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TCA9554A

Pujan Shah
Prodigy 10 points
Other Parts Discussed in Thread: TCA9554A

Hello Sir/Madam,

I was looking TCA9554A chip to use as a I/O expander to I2C. I have a mechanical keypad (6keys) with 2-Rows and 3-Columns. So I need only 5 port pins. My CPU has an I2C channel so I will convert these 5 I/O signals into I2C via your chip.

I would like to know, basic theory of operation behind the chip, in other words, how it converts I/O signals into I2C interface. Also what should I do with remaining 3 port pins (that I am not going to use)? Should I keep open? or Should I connect to ground?

Can you have application note for this chip which describes detail operation technically?

Thank you,

Pujan Shah

 

  • 0
    TI__Mastermind 30310 points

    Pujan,

    Why do you need to create a matrix of these keys? There isn't really a benefit of trying to accomplish a "key scan" application since the TCA9554A has enough input ports to accommodate all 6 keys individually. Creating a matrix would only be needed if your # of keys exceeded the number of I/O Ports on the TCA9554A.

    Now you would only have 2 I/O ports that are un-used. They can be left floating because they have internal pull-up resistors (100kOhm) to VCC.

    The basic theory of operation is shown in "Figure 1. Functional Block Diagram" and "Figure 2. Simplified Block Diagram" on page 3 of the datasheet. 

    Regards,

    Brian