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[geda-pcb/whiteaudio.git] / doc / gs / fb-blinker.texi

@node Blinker Board
@section Blinker Board

This next board will introduce some additional concepts in @code{pcb}
that will help you with more complex board.  It is assumed that you've
gone through the previous board, and those concepts will not be
re-explained.  This board will be another single-sided board, but with
additional components.  We will use a schematic to describe the
circuit, create some custom symbols and footprints, and learn to use
the autorouter.

We will begin by creating our custom symbols and footprints.  First,
we must create local symbols and footprint directories and teach the
tools to use them.  My preference is to create subdirectories in the
project directory called @code{symbols} and @code{footprints}:

@img{fb-blinker-1}

We then create some files to tell @code{gschem} and @code{gsch2pcb} to
look in these directories.  The first is called @code{gafrc} and
contains just this one line:

@example
@include gafrc
@end example

The second is called @code{gschemrc} and contains just this one line:

@example
@include gschemrc
@end example

The third is project-specific.  The @code{gsch2pcb} program can read
its commands from a project file, and we will use this to tell it
about the @code{footprints} directory.  The file is called
@code{fb-blinker.prj} and contains:

@example
@include fb-blinker.prj
@end example

This project file tells @code{gsch2pcb} where to get element
descriptions, which schematics to read (we only have one), and what
base name to use for the various output files.

We must create two custom symbols for this project.  The first is for
our power jack, and is a purely custom symbol.  Creating such symbols
is beyond the scope of this tutorial.  Please refer to the
@code{gschem} documentation for that.  The second symbol uses the
@code{djboxsym} utility which you can download from the web (see
@url{http://www.gedasymbols.org/user/dj_delorie/tools/djboxsym.html}).

The first symbol is called @code{symbols/powerjack.sym} and looks like
this:

@img{powerjack}

There's a copy of this symbol in the source distribution for this
documentation.  The second symbol is built from this @code{555.symdef}
file:

@example
@include 555.symdef
@end example

and looks like this:

@img{555}

Now, using those symbols, create your schematic, and name it
@file{fb-blinker-sch.sch}.  There's a copy of the schematic file in
the source distribution also.  It should look like this:

@center @image{fb-blinker-sch,367pt,284pt}

Using @code{gschem} and/or @code{gattrib}, set the @code{footprint}
and @code{value} attributes as follows:

@multitable @columnfractions 0.25 0.15 0.15 0.15
@item @tab @b{refdes} @tab @b{footprint} @tab @b{value}
@item @tab C1 @tab RCY100 @tab 1uF
@item @tab J1 @tab pj102.fp @tab PJ102
@item @tab LED1 @tab RCY100 @tab RED
@item @tab R1 @tab ACY400 @tab 100k
@item @tab R2 @tab ACY400 @tab 100k
@item @tab R3 @tab ACY400 @tab 3.3k
@item @tab U1 @tab DIP8 @tab LM555CN
@end multitable

Now we must create the custom footprint for the power jack.  While
there are various contributed tools that can be used for large
footprints (like BGAs), for small parts like this the easiest way is
to create the footprint in @code{pcb} itself.  This is done by
creating a ``board'' with vias and lines, then converting it to an
element and saving it.

Change to the footprints subdirectory and start @code{pcb}.  It
doesn't matter how big the working area is, or the layer stackup.
Looking at the specs for our power jack, we note that measurements are
given in tenths of a millimeter, so we'll use a metric grid.  To
start, set the grid to @b{1mm}, move the crosshairs to the center of
the board, and press @b{Ctrl-M} to set the mark.  This will be the
reference point for all our measurements.  By doing this with a large
grid value, we ensure that it will be easy to click on the same spot
later on if needed.

Now set the grid to @b{0.1mm}, which we'll use to place all our vias
and lines.  We're using vias to create pins, so we need to set the via
size and drill diameter.  Click on the @b{Route Style} button to bring
up the route styles dialog, and set @b{Via hole} to 1.6mm and @b{Via
size} to 3.6mm.  While we're here, set @b{Line width} to 0.15mm, we'll
need that when we draw the outline later.

Now, zoom in enough to see the grid points.  Place one via 3mm to the
left of the mark, one 3mm to the right, and one 4.7mm above.  Sequence
is important!  The pins will be numbered in the same order as the via
creation.  To place a via, select the @b{Via} tool, position the
crosshair, and press the left mouse button.

@center @image{fb-blinker-2} @image{fb-blinker-3}

Using the line tool, the same tool you used to draw copper traces in
the first board, we will draw an outline of the jack on the silk
layer.  Select the line tool, and make the silk layer active.  Draw as
much of a box as you can which extends 10.7mm to the right of the
mark, 3.7mm to the left, and 4.5mm above and below.  Be careful not to
draw on top of your pins, or your board will have ink on the pins.  It
should look something like this:

@img{fb-blinker-4}

Now, set the grid back to 1mm so we can easily click on the mark.
Select everything by using the @mnuu{Select,Select all visible objects}
menu button.  Position the crosshair on the mark and press @kbd{Ctrl-C}
to copy all the objects to the buffer.  Use the @mnuu{Buffer,Convert
buffer to element} menu button to convert the buffer to an element.
You can now click somewhere else on the board to paste a copy of your
new element for inspection.

The first thing to do is check the pin numbers.  Place the crosshair
on the mark and press the @kbd{D} key to turn on the pin numbers.
Check to make sure they're correct, then press @kbd{D} to turn them
back off again.

@img{fb-blinker-5}

Now, we're going to set the default position of the label.  Place the
crosshair on the mark and press the @kbd{N} key.  Change the element
name to @code{J?}.  By default it shows up at the element's mark.  Use
the selection tool and @kbd{S} key to position the label as shown
below.

@center @image{fb-blinker-6} @image{fb-blinker-7}

Using the selection tool, position the crosshair on the element's mark
and click on it to select it.  Press @kbd{Ctrl-C} to copy it to the
buffer, and use @mnuu{Buffer,Save buffer elements to file} to save your
new footprint to a file.  Save it as @code{pj102.fp} in the
footprints directory.  Note that the name of the file must match the
footprint attribute you used for the power jack in your schematics.

Congratulations!  You've created your first custom footprint.

Now that we have our schematics and custom footprint, we need to
figure out how to start the board layout.  The tool we will use is
@code{gsch2pcb}, which reads schematics and can create or update a
board to match.  Since @code{gsch2pcb} doesn't use the same defaults
as @code{pcb}, we will create the board in @code{pcb} and only use
@code{gsch2pcb} in update mode.

When creating a non-trivial board, it's a good idea to start with a
larger board than your final size.  For this project, the final size
will be 1.4 inches wide by 0.9 inches high.  However, we'll start with
2 by 2 inch board to give us some room to move things around.  Run
@code{pcb} and create your board, setting up the size, layers, and
styles just like in the last project.  Make sure you set a 100 mil
grid, since the parts we're using are all designed with 100 mil
spacing in mind.  Also, make sure @mnuu{Settings,Crosshair snaps to
pins and pads} is checked.  Save this empty board as
@code{fb-blinker.pcb} and exit.

Now we run @code{gsch2pcb}, passing it the name of the project file:

@example
$ gsch2pcb fb-blinker.prj 

---------------------------------
gEDA/gnetlist pcbpins Backend
This backend is EXPERIMENTAL
Use at your own risk!
---------------------------------

Using the m4 processor for pcb footprints

----------------------------------
Done processing.  Work performed:
1 file elements and 6 m4 elements added to fb-blinker.new.pcb.

Next steps:
1.  Run pcb on your file fb-blinker.pcb.
2.  From within PCB, select "File -> Load layout data to paste buffer"
    and select fb-blinker.new.pcb to load the new footprints into your existing layout.
3.  From within PCB, select "File -> Load netlist file" and select 
    fb-blinker.net to load the updated netlist.

4.  From within PCB, enter

           :ExecuteFile(fb-blinker.cmd)

    to update the pin names of all footprints.


@end example

What gsch2pcb does is remove elements from your board that don't exist
in the schematic, provide new elements that need to be added, generate
an updated netlist, and create a script that renames all the pins.
You don't need to use all these - for example, I rarely use the pin
renaming script - but we will this time, so you can learn how each
file is used.

We will do as the hints above tell us to do.  Run @code{pcb
fb-blinker.pcb} to bring up the empty board.  Load the new element
data, which automatically changes you to the buffer tool.  Click on
the board to place all those new parts.  They'll all be in the same
place, but we'll fix that later.  Load the new netlist, and run the
script.  After closing any dialogs that may have come up, your board
should look like this:

@img{fb-blinker-8}

The next step is to separate the elements so we can start laying out
our board.  Use the @mnuu{Select,Disperse all elements} menu option,
which spreads apart the elements.  Then, use the
@mnuu{Connect,Optimize rats nest} menu option (or the @kbd{O} key) to
draw all the rats on the board.  These will help you figure out an
optimum layout of your elements.  Your board should look something
like this (yours may vary depending on how the dispersal worked):

@img{fb-blinker-9}

If you position the crosshair over U1 and press the @kbd{D} key,
you'll see that the pins are now labelled with the same labels as in
the schematic.  You can use the @mnuu{View,Enable Pinout shows
number} menu checkbox to toggle between the symbolic labels and the
original pin numbers.

@img{fb-blinker-10}

Now, as before, we want to rearrange the elements to minimise and
simplify the connections.  This is where the rats come in handy.  As
you rearrange the elements, the rats follow, so you can see how
rotating and moving elements affect the layout.  As you move elements
around, press the @kbd{O} key to tell @code{pcb} to figure out the
best way of connecting everything in their new locations.

As you move the elements around, remember to pick up the power jack by
its mark, as the power jack's pins have metric spacing.  The other
elements should be picked up by their pins, since they have inch
spacing.  By picking up elements by their pins, you ensure that their
pins end up on the grid points when you put them down.

Rearrange your elements so that they look like this, somewhere near
the center of your board.  Note that the rats nest will tell you when
you have the resistors backwards, since they don't have ``polarity''
like the LED or IC have.

@img{fb-blinker-11}

As before, we want to move the refdes labels around so that they're
both visible and out of the way.  To make this easier, use the
@mnuu{Settings,Only Names} option to keep the tools from
accidentally selecting elements or rat lines.  Shut off the grid, and
use the selection and rotate tools, and the @kbd{S} size key, to make
the labels like this:

@img{fb-blinker-12}

Now use @mnuu{Settings,Lock Names} to keep from accidentally moving
our labels later.  We're still using our over-sized board.  Now is the
time to reduce it to the final size.  First, we have to move the
elements to the upper left corner of the board.  Set the grid back to
100 mil, @mnuu{Select,Select all visible objects}, grab one of the
pins, and move everything up to the corner, as close as you can get
without touching the edges:

@img{fb-blinker-13}

Click to de-select and change the board size to 1400 mils wide by 900
mils high.  Don't forget to save often!

Again, we're planning on hand-soldering this board, so select
everything and make all the pins 10 mils bigger than the default.

Rather than route all the traces by hand, for this board we will use
the autorouter.  There are a few key things you need to keep in mind
when using the autorouter.  First, the autorouter will use all
available layers, so we must disable the layers we don't want it to
route on.  To do this, click on the @b{component} button to disable
that layer:

@img{fb-blinker-14}

The autorouter also uses whatever the default style is, so select the
@b{Fat} style:

@img{fb-blinker-15}

The autorouter uses the rats nest to determine what connections will
be autorouted, so press @kbd{O} now to make sure all the rats are
present and reflect the latest position of the elements.  To do the
autorouting, simply select the @mnuu{Connects,Autoroute all rats}
menu option.

@img{fb-blinker-16}

In theory, you could consider your board ``done'' now, but to make it
look more professional, we will do two more steps.  Use the
@mnuuu{Connects,Optimize routed tracks,Auto-Optimize} menu option
twice (or until no further changes happen) to clean up the traces left
by the autorouter:

@img{fb-blinker-17}

And finally, select @mnuuu{Connects,Optimize routed tracks,Miter}
to miter the sharp corners:

@img{fb-blinker-18}

Your board is done.  As before, you can print your design or produce
Gerber files, according to how you're going to have your board made.