Hey, i have a problem that i have been at for over a day now, and i can not solve this with my skills. So the problem is as follows. I am trying to get an output from a 4x4 keypad, which would not be a problem but input and output are on the same pins. I know that the 74hc573 should keep the information after LE goes low, but i just can not figure out how to read output from 74hc541 without giving new information to the previous chip, because then the state changes again. At the moment i can only read the keys diagonally, because input and output match in that case. The schematic of the whole circuit can be seen here
:http://i.imgur.com/FWcJRvP.png and the problematic part here :http://i.imgur.com/i7vwFXs.jpg
Hope you guys can give a tip and help me understand this. Thanks
Keep track of what the output is in a variable.
I tried doing that already, but the output and input update at the same time when i am trying to write onto the input.
I tried starting poking the RD and WR directly, even tho they should be controlled automatically, did not have any luck either.
That's not a very well thought out circuit!
IMHO it'll be best to do a redesign.
Actually the circuit is pretty well designed. Some of the things i have messed with and gotten working make things really simple in the long run. The fact that keypad i/o are on the same pins is bothering me a bit, but it is possible to make it work. The circuit can not be redesigned because it has already been printed.
Actually the circuit is pretty well designed
If you have to jump through hoops to do something as simple as scanning a 4x4 matrix, then it's not a well designed layout.
But anyways, this is not in any way, shape or form a Keil related question.
I turned here because i really needed help, and did not really know where to go. Since it is related, i did not think it would be that much off. Sorry for bothering you
Actually the circuit is pretty well designed.
but it is possible to make it work.
Those are two very strange statements to come from the very person who just admitted he could not make that circuit work!