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!

[michaeld]

Thanks for you response.

Here you can find my schematic: http://i.imgur.com/E9M6FVs.png

I measured the voltage with the switch open its is 3.2V and the supply voltage is also 3.2V. So I really don't understand why it's not triggering at 470K ohm. When pressed it is 0V as expected. Only with the 1M and 10M I measured 2.2V and 1.45V at the pin.

I configured the pin like this:

		nrf_gpio_cfg_input(LEFT_BUTTON, NRF_GPIO_PIN_NOPULL);