Software stack gets USB controller On-The-Go

Mentor Graphics has developed a USB software stack purpose-built to complement its popular line of On-The-Go (OTG) controllers.

Mentor Graphics has developed a USB software stack purpose-built to complement its popular line of On-The-Go (OTG) controllers.

The Mentor Graphics Inventra dual role controllers support both the host and function capabilities of a device and the ability to swap those roles dynamically.

The software stack has been tuned for small footprint and power efficiency, making Mentor Graphics the only company to provide an integrated USB OTG software solution optimised for its hardware intellectual property (IP).

Target applications for USB OTG include digital cameras, PDAs and mobile phones.

Embedded designers have typically relied on USB OTG software stacks that are based on PC-centric solutions.

These solutions are designed to execute on computers with effectively limitless performance and power and do not translate well into environments where battery life and memory are major concerns.

In addition, these PC-centric solutions were not designed to cope with the dual-role nature of OTG devices, which requires them to act as a host one minute and as a function the next.

Mentor Graphics designed its software stack from the ground up to specifically integrate with its USB OTG hardware IP.

"With a history of expertise in embedded software and hardware design, Mentor Graphics has the unique capability to provide standard-certified combinations of both software and hardware IP solutions", said Mark Saunders, Director of Strategic Marketing for the Mentor Graphics Intellectual Property division.

"Customers can leverage our complementary technologies to reduce months of extra engineering effort to attain compliance with a complex specification".

The USB OTG software stack detects the connection of a function or a host device and switches automatically to the appropriate mode.

For OTG-to-OTG connections, the stack supports the Host Negotiation Protocol (HNP) that allows the software to respond to requests for a role change and enables the device to switch seamlessly between modes.

To comply with the USB standard, current software stacks need to support up to 127 function devices.

For this level of support, a complex scheduling algorithm is needed to ensure efficient allocation of the available bandwidth.

These processing needs can overload the most powerful PC and can prove nightmarish for the low-power, limited memory embedded environments that are adopting USB today.

Mentor Graphics has developed a scheduling algorithm that can distribute bandwidth among a limited set of connected devices, while reducing the footprint of the stack to a fraction of that typical of a re-purposed PC solution.

The USB OTG software stack allows the designer to limit the number of connected devices and supported endpoints to suit CPU performance and available memory.

The USB OTG software stack employs a Linux-like API that allows software developers familiar with Linux to build custom drivers for the stack.

The stack's class loader enables both static and dynamic linking of drivers.

Ever-present devices such as keyboards and mice can be permanently linked to the stack.

Alternatively, functions that are regularly connected and disconnected, such as printers and PDAs, can be loaded dynamically as the physical connections change.

The Mentor Graphics Inventra USB OTG software stack is available now and pricing information is available by contacting a Mentor Graphics sales representative.

Deliverables include: complete C language source code; sample build scripts and make files for popular platforms; source for class drivers; and user documentation and integration guide.

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