Thanks, all of you guys. Specially Dan, your explanation of pin names and numbers was desperately needed.
Here is the problem. In PCB, pins have a name and a number. The number is specific to the package and the name is specific to whats inside the package. Lets take a SO8 package that happens to house an op-amp. In the schematic you have pin numbers and pin labels. You might have pin 2 labeled as "IN-" and pin 3 labeled as "IN+" and pin 7 labeled as "OUT". When you netlist, you refer to pin numbers. So for example, U1-2 and U1-3 and not U1-IN- and U1-IN+. The pin numbers define all of your connectivity information. The pin labels are simply informative. Now you load PCB. The rat lines key off of the pin number and uses the pin number in the netlist. Pin names are not used at all. So if pin numbers are broken in your symbol or footprint, thats it, game over, things are just broken. Now that the .cmd file does is it goes through and says "U1-2 (i.e. pin #2 of U1) happens to be called the "IN-" pin on this particular op-amp". And it makes all those changes. Now if you query that pin in pcb, it will tell you pin #2 and "IN-". This is useful when you're working with a big part and you don't know the pinout by heart or via the context and you want to quickly see the name of the pin you're connecting too. Thats all the .cmd file does. If you don't ever load it, nothing bad happens other than querying U1 pin #2 will just report "this is pin #2. It is called '2'" instead of ..... It is called "IN-".
This ought to go in a FAQ, and also into the gschem->pcb tutorial. This explanation is a MUST. I have read perhaps 100 A4-sized pages of text on gschem and pcb and the connection between the two, by going through the info pages for PCB and online tutorials and FAQs. And I remember feeling very uneasy about the names-versus-numbers issue. But I do not remember reading any good explanation. Your text above should not be allowed to be lost. In addition, the tutorial should add some explanation of the .cmd file generated by gsch2pcb, and also spend a bit more time explaining what refdes_renum does. (And references to the "Screen" menu in PCB should be removed.. the version of PCB I am seeing (200608xx) does not have a "Screen" menu at all.) Can you please put it in the gschem->pcb tutorial? I guess Bill Wilson is also on this mailing list? If there is something I could do, please tell me. Tarun -- _______________________________________________ geda-user mailing list geda-user@moria.seul.org http://www.seul.org/cgi-bin/mailman/listinfo/geda-user