i would like to be able to build a circuit that allows 2 or more deives to be controlled at the same time with the same parallel port... i.e.- a hd44780 character lcd and an led display, (or whatever).
i don't have any experience with programming, so i'd like the whole project to be primarily hardware based. if possible, soley hardware based!
here are some of the thoughts i have had so far-
the pins on the parallel port consist of this:
8 data out pins
5 input/status pins
4 control lines
(then the rest are ground pins)
when interfacing the hd44780 to the parallel port, all 8 data pins are used, and 3 of the control lines. BUT, depending on the software used, one of those control lines is not always used by the lcd.
so, here's what i'm thinking- i can somehow use the 2 left over control lines as device selectors (with some 74 series latches or something). i.e.- maybe there could be x number of devices at one time, each having it's own address. 0,0....0,1....1,1....1,0.
when one device is selected, the output is enabled on it's latch, and the data from the parallel port will reach that device. the other devices will not display the data being sent through the port because outputs are disabled on those device's latches.
does that make sense?
comments?
i don't have any experience with programming, so i'd like the whole project to be primarily hardware based. if possible, soley hardware based!
here are some of the thoughts i have had so far-
the pins on the parallel port consist of this:
8 data out pins
5 input/status pins
4 control lines
(then the rest are ground pins)
when interfacing the hd44780 to the parallel port, all 8 data pins are used, and 3 of the control lines. BUT, depending on the software used, one of those control lines is not always used by the lcd.
so, here's what i'm thinking- i can somehow use the 2 left over control lines as device selectors (with some 74 series latches or something). i.e.- maybe there could be x number of devices at one time, each having it's own address. 0,0....0,1....1,1....1,0.
when one device is selected, the output is enabled on it's latch, and the data from the parallel port will reach that device. the other devices will not display the data being sent through the port because outputs are disabled on those device's latches.
does that make sense?
comments?