Hi,
I’m working on a board that has numerous vias where tracks suddenly end on the front side and continue on the back of the board.
I cannot find a way to designate tracks in Eschema as being on any side other than the front side.
Am I missing something? Placing all tracks regardless of which side they will actually be on in the PCB seems to be an inefficient way of laying out the schematic?
Should there be a choice of FRONT SIDE wire AND BACK SIDE WIRE in Eschema?
Seems to me the ability to place wires on the back side in Eschema and color them Green by default with Front side wires being Red to match PCBNew would be wonderful as also blend into PCBNew better?
I could be totally wrong here of course. I’m relatively new to KiCAD which by the way I regard as an incredibly genius work of art by some extremely talented developers.
The short answer is, you start on the layer your pad is on (any layer if it is through hole). If you want to switch sides, you press ‘v’ for via. It places a via and switches to the other side.
To choose the layer that you want to start on you can click it in the right layer list (like F.Cu or B.Cu), or you can press + or - to toggle between layer pairs.
You can set up layer pairs in File > Board Setup. The click on “Layers” in the left tree that pops up. There you can setup the number of signal layers for your board.
No !!
There is no reason to design pcb at schematic.
You can cross wires at schematic and they are not connected with each other. You can’t cross tracks at the same layer at PCB to not be connected with each other.
I still think having a choice of Red or Green wire in Eschema (designating front or back side in Eschema) would be a better way to lay out the schematic.
You wouldn’t be designing the pcb at schematic, you would be simplifying the schematic and making it integrate into PCBNew easier.
it would also dramatically simplify visual layout of the schematic.
At least this is the way I see it. I don’t yet see a valid argument against this.
Sorry, I guess I was not following the initial question completely. There is no reason to designate the layer in the schematic. It is meant to help translate the conceptual to the physical by showing conceptually the connections between parts. The layout in PCBnew guides you in physically making those conceptual connections a reality, and that is when and where you choose how your tracks are run.
There is no way to choose a PCB layer, front or other, for a net in eeschema (or any other schematic capture tool I’m aware of). Note that Eeschema does not have a concept of tracks, it has a concept of nets.
The schematic is an abstract representation of the circuit. It does not directly map to how the circuit is physically realized. You can design an infinite number of PCBs for a single schematic, each with components and tracks placed differently.
Layout is when you make choices such as which layers tracks are on, which side of the board components are on, where components are placed, etc.
It doesn’t make sense to plan which side of the board a trace will be on during schematic capture; that choice depends on many other factors which are not obvious until you’re working on the layout. This is true even for 2-layer boards, but is increasingly true for boards with more layers (4- and 6-layer boards are quite common, and kicad supports up to 32 (?) copper layers).
Also, a given net may be on more than one layer – traces often span front & back, and/or inner layers.
As gkeeth already wrote, the schematic is an abstract presentation of how an electronic circuit works. The main purpose of a schematic is not even to make a netlist for the PCB, but it’s main goal is to present an electronic circuit in an easy to understand way to the designer (and his friends, co-workers, repair-people, etc). To make schematics easier to understand it makes a lot of sense to have a signal flow from left to right over the schematic, and voltages from the top to the bottom.
The PCB is made with a whole lot of other constraints in mind. The PCB has to fit in some cabinet. Connectors have to be accessible. some connectors (such as edge connectors that fit into a backplane) are fixed in their position.
It is just not possible to predict where copper tracks are going to end up at the time the schematic is designed.
I was wondering why you asked this question in the first place. Maybe you’ve used a “tool” (if that’s a proper word for that contraption) like Fritzing, where the “schematic” is a presentation of a breadboard with wires. Fritzing is not a tool for designing electronic circuits. The main purpose of Fritzing (if it has any) is to make pretty pictures to be printed in magazines.
Imagine 3 points at schematic 1,2,3 from left to right and connected with each other 1-2-3.
While designing PCB you got it connected 1-3 at top and 3-2 at bottom. Now what colors you will assign to wires 1-2 and 2-3 at schematic?
There is no sense to draw wire from 1 to 3 and then back to 2 at schematic as it makes schematic more difficult to understand.
And suppose you have planty such nets at schematic and 8 or more layer PCB.
Schematics have never had a direct connection to the PCB layout. Often analog designers will create schematics that “flow” along some desired signal path.
Any PCB requirement can be noted in the schematic either in notes or the use of multiple ground designators etc.
High current traces any design requirement specifics should be on the schematic or perhaps a design document. I personally like to put as much about the design on the schematic as possible.
I realize the above apply more to production designs than hobby designs but some things are still good to document, especially if some time in the future you want to build another device using your schematic.
I agree, important design considerations that are critical to the functioning of the circuit should be noted in the schematic, or accompanying documentation, or both.
High current traces, transmission lines, length requirements, shielding, guarding, special grounding, possibly mechanical considerations, etc.
In another thread you say you make boards with hundreds of components. I wonder how do you foresee the nets that will go on the back or top layer.
I don’t aim to attack you, I’m just curious.
On a complex board a track may change from top side to bottom side many times, how would this be shown on a schematic?
Also on a mixed technology board I never really know if through hole component part tracks are going to start on the top or bottom until starting to lay down tracks.
If you were to deviate from the layers defined in the schematic and found you had to change this when laying out the board how would the schematic colours be updated.
I don’t believe there is a program that has this feature and I can see any that has being very confusing and messy to use,
KiCad-nightly V5.99 has a new feature in which the width of wires and their color can be coupled with a netclass. It’s in: Schematic Editor / File / Schematic Setup / Project / Net Classes In there you see the same net classes as you have defined on the PCB in: PCB Editor / File / Board Setup / Design Rules / Net Classes, but with the difference that you only set wire thickness and color instead of track width and Clearance.
So if you have set a bit thicker or darker line in the schematic for the “GND” net, then as soon as you attach a “GND” label to a wire, it’s thickness and color change. Nice new feature!
Once you stop thinking in terms of “front” and “back” sides but rather in terms of “layers” it will become more clear just how impractical this idea is. Besides, on anything but the simplest two layer board it is almost impossible to know in advance on which side of the board a trace should be. Using your approach, routing a trace on the opposite side would require going back and editing the schematic. More complex boards require four or more layers, sometimes a board that was intended to be a four layer board needs to be routed as a six or eight layer board. Imagine the work that such a change would require to change the schematic. As has been pointed out by others, the schematic is an abstraction of the PCB, it is not practical, perhaps not even possible, for a schematic to include every detail that needs to be considered when laying out a board. It’s not always known, while designing the schematic, how many layers a board will need as there are often other constraints that determine the number of layers required.
As far as I know, KiCad still has the limitation that “components” can only be placed on the top or bottom layers, but even knowing on which layer a component should be placed is not always obvious while designing the schematic.
And it’s a real limitation. Some people are hacking into the PCB file to place net-ties on internal layers. Pads for capacitive sensors could be buried, and there are also designs of combined flex / ridgid PCB’s where not even all layers exist over the full surface of the PCB.
Well,
When I am laying out a schematic right now everything (every line connecting components) is green.
I have not considered 3,4,5 or greater boards. I was only thinking of 2 sided boards and no internal layers… Anyway, when I’m laying these out it gets visually confusing remembering which ones are going to be on the back or front.
When I’m laying out boards, I manually route them. If I know ahead of time I want certain tracks on the front side, I could make them red to stand out from the green front side ones.
It could be I’m not thinking this through thoroughly. I was just laying out a schematic today and wanted to place a via in the schematic, then I realized there was no “Via” in Eschema. I could use a Mounting hole instead. I just finished a board that had a large number of mounting holes.
I dunno. After some more thought maybe the light bulb will come on as to why it’s not a good idea.
Thanks for all the replies. I have no doubt you are right and I’m not.
So I ask, what different would you do if what you ask for was doable. Would you change how you design the PCB? would you redo you PCB component layout as a function of the schematic wire vias?
Perhaps you find the existence of VIA and layer information helps you understand the worth of the design…
