Author Topic: Difference in Schematic Layout and Footprint with DipTrace  (Read 6170 times)

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Offline TripleFaultTopic starter

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Difference in Schematic Layout and Footprint with DipTrace
« on: April 10, 2012, 03:39:45 pm »
Hi guys!
This is my first post here.

Could anybody tell me, Dave or somebody else, why Diptrace seems to make the Schematic representation of a component different than the footprint of the component.
For example: I was creating a Schematic with a dsPIC30F4011 and they seem to group all the pins by functionality instead of numerically.
This makes the schematic look like a dogs breakfast when you try to connect to 2 consecutive numbered pins, and instead you have to run the wires to 2 different sides of the chip.

Is it necessary to redraw my own Schematics and/or Footprints for each component I use and is this how they designed the program?

Any help would be most appreciated!

Cheers  ;)
Go forth and Amplify
 

Offline kaz911

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Re: Difference in Schematic Layout and Footprint with DipTrace
« Reply #1 on: April 11, 2012, 05:18:33 am »
Schematic representation has as many "variants" as opinions. Each designer does it different - each CAD vendor does it differently.

Some like all the fx ADC's grouped together - some like it to look like the chip pinout. I think Dave talked about it at some point - might have been on the AmpHour show?

I like grouping .. I like Vcc on top - and ground on bottom on the schematic. PIC pins are not usually that way :-)

But components are easy to edit in DT.. - So go ahead and make your own :-)

/Kaz
 

Offline graynomad

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Re: Difference in Schematic Layout and Footprint with DipTrace
« Reply #2 on: April 11, 2012, 06:02:42 am »
Quote
Schematic representation of a component different than the footprint of the component.
That's normal and I would argue the preferred way.

Beginners like to have the schematic representation of a chip look like the real thing but that normally is what makes things look like a dog's breakfast.

In general the pins should be moved around to make the schematic as readable as possible, VCC on the top, GND on the bottom, inputs on the left (or right), outputs on the right (or left) etc etc. as appropriate for the circuit.

I've not used Diptrace but I would think it's easy to modify the components to suit your preferences. Certainly in Altium this is easy and I have 100s of components and footprints, all hand drawn and often with several variations for each chip.

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Rob
« Last Edit: April 11, 2012, 06:04:44 am by graynomad »
Graynomad, AKA Rob Gray www.robgray.com
 

Offline sacherjj

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Re: Difference in Schematic Layout and Footprint with DipTrace
« Reply #3 on: April 11, 2012, 04:30:04 pm »
A good simple example of this is a quad op-amp.  It would make things much more complicated in the schematic to have a single schematic element, vs 4 op amps.  However, it would help you pick the best op amps to choose to make layout easier.
 

Offline harnon

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Re: Difference in Schematic Layout and Footprint with DipTrace
« Reply #4 on: April 11, 2012, 05:14:08 pm »
Hi TripleFault, welcome aboard.

This will be the same with any EE CAD program as the schematic layout depends on the component library you are using.  As noted above, its generally meant to make the schematic more readable.  If the "default" layout you are using doesn't suit your schematic its normally pretty straightforward to edit the footprint or schematic layout. 

There are plenty of tutorials around (I've linked some in the Diptrace forum) that describe how to edit a part.  Good Luck!
 

Offline TripleFaultTopic starter

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Re: Difference in Schematic Layout and Footprint with DipTrace
« Reply #5 on: April 12, 2012, 06:43:57 pm »
Thanks guys for all your help.

I will check out all those tutorials on creating Components.

I always have that niggling feeling in the back of my mind, that when I make a Schematic that because the schematic doesn't match the actual footprint then when it comes to manufacture time, the traces will all be wrong, and I will screw the pooch.  :P

Thanks again all you guys for your great help.  :)
Go forth and Amplify
 

Offline graynomad

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Re: Difference in Schematic Layout and Footprint with DipTrace
« Reply #6 on: April 12, 2012, 09:52:08 pm »
Quote
because the schematic doesn't match the actual footprint then when it comes to manufacture time, the traces will all be wrong
The CAD package will tell you that when you run the DRC (Design Rule Check), also there will be "air wires" to show you what traces to run so it's almost impossible to get it wrong.

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Rob
Graynomad, AKA Rob Gray www.robgray.com
 

Offline Mechatrommer

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Re: Difference in Schematic Layout and Footprint with DipTrace
« Reply #7 on: April 12, 2012, 11:55:54 pm »
maybe he meant if schematics doesnt match footprint, laying pcb job will be a little bit harder, too much or non optimum criss crossing traces.
edit: ps: an ugly spaghetty dog's fart breakfast schematics might just turned into beautifully crafted pcb. or vice versa. YMMV.
« Last Edit: April 13, 2012, 01:10:10 am by Mechatrommer »
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Offline graynomad

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Re: Difference in Schematic Layout and Footprint with DipTrace
« Reply #8 on: April 13, 2012, 12:44:27 am »
Yes you have to be very careful when making a new component, any screw ups there will propagate right through the design and the aforementioned CAD features will not help.

When I design a new component I actually do do it as per the physical layout of the chip, this allows me to visually compare the drawing with the data sheet. I keep this as the "generic" version of the component.

Then I duplicated the component and rearrange the pins according to logical groups etc. I then sometimes (over time) make a third, fourth etc versions that are appropriate for various schematics.

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Rob
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