USB CDC/ACM Class Driver for Windows 2000, XP, Vista, 7
Features Supported Platforms Demo Documentation Prices
Thesycon’s USB CDC/ACM device driver provides a serial port emulation on Windows operating systems by implementing a serial link emulation protocol on USB. The driver exposes a Win32-compatible COM port and in addition provides some unique features such as a Plug&Play compliant device instance enumeration method. This avoids confusion about COM port numbers and improves usability.
The driver supports all Windows desktop operating versions (e.g. Windows 2000, Windows XP, Windows Vista and Windows 7). A similar driver is also available for Windows CE. See USB CDC/ACM Class Driver for Windows CE for more information.
The driver works with devices that are compliant to the Communication Device Class (CDC) specification, subclass Abstract Control Model (ACM). However, the driver supports three different USB protocol flavours which are described in more detail below.
Thesycon also offers the Embedded USB Device Stack with CDC/ACM device class for implementing the firmware of a USB CDC/ACM device. With these development kits Thesycon provides the support for implementing the firmware and the device driver for USB CDC/ACM devices quickly and cost-effective.
Supported USB Protocols
CDC/ACM Compliant Protocol
The device needs to implement the Abstract Control Model (ACM) subclass defined in the USB Communication Device Class (CDC) specification. This protocol requires two USB interfaces, a data interface which consists of two endpoints (bulk in + bulk out) and a control interface which consists of one interrupt in endpoint. Furthermore, on EP0 the device needs to implement the class-specific requests defined by the CDC specification. Because this USB protocol is compliant to the CDC/ACM standard on some operating systems (e.g. Linux, MacOS) the device can work with in-box drivers.
Reduced CDC/ACM Protocol
This mode uses the CDC data interface (bulk in + bulk out endpoint) only. No control interface (interrupt in endpoint) is required. The device needs to implement the CDC class-specific requests. So it is still possible to support baud rate settings and serial control/status lines. This mode is useful if the number of available endpoints is limited by hardware restrictions. However, as the protocol is proprietary a specific device driver is required for every operating system platform to be supported by the device.
Bulk-only Protocol
The device implements the data interface (bulk in + bulk out endpoint) only. The device does not provide an additional control interface and does not need to implement any class-specific requests on EP0. Because bulk transfer mode provides flow control there is no need to support serial control/status lines. The advantage of the bulk-only protocol is that the implementation efforts on the device side are reduced to a minimum. However, because the protocol is proprietary a specific device driver is required for every operating system platform to be supported by the device.
USB CDC/ACM Class Driver Features
Depending on the driver configuration the CDC/ACM device driver exposes an emulated COM port or a modem. The standard Windows mechanism is used to assign a COM port number to each device instance. This COM port can be opened and used by standard programs such as HyperTerminal.
In addition to the COM port naming scheme the driver supports a PnP compliant enumeration mechanism which is based on device interfaces. Custom applications can enumerate and open available device instances by using Windows API functions such as SetupDiGetClassDevs and SetupDiEnumDeviceInterfaces. So the user is not required to enter a COM port number. Applications can automatically locate, identify and open available device instances. By using the function RegisterDeviceNotification applications can receive notification messages when devices are connected or disconnected. Thus, an application can implement full USB Plug&Play support.
Feature Summary
- Supports USB 1.1 and USB 2.0
- Supports Windows 7 x86, Windows 7 x64, Windows Vista x86, Windows Vista x64, Windows XP embedded, Windows Server 2003 x64, Windows XP x86, Windows XP x64, Windows 2000
- Exposes a virtual COM port that is compatible with the Win32 serial port API
- COM port can be used by standard Windows programs such as HyperTerminal
- Can be configured either as a serial port or a modem device (using unimodem driver)
- COM port name gets assigned automatically
- Hot plugging of devices is fully supported
- Supports add/remove notifications and a Plug&Play compliant port enumeration and identification method that is not based on COM port names
- Optional static COM port behavior to support legacy applications. The application can keep the COM port opened while the device is removed and continue the communication if the device is reconnected.
- Design and implementation complies with the Windows Driver Model (WDM). The driver is certifiable by Microsoft Windows Hardware Quality Labs (WHQL) for all current 32 bit and 64 bit operating systems.
- Supports two or more COM ports for Multi-Interface devices with Thesycon’s USB Multi-Interface Driver
- Support for Windows CE and Windows Mobile based devices
A similar driver is also available for Windows CE. See USB CDC/ACM Class Driver for Windows CE for more information.
Easy Installation
Using Thesycon’s PnP Driver Installer it is very easy to create a specific setup wizard that handles driver installation, un-installation and update in a comfortable and reliable way. For more information on PnP Driver Installer, check out http://www.thesycon.de/pnpinstaller.
Free Demo
The demo version is time-limited but has full functionality. After the device is connected the driver can be used for used for 4 hours, then the driver disables itself and the computer must be rebooted in order to use the demo again. The demo package includes the driver and the documentation.
Current Version: 1.86
USB CDC/ACM Class Driver Demo Package
Documentation
Licensing conditions & Prices
USB CDC/ACM Software License Agreement 
USB Vendor and Product ID
When designing a USB device you need an official USB vendor ID (VID) which is unique world-wide. Vendor ID's will be assigned by the USB Implementers Forum (www.usb.org). There is a fee of $1500 US.
Thesycon owns a USB vendor ID and provides a subset of product ID's (PID) to customers who licensed our USB software.
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