Microchip Launches mTouch Development Kit

Touch sensing is fast becoming an alternative to traditional push-button-switch user interfaces, because it requires no mechanical movement, and it enables a completely sealed and modern-looking design.

Now expanding beyond the consumer market, touch sensing is beginning to take hold in medical, industrial, and automotive applications for reasons such as aesthetics, maintenance, cost, and cleanliness.

Microchip’s mTouch Solution is a free and open source which enables designers to add this leading-edge user interface to applications utilizing PIC microcontrollers, without the cost of fee-based licensing and royalty agreements.

Being a source-code solution further helps engineers quickly integrate touch sensing functionality with their existing application code in a single microcontroller, thus reducing the total system cost associated with current solutions.

To create an mTouch system, three things are needed:

1. Touch sensors - These are just conductive pads, separated from the user by an insulator.
2. A capacitance to digital converter, The mTouch system accomplishes this task by using the capacitance of the sensor as a frequency determining element in a relaxation oscillator. The frequency of the oscillator is then measured, and any shift due to a user’s touch is detected and validated in software.
3. A method to detect and decode the output of this converter. This solution is a combination of a running average, a comparator and some decoding algorithms.

The current version of the mTouch system uses the dual comparator module with the SR latch output mode to create a relaxation oscillator which measures sensor capacitance. In addition, both TMR0 and TMR1 are required to perform the frequency measurement necessary to determine a capacitance shift due to a user’s touch. Therefore, to implement the current mTouch capacitive touch system, a device with two comparators, the SR latch mode, TMR0, and TMR1 is required.

Microchip provides a wide variety of microcontrollers with these features. The smallest device is the 14-pin PIC16F610 microcontroller. The next size device is the 20-pin PIC16F690, and the largest are the 28/40-pin PIC16F887 family of devices.

The PICDEM Touch Sense 1 Demo Board is an application example using three different touch sensor configurations in the form of a Directional pad, Keypad, and Slider section. A factory programmed firmware application provides the user immediate access to all of the board’s features through the use of the accompanying Windows(R) based Diagnostic Tool and PICkit Serial Analyzer. The Diagnostic Tool provides the user a platform to analyze application critical information in real-time as it relates to touch sensor behaviour.

The mTouch solution:

• Free mTouch Touch Sensing Software
• No Licensing or Royalty Costs - Free & Open Source
• A Single Chip Solution
• Runs on a choice of PIC microcontrollers from 14 pins to 40 pins

Microchip’s mTouch solution is targeted at all forms of user interface including:

• Replacement of IP based touch sense solutions
• Replacement of traditional mechanical keypads
• Hand held instrumentation
• Automotive - dashboard controls
• Medical Equipment
• Appliance Controls
• Consumer Products

Product information table: