can inherit.

1 comment

luciano fumagalli
15 Dec 2016
Hi Romilly, me again Luciano. No problem for the SDA and SCL pins dell'F411RE, know what they are and I am sure of their operation. What I would like to know from you the exact connection between the PCF8574 and 20x4 LCD. In short I expect a standard table: Pin xx PCF874 connected to Pin yy of LCD20x4 (or rather the name of the signal) I believe that the problem lies precisely in this type of connection because the individual works via I2C PCF8574 no problem with a program that allows you to write in sequence its output ports. Thanks again for the help.

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