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TCA8424 - Windows 8.1

Fernando Lopez
Expert 8230 points
Other Parts Discussed in Thread: TCA8424EVM-038, TCA8424

Hello all,

I have a couple questions regarding the TCA8424. We are using the TCA8424EVM-038 plus the MSP430 Launchpad for evaluation.

1)      Can this chip be programmed more than once, or can you only burn each chip once?

2)      Are there any sample OTP files?  This document ( http://www.ti.com/lit/an/scda013/scda013.pdf ) does not explain enough to create one from scratch.

3)      The default values in the registers (un-programmed chip) make no sense for the 512 byte OTP.  Are these chips expected to have a sample keyboard map and working HID descriptors at default, or are these expected to be programmed first before being functional?  The datasheet ( http://www.ti.com/lit/ds/scds341/scds341.pdf ) leads me to believe that “The device also comes with a preprogrammed keyboard map that is compatible with most standard laptop/notebook keyboards”.

4)      Is there a sample ACPI table entry for configuring this chip to work with Windows 8.1?

Thanks.

  • 0
    TI__Genius 16430 points
    Hello Fernando,

    Thanks for the questions.

    I'm looking into these for you.
  • 0
    TI__Genius 16430 points

    Hello, Here are some answers to your questions.

    1) The chip can only be burned once.

    2) There is a sample Excel file that goes with the document you linked to. You can find it under the "Technical Documents" tab on the TCA8424 product folder. You need to click on the "Read Abstract" link next to "OTP Creation Guide". There is a zip file under "Associated Files", which contains this sample excel document.

    www.ti.com/.../litabsmultiplefilelist.tsp;docCategoryId=1&familyId=1652

    3) These chips are expected to be flashed with your keyboard map and settings before it will be functional.

    4) There is no sample ACPI table entry for configuring this chip to work with Windows.

  • 0 in reply to Jonathan Valdez
    Prodigy 10 points
    Thank you. That answers some of the questions. Unfortunately, the excel file is essentially blank. It lists the decimal and hexadecimal addresses, and explains what the first few bytes are, but the Contents column is blank. The first few bytes were also already covered in the part datasheet. What I need is the Contents column filled out. I understand that the keyboard map is going to be different for each design. I don’t understand Report Descriptors, or how to create one (which starts at Byte 32 and goes up to Byte 223. The datasheet (www.ti.com/.../scds341.pdf ) on page 8 at the bottom says “(1) Report descriptor contents may vary depending on version of device. Please contact TI for device for different Report Descriptor contents”. Also, I don’t know what to program in for the last several bytes (specifically 481 through 510). The fact that I can only burn this once means I have to get it right the first time. We have ordered some extra chips that should get here next week though.

    I’m sure someone at TI has an example OTP file for this. It would be extremely helpful to see a sample design, including how the keyboard is laid out, and have the OTP file that matches. Then I could better understand what changes I need to make from there. Having to learn USB HID, and HID over I2C, and Report Descriptors is what we were trying to avoid by selecting this part.
  • 0 in reply to Zeb Johnson
    TI__Genius 16430 points

    Hello,

    Please see the attached zip file. Within it, you will find 3 files

    Report Descriptor.txt: Report descriptor values, this is from the HID standard (can be found in the USB HID Usage tables spec, for example)

    TCA8424-Test_V1.0.xlsx: Example OTP table with the keymap values filled out as well

    Keyboard Map in hex(Usage IDs).txt: The keyboard map in another view to make it easier to see, also uses the HID standards.

    Of course, these files are for testing purposes, but they should help guide you with some of the questions you have. I would suggest looking over the I2C HID spec or over USB (since there are some aspects shared)OTP Example.zip