I'm using LPC1768 and I intend to use the Deep Power-Down mode to minimize the power consumption and got pretty good results but I still do not understand how the GPIO works after going into this mode or what are their state in this mode.
In the documents AN10915: Using the LPC1700 power modes it has said :
1. All General Purpose I/O pins (GPIO) default to input with pull-up resistor enabled. Using the PINMODEx registers, first, disable the internal pull-ups on all general port pins. Second, configure the IOs as GPIO outputs and drive them low,
Now I did this and the current consumption increased by the factor of 50 !
Before this the whole current was 170uA but after adding this part it turned out to be 40mA !
I don't know what was wrong. I even used the NXP sample. So I wiped out this part of the code.
Now I have a weird problem. I have this DS3231 RTC Module connected to my board and I connected its VCC to a LPC1768 GPIO and in ON state it draws about 1mA but when the controller goes to Deep Power-Down mode it still has a voltage about 1.3V and it adds about 280uA to the board's whole current consumption.
Now why there would be any power coming from a GPIO after going into Deep Power-Down mode? Isn't all peripherals supposed to be turned off?
What actually happens to GPIOs?
Does it really matter to set a state before going into Deep Power-Down mode?
By the way this is the RTC module I'm using.