As I understand the GPIO requires an input voltage to be either 0v or 3.3v for bit 0 and bit 1 and I'm also guessing this is controlled by a schmitt trigger prevent logic state bouncing.
Does anyone know what the exact voltage ranges for bit 0 and bit 1 are i.e. 0 - 1v, 3 - 3.3v etc, is this the same for every Pi or can the thresholds fluctuate due to temperature??
Richard S.
Re: GPIO input voltage levels??
Does http://www.scribd.com/doc/101830961/GPIO-Pads-Control2 answer your question?
Re: GPIO input voltage levels??
Thanks for the tip the information has certainly proved interesting.
According to the docs the maximum low level voltage is 0.8v and minimum high level voltage is 1.3v (which is surprisingly quite low from 3.3v).
Does that mean I could use the voltage drop of red LED (approximately 2.0v) with load resistors at the source and input pin to provide GPIO input detection and protection??
Richard S.
According to the docs the maximum low level voltage is 0.8v and minimum high level voltage is 1.3v (which is surprisingly quite low from 3.3v).
Does that mean I could use the voltage drop of red LED (approximately 2.0v) with load resistors at the source and input pin to provide GPIO input detection and protection??
Richard S.
Re: GPIO input voltage levels??
I'm afraid that's a bit beyond my knowledge! 
You might find the "Buffered I/O, LEDs, and pushbuttons" section in the Gertboard manual interesting?
You might find the "Buffered I/O, LEDs, and pushbuttons" section in the Gertboard manual interesting?