Comment by Aurornis | Hacker News Reader

Comment by Aurornis | Hacker News Reader

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> - How comprehensive is the part library?

It wouldn’t make sense to add yet another giant parts library to the world of PCB design. Make it easy to import from the major part and footprint libraries found linked from DigiKey.

Don’t try to reinvent the wheel.

> - Is there auto-routing? How good is it?

Autorouting is of very limited value for only certain narrow use cases. Even the high dollar CAD packages won’t route your board for you in a reasonably good way, but they can be useful for routing length-matched buses and such after the user has set up all the constraints properly.

> - "Import formats: DXF". For what, the board outline? DXF is for mechanical CAD. You can't import a board layout or schematic that way.

DXF import is a very common operation in PCB layout, not just mechanical CAD. It’s used all the time to pull in board outlines, important silkscreen items, and other features.

These criticisms are really a stretch for a project like this that is just getting started. If you’re expecting a feature set identical to four and five-figure CAD programs that have been developed for decades then, yeah, you’re going to be disappointed. Can we not just appreciate that this project is ramping up and providing more options?

Autorouting is of very limited value for only certain narrow use cases. Even the high dollar CAD packages won’t route your board for you in a reasonably good way, but they can be useful for routing length-matched buses and such after the user has set up all the constraints properly.

I think you have forgotten when you were a beginner.

Autorouting is the most difficult when you are a beginner, because you don't know how to define the constraints and don't know what results are acceptable. I'd even argue that routing is the easy part of PCB design. Figuring out the circuit is hardest, specifying design rules is confusing, determining the component placement is tough, and on the easy end, drawing the schematic and routing the PCB are roughly on par. Routing is the part at the end where you can relax and enjoy yourself while you untangle the ratsnest.

As a beginner, I find autorouting entirely unnecessary for the level of complexity I work with. Routing is pretty much the simplest part of the process to understand and somewhere between a fun puzzle and a tedious but simple chore depending on the specific design. I'm pretty sure there used to be a very popular mobile game that, while visually completely different, had the exact kind of "mechanics" as manually placing traces on a PCB does.

What would be helpful, however, are some better checking tools. Some mistakes, like running a trace right through the bottom side of a through-hole and creating a short that wasn't there on the schematic, seem very easy to detect and warn the user about before they end up spending hours cutting traces and running bodge wires.

Some of the softwares have live DRC, so it will either prvent you from doing it or mark the nets as violating design rules.

I have not checked if kicad or Librepcb have it, but PADS and Altium do.

KiCad wont let you do this as part of the design rules. The DRC will also flag the error.

Yep. LibrePCB has it too (both DRC and ERC).

"Can't live without Electricity" rings a bell there for me.

Have you? I routed my first board a year or two ago and found pretty quickly that autorouters suck even at simple tasks. The only way to get usable results is to simplify with smaller autoroute jobs and better placement, at which point you could easily do it by hand anyway.

> simplify with […] better placement

Have been designing PCBs off and on for 20 years. This is what I use the autorouter for. I put together a placement that has logical clustering and flow to it and try running the autorouter. If it has a really hard time with lots of vias, I focus on tuning the placement in that area until it can get a relatively ok autoroute. Then I tear up the traces and manually route. I figure “I can do cleaner routing than the autorouter, but if it thinks the best it can do is 20 vias on this group of traces I don’t stand a chance”

Why is auto routing a PCB so different from IC design? It's not reasonable to expect humans to route a full IC with hundreds of thousands of standard cells, so constraints are defined and the auto router is sicced on the mess. Do PCBs just fall in the range where designs are still simple enough for humans to do by hand, and due to board size limits, will not go beyond that range?

It's in large part the complexity of the constraints: PCBs generally contain a heterogeneous mix of parts with different concerns. Digital portions of ICs are a lot more regular, especially with standard cells. If you were to make old-school PCB-level digital circuits, the autorouter could probably help a lot with that (and indeed it was not uncommon to see it done that way). Likewise, analog portions of ICs are still generally laid out by hand, or have ad-hoc optimisers written for them.

But for the average PCB, which has mix of switch-mode power, analog, high-speed digital, and low-speed digital, it takes longer to specify the constraints so the autorouter can do a good job, let alone wait for it to hopefully complete. So it's rarely used outside of particularly tedious but regular tasks, like hooking up a wide memory bus.

(I do think this is something where AI could make a big improvement. If it could infer most of the constraints from the circuit then it would help with saving time. The challenge then becomes marrying the ML-generated output with the hard constraints effectively)

Autorouting is least useful for beginners because they're working on small projects that can easily and quickly be routed by hand (with much better results).

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