STMT04E

描述

The FingerTip uses a unique capacitance-to-voltage conversion acquisition. This allows the measurement of up to 209 mutual capacitance nodes. Coupled with the flexibility offered by the internal processor engine, the entire touchscreen sensing solution can measure, classify and track a single finger touch in under 10 ms. A built-in movement tracking engine tracks up to 10 independent touch movements.

The acquisition engine uses an optimal measurement approach to ensure almost complete immunity from parasitic capacitance on the receiver inputs (X lines). The engine includes sufficient dynamic range to cope with touchscreens of different size and configuration. This offers great flexibility for use with multiple touchscreens with different ITO designs and overlay materials. One and two layer ITO sensors are possible using glass or PET substrates.

The device uses a proprietary analog filtering scheme for noise avoidance, reduction and removal. The noise reduction mechanism is based on sophisticated algorithms that combine power and performance with different sources of noise reduction. The main processor engine offers flexibility with required performance by performing pre-processing, post-processing and housekeeping in an efficient way. This gives ample scope for the sensing algorithm, touch tracking or advanced shape-based filtering and event reporting. Built-in associated memory (ROM, RAM) of the processor is optimized to run the desired fixed program codes in the ROM and to maintain the data, event stack and system variables in a RAM. An additional patch RAM can be used for implementing additional codes or algorithms. The 16 Kbyte patch RAM loading time with 400 Kbps I²C is estimated to be 400 ms. This time can be further reduced if the SPI interface is used.

The device supports multi-finger detection and tracking, enabling smooth multi-touch performance on touchscreens while detecting and rejecting large areas such as a palm or hand on the touchscreen. The device can work with light single or multiple finger touches. The device also supports touch keys using the same ITO as for the touchscreen.

The device has an external SYNC pin for LCD noise filtering for display touchscreen technology. The synchronization of the signal acquisition with the LCD SYNC signal helps in removal of LCD noise by providing extra filtering in the device. This allows the touch module manufacturer to utilize glass screens with ITO to be used without any GND shield which significantly reduces the cost of the touch module. Additionally, it provides a better and brighter display experience for the user.

The internal device ROM can be used to store the initialization and configuration data (supplier default settings). The configuration settings can be changed by the host (I²C interface or SPI interface) by writing to the registers, if needed.

The RESETB pin provides a mechanism for a hardware-based reset from the processor which adds flexibility to the system while the INTB pin provides a hardware-based interrupt to the processor upon any pre-programmed event detection.

Additionally the device integrates GPIOs which can be fully configured as inputs or outputs and these also serve various alternate functions.

This device represents a marked improvement over competing technologies by providing an optimal mix of low power, small size, low external part count, versatile features with unmatched true multi-touch performance in a single, touchscreen controller FingerTip device.