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So, most of the examples use USB CDC driver and they bridge UART. I'm not embedded guy and learning the stuff one by one. So, I understand UART... But I'm a bit confused how this bridging works. Is uart a virtual driver kind of thing or physical component inside the MCU. How does this bridge of USB CDC driver work though USB and UART are components by themselves ?

I read this question, Does USB CDC always use a UART channel?

But I need more insight to understand this bridging. Please explain the bridging thing as well in details.

Because the confusion is UART itself needs pins configurations... so pins are physical and how the bridging works.

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  • \$\begingroup\$ There is code that copies the input from one interface to the interface of the other one. This is just a software function. You should be able to determine that from the examples you cite. \$\endgroup\$ – Daniel Apr 26 '16 at 23:45
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The USB protocol can contain other protocols inside it. CDC or Communication Device Class is one such protocol. If both ends of the USB connection support CDC you can setup a serial communication between them.

For example, you can have an FTDI chip at one end of a USB cable and a Windows PC at the other. The FTDI will convert serial RS232 data into a USB signal by first putting the RS232 data inside a CDC signal then putting that inside the USB signal. At the PC end Windows will unwrap the USB signal then the CDC signal then make the RS232 data available on a virtual COM device within Windows.

A UART usually refers to a physical device (usually a constituent of an embedded processor) that can support RS232 protocol and perhaps a few other serial protocols.

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  • \$\begingroup\$ I used UART instead of RS232. I'm going to switch is in the above answer as UART is normally used to describe a physical device or a physical component of many contemporary embedded processors. \$\endgroup\$ – st2000 Apr 27 '16 at 4:38

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