| ??? 10/04/04 02:52 Read: times |
#78656 - RE: Simplified and working schematic Responding to: ???'s previous message |
If this is the case, means if signal integrity is degraded by cross coupling, then you could try to use a flat ribbon cable, with every second line connected to ground, and this at both ends of cable! I'd like to avoid that if I can. I'm aiming for a circuit that requires a standard DB25 cable with a male connector on the computer side of the cable and a female connector on the MCU side of the connector. By the way, where do you place the buffer: Next to AT89S8252 or to printer port? How long is your cable? Which cable do you use? I'm using a standard DB25 straight-through cable with a male connector on the computer side and a female connector on the AT89S8252 side. The cable is about 1.5 meters long. The buffer is right next to the AT89S8252. The buffer then goes to a 26-pin DIP connector into which plugs a 26-cm ribbon cable that goes to a DB25 male connector to which the female side of the DB25 cable then connects (which then goes to the computer's parallel port). Why the extra step of the 26-pin DIP connector to the DB25 male connector? Because I can't get any stinkin' DB25 male connectors to solder onto the PCB anywhere in the entire city of Monterrey Mexico. ARGH! So the ribbon cable->DB25 male is from a part I canabalized from an old PC (ribbon cable used to connect to a PC motherboard). Looking again at the parallel port pinout I'm now observing that I've only connected pin 25 of the DB25 to ground. Considering what you suggested about using a ground every other line, may I assume it would be appropriate to go ahead and connect the other 7 ground lines on the DB25 to ground as well? (I'm thinking that may be a stupid question and the answer is "yes"). Thanks for your help. Regards, Craig Steiner |
