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how could we config the input IO for low power design？

The Seven
Guru 11440 points

Other Parts Discussed in Thread: CC2530

Hi everyone

     i have a question of pullup and pulldown for the IO config.

     i want to set the P01 and P04 as input，keep low in normal and receive high means active.

     What could i config those Pins in software（pulldown ， pullup or tristates）although  i have set a external pull-down resistor on those Pin.

     And which config should be better for low power consumption design？

     is that need to set a external resistor （pull-down or pull-up）？

     what kind of external pull-down resistor should i choose？ 

  • 0
    TI__Expert 3050 points
    Hi,

    Depending on the mode of operation you are using, there would be different approaches for optimizing the power consumption.

    If you are forced to use interrupt mode, e.g. you must catch any change of the IO immediately:
    As you can see in the CC2530 datasheet, the internal pull resistors have a typical resistance of 20kOhm.
    To optimize current consumption, consider disabling the internal pulls, and use external resistors with greater resistance, e.g. 50kOhm.

    If you can use the IOs in polling mode, then I suggest using the internal pulls as follows (and avoid connecting any external pull):
    In idle state (i.e. when not reading the IO input), disconnect the internal pull. Whenever you are about to read the input value, connect the internal pull, read the IO value, and disconnect the pull again. Please note that you may need a short delay after connecting the pull resistor and before performing the read, since capacitance on the input signal may cause it not to reflect the right value immediately.

    Regarding the registers you need to write to in order to control the pin configuration, please consult the CC253x user guide (http://www.ti.com/lit/ug/swru191f/swru191f.pdf)

    Best regards,
    OD
  • 0 in reply to OD
    Guru 11440 points

    Hi OD

    thanks for your reply，happy new year！

    i use the interrupt mode，and there is a external pulldown resistors for keeping the input as low in normal state.

    so ，i need to disable the internal pulls ，is that right？

    and it means  i need to set the IO state as 3-state （ PXINP = 0xFF） ?

    and is that right？ the greater of the external resistor i use  ， the better for optimizing current consumption i get ？