I’m just getting started with KiCad and CAD in general. So I have a printed (.pdf) schematic that I want to copy/enter into KiCad’s Schematics editor so I can start in on a new board.
Bear with me (please!) my understanding right now is at this level, Footprint goes in PCB, Symbol goes in Schematic editor I found a footprint in KiCad for an LQFP-48 (which is perfect) but can’t seem to find a Symbol for the same.
Can they be converted or something? How can I get the equivalent footprint in a Symbol?
There are no generic symbols for these complex units. The generic symbols are provided for simple elements like: resistor , capacitor, diode, etc. So, you need to draw it yourself. But you have to know that this is the bad approach.
It’s better to take a look at the source schematic once more, find the real type of that unit (probably microcontroller) and search for it or draw but not as a “black box”.
Hi
No worry, I am newbe too:)
You want to make some circuit. First, you draw it in schematic. You don’t worry too much about footprints. In fact, you can use many different footprints to create some versions or flavours of your circuit.
For example, what I do quite often, when my schematic is ready, I assign thru-hole components and make a board with them. The I send it to produce a pcb in smart-prototyping.com and I solder myself. Then, when the circuit works I redesign it using SMD components to save cost and space.
So, schematics goes first. Footprint goes later.
Ok.
You found some fancy chip with huge amount of legs. You cannot find it in schematics library. You can very easily design this chip, the only thing you have to take care of is exact numbering - PIN number must be the same as LEG or pad number. It is very simple, to see how, watch this video: http://youtu.be/ys_VjSTRjQI
I recommend this course, it shows a lot about Kicad.
This schematic you got there… does it have a symbol for the 48-pin device? What is the identification of the 48-pin device? What’s it’s ‘name’?
For workflow: Unless you know what you’re doing (you apparently do not at the moment) you always start with the schematic (all devices are in there and connected with all wires needed to make it work) After that is done, you select the housings for the devices (if there are choices) and then you create the layout by arranging footprints and putting tracks down. You never start with the layout, unless you know what you’re doing (reverse engineering, etc. pp).
I got it (!!!) After some work I finally made my first .lib file, and I have to say, it looks pretty darn good It’s a LQFP48 aka SOT313-2.
I was debating about just going straight to PCB design (skip the schematics) as this is the way I am used to working but…my thinking was that if I were going to make the changeover to KiCAD then I would also try and do this in an ‘industry-standard’ fashion with a proper schematic first.
The weird thing is, KiCAD does have a LQFP-48 footprint, but it seems, no schema (.lib) file for it. At least, not one that I could find. Oh well, at least I don’t have to make that and they are usually much harder as they have to be perfect.
Interesting…apparently you can take a screenshot of a component (like from a .PDF or what have you) and then save it as a .bmp and then import it into KiCAD’s library…
I just tried it real quick, it didn’t look too good, has anyone done that/had success with creating new components that way?
KiCAD’s schematic libraries have all kinds of devices with 48 pins in there, but are labeled/ID’d by the device’s names, not by the generic housing name that all manufacturers use if they need a 48 pin xQFP housing…
AGAIN, what does the pdf schematic you got there tell you about the 48 pin IC? What’s it’s name?
For example, here is the pdf for a 48 pin TQFP (=LQFP, just a tad higher housing) for an Atmel SAM D20 (page 13).
And you know what, it will be in the EEschema atmel library under ATSAM20G14… let’s see…
That has nothing to do with ‘industry standard’, this has to do with doing it in a way to reduce mistakes and get as much help from the computer as possible while doing 10 things at once - the A in CAD stands for Aided.
If you do the schematic first and proper, KiCAD will be able to get you:
a copy&paste list of devices you can use to order at DigiKey/Farnell/whathaveyou
a check for correct wiring of your devices (power inputs/outputs correct?, any wires left open? …)
a check of your layout (all tracks layed down so they resemble the logic of your schematic? distances between tracks correct? …)
a set of gerber files that will have the devices identifier on them and even on the fabricated board for troubleshooting/assembly/getting it to work the first time
and way more…
Do yourself a favor and read the 101 tutorial on the KiCAD website.
And then sit down on Chris’s videos… he’s got a beginner series that runs you through 3-4 videos from schematic creation to gerber file output. You need that. It will cost you 4-5 hours of your time now, but will safe you 5-10 days troubleshooting what you do wrong within the next month.
PS: The knowledgeable & helpful people here will tolerate wild-bill-style for the first 2-3 questions/approaches to do things with KiCAD, my limit is reached already as I had to post the same question 2 times. Good luck.
I do The pinout’s in your first pic look perfect but the second pic looks very different. No matter though, I managed to make one up pretty easily once I got the hang of it. The specific MCU is a NXP/Freescale MC9S12C64CFAE
I agree - I’ll set down and spend some time going over the basics with the videos. I appreciate your directing me to where I need to be to get a better foundation with KiCAD. The important thing right now is that I made some real progress and that makes it much easier to want to spend time learning KiCAD
The pinout is the manufacturers way telling the customer/engineer which pin on the housing has got which function bound to it.
The schematic symbol can copy that, yes … BUT, here is the catch:
A schematic has two main functions:
create a symbolic diagram of the function of the circuit
make it easy for anyone who reads the schematic to UNDERSTAND what is going on
A schematic is not there to replicate the physical appearance of the layout or any devices that are needed to create the function of the circuit, most of the times it is diametrical to the above aims.
For example, most ICs have got Vcc and GND distributed AROUND the periphery of the housing.
In a schematic people usually want to supply Vcc and GND from top/bottom in a simple and clean manner.
That’s why the symbol for the AT SAM up there has got the pins redistributed, to make the schematic easier to digest for you or anyone else reading it.
Then there are functions inside the IC that are grouped, but that is not necessarily mirrored in the pins location on the housing. For example, the ports B10 and B11 are sitting between ports A11 and A12. If one is searching for them it would make more sense to order them into the (incomplete) other port B pins that are routed out of the chip.
Also, some pins are special… like the crystal pins and people would like to get those + the needed components in the schematic out of their way and position them to the left/right bottom of the symbol.
Also, there are ICs or devices out there that contain 2 or more copies of the same function (device) in one housing, like a BC807DS… that one has got 2 PNP transitors in a SOT457 housing.
There is 2 ways to deal with this:
Draw a symbol that represents the physical appearance of the device it’s using. This naturally means if you want to use both transistors in your circuitry at different logical places, that you need to draw wires all over the place and your understanding of the schematic will be hampered (imagine this for 4 different devices).
Or create a symbol that splits up the 2 sub devices into 2 symbols that you can place ANYWHERE on your schematic, so it helps to read the logic of the schematic.
my co-worker prefers a modification of version 1) which makes it easy for him to use them in a schematic - he’s a 60+ year old power electronics engineer who grew up when the first transistors were developed and usually doesn’t use the 2nd transistor at the other end of the circuitry but right there. He even draws up a layout on 5x5 grid paper before he hands me the schematic over to get it into KiCAD for layouting - really old school, but I like it and he’s efficient
note the ‘wrong’ order of the pin numbers to get the transistors roated/mirrored for better understanding:
Joan, that’s one heck of a well-thought out reply - thank you very much. Your point about the schematic not being designed to replicate the physical layout is well-taken and it’s something I had not consciously thought of. I do understand (from automotive experience) the importance of an easy to understand wiring diagram. I’ve seen all sorts from excellent to ones you have to take 30 minutes to wrap your head around before the lights come on. I will roll that into this schematic and make it a great reference.
I’m already on part 3 of the videos and have already picked up a few things. My learning method is a little odd, I like to force my way into a program (to get familiar with it) and then back-fill with proper instruction. So those videos are really helping. It’s a bit of an odd way of doing things but unless I have some hands-on experience I just don’t have any reference points and my eyes glaze over.
But I am already seeing how powerful KiCAD can be - and this is just the beginning. I’ve already got a massive amount done on the first page of the schematics but I think I’ll reign myself in a bit based on your suggestions of spending a few hours now then paying for foundational issues later…
I found a footprint in KiCad for an LQFP-48 (which is perfect) but can’t seem to find a Symbol for the same.
After some work I finally made my first .lib file, and I have to say, it looks pretty darn good 
