Hi,

I'm having trouble reading an 8bit port setup as input with no internal pull ups enabled. I keep getting strange values, sometimes it'll settle on the correct value but mostly appears random.

I am reading 8 lines off a 74HCT245 driven by 5volts and my portb IO is 5volt tolerant. On my scope I can see the I/O all the way to the micro pins are fine but the read of the input fails most of the time. Perhaps if I wait a second or to, it'll settle however its not following the true signal.

I have noticed an errata in the datasheet showing possible problems with output impedance<500 but the 245 is directly wired to the micro and it can easily drive high enough currents. I can certainly see the change with my scope.

Cheers,

DC

On the SAM7 parts you have to enable the PMC for the GPIO you are reading. If the pins are on GPIOA, you have to enable that peripheral in the PMC, if they are on GPIOB you have to enable that peripheral, otherwise reading them will give erroneous data.



The above code was used on a SAM7A3. Double check your part to make sure its the same.