RoadTest: CapSense MBR3 Evaluation Kit
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?: For this application I'd usually consider membrane switches. For the hobbyist these are typically going to be fixed shapes and sizes such as a keypad. However given that flexible materials are now available for 3D printing it is possible that custom shapes and designs could be implemented for small batches or one-off projects. One direct competitor to the MBR3 would be the CAP1188, I've only briefly looked at this but price, formfactor and features seem very similar. There also seems to be similar documentation and design guides. For the hobby market something like the MaKey MaKey is also a possibility. http://www.makeymakey.com/ or one of these boards from AdaFruit https://learn.adafruit.com/adafruit-capacitive-touch-sensor-breakouts/build-a-capacitive-touch-control-panel
What were the biggest problems encountered?: Understanding the terminology and the relevance of the different settings was the biggest barrier to entry.
Evaluation of the CapSense MBR3 in a hobbyworkshop environment
I do think this technology would be good for a hobby workshop to create panels for CNC or measuring equipment. Using a single chip, a few discrete components and a double sided PCB, a control panel can be produced. The PCB would then be mounted in a sealed box as it does not need any components to be on the outside. I've not actually tried to produce a working sensor PCB but following the design guide and allowing for the ability of the MBR3 chip to automatically adjust it should be a practicable proposition. The price of the MBR3 chips is compariable with a membrane switch so assuming that the PCB manufacture does not add a lot of cost it should be possible to build a control panel for equal or less than non capacitive technologies.
The instructions were clear and detailed and completing the evaluation was not particularly difficult. As mentioned above one of my difficulties was understanding the termology and how the configuration settings related to each other. However, after a few goes with the EZ-Click software I now feel confident that I could correctly configure a chip.
One thing that took me a while to figure out was the mappings of the GPO and sensors, these are one to one mappings, these can be enabled or disabled but not remapped. This is covered in the data sheet "Pin Diagram and Definitions" e.g For a CY8CMBR3116 pin 1 when configured as a sensor can drive pin 16 when it's configured as an output . Pin 16 can also be configured as a sensor but there is no output for it to drive. For pins that are configured as an output with no mapped sensor these can only be set by setting the registers using the I2C connection, so you could for example use these for controlling status LEDs on a panel.
The sensitivity settings also took me a while figure out. The best documentation for these seems to be in the "ControllersRegisters Technical Reference Manual", perhaps the UserGuide section on sensitivity could be extended?
The evaluation board performed well in all the tests I completed and coped well with a range of front panel materials from thin plastics through to heavy duty toughed glass. There were two tests I've not completed, firstly the board working with equipment in the vacinity and also testing with oils and metalic dust on the front panel. I felt it was more important to complete the report and those tests can be added as blog entries at a later date. Also if I attempt to build a PCB that will also be added as a blog on Element14. It might be good to try a conductive tape approach as suggested on the Adafruit site.
I found a couple of the tests on the evaluation board a bit fiddly, in particular the need to solder links for the Arduino Uno gave me concern as I did not want to destroy the board.
The demo code for the Arduino worked well and demonstrated the programming via I2C and the host interupt mechanism very well.
As a hobbyist the chip form factors are my main concern, the CY8CMBR3110 comes as 16-pin SOIC so should just be hand solderable and has 10 inputs. However I'd suspect that one of those would get used up by a shield electrode and another for a host interupt leaving just 8. That's enough for most panels but if a numeric pad was needed then you'd need one of the 16 input chips and those only come in an QFN format. I'd be reluctant to use one of those unless it was supplied on a breakout board or if I had a suitable SMD reflow oven.
More detail in my blog entries