PCF8574 - wait what?

A project log for LAMEBOY - another ESP12 handheld

fully portable ESP12 project with battery charging and power muxing

davedarko • 08/15/2017 at 22:52•4 Comments

Although I had my run on some designs using this chip, I had to check the datasheet again and noticed something weird. Everyones project I've seen just uses a button that pulls the pin to ground. But what can we observe here on P5? A pull-up resistor of 100kOhms pulls up the input, until you push a switch that connects it to even more pull-ups? I should sleep and tomorrow remove my pull-up stuff from the board.

https://www.mikrocontroller.net/articles/Port-Expander_PCF8574

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Discussions

deʃhipu wrote 08/16/2017 at 12:10

That makes little sense. Maybe they meant Vss in there?

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davedarko wrote 08/16/2017 at 13:47

indeed. but that's also a lot of resistors to add, if they're really needed.

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deʃhipu wrote 08/16/2017 at 13:50

https://www.aliexpress.com/item/100pcs-10K-Ohm-10-Kohm-5-0603-8P-2-4P-SMD-Thick-Film-Chip-Resistor-Network/32767249452.html

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davedarko wrote 08/16/2017 at 21:46

yep, I'm aware of them - but I go the easy route with just switch to ground for now. I still have 4 arrays on there.

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