I can draw schematics all day long, but layout is a weak point with me…
Are there any board layout services or really good help on getting a board laid out? I have a relatively basic board that I can’t seem to get laid out in an efficient manner.
If it’s something you’d feel comfortable sharing (isn’t for work, etc.), you could always post the layout files, and we can have a peek.
Layout seems to be something you get better at with some practice, but having another person to have a look at your work and give suggestions is often very helpful (at least to me)!
I agree. Start with a small board and work up from there. It’s not all that hard once you get going. Here are some thoughts:
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use ground planes/polygons. this cuts down on the number of wires to route.
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play around with part location and orientation. look for minimal crossing of airwires. good layout can make a huge difference.
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group components by functional areas
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on 2 layer boards, try running horizontal on one layer, vertical on the other.
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it’s ok to mix surface mount with through hole and to put components on both sides of the board. surface mount bypass caps are good with TH chips.
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use pin swap/gate swap. this can help minimize the number of crossing wires.
You haven't told us what toolchain you are using.Shifted:
I can draw schematics all day long, but layout is a weak point with me…
Doing this well is an art. Many hobbyists go asShifted:
Are there any board layout services or really good help on getting a board laid out? I have a relatively basic board that I can’t seem to get laid out in an efficient manner.
far as getting a PCB design working, but its not
very pretty and may have violated the rules of
the PCB house that fabs the board.
Like learning to ride a bike, you can read all you
want, watch a demo all you want, but you won’t
“get it” until you try for yourself and fall off a
few times.
There is no such thing as a perfect PCB design.
Once the basics have been mastered there is
room for personal style and preferences. Like
music, art, or stage performance, there will be
critics and you’ll have good days and bad days.
If you have an auto-router turn it off and leave
it off. In the long run the best “auto-router” is you.
From the school of hard knocks I would say that
the most important step in the PCB layout process
is placement of the parts before you route the
first trace/track.
For a beginner do not attempt to use fills or
polygons (ground planes or power planes).
Very, very, few circuits need them, and if you
have a circuit design that does, a novice would
have to master many other subtle factors to
complete the layout.
^ Completely agree with bigglez’s above post. ^
Actually the project is somewhat open source…
http://www.shiftedtuning.com/linuxecu.zip
Those are the project files and the two custom libraries. This uses the Atmel AT91SAM9260, 2 SDRAM chips, a NAND flash, and an ethernet connection. This is a “brain board” that connects to a daughterboard through the EXT connectors. The daughter board will have all the IO connectors (analog inputs, digital outputs, etc). As you can see from the name, this is a Linux based Engine Control Unit.
Before anybody jumps down my throat about latency, the Linux part is only the main controller, there is a sub-controller that handles all the timing, which will be an Atmel AVR UC3A. The Linux part will only be the tuning interface, storage, and main controller.
The schematics are done in Eagle 5.0 professional. There are 10 sheets so I’m not sure if people without professional will be able to view them.
This isn’t my first board, but it is my most complicated one. I’m definately using a ground plane to make a lot of the routing easier. I plan on routing this by hand since I’ve made 5 different layout attempts with the autorouter and could only get about 60% of the board routed.
From Cadsoft's website:Shifted:
“The schematics are done in Eagle 5.0 professional. There are 10 sheets so I’m not sure if people without professional will be able to view them”
CadSoft Online:
LimitationsThe following limitations apply to the EAGLE Light Edition in general:
The useable board area is limited to 100 x 80 mm (4 x 3.2 inches).
Only two signal layers can be used (Top and Bottom).
The schematic editor can only create one sheet.
Apart from these three limitiations the EAGLE Light Edition can do anything the Professional Edition can do. You can even load, view and print drawings that exceed these limits!
Hey Shifted,
Have you had a look at the AT91RM9260 evaluation boards from Atmel? If I remember correctly, the schematics and board layout files for those boards is available for download. (At least, it is for the AT91RM9200). I think the evaluation boards generally contain most of the components you’re looking to populate your board with, too, so they’d be great to look at for an idea on layout.
I also remember hearing that most people haven’t had much luck with the AT91RM9260 and a 2-layer board. I haven’t had the chance to check your layout file, so I can’t check to see if you’re using a 4+ layer board or not :).
I’ve recently designed and constructed a board based on the AT91RM9200, with one SDRAM chip and an SPI flash, similar to several of the boards already out there (an open source one is the Linux Stamp, that includes schematics and a board layout file – though I wanted to do the layout myself, so I started from scratch 
). The site is http://www.opencircuits.com/linuxstamp – you may want to have a peek and see if it helps!
The schematic that I took a lot of the design from was the Olimex AT91SAM9260 Evaluation board. I am using a 2 layer board, I think I can get away with it (Olimex seems to have done it). I have the Olimex board here, but they don’t publish the layout so I can only go by what I can see with my eyes. They use some really tiny via’s and tracks, so its difficult to follow.
Thanks for the links, I’ll definitely check them out.