LPC824 PIO0_4 floating input and WAKEPAD_DISABLE register

Discussion created by lpcware Employee on Jun 15, 2016
Latest reply on Jun 15, 2016 by lpcware
Content originally posted in LPCWare by joepbrown on Mon Apr 27 11:11:39 MST 2015
I'm trying to use PIO0_4 as a GPIO to detect if the pin is high or low. I have an external 1M pulldown resistor and want to use the pin as a floating input. I've tried many things but can't seem to disable the internal pullup on PIO0_4 so the pin is stuck high.  Furthermore PIO0_4 looks like, by default, it is configured as the WAKEUP pin but the documentation seems inconsistent.

Here's a few things I've tried to make the pin a floating input:

  [*]Setting the pin as an input (which I thought was the default IO state for most pins) with

  [*]Disabling the pullup with

  [*]Explicitly disabling the WAKEUP pad with


None of this allows the pin to float and it is still pulled high.

When I read Table 63 (DPDCTRL register description) in the manual it says:

WAKEUP pin disable. Setting this bit disables the wake-up pin, so it can be
used for other purposes.

Remark: Never set this bit if you intend to use a pin to wake up the part from
Deep power-down mode. You can only disable the wake-up pin if the
self-wake-up timer is enabled and configured.

Remark: Setting this bit is not necessary if Deep power-down mode is not

0 Enabled. The wake-up function is enabled on pin PIO0_4.
1 Disabled. Setting this bit disables the wake-up function on pin PIO0_4.

Reset value: 0

But when I'm connected to the device the reset value is 1(disabled) not 0. So I'm not really sure if the WAKEUP is enabled or disabled by default, or what I need to do to disable it, or if I even need to disable it.

Does anyone know how to make PIO0_4 a floating input?