Years ago, I wrote an article describing different I2C-on-a-connector ecosystems, explaining their strengths, weaknesses, and implementation details, as well as piling on a heap of fun stories. Looking back at it, it’s a great reference article, if I do say so myself. In particular, I highlighted QWIIC, which is a Sparkfun-borne standard for putting 3.3 V I2C on a JST-SH (or compatible) 4-pin connector.
I’ve since implemented a fair bit of QWIIC, and grew to like it so much more. I’m here to explain to you why you ought to be putting those JST-SH connectors in everything you design that touches I2C, all the cool things they let you do, where to buy a lot of cheap cables at once, and all the references you could need. I will also tell you about my USB pinout for QWIIC, something you should definitely know about.
