CH554 USB CDC

This demo emulates a USB CDC, which is equivalent to a UART port. (本演示程序模拟了一个USB CDC设备, 可以当作串口使用):

Author(作者): Rikka0w0 (小六花) Original Author(原作者): rgwan (Zhiyuan Wan)

• 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)

Hardware Setup(硬件配置):

• 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)
• P1.5 = I2C SDA, P1.4 = I2C SCL, defined in i2c.c, each pin is pull-up by a 1k resistor to 5V. (I2C引脚定义在i2c.c里面，每个脚都要一个1k的上拉电阻，上拉到5V)
• Pin 1 to pin 4 of 24LC512 are connected to ground, Pin 8 connect to 5V, Pin5 is I2C SDA and Pin6 is I2C SCL, Pin7 is floating. (24LC512 EEPROM的1到4脚都接地，8脚连接5V，5脚对应I2C SDA，6脚对应I2C SCL，七脚悬空)

Capabilities(能做到什么):

USB Mass Storage Device (USB大容量储存设备)

• Emulate a 512Kib I2C EEPROM 24LC512 as a 64KB USB Drive (用512Kib的I2C总线EEPROM 24LC512模拟了一个64KB的U盘)
• Read, write, delete and format operations are fully supported. (完全支持各种读写删除还有格式化操作)
• Support safe media ejection in Windows, Linux and Mac OS X (在Windows, Linux和Mac OS X上支持安全弹出介质)
• Use USB Endpoint 3 IN and OUT, Interface 2, Bulk-only transfer (使用了端点3的IN和OUT，2号接口，BOT传输)

USB Keyboard (USB键盘)

• Simulate key press and release, and send them to the host. (可以模拟键盘按键操作并发往主机)
• Use USB Endpoint 1 IN, Interface 1, Interrupt transfer (使用了端点2的IN，1号接口， 中断传输)

USB Vendor-Define HID (厂商自定义的USB HID设备)

• Exchange data (receive and send) with host, up to 64 bytes each time (可以和主机交换数据，每次最多64字节)
• Use USB Endpoint 2 IN, Interface 0, Interrupt transfer (使用了端点2的IN， 0号接口，中断传输)

UART (串口)

• UART0, no function re-mapping (0号串口，没有io重映射)
• Exchange data (receive and send) with host (可以和主机交换数据)
• Support printf (支持printf)

I2C

• CH55x does not have built-in I2C peripheral (CH55x系列木有内置I2C通信外设)
• Implement and emulate a I2C peripheral with GPIO (用GPIO来模拟I2C总线通信)

File Structure(文件结构):

main.c

• void main(void) {}
• USB Device Interrupt Entry(USB设备中断函数入口)

Delay.c Delay.h

• Delay (延时函数)

ch554_platform.h

• Define uint8_t, uint32_t e.t.c (定义uint8_t, uint32_t等等标准类型)
• Handle the difference between Keil C51 and SDCC (处理Keil C51和SDCC编译器之间的差异)
• U16B0 returns the lowest byte of a 16-bit integer, regardless of endian, similar defination for U16B1, U32B0 e.t.c (U16B0会返回一个16位整数的低字节，与端无关，U16B1, U32B0等也是类似功能)
• U16_XBig converts a big-endian 16-bit integer to fit the local endian, vise versa, similar defination for U16_XLittle, U32_XBig and U32_XLittle. (U16_XBig用于将一个大端储存的16位数转换成当前的端方式，也可以用于反向转换，U16_XLittle, U32_XBig和U32_XLittle的作用类似)
• Instead of using sbit led=P1^1, use SBIT(var, port, bin) to declare a bit variable, for example, SBIT(led, GPIO1, 1), this facilitates compilation under different compilers. (最好用SBIT(var, port, bin)来声明位变量，比如SBIT(led, GPIO1, 1)来代替sbit led=P1^1，这样有助于在不同编译器下编译程序)

ch554_conf.c ch554_conf.h

• Configure system clock (配置系统时钟)
• Initialize USB Device (初始化USB设备)
• Initialize UART0 (初始化串口0)
• Set system clock frequency and UART0 baud rate in ch554_conf.h (在ch554_conf.h里设置系统时钟频率和UART0的波特率)

i2c.c i2c.h

• Emulate a I2C bus host with GPIO (用GPIO来模拟一个I2C总线主机)
• I2C_DELAY(void) controls the I2C clock frequency
• I2C_WriteByte() sends the data byte in I2C_Buf to I2C bus and return the ACK status in bit 0 of I2C_Buf then release the I2C bus, 0 means ACK and 1 means NACK. (I2C_WriteByte()会把I2C_Buf里的一个字节发送到I2C总线上并在I2C_Buf的最低位返回ACK的状态然后释放I2C总线，0为ACK，1为NACK)
• I2C_ReadByte(void) reads a byte from I2C bus and store it in I2C_Buf. (I2C_ReadByte(void)从I2C总线上读一个字节然后放在I2C_Buf里面)

usb_it.c

• USB interrupt service routine (USB中断处理函数)
• Handle USB bus reset/suspend/wakeup (处理USB总线重置/挂起/唤醒)
• Dispatch incoming requests to EndPoint service functions (把主机发来的请求分发给端点的处理函数)

usb_endp.h

• Declear EndPoint buffers (声明端点的缓存)
• Toggle certain EndPoint service function (开启或者关闭相关的端点处理函数)

usb_endp.c

• Define EndPoint buffers (定义端点的缓存以及大小)
• USB_EP_HALT_SET(ep) and USB_EP_HALT_CLEAR(ep) stall or restore an EndPoint as the host requests (USB_EP_HALT_SET(ep)和USB_EP_HALT_CLEAR(ep)根据主机请求挂起stall或者恢复端点)
• Optionally, add your EndPoint service functions here (如果愿意可以把USB的端点处理函数放在这里)

usb_ep0.c

• Contain service routine for EndPoint 0 SETUP/IN/OUT (包含端点0的SETUP/IN/OUT事务的处理函数)
• Handle requests sent by host during enumeration phase (在枚举的时候负责回应主机的请求)

usb_desc.h

• Define the total length of Config Descriptor, including Interface Descriptor e.t.c (定义配置描述符的总大小，包含接口描述符等)
• Define the total number of String Descriptor (定义字符描述符的数量)
• Define length of HID Report Descriptors (定义各种HID报告描述符的大小)

usb_desc.c

• Define Device Descriptor (定义设备描述符)
• Define Configuration Descriptor and Interface Descriptor (定义配置和接口描述符)

usb_string_desc.c

• Define custom String Descriptors (定义自定义的字符描述符)
• String Descriptor 0 is reserved for language configuration (0号字符描述符是为语言标识保留的)

Notes:

• 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)