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USBH CDC ACM Virtual Com Port Question

In Keil's Run Time Environment

I will only use USB Port
I use it as virtual com.

When I coding USB Host Virtual com
as usbh cdc acm, usart port included, why??

//////////////////////////
extern ARM_DRIVER_USART Driver_USART9;
#define ptrUART_USB (&Driver_USART9)
////////////////////////

In keil's "manage run time environment" configure
mcu : stm32f207vc
CMSIS : core
RTOS : Keil RTX
CMSIS Driver : USART(API) : CDC, USART
USB Host(API) : Full Speed
Device : CStartup, classic
Device : common,Cortex,DMA,GPIO,RCC
USB : Host :CDC

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  • Hi Milorad Cvjetkovic

    My ultimate goal is that my device can communicate with USB device that has vendor specific class but protocol of USB device is a serial, text-based protocol

    that USB device only require but vendor specific class.
    8 data bits;
    no parity bits;
    1 stop bit;
    19200 baud rate.

    Does this "USBH CDC ACM Virtual Com Example" not support it ???
    Do I must know if USB has vendor specific class protocol ?

    Thanks.

  • Hi Hojin,

    you should take a look at following documentation page: www.keil.com/.../host_cust_tutorial.html

    it explains how USB Host is used with Prolific PL2303 USB-to-UART dongle, that device also uses Vendor Specific class.

    And yes, you can not use CDC for communicating with such a device as Vendor Specific means it is not standardized so you need to know the protocol, CDC device is standardized.