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Decrease I/O Pull up current consumption

michaeld

Hello,

I found this on the forum:

According to nRF51822 PS v3.1 section 8.23 pullup and pulldown resistors have a typical value of 13kohm. if you have e.g. a button that connects a certain pin to ground when pressed, and the pin is configured as input with pullup, and you have supply power of 3.0 volts for the nRF51, then the current consumption is 3/13k = 230uA when the button is pressed.

Now my question is what would be the highest possible pull up resistor value for the I/O to still be detected?

I tried using a 10M, 1M and 470K ohm resistor for external pull up with the internal pull up disabled but then the I/O change event is not detected. I want to reduce the current consumption of 230uA would be to high for my application.

Thanks!

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    ok those voltages are pretty much what I'd expect. Surprised it sags as low as 2.2V with just 1M, that's worth knowing.

    Going back to your original question, you say the I/O change event 'is not detected'. What are you using to detect it? I'm pretty sure if you read the GPIO INPUT register it will change when you press the button, if you are using a GPIOTE PORT event however you need to set up the pin to have some kind of SENSE on it, the nrf_gpio_cfg_input() function sets it to SENSE_Disabled.

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    ok those voltages are pretty much what I'd expect. Surprised it sags as low as 2.2V with just 1M, that's worth knowing.

    Going back to your original question, you say the I/O change event 'is not detected'. What are you using to detect it? I'm pretty sure if you read the GPIO INPUT register it will change when you press the button, if you are using a GPIOTE PORT event however you need to set up the pin to have some kind of SENSE on it, the nrf_gpio_cfg_input() function sets it to SENSE_Disabled.

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