STM32F103 USB CDC CMSIS provires a simple low weight firmware for STM32F1 serie to implement Virtual Com Port. Current implementation create Virtual Com Port with next settings: 115200, 0, none, 8, but you can change these settings as you want.

• Add usblib.c and usblib.h to your project.
• Make sure you have configured USB to 48 MHz clock and RCC to 48 MHz or more (72 MHz is recomended).
• It's strongly recomended to use 1,5K GPIO driven pull-up rezistor to have full controll of USB line initiate sequence.
• Call USBLIB_Init(); to enable USB and make initial configuration of USB registers. Please note - USBLIB_Init(); will trigget USB RESET sequence.
• Enable 1.5K pull-up resistor to allow host detect device connection.
  • If your device connected to Windows host use RemoteSwitchHUB.inf to install a default Windows driver. After installation you will see new COM port named RemoteSwitch HUB (If you want to change this name you need to edit it in usblib.c and inf files).
  • If your device connected to Unix systems then you will see a new device in /dev/ dir.
• Implement void uUSBLIB_LineStateHandler(USBLIB_WByte LineState) in your code to handle line state. See main.c for example. NOTE: you can't send any data to host when port is closed! To controll when port is opened use this condition:

if (LineState.L) {      //App connected to the virtual port
    USBLIB_Transmit((uint16_t *)"Welcome to the club!\r\n", 22);
}

• Inplement void uUSBLIB_DataReceivedHandler(uint16_t *Data, uint16_t Length) in your code to accept data from host. See main.c f.e.

Code well tested on Windows7, MacOS 10.13 (High Sierra) and Raspbian OS.