On Sat, 2011-04-02 at 19:02 -0300, Daniel B. wrote: > Hi geda-user@, > > I'm kinda new to gschem (in fact, first time learning a electronics > cad software) and a little confused about the power pins issue. I read > the geda-faq:gschem and found that it's a good practice to NOT hide > the power pins. > > Is this related to the design of the symbol? Are there some (generic) > attribute common to all symbols that makes the power pin visible? > > I'm trying to draw a circuit that uses 2 different power supplies, 12V > and 5V. Are there any other good way to design this type of circuit? > > Any old topic in archive might be helpful too. > > Thank you in advance. >
A difficult point for beginners -- we should have an entry in the FAQ for this. Short answer: Symbols can have invisible power pin, i.e some logic gates symbols have entries like net=GND:7 or net=+5V:14 or net=VCC:14 If you put multiple such symbols on your schematic these pins (pin 7 or 14) are connected for the netlist, and later on the PCB board. Today often multiple voltages are used, so hidden power pins can generate problems, use of something like VCC can be bad, because it may stand for 3.3V and 5V and may generates unwanted shorts. So it may be better to always use explicit visible power pins -- use power pin like other ordinary pins, connect pins with nets. You may use Power-symbols like GND to give names to these nets, or you may use the netname attribute to give names to nets. Nets with the same name become connected. There is no magic to switch between visible and invisible pins, the author of the symbols decides how he wants it. Things become even more complicated when we put the visible power pins to a separate symbol instance. You may find examples for all kinds of symbols at http://www.gedasymbols.org/ DJs and Wilsons tutorial may help http://www.delorie.com/pcb/docs/gs/gs.html http://geda.seul.org/wiki/geda:gsch2pcb_tutorial It is not easy for beginners, and my english is really bad today, sorry. I hope someone other can explain it in better words. Best regards, Stefan Salewski _______________________________________________ geda-user mailing list [email protected] http://www.seul.org/cgi-bin/mailman/listinfo/geda-user
