I have a Raspberry Pi2 B+ model, with noobs distro installed.
I had some programs using wiringPi library and an ultrasound component working (tested them using a separate monitor via HDMI). However, after connecting the official Raspberry Pi touch screen display these programs are not working anymore.
On further analysis I realized that the ECHO signal from same ultrasound device was never captured (checked using voltage value on one of the INPUT mode GPIO pins)
Referred to questions: GPIO pins NOT working when using touchscreen and Touchscreen drivers disable GPIO interface in Python
However, I don't think this is the problem because if I disconnect the touch screen and plug in HDMI again, the same programs with same ultrasound connections work flawlessly. (Note: also tried a simple LED program, but that doesn't work either)
Any ideas? The questions I referred to mentioned that the drivers for touchscreen might have disabled the kernel level access for GPIO library (Python library in those questions, wiringPi C library in my case) I just did a full update and upgrade from apt-get to get the screen working, no special drivers installed separately.