This demo implements a USB PD sniffer, which receives PD packets from CC line and send them to PC via USB. (本程序试图实现一个USB PD的抓包器):

Author(作者): Rikka0w0 (小六花)

• keilc51\CH554.H, Delay.C and Delay.h comes from official CH554 demo (WCH), the USB MSD implementation is inspired by the USB MSD demo for STM32 (ST). (keilc51\CH554.H, Delay.C和Delay.h是从WCH官方的示例代码里提取的，U盘部分程序参考了STM32的USB MSD示例)
• All file in folder includes comes from Github repository Blinkinlabs's ch554_sdcc. (includes文件夹中的文件是从Blinkinlabs's ch554_sdcc里复制的)
• Compiler/IDE: Keil uVersion & SDCC. (编译器/开发环境：Keil 礦ision和SDCC)
• A Wiki page describes how to setup SDCC on Windows and Linux. (Wiki中会介绍如何在Windows和Linux上搭建SDCC编译环境)
• Feel free to use this demo as the template/start of a open-source or non-commercial project, modifying source code and republishing is allowed. (对于开源项目和非商业项目，可以是用本演示代码作为起点或者模板，作者允许修改并重新发布这份代码)
• However you MUST contact the author for permission prior to use this demo for commercial purposes. (如果用于商业目的的话，必须提前得到作者的允许)

• The hardware is based on the minimal circuit setup of CH554 (硬件基于CH554的最小系统)
• Chip is directly powered by Vbus, which is approximately 5V (芯片直接由Vbus驱动，大约是5V)

__ Incomplete yet__

The aim is to read PD traffics on the Type-C CC line between a DFP and a UFP, and forward them to PC via USB. (本项目试图把CC线上的PD通信转发到PC上) __ Incomplete yet__

• The only difference between CH554 and CH552 is that, CH552 only supports USB device mode while CH554 can also be programmed as a Host. So this demo may work on CH552 as well. (CH552只能作为USB的设备，而CH554还可以作为USB主机，这是两种芯片唯一的区别。因此本Demo可能也能在CH552上正常工作)
• 8051 systems including CH554 is big-endian while x86 and ARM processors are little-endian. (8051系统包括CH554是大端存储的，即数据的高位放在低内存地址中，而x86和ARM处理器都是小端存储的)
• USB packets are little-endian, keep this in mind! (USB包都是小端的，特别需要注意！)
• SDCC requires that all interrupt service functions must be written inside the same .c file containing void main(void), otherwise SDCC can not find them. According to official SDCC documentation, it's not a bug but a feature. Keil C51 doesn't have this limitaion. (SDCC要求中断处理函数必须和main函数放在一个.c文件中，否则SDCC没办法找到这些函数。根据SDCC官方文档，这是一个特性不算Bug，Keil C51编译器没有这种限制)