Tablets are the hot item in stores and their multitouch interface is one reason for their popularity. Multitouch support does away with the need for real keyboards. Developers will need chips like Atmel's mXT1386 and mXT616 to handles screens up to 15-in.

The mXT1386 (Fig. 1) is a 4-chip solution designed for screen sizes from 8- to 15-in. The 3-chip mXT616 solution handles screens from 5- to 10.1-in. Atmel's technology can handle an unlimited number of touches but the on-chip software is limited to 16. That should be more than enough for most applications. The need for more than 10 occurs when you consider that parts of the hands other than fingers might come in contact with the screen such as the palms.

The chips have a report rate over 150 Hz providing faster application response time. It can handle finger pinch separation under 9mm. Accuracy and linearity are under 1mm, close to 0.5mm. Stylus tip sizes can be under 4mm.

Gesture recognition can be handled by the hardware or touch information can be processed externally. The system hands automatic grip suppression thereby ignoring hands holding sides of tablet. The same is true for palm rejection.

The chips have USB and I2C interfaces. Atmel provies a full suite of drivers include I2C for Linux and Android as well as USB drivers for Windows XP and Windows 7. A evalution kit is available as well (Fig. 2).