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DigiCDC - Digispark USB CDC Serial Library

The DigiCDC library allows the Digispark or Digispark Pro to appear to a computer as a Virtual Serial Port when connected by USB. This makes it appear just like a standard Arduino and allows the use of the Serial Monitor built into the Arduino IDE.

DigiCDC was based on the V-USB project and avrcdc project - the first version (the hard work) was created by ihsan Kehribar ( and then turned into an Arduino library and refined by Erik Kettenburg (Digistump)

Limitations and Usage

The DigiCDC library is based on V-USB - because the Digispark does not have hardware USB support. This presents some unique limitations in how it works - outlined below:

  1. You must explicitly include the DigiCDC library - by placing the following at the top of your sketch
    #include <DigiCDC.h>
  2. It uses a lot of RAM - half of the Digispark's RAM - so only include it when needed and watch your RAM usage. You can wrap strings in F() (ie. SerialUSB.print(F(“test”)) ) to put the string in flash memory instead of RAM
  3. You use it the same as Serial on an Arduino but with SerialUSB instead (ie. instead of ) - The Pro also has Serial defined - but that refers to the hardware Serial port on Pins 6 and 7.
  4. The begin statement does not need a baudrate - it is a CDC device so it does not have a set baud rate - just use SerialUSB.begin()
  5. You must install the driver for windows - it is part of the driver package found in the Digispark Arduino release.
  6. It is slow - it transfers data very slowly (5ms per character) - because it is a low speed USB device doing the job of a Standard speed device - and doing it all virtually without actual hardware support!
  7. Like all of our V-USB libraries you must use its delay function instead of delay() - so use SerialUSB.delay() when you need a delay in your code.
  8. SerialUSB.delay() or SerialUSB.refresh() must be called every 10ms or less in your code if no other SerialUSB call is made in that code.


Examples can be found in the Digistump Arduino release (1.5.8C or higher) under File→Examples→DigisparkCDC

Android Devices

DigiCDC can be used to make the Digispark appear as a Serial device to an Android device when attached to an Android device's OTG port. The device must support Serial/CDC devices via OTG

Android App Examples (using phonegap/cordova and editable with only working knowledge of javascript and HTML):

Phonegap/Cordova Plugin used in the examples above to connect to a DigiCDC device:

(plugin use FTDriver by Keisuke SUZUKI

digispark/tutorials/digicdc.txt · Last modified: 2016/06/09 12:03 (external edit)