USB Interface Chip Simplifies Touch Screen Application Development for Mobile Devices

Analog and mixed-signal semiconductor manufacturer Silicon Laboratories (News - Alert) (www.silabs.com) has developed a universal serial bus (USB) touch screen bridge IC that streamlines the connection between touch controllers and host CPUs in computing systems with large displays. Silicon Labs’ new CP2501 USB touch screen interface chip provides a programmable, easy-to-use bridge for laptops, tablets, eBooks, mobile Internet devices (MIDs), kiosks, ATMs and other point-of-sale (POS) equipment with touch screen displays.

According to the supplier, CP2501 is the only semiconductor device of its kind with pre-programmed touch screen USB interface software, providing out-of-the-box USB support for large touch screens.

Presently, touch screen systems in computing applications frequently use a USB interface to communicate between the touch screen controller and host CPU, said the maker. However, most touch controllers in the market do not support USB directly, requiring a separate IC to bridge the communications gap. Consequently, the prevailing method for developers is to use a standard microcontroller (MCU) as a bridge chip and develop touch screen USB interface software or acquire it from resellers, a costly, time-consuming process that requires USB expertise.

On the other hand, CP2501 touch screen bridge eases touch screen application development by providing pre-programmed firmware that enables developers to configure touch screen settings quickly and easily, streamlining software development and speeding time to market. The USB interface is Microsoft (News - Alert) Windows 7 touch interface compliant and supports the USB human interface device (HID) digitizer class driver, said Silicon Labs.

Additionally, the CP2501 is also supported by a GUI-based configuration wizard from Silicon Labs that allows developers to connect a touch controller to a USB system without developing customized USB firmware. Using the configuration tool, developers can create the firmware project, customize USB parameters and generate USB touch screen descriptors. A pre-programmed USB bootloader also supports easy in-system firmware updates.

According to Mark Thompson, vice president of Silicon Labs’ Embedded Mixed-Signal products, “The CP2501 USB touch screen bridge uniquely addresses the growing application need to integrate large touch screens within computing systems – quickly, easily and with minimal USB software expertise.”

The CP2501 IC supports capacitive and resistive touch screen technologies and offers interfaces to the inter-integrated circuit (I2C), universal asynchronous receiver/transmitter (UART) and serial peripheral interface (SPI) buses.

Plus, it features a high-performance 8051-compatible MCU core running at 48 MIPS with 53 kB of flash memory and 3.5 kB of RAM (News - Alert) available for application software. The high-performance MCU core and generous memory provide ample headroom for developers to perform sophisticated algorithms such as noise filtering, position calculation and gesture interpretation. Sixteen GPIO pins enable developers to control LEDs and/or haptics, saving precious pins from the touch controller and reducing the processing burden on the host CPU.

The company recommends pairing the CP2501 IC with its QuickSense human interface products such as the F99x, F8xx and F7xx capacitive touch-sense MCUs and the Si11xx ambient light and infrared sensors to enable sophisticated proximity sensing and intuitive touchless interface solutions. Additionally, it can also be combined with Silicon Labs’ Si24xx modem in notebook and tablet applications.

For rapid evaluation and faster turn around, the supplier offers development kits. Sampling now in a 5 mm x 5 mm QFN32 package, the pricing for the CP2501 begins at $4.37 in 10,000-unit quantities.