This discussion is the easiest: https://forum.digikey.com/t/simple-way- ... a-15w/7016

Essentially you just have a 5.1k resistor to ground from CC1, and a second 5.1K resistor to ground from CC2. These are both pins on the 14-pin USB-C connector.

I tried to charge my ATS25 using a google supplied USB-C power supply and cable. This doesn't work. However, using a dumb USB-C cable does work. This implies that the CC1/CC2 pins are not wired correctly on the ATS25. This is not an unusual problem, and the Raspberry Pi 4 suffered from the same prob...