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Question Regarding "MSP430 Low Cost PinOsc Capacitive Touch Keypad" Wiki/Example

Kyle Hunter
Prodigy 120 points

Hi all,

I am currently working on creating a capacitive touch keypad (previously mentioned throughout recent posts). The capacitive touch keypad I am designing has eleven touch pads - currently on the path of using a 4x3 (rowxcolumn) linear row-column array sensor pattern in my schematic. I am designing this printed circuit board (PCB) using EAGLE 6.4.0 Light. I came across a great Texas Instruments Wiki page (http://processors.wiki.ti.com/index.php/MSP430_Low_Cost_PinOsc_Capacitive_Touch_Keypad) I am using as a reference.

I have a few questions: 1) It looks as if this was designed in OrCAD, what command was used to make the actual touch panel for the remote in OrCAD? Was it simply just a line and the designer chose the pattern of the plate? 2) What was the command used for the array sensor pattern? Also, in regards to this array sensor pattern, I am assuming this is copper? Many capacitive touch designs appear to be made of copper I have seen throughout my research.

If anyone has any knowledge or insight they can share it would be greatly appreciated!!

Thank you in advance for your help!

  • 0
    Guru 25210 points

    Typically you would create a custom PWB decal for the entire array and a corresponding custom schematic symbol (I'm using Mentor PADS/DxDesigner terminology here). That looks to be what they did for the reference article you linked.

    You may also want to consider ENIG plating for your board as well, the gold will have longer corrosion resistance than a HASL finish.

  • 0 in reply to Brian Boorman
    Prodigy 120 points

    Brian Boorman said:

    Typically you would create a custom PWB decal for the entire array and a corresponding custom schematic symbol (I'm using Mentor PADS/DxDesigner terminology here). That looks to be what they did for the reference article you linked.

    You may also want to consider ENIG plating for your board as well, the gold will have longer corrosion resistance than a HASL finish.

    If you don't mind me asking - what do the acronyms PWB, ENIG, and HASL mean? Are you saying that I should create the array as a separate library as I did with the MSP430G2553IRHB32 and import it into my projects schematic?

    Thank you for your reply!

  • 0 in reply to Kyle Hunter
    Guru 25210 points

    PWB = Printed Wiring Board.

    ENIG and HASL are two PWB surface finishes.

    HASL = Hot-Air Solder Leveled meaning they finish the board with a solder "plating" and use a hot-air knife to level the surface.

    ENIG = Electroless Nickel, Immersion Gold, this is a finish where nickel is plated onto the copper, then a fine layer of gold over that.

    I am saying that your array should be a "component" in your layout library, and create a schematic symbol for that component. Just the same as you would for an IC, resistor, etc. Only difference is that you aren't actually soldering a physical component on the board at assembly time.

  • 0 in reply to Brian Boorman
    Prodigy 120 points

    Thank you very much for the explanation for the acronyms. I truly appreciate that!

    I apologize for the lack of expertise behind this subject at hand. Am I understanding you in saying that there are default arrays within the design software? Or am I to create the component and import it into my schematic?

  • 0 in reply to Kyle Hunter
    Guru 25210 points

    I am not familiar with your design software. Most likely you have to create the decal/footprint yourself. Or check on the forums for your layout software and ask there if anyone has created one and is willing to share.

  • 0 in reply to Brian Boorman
    Prodigy 120 points

    Alright I will do that, thank you for your response Brian! Are you familiar with OrCAD by any chance?

  • 0 in reply to Kyle Hunter
    Guru 25210 points

    Kyle Hunter said:
    Are you familiar with OrCAD by any chance?

    No. I was raised on Mentor Graphics PADS systems. :-)

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