[John Larkin]

On Fri, 07 Aug 2009 18:13:37 -0700, John Larkin


On Fri, 07 Aug 2009 15:52:56 -0700, John Larkin

John Larkin wrote:
John Larkin wrote:
krw wrote:
krw wrote:
[...]


b. I often have situations where, say, an opamp or comparator switches
the supply of another. This can become next to impossible to understand
by other engineers, especially younger ones.
In our case there is always a PIC in the middle. I don't know how to
show the power control code on the schematic. ;-)

So far I never had a PIC in the middle ...
When I first wrote "PIC" I was kidding; the answer to every question
is "PIC". The fact is that we do have a PIC in the middle, on top of
a DSP.

Dead-bugged on top of it with liquid nails glue ...?


Cadsoft Eagle allows a very nice flexibility here: You can call up the
power pins via the "invoke" command. The CAD symbol is usually drawn so
it slides over the A-device (or another if you wish) and fits as if it
was part of the symbol. You can also place it near the group in the
schematic, or down at the bottom for simpler architectures. That's how
it ought to be, gives the designer all the freedom.
That sounds like it solves all the problems.
Sure does. That CAD program is very close to perfect. With one major
deficiency and that makes it IMHO useless for any larger design: No
hierarchical sheet structure :-(
Monday we had the design review for the widget I'm working on. My
boss really liked the hierarchical (turtles all the way down)
organization. I'm not so sure about the other hardware engineer
though. ;-) I'm still not to where I can easily determine where to
add a hierarchical block or another sheet though. More than one block
for a component (FPGA) just seems wrong.
Yes, I would never, ever, split a component across several sheets or
even just blocks. That makes a royal mess out of a schematic.
Thing I'm doing now, the PLX PCIe chip is three "gate sections" (pcie,
backside bus, power) across two sheets. The FPGA is 8 sections (one
for each bank, 450 pins or so total) across three sheets. This one
board is a 22 sheet schematic... B size sheets.

You never split gate or opamp sections between sheets?

Nope. Only exception is simple logic gates but even then you'd almost
have to twist my arm.


I never do hierarchical schematics. Everything's flat.

Then we have almost opposite CAD habits. But at least we have similar
beer taste, only the good stuff

What happens to reference designators in a hierarchical schematic?


Typically it numbers right on through if you hit auto-number. But it
really never mattered to me in my Orcad days because most clients wanted
a back annotation anyhow, so that the top left of the physical PCB
started with R1, C1 and the bottom right would end with R542, C367. Then
that got fed into the schematic, I updated my module spec with the new
refdeses, done.


I don't understand that. If the schematic has a main controller part
and, say, 16 channels, and you draw one instance of the channel,
abstract that into a block, and draw 16 of the blocks - which is what
a hierarchical schematic does - how does each instance have its own
reference designators, sequantial across all the modules?

Capture renumbers - flat - them for each instance.

How do you print the schematic for field service? Where the hell is
R325 in one of the instances when only one sub-module schematic
exists?

They all exist. You print all the sheets. Ugly as hell, but it's
really not much worse than flat schematics. Much better if you use a
viewer.

Then the hierarchical thing doesn't seem to be much different than
just doing it flat.

If the most important thing in life is the cost of printer paper, you
may have a point. OTOH, hierarchies are easier to understand,
simulate, and reuse; sorta the point of schematics.

Somehow I don't have trouble understanding 16 sheets that are labeled
CHANNEL 0 through CHANNEL 15, each with all the reference designators
and connector pins in plain view.

And nothing would change if those sixteen sheets were instances of a
hierarchical block, except you'd have another higher level block that
would show their interconnect. IOW, more information.

IOW I'd have to chase all over various sheets to see which connector
pin is ultimately connected to U12 pin 5.

Progress?

John

 

[John Larkin]

On Sat, 08 Aug 2009 02:05:30 -0500,

Somehow I don't have trouble understanding 16 sheets that are labeled
CHANNEL 0 through CHANNEL 15, each with all the reference designators
and connector pins in plain view.

Hierarchical software has to be smart enough to view/edit/print
both the skeleton view and the per-instance views.

You need the per-instance info for debugging and probably at
the times.

The advantage of a hierarchical system is that if you fix
a bug, you only have to make the edit once rather than N times.[/QUOTE]

If I create a bug 16 times, I deserve to have to fix it 16 times.

I'm paranoid about that sort of problem. Sure, with a bit of
planning you can put check-them-all on your checklist. I'd
rather spend the time working on something else.

I'd rather check my work very carefully so I minimize board spins.

John

 

[John Larkin]

On Fri, 07 Aug 2009 18:13:37 -0700, John Larkin


On Fri, 07 Aug 2009 15:52:56 -0700, John Larkin

[...]

How do you print the schematic for field service? Where the hell is
R325 in one of the instances when only one sub-module schematic
exists?
They all exist. You print all the sheets. Ugly as hell, but it's
really not much worse than flat schematics. Much better if you use a
viewer.
Then the hierarchical thing doesn't seem to be much different than
just doing it flat.
If the most important thing in life is the cost of printer paper, you
may have a point. OTOH, hierarchies are easier to understand,
simulate, and reuse; sorta the point of schematics.

Somehow I don't have trouble understanding 16 sheets that are labeled
CHANNEL 0 through CHANNEL 15, each with all the reference designators
and connector pins in plain view.

That will drastically change when it's a bigger board that has lots of
other things besides those 16 channels.

I don't see that. What's wrong with CHANNEL 0 through CHANNEL 99?
Sooner or later you're going to have to know where everything is.

John

 

[Rich Grise]

IOW I'd have to chase all over various sheets to see which connector
pin is ultimately connected to U12 pin 5.

Progress?

If the hierarchical sheets were done "right", the end user/tech wouldn't
have to search for anything - all you have to do is put "see sheet n" on
the source sheet.

I never had any trouble at all reading military prints, and in the
military, EVERYTHING is hierarchcial.

Cheers!
Rich

 

[Joerg]

On Fri, 07 Aug 2009 18:13:37 -0700, John Larkin


]

How do you print the schematic for field service? Where the hell is
R325 in one of the instances when only one sub-module schematic
exists?
They all exist. You print all the sheets. Ugly as hell, but it's
really not much worse than flat schematics. Much better if you use a
viewer.
Then the hierarchical thing doesn't seem to be much different than
just doing it flat.
If the most important thing in life is the cost of printer paper, you
may have a point. OTOH, hierarchies are easier to understand,
simulate, and reuse; sorta the point of schematics.
Somehow I don't have trouble understanding 16 sheets that are labeled
CHANNEL 0 through CHANNEL 15, each with all the reference designators
and connector pins in plain view.

That will drastically change when it's a bigger board that has lots of
other things besides those 16 channels.

I don't see that. What's wrong with CHANNEL 0 through CHANNEL 99?
Sooner or later you're going to have to know where everything is.

One board I designed had xx channels, then a digital section which
contained a VME-style interface, a few serial links, a processor, a
sensor interface page. Then an analog signal processing with several
pages. Sure, I knew where everything was because I designed it. But the
other guys appreciated that it was all nicely displayed in a hierarchy.
A click on the digital block on the top sheet descended onto a sheet on
layer 2 which had all those blocks described above. Click on "Serial
Interface" and you can see the schematic of that. Makes life a lot
easier for others.

 

[Joerg]

If the hierarchical sheets were done "right", the end user/tech wouldn't
have to search for anything - all you have to do is put "see sheet n" on
the source sheet.

You don't even need that. Usually the connectors are on the top sheet or
dedicated sheets. A well drawn set of schematics makes it very clear
what goes where. Then there is always the search function.

I never had any trouble at all reading military prints, and in the
military, EVERYTHING is hierarchcial.

Oh yeah. Not honoring that rule results in a face about 10" from yours
and hollering, plus 20 extra push-ups or an extra round on the tracks in
100F weather with the mask and full gear on.

 

[Joerg]

This is how Pulsonix does it as well, although I have used CAD packages that
would generate U1.1, U1.2, U1.3, etc. for each instance of a hierarchical
block, which does make things a little nicer, at least if you don't mind your
silkscreen also saying U1.!, U1.2, etc. The problem with this is that you're
then usually forced to use that package's layout tool as well, since AFAIK
there isn't a widely used PCB netlist format that really supports hierarchy.
I have heard of a few enterprising individuals who wrote netlist translation
tools so that U1.1 would get turned into, e.g., U101, U1.2 becomes U102, etc.,
though -- and I've known people who did something similar manually for small
designs.

Usually I can't do that because the layouters all use other systems than
I do. When you must backannotate it's all over anyhow, it'll start with
U1 in the upper left of the board and so on.

I am all for printing everything out at some point, but these days your tech
is going to be sitting in front of a computer anyway, so sometimes it's faster
if they just pull up the schematic electronically and search for, e.g., R265
and some techs prefer this -- particularly field service guys -- since they're
not having to carry all those dead trees around.

Last year I taught a tech who was populating a prototype the use of a
Gerber viewer. That sure made life a lot easier for her.

 

[Joerg]

Fine, but you didn't create a bug 16 times -- you created it once and copied
and pasted it 15 times.

I court that would be one count of inattentiveness and 15 counts of
negligence. And John agreed that he'd be willing to bring punishment
onto himself should that ever happen ;-)

 

[Joerg]

Joel Koltner wrote:

[...]

Hierarchy also tends to make for somewhat cleaner-looking schematics, although
this is sometimes a two-edged sword: It potentially makes the schematic easier
to understand for those looking to analyze the circuit, but it can also make
life harder for the tech who has to repair your widget if everytime you used,
say, a MMIC amplifier you just dropped in a hierarchical block and it's the
block that contains all the biasing and coupling components.

I'd be curious to hear from, e.g., Jim as to whether or not he uses
hierachy -- I can't imagine the guys doing multi-million-gate digital ICs do
not, but for stuff like op-amps or PLLs where you're probably still talking
just hundreds or thousands of transistors, a flat design probably still works
OK. Jim?

I don't think chip design is possible without a hierarchy. Ok, maybe
except for stuff of the complexity level of a uA709.

 

[John Larkin]

I court that would be one count of inattentiveness and 15 counts of
negligence. And John agreed that he'd be willing to bring punishment
onto himself should that ever happen ;-)

We use red kluge wires, like the Scarlet Letter, to make the shame
more public.

John

 

[John Larkin]

John Larkin wrote:

On Fri, 07 Aug 2009 18:13:37 -0700, John Larkin


On Fri, 07 Aug 2009 15:52:56 -0700, John Larkin

[...]

How do you print the schematic for field service? Where the hell is
R325 in one of the instances when only one sub-module schematic
exists?
They all exist. You print all the sheets. Ugly as hell, but it's
really not much worse than flat schematics. Much better if you use a
viewer.
Then the hierarchical thing doesn't seem to be much different than
just doing it flat.
If the most important thing in life is the cost of printer paper, you
may have a point. OTOH, hierarchies are easier to understand,
simulate, and reuse; sorta the point of schematics.
Somehow I don't have trouble understanding 16 sheets that are labeled
CHANNEL 0 through CHANNEL 15, each with all the reference designators
and connector pins in plain view.

That will drastically change when it's a bigger board that has lots of
other things besides those 16 channels.

I don't see that. What's wrong with CHANNEL 0 through CHANNEL 99?
Sooner or later you're going to have to know where everything is.

One board I designed had xx channels, then a digital section which
contained a VME-style interface, a few serial links, a processor, a
sensor interface page. Then an analog signal processing with several
pages. Sure, I knew where everything was because I designed it. But the
other guys appreciated that it was all nicely displayed in a hierarchy.
A click on the digital block on the top sheet descended onto a sheet on
layer 2 which had all those blocks described above. Click on "Serial
Interface" and you can see the schematic of that. Makes life a lot
easier for others.

As long as those others have the same CAD software running on their
laptops, and took the course to know how to use it.

John

 

[FatBytestard]

So, have you been on the design team?

Did I state any such thing, dumbfuck?

First it was written for DOS, then ported to Windows.

So, you are saying that Linux was an afterthought?

That's odd. I thought it was the initial development platform.

 

[John Larkin]

One major benefit is that when you want to change, e.g., one resistor value,
you change it *once* rather than, e.g. *16 times* (if you had 16 channels or
whatever) -- giving you that many fewer chances to mistype the number.
(Granted, if you do get it wrong, all 16 are then immediately wrong, but
still... ) Similarly, if you need to add or delete a few components,
doing it once is a lot faster. And if adding components requires shoving
components out of the page/enlarging the page, there's also a lot of time
saved and you don't inadvertently forget to hook something back up from one of
the channels that had something disconnected when you temporary shoved it out
of the way as you were modifying the previous channel.

Hierarchy also tends to make for somewhat cleaner-looking schematics, although
this is sometimes a two-edged sword: It potentially makes the schematic easier
to understand for those looking to analyze the circuit, but it can also make
life harder for the tech who has to repair your widget if everytime you used,
say, a MMIC amplifier you just dropped in a hierarchical block and it's the
block that contains all the biasing and coupling components.

I'd be curious to hear from, e.g., Jim as to whether or not he uses
hierachy -- I can't imagine the guys doing multi-million-gate digital ICs do
not, but for stuff like op-amps or PLLs where you're probably still talking
just hundreds or thousands of transistors, a flat design probably still works
OK. Jim?

---Joel

And you don't replace transistors and resistors inside ICs like you do
on PC boards.

John

 

[FatBytestard]

I can add one that crashes more, on all computers here: Adobe Acrobat
Reader. But I guess everyone knows that.

[...]

Mine is all updated, and has NEVER crashed.

When you attempt to print a large pdf, you should locally spool the
print job first. If you do not know how to set your printer/computer up
to spool properly, you deserve to have crashes until someone guides you
through the process.

Operator error... again.

Adobe is bloatware spyware crap. Even if it didn't crash, it's
amazingly slow. Get Foxit Reader and CutePDF and see the difference.

John

No thanks.

You may also find that "Reader" has changed since the customer
complaints of the last few iterations. That will not happen, however, if
you are too pussified to look into it.

 

[FatBytestard]

Always Wrong!

Yes, John, you usually are just that. In this instance absolutely so.

When you print ANY pdf, the print job is a fully rendered bit map type
print job. No fonts are passed, no fonts are referenced. The entire print
job is a bit mapped graphic, and when you view it, it is as well.

That is why it supports zooming up to 4500%. Not that an idiot like
you could ever figure out that continued zooming on non-bit mapped
renderings results in jpeg jaggies. That will NEVER happen on a zoom of
a PDF. Yet one more reason why they are better for so many things
document related.

 

[FatBytestard]

Adobe hangs up, just viewing files, on every machine I own: Dell, HP,
Sony Vaio. Sometines it's so slow it might as well be hung up.

Never hangs on ANY of my machines, and I have e-books of nearly any
electrical/physics book that is worth a shit you can name.

Funny how the assholes have problems, but those of us that you call
assholes do not. Maybe a greater power is at work. Manson's voodoo
dolls! "This is you..." -C, Manson

Bwuahahahahahahaha!

 

[life imitates life]

We use red kluge wires, like the Scarlet Letter, to make the shame
more public.

John

Red is less visible than blue on the circuit card assembly. Neither is
glaringly obvious to anyone examining a board unless he is specifically
looking for such things.

Also, not all are kludges. Some get approvals, and all future boards
have to be built that way, or it simply does not qualify to be called
that particular assembly.

Some changes cost several tens of thousands of dollars to implement.
Some even more. Do you know how much a certification for Tempest level
shielding costs?

 

[John Larkin]

I can add one that crashes more, on all computers here: Adobe Acrobat
Reader. But I guess everyone knows that.

[...]

--
Regards, Joerg

Mine is all updated, and has NEVER crashed.

When you attempt to print a large pdf, you should locally spool the
print job first. If you do not know how to set your printer/computer up
to spool properly, you deserve to have crashes until someone guides you
through the process.

Operator error... again.

Adobe is bloatware spyware crap. Even if it didn't crash, it's
amazingly slow. Get Foxit Reader and CutePDF and see the difference.

John

No thanks.

You may also find that "Reader" has changed since the customer
complaints of the last few iterations. That will not happen, however, if
you are too pussified to look into it.

Even if they stop Reader from crashing, it's still pig-slow spyware.

And CutePDF generates PDF files so fast that, at first, you think it's
not working. It is.

I do use Adobe Reader, maybe a couple of times a year, when I have to
fill out a PDF form that Foxit doesn't like. But it's too big a dog
for everyday use.

John

 

[Joerg]

We use red kluge wires, like the Scarlet Letter, to make the shame
more public.

We had a more brutal method of shame at my first job: Every jumper
resulted in a scratch mark behind your name on a bulletin board in the
tech area. Plus 5c into the beer kitty. When $10 had accumulated another
crate of brewsky was purchased.

 

[Joerg]

John Larkin wrote:

On Fri, 07 Aug 2009 18:13:37 -0700, John Larkin


On Fri, 07 Aug 2009 15:52:56 -0700, John Larkin

[...]

How do you print the schematic for field service? Where the hell is
R325 in one of the instances when only one sub-module schematic
exists?
They all exist. You print all the sheets. Ugly as hell, but it's
really not much worse than flat schematics. Much better if you use a
viewer.
Then the hierarchical thing doesn't seem to be much different than
just doing it flat.
If the most important thing in life is the cost of printer paper, you
may have a point. OTOH, hierarchies are easier to understand,
simulate, and reuse; sorta the point of schematics.
Somehow I don't have trouble understanding 16 sheets that are labeled
CHANNEL 0 through CHANNEL 15, each with all the reference designators
and connector pins in plain view.

That will drastically change when it's a bigger board that has lots of
other things besides those 16 channels.
I don't see that. What's wrong with CHANNEL 0 through CHANNEL 99?
Sooner or later you're going to have to know where everything is.

One board I designed had xx channels, then a digital section which
contained a VME-style interface, a few serial links, a processor, a
sensor interface page. Then an analog signal processing with several
pages. Sure, I knew where everything was because I designed it. But the
other guys appreciated that it was all nicely displayed in a hierarchy.
A click on the digital block on the top sheet descended onto a sheet on
layer 2 which had all those blocks described above. Click on "Serial
Interface" and you can see the schematic of that. Makes life a lot
easier for others.

As long as those others have the same CAD software running on their
laptops, and took the course to know how to use it.

Well, we do live in the 21st century now ;-)

After steam locomotives and Edison electric light had been invented,
there were born: Free and simple to use viewer software, linked and
clickable PDF documents, HTML sheet structures, and so on.

You could probably also put this on a Kindle. But after reading a story
of pulling back reading material remotely I don't think I'd want to have
one.