Bus breakouts in schematics, what are the conventions? - Page 1
Forum section: electronics / projects

author: knotlogic
author_rank: Regular Contributor
timestamp: April 15, 2019, 06:03:20 am
content: This one has been bugging me a while because I can't seen to find any information on it on the web. (Maybe I'm using the wrong keywords.)When drafting a schematic, is there a convention on which way the angled portion of a bus breakout should go? In the example I attached these are the green diagonals going bottom left to top right.

author: iMo
author_rank: Super Contributor
timestamp: April 15, 2019, 10:33:03 am
content: Like in this video the predefined bus taps are drawn "automatically", I would follow the convention the Eagle suggests..

author: ajb
author_rank: Super Contributor
timestamp: April 15, 2019, 02:28:39 pm
content: Whichever direction the signal 'flows'. If in the middle of a bus, then whichever looks better

author: Ian.M
author_rank: Super Contributor
timestamp: April 15, 2019, 03:44:36 pm
content: Its a clue where to look for the other end of the wire. If there's only two connections its easy - always towards the other end. If its a multi-point connection its more difficult: At slave devices, it should be angled towards the master device. At the master device it should be angled in the direction with the most slaves. It may be impossible to be 100% consistent.

author: IDEngineer
author_rank: Super Contributor
timestamp: April 15, 2019, 05:19:33 pm
content: This is a particularly irritating aspect of "modern" schematics. In the original post's illustration, there is a signal called PA0. Once that designator is defined, it can be used ANYWHERE in the schematic. A pin can come off a part and terminate with a short line to the characters "PA0" and that means it's connected to every other instance of "PA0" anywhere - EVERYWHERE - on any/every page of the schematic. I personally do a two-person fine-detail review of every PCB that is designed from my schematics, and the advent of CAN based schematics and PCB layouts has made this behavior the default. It's made slightly easier when I'm the guy who drew the original schematic (before it was translated into Cadence or whatever) but it's still a royal PITA when I'm on the artwork side of the review, and can see that the trace continues, yet my schematic sidekick says "No, that signal doesn't go anywhere else" because there's literally no indication whatsoever that "PA0" appears on other pages. Looking solely at the schematic, you can easily - WAY too easily - completely miss that the signal appears across the page, or on other pages, etc.Sorry, had to get that Rant d'Jour off my chest. We now return you to your regularly scheduled thread.

author: knotlogic
author_rank: Regular Contributor
timestamp: April 16, 2019, 02:44:15 pm
content: Quote from: imo on April 15, 2019, 10:33:03 amI have Eagle, and it doesn't do it automatically... though to be fair that's because I have an older non-Autodesk version. Looks like they've made a lot of changes (hopefully improvements?) to the software. But 0:13 of that video was helpful, it suggested a pattern to the breakouts which seemed to be ...Quote from: Ian.M on April 15, 2019, 03:44:36 pmThanks! Now to go back over the stuff I've done recently and correct it...