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LPC1769 issue with NXP PCF8574P

Question asked by Fernando Resquín on Aug 19, 2016
Latest reply on Sep 20, 2016 by Fernando Resquín

Dear All:


Please can you help me with this?

I´m trying to add 16 additional digital outputs to LCP1769FBD100, using two PCF8574P. For test purposes, I´m using a single PCF

for now. The problem is the PCF doesn´t send the ACK. The curious thing is I´ve tried with 4 different units and one of them worked perfectly

and the rest don´t. 

I know it´s not an address issue. The PCF units are all identical and was tested in the same circuit. For your knowledge, my pullup resistors are



There is any known issue of incompatibility between these two ICs that can depend of dispersion of the chips or I should assume they sold me three

damaged PCFs?


Thank you.


Best Regards.