7 years, 8 months ago.

How do you set special pins on the LPC11U24?

I have recently soldered up my own board using the LPC11U24 processor. The usb works and I am able to program the processor. The main issue I am having right now is that I want to pullup pins PIO0_4 and PIO0_5 which are default set to open-drain mode (they are the I2C pins). My goal is to get these pins to work as digital input for the two buttons that I have connected to them. These buttons go to ground when they are pressed. Everything I have tried so far (digitalout, DigitalIn pull-up mode) has not caused the pins to change their voltage and I am pretty sure they are not both connected to ground. From what I have been able to decipher from the UM10462 manual, I need to change the pin mode of these pins, but I am lost as to the specific command I should use while working with the mbed libraries. Any help would be greatly appreciated.

1 Answer

7 years, 8 months ago.

Those two pins are open-drain pins, that isn't just their default, it is the only hardware they got: They are special I2C pins. So if you really want to use them as DigitalIns for your buttons you will need external resistors.

Accepted Answer

I see. I'll probably have rewire those two or jury rig something else. That's just what I needed to know though, thanks.

posted by Michael Swan 14 Mar 2013