I tried using different USB C splitters claiming they can separate power and data but only one worked in practice. This device actually does this. I have tested it with my Oneplus 7T and a JVC and Joying head units and both read the data as the phone charges. The best way to achieve this was to first connect the power cable and designated data cable to the adapter, AND THEN to the phone. Any other order and it'll just read one or none.
In my Nissan Maxima, the AV unit's USB port only supplies 500mA of charging current which is not enough to charge up my Galaxy S22. I also have a separate fast charger with USB-C PD output. I wanted a way to fast charge my phone while having a data connection to my car so that I can use Android Auto. I originally tried a USB hub but that didn't work. Then I found this device on tindie, got it within a couple of days and plugged it in. To my disappointment, it didn't work. However, I decided to give it another try with a different set of 1-foot long USB-C cables and to my pleasant surprise it worked! I did have to flip the cables around until I figured out the right orientation. USB-C is supposed to work in either orientation but that unfortunately isn't the case with this power splitter however since it's a one time setup it's not a big deal. While this is a very simple board that only consists of a couple of resistors and USB ports, it does the job that I need it to do and is valuable to me.
Response from Essence Engineering | May 8, 2023
So glad it worked for you! Due to the variation in USB-C cable internal connections (some don't have USB2.0 data connected, some only have power negotiation connected) one may have to play around and try a few configurations to make it work. Thanks for leaving a detailed review too! :D