IO pin protection
Moving from basic stamp to propeller, with the basic stamp it is/was common practice to use a 220 ohm resistor in series with IO pins , is this still the case with the propeller?
I could not find an answer during numerous searches
I could not find an answer during numerous searches
Comments
I'm designing a breakout board to use with a USB proto board. Basically an easier way to to connect IO Pins ect using pc board screw type type terminals , since I have a habbit of switching stuff around a lot. Was wondering if I should wire 220 ohm resitors as a small protection for the IOs?. (I have done similar stuff with the stamps)
Gonna do the dame with the prop, but using 32 bit math and higher sampling rates
About the resistor, you need it for protecting the I/O pin.
Lets say you don't use a resistor and the line is 1 ohm with
3.3 volts. A direct output pin is high and shorts to ground.
According to ohms law,
E = I R I = E/R
I = 3.3/1 = 3.3 AMPS
it would draw 3.3 amps which is beyond the safe operating
range. You're likely to see smoke.
If you keep the pin as an input, in a typical pushbutton circuit
(for example, page 44 - Propeller Education Kit Labs: Fundamentals)
can go from the pin on one leg to 3.3 volts on the other leg. The pin
also routes to a 10K ohm resistor and ground. Read the information
on pullup and pulldown circuits.
humanoido