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+--- Thread: New port expander plugin (/showthread.php?tid=265)
New port expander plugin - dan - 2021 Oct 19
Astro Gerard has contributed an excellent plugin that allows for a large number is stations to be easily and inexpensively added to SIP.
It is called "pcf857x_plugin" and is available from the SIP plugins repo through SIP's plugin manager page. It used i2c and requires SIP to be running under Python 3.
Gerard is keen to receive user feedback on his plugin so please post here with any comments.
Dan
RE: New port expander plugin - HereComesTheRain - 2021 Oct 31
@astrogerard
Hello Gerard
Received my order of (5) pcf8574 modules today.
Songhe PCF8574 PCF8574T IO Expansion Board I/O Expander I2C Evaluation Develop Module (5pcs)
https://www.amazon.com/dp/B07XD2K4GH
Sorry in advance for the NOOB questions.
Was wondering how to connect them to my 3B+
I understand that the Pi has two I2C connection pins.
Furthermore how do I avoid pulling too much power over those pins and causing damage to the 3B+?
I have read that some have killed their Pi because of that even though the modules were powered by an external source.
How do I mount the PCF8574s? There are no mounting holes and I can’t imagine letting them dangle in the air.
Thank you for your time and assistance.
RE: New port expander plugin - astrogerard - 2021 Oct 31
Hi Rob,
Do you have read the documentation? Especially the section about connecting the modules and powering can be found here.
It is advised to start first with one or two modules. If these are working fine you can add extra modules.
Since every module has pull-up resistors I would disable these on all except one (or two). Disabling these resistors can be done by simply cutting the resistors with a small side cutter. See also Note2 in the documentation.
Mounting depends on your situation but I usually use hot glue and/or tie raps. Hot glue is also great for fixing the breadboard wires to the connectors.
If you have questions or need other assistance please let me know.
--Gerard