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LM8330: Keypad for Laptop PC

Tamio Yokokura
Expert 3670 points
Part Number: LM8330
Other Parts Discussed in Thread: TCA8418E, TCA6424A, TCA8418

Hello, LM8330 support team

I have a simple question. Can LM8330 use as a keypad controller for the following keypad?

Regards,

Tamio

  • 0
    Guru 279540 points

    The LM8330 can read keys from a keypad matrix. I do not know whether that keypad is organized as a matrix.

  • 0
    TI__Mastermind 31353 points

    Hi Tamio,

    LM8330 reads from keypad matrix scheme. 

    So does the TCA8418E. However, I counted 85 keys in the picture. TCA8418E supports up to 80 keys in a keypad matrix scheme. 

    How is the keypad in the above picture connected? 

    Regards,

    Tyler

  • 0 in reply to Tyler Townsend
    TI__Expert 3670 points

    Hi, Tyler,

    Thank you for quick reply.

    The below is the connection circuitry for a keypad in main board. The connector right side is FPC connector. Basically, each signal is connected to EC.

    For this reason, I believe that by placing the keypad controller in the keypad unit, I2C connection can be made and the pin count can be reduced.

    Pin1 to Pin24 is assigned to SENSE(0-7) and DRV(0-15). I think these signal lines can be replaced with I2C by using TCA8418E.

    How do you think?

    Thanks

    Tamio

  • 0 in reply to Tamio Yokokura
    TI__Mastermind 31353 points

    Hi Tamio,

    This application seems reasonable. It seems you have SENSE and DRV lines that are input signals that need to be handled / parsed through I2C? Then a device such as TCA8418 or TCA6424A might be a good solution here. 

    Would you make a keypad matrix with the SENSE and DRV lines? Then TCA8418E is the more appropriate solution. 

    Regards,

    Tyler

  • 0 in reply to Tamio Yokokura
    TI__Expert 3670 points

    Hi, Tyler

    As you said, customer keypad is 84keys. So I think I would like to consider LM8330 instead of TCA8148E. The matrix scheme will be as below. This is just my idea.

    And the block diagram will be as below. This change will reduce the number of pins by 21, if I'm thinking correctly.

    If my thought is wrong, please give me your advice.

    Thanks

    Tamio

  • 0 in reply to Tamio Yokokura
    TI__Mastermind 31353 points

    Hi Tamio,

    Looks like the TCA8418E is short a few COL pins. 

    LM8330 looks to have the appropriate number of rows/cols pins for your application. 

    For the "other 15" GPIO's, you might be able to interface with some of those input/outputs over i2c via LM8330. LM8330 has 8 row pins and 12 col pins for a total of 96 inputs. Some of these pins have dedicated PWM functionality for driving LED's, however, I believe you can only use one function at a time. It is either part of the keypad matrix, or a PWM output. 

    See the pin out table in the datasheet. 

    If we can offload some of these extra 15 pins, we might be able to reduce the total size of the FPC connector, which I believe is what you are attempting to do here?

    Maybe not driving LEDs, but some of the TP4 pins might be suitable over i2c. 

    Regards,

    Tyler