Elegant and Robust Capacitive Touch Interfaces - Review

Table of contents

RoadTest: Elegant and Robust Capacitive Touch Interfaces

Author: Workshopshed

Creation date:

Evaluation Type: Evaluation Boards

Did you receive all parts the manufacturer stated would be included in the package?: True

What other parts do you consider comparable to this product?: Cypress’s CapSense® MBR3 (as previously roadtested) Freescale’s MPR121 capacitive touch sensor controller Atmel QTouch devices such as the ATmega328PB

What were the biggest problems encountered?: No big problems.

Detailed Review:

This review is a summary of the testing that I've done on this kit, for more details see the links at the end.

 

Product performance and functionality

The capacitive sensors coped well with all but the thickest of front panels I tested with. Even that one should be usable if the sensor pads on the PCB were larger. The sensors also coped well with the gloves and could adapt for different gloves without the need to change any settings. Because the sensor controller is also an MCU it's possible to build in other functionality into your panel such as the swipe direction indicators on the proximity demo. The proximity sensing was very good and it's nice that a pad can be both a proximity sensor and a capacitive sensor at the same time.

 

Designing your own board

TI do seem to give you everything you'd need here. The data sheet includes details of the minimal components you'd need to get an MCU operational, a handful of capacitors and a crystal for the oscillator. There are several reference designs including the evaluation kit itself. The code examples provided are clear to read and the Design Centre software provides a template to get started with your design.

One of the reference designs

 

Demo and Software

There seemed to be a few issues installing the software but even with me ignoring all the warnings that TI could throw at me, it still worked just fine. The different demo boards provided all worked and showcases the technology well. The software was easy to learn and use.

 

Support materials

There is extensive support material for this solution, from videos to reference designs to extensive documentation on how to design your sensor pad. The APIs provided in the software are also clearly documented with explanations and examples. There are also labs and workshops you can work through to understand the technology, I really can't fault TI in this category.

 

Example schematic

 

Price to performance ratio

The evaluation kit is quite expensive at £71.56 so I've marked TI down a little for that. The kit is excellently engineered and uses top quality components and connectors. Perhaps 3 different examples is overkill? Included in the kit price is the programmer which you could potentially use in your own projects. The kit should also mean your initial time to get a prototype up and running should be reduced.

 

TI's site suggests that the MCU devices should be around $0.5 however the device used in the evaluation kit is £ £4.14 on the UK site for Element14, which is about twice that of the ATMEGA328PB. Note that there could be cost savings compared to other products as you don't need to have a host MCU as well as a controller chip, which you'd need with the Cypress MBR3 technology.

 

Overall

The technology holds up well to the mock workshop environments I threw at it. The CapTIvate MCUs to have good range of functionality and you could easily use one of these along with the sensing technology to meet all of your front panel requirements and potentially more.

 

Further reading

Elegant and Robust Capacitive Touch Interfaces - Part 1 - Intro

Elegant and Robust Capacitive Touch Interfaces - Part 2 - Software

Elegant and Robust Capacitive Touch Interfaces - Part 3 - Uploading new code

Elegant and Robust Capacitive Touch Interfaces - Part 4 - Front Panel Materials

Elegant and Robust Capacitive Touch Interfaces - Part 5 - Gloves

Anonymous
  • Hi Andy,

     

    A very nice review!

    This is also helpful for my actual projects with touch sensors.

    One of this i use the TIs LDC1xxx series, also the MCP devices from Microchip.

     

    Thanks!

     

    Best Regards,

    Gerald

    ---

  • Nice update Andy.

     

    I agree that some of TI's devices are a little pricey, but they have always done a good job on the boards and the tools they send out.

     

    I still give them high marks for quality and robustness.

     

    Though everyone can improve.

     

    DAB