user10196: Arduino Mega ADK is working well but it is not working circuit in which pull-up/down resistors. It is generating wrong results. I guess, pull-up/down resistors fried. What can i do? 

user6959: If you want internal pullup or pulldown resistors on input pins, you can use external ones to do the same job as internal ones if you wish to. Generally, if you use say 100 k Ohms from a pin to V+ or ground then it will act as a pullup or pull down respectively on an input pin, but have much effect on an output pin - which is what you want to happen. 
However, it is unlikely that 'fried internal resistors is the reason for code not working and, if this is the case, there is probably unknown and unknowable other damage as well. Pull up/down resistors are usually not actually resistors. They are FETs with high Rds_on values that look resistor like when on. Anything that "fries" them has a reasonable prospect of doing other damage as well.

10196: <p>Arduino Mega ADK is working well but it is not working circuit in which pull-up/down resistors. It is generating wrong results. I guess, pull-up/down resistors fried. What can i do? </p>
 6959: <p>If you want internal pullup or pulldown resistors on input pins, you can use external ones to do the same job as internal ones if you wish to. Generally, if you use say 100 k Ohms from a pin to V+ or ground then it will act as a pullup or pull down respectively on an input pin, but have much effect on an output pin - which is what you want to happen. </p>

<p>However, it is unlikely that 'fried internal resistors is the reason for code not working and, if this is the case, there is probably unknown and unknowable other damage as well. Pull up/down resistors are usually not actually resistors. They are FETs with high Rds_on values that look resistor like when on. Anything that "fries" them has a reasonable prospect of doing other damage as well.</p>
