Problems with PCF8574 Node

General
1

Hey all,
I want to use this Node here:


to read inputs of a PCF8574.

I'm not really sure how to configure it.
Can someone help me and tell how to configure cluster configurator correctly?

Is the index number that of the hardware pin?

Thanks a lot for your help !

2

If I check the inputs with i2c tools, it works without problems.

3

I had problems with this node too - it was a year ago. Used the generic i2c node instead and it worked. Sorry I can’t send you a flow because the system don’t exist any more

4

Ok I didn't know that there is a universal i2c node. I find hits one here:


But if I'm honest, I can't deal with it. Unfortunately, google isn't much help either.
You can find a few forum posts about it, but none about the PCF8574

5

I could not remember which node it was, I think it was automatically installed by Scargills script

But the node-red-contrib-i2c looks familiar. First you should use the scan node to detect your i2c device and get the address (A2-A0 as the jumpers on your pcb are set) .

Then you have to use the i2c in node which sends the command and reads the answer. All commands (as I remember) are one (read) two (write) bytes. See datasheet 8.3

http://www.ti.com/lit/ds/symlink/pcf8574.pdf

image

so I think you have to write 0100 A2 A1 A0 1

and you will get a byte back with the state of the 8 ports. It took a little bit of try and error but in the end it was a good experience learning to read a datasheet and not only using a library or custom node.

Good luck.