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  • Compatibility with different CDC devices
  • Ability to send and receive data
  • Ability to set various parameters, such as baud rate, number of stop bits, parity
  • Handling of multiple CDC devices at the same time
  • Notifications about CDC connection status
  • Ability to query the CDC line and modem status
  • Small memory footprint in RAM and ROM

emUSB-Host—Device Class CDC

The USB Communications Device Class (CDC) provides access to COM port devices via USB. This enables communication via modems for mobile networks such as GSM/3G/LTE or cable based network modems.


The communitcation device class is primarily used and supported by modems, ISDN and also by fax machines.

Typical Applications

The communication device class is primarily used and supported by

  • Modems
  • ISDN
  • Fax machines

Example Code Included

An example application which uses the API is provided with any shipment or eval software including emUSB-Host. This example displays information about the CDC device in the I/O terminal of the debugger. In addition the application then starts a simple echo server, sending back the received data.

Resource Usage by this Component

ROM usage RAM usage
App. 5.2 KByte + (emUSB-Host core incl. driver)  48 Byte + < 1 KByte per each device + (emUSB-Host core incl. driver)