Suppose the device being read supplied 50V. What would the resistor do? Suppose the device was capable of supplying 500mA, but the Arduino was only drawing 10 mA. What would the resistor do?
Okay, maybe I am thinking too much here, but what I figured was, that there must be some finite lower limit of current which the transformer supplies, say 50mA, so say the Arduino takes in 10mA, the other 40mA (so as to say) will go through the resistor.
What does the data sheet for the IC7447 say? What would the resistor do?
Unfortunately the data sheet only talks about the outputs of the IC7447, which are open collector type, ie, current sinks...
But found something here:74 Series Logic ICs
It says the inputs to the 74XX series are high impendance state and should be either grounded or tied to Vcc...So I figure no harm in connecting it directly to the digital output pins of the Arduino??
You would use either digitalRead to read one pin, or direct port manipulation to read all pins on a port. Not both.
Okay, agreed. But In my particular application I have lots of conditional statements according to which, sets of three output pins take varying output values. So its way easier to use the digitalWrite() function, then go about using PORTB/D while remembering not to disturb the other 5 pins addressed by the register.
So my question is:It shouldn't matter if I declare the pins as OUTPUT type using DDRB/D but then use digitalWrite() to output the actual values, right??