USB PD message interaction process diagnosis solution

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USB PD message interaction process diagnosis solution

Apple MacBook parses the PPS message in SRC_CAP into a fixed voltage file (38.8V/2.96A), and requests 1.5A of 38.8V according to the request of USB PD2.0, so that the MacBook shows 60W charging.

The understanding of the charger and the powered MacBook is inconsistent, and the subsequent voltage detection and the like are not correct, so the failure of the Hard Reset reset will always occur. After all, the charger is a passive device, the key issue is the reason why Apple MacBook can not correctly identify PPS messages.

According to industry engineers to the charging head network, Apple considered PPS in USB PD2.0, but did not deal with PPS caused this problem. In the actual interconnection, we also found that the Dell XPS notebook has similar problems, but the XPS problem goes further. As long as the charger sends a PPS message, the notebook will repeatedly send a Hard Reset and reset the charger. Request voltage.

Speaking of this, the laptop is a valuable item, the charger can not charge the notebook; the first reaction is not a notebook problem, but the charger is broken. In fact, the charger is not broken, but the USB PD handshake protocol of the notebook does not match the charger, resulting in the failure to charge.

Laptop manufacturers are giants. They warn consumers to use original accessories in the warranty card and manual to get the best performance, but consumers have demand for third-party accessories. How to do it?

1. The third-party charger does not use USB PD3.0, and uses the protocol of pure USB PD2.0 to interact;

2. Add a system judgment strategy to the charger. When the charger finds such a phenomenon, after passive reset, the USB PD2.0 protocol is re-issued to support such devices.