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Debounce disable registers in TCA8418

sunil c r
Prodigy 60 points
Other Parts Discussed in Thread: TCA8418

With reference to TCA8418 datasheet (SCPS215B –SEPTEMBER 2009–REVISED MARCH 2010) , i want to clarify the following regarding the usage of Debounce disable registers.

  • I am using an 8 * 10 keypad
  • I have configured Keypad mode by writing to the registers (0x1D to 0x1F),

i.e  Reg[Addr] = value

Reg[0x1D] = 0xFF

Reg[0x1E] = 0xFF

Reg[0x1F] = 0x03

  • In order to use debounce disable registers, should i only write '1' to the input pins ( ROWs incase of keypad mode)?
  • Should i also write to the debounce registers which correspond to columns in keypad mode?
  • 0
    TI__Genius 9085 points

    Hello Sunil,

    Yes, to disable the debounce, you will write a 1 to the ROWs of the keypad.

    No, you do not need to disable debounce in the registers that correspond to columns. Debounce has no effect on these since columns are configured as outputs in keypad mode. 

  • 0 in reply to Hattie
    TI__Genius 9085 points

    Sunil,

    I'm sorry, I was mistaken.

    The debounce circuit has no impact on IOs configured as Keypad ROWs or COLUMNS. These have a 50ms automatic debounce setting that is configured separately from the 50us debounce from the register.

    This 50us debounce is only for GPIOS configured as inputs. Again, changing this register will have no effect on inputs configured in Keypad mode. 

  • 0 in reply to Hattie
    Prodigy 60 points

    Hattie,

    Thank you!

    Since i have configured "KEYPAD" mode,i need not write anything to those Debounce disable registers , is that correct?

    According to you ,the automatic setting of 50 ms debounce time will come into action no matter which mode (either keypad or GPI) you are working in??