Building a custom I2C chip for Wokwi simulation - PCF8575 [full walkthrough]

Get from datasheet to digital simulation. This guide will walk through all the steps to getting a fully modeled custom chip, that may be used in any wokwi circuit simulation.

We'll look at the datasheet and figure out how the chip works, test understanding in simulator and real life, define a test scenario and circuit and implement everything to get this PCF8575 (an I2C I/O expander) usable in any circuit.

If you haven't seen the custom chip intro video, it's a useful foundation that goes over the basic concepts, including the types used and reasoning behind much of the structure of custom chip implementations (init, callbacks, pin watching etc):
   • Custom Chips: Test any digital circui...  

Here, we'll dive deep into the I2C chip itself and look at the way I'm figuring out how things work prior to coding, finishing up with actual implementation. The important sections are:

00:00 - Intro
00:35 - Goal and plan
01:30 - Device Analysis
06:50 - Test + real device
08:44 - simulating open drain
12:20 - Custom chip test circuit
15:07 - Implementing the custom chip
23:50 - Arduino test driver

You can play with, and download a copy of, the PCF8575 custom chip and test code on wokwi, at:
https://wokwi.com/projects/3741577749...

If you're curious about that opendrain test, it's also available:
https://wokwi.com/projects/3740569169...