> Tamas Szabo <[email protected]> writes: > I would create a schematic symbol for AT91SAM7 device: 64 pins, lots > of them with multiplexed functions. > 1. I can number pins round, 1 to 64 sequentially: > [snip] > 2. I can separate pins by functions, without keeping the pins' order: > [snip] > Furthermore, since the above mentioned device has at least 3 function > for 32 pins, it is more difficult to setup a suitable pin placement > applying the second option.
It is only really difficult if you're working on a breakout board or other generalized schematic, and have to try to make all possible configurations look good. A normal project will have these peripherals hardwired to a peripheral using only 1 of their functions, so it's a very easy task to organize the pins logically. > By the way, I saw the first option in many places (for example my company > also provide schematic this way). In my estimation, the reasoning behind this practice is not because it's the most logical, but because it's the easiest to execute and to coordinate. The draftsman doesn't have to make any decisions and different symbols from the same company by different draftsmen will all look the same. > However, since in my opinion schematic is a logical thing, I prefer the > second option. > Which is the better solution? I agree that the schematic is a logical thing, and prefer the second option, but in the end it's a matter of personal preference. I'd suggest grouping the pins by one of two functions: PIO/Peripheral vs. chip management. Some, like JTAG and USB (if you have that) could go on either side. The power side will largely stay the same between projects. On the other side, you can either order the pins by their GPIO number, or group them by peripherals. See an example of the former by Bob Starr for the Eagle library here: http://imgur.com/D96os.png - as you said, it will be hard to do the second in a general manner. If you want to try, I'd suggest using the chip block diagram on page 5 of the datasheet as a starting point. My preferred method, Option 4, would be to make one symbol like the linked image, and then shuffle the pins around for your project. Then, when you have a different project with different peripheral use patterns, it's easy to copy the symbol and move the pins around into the grouping that fits your project. Save the master symbol in your global symbol folder, and the customized symbols in each project folder. This does make comparing schematics between projects more difficult, but it's likely that the peripheral you're investigating in this case will be grouped in both schematics. -- Kevin Vermeer _______________________________________________ geda-user mailing list [email protected] http://www.seul.org/cgi-bin/mailman/listinfo/geda-user
