Hi, I did a board based on the schematic shown on the attached picture. The first time i ran it it looks to work fine. On my second try it didn’t work any more. I decided that there is some wire connection problem. I measure all of the connections. Everything looks normal. And the board sometime works sometime not. So I did another board and another one ( 3 of them) completly different parts. And the same problem. I’m using TI’s PCF8574A, the schematic is for the NPX’s chip. Is there any differeneces between them. May be TI’s chip need pull-up resistor (I think I saw it somewhere…). Thanks!