First of all, Let`s see a picture about sourcesink connection.
This picture is copyed from another bloger, and this is the link:https://blog.csdn.net/a6588621/article/details/85049539
In this picture, we can see two module the source and the sink.
Do you remember what I said before that host has a pulled-up resistance and device has a drop-down resistance.
So that you can obviously choose source as host and sink as device.
OK, next I will tell you about how they connect.
Step1 : cc1 and cc2 at the source end are all pulled up to hight level(5V), and the sink insertion is detected at the same time.When Rd drop-down resistence is detected. the sink is detected, The resistence of Rp indicates the level of power that host can provided.
Step2: The Source side reverses the USB data link based on which CC pin in the Cable is Rd drop-down, and decides that the other CC pin is VCONN
Step3: after that, source start to provide power in VBUS and VCONN
Step4: Souce can adjust the tolerence of Rp dynamically to represent the change of sending current to sink and inform the maximum usable current.
Step5: Source will detect the presence of Rd continuously and once the connection is cut off , the power will be turned off
Step6: The cc pins can be used for communication if source supports advanced function (PD or Alternate Mode)