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'[EE] Plugging a 28-pin dip into a 40-pin socket'
2006\01\14@111914 by John Nall

picon face
This is a strange little problem, and I'm trying to figure out the best
way to do it.  I have a little prototype board with a 40-pin socket
soldered into it (originally there was an 18F452 plugged into it).  For
an project that I am doing, I want to plug a 28-pin dsPIC30F3013 into
that socket.  Obviously some pins will go unused, but that is OK.  One
way, which seems pretty awful, would be to just hard-wire a 28-pin
socket to the appropriate pins of  the 40-pin socket.  Seems like there
should be a more elegant way, though.  Ideally, I'd like to do it in a
manner which will allow me to go back to plugging the 18F452 in when I'm
done.  Any suggestions?

2006\01\14@113857 by olin piclist

face picon face
John Nall wrote:
> This is a strange little problem, and I'm trying to figure out the
> best way to do it.  I have a little prototype board with a 40-pin
> socket soldered into it (originally there was an 18F452 plugged into
> it).  For an project that I am doing, I want to plug a 28-pin
> dsPIC30F3013 into that socket.

This is going to be difficult.  The dsPICs have a different pinout in the
same packages as the 16 and 18 families.  For example, you couldn't plug a
30F3013 into a socket intended for a 16F876 or 18F2520.

The best answer is to make a PC board that is a converter.  Worst case is
probably a flying adapter with the bottom of a 28 pin socket connected with
wires to the top of a 40 pin machined socket.  You might eventually get
everything right and have it work once or twice until a wire falls off.
Making a converter on perf board is somewhere between these two extremes.


******************************************************************
Embed Inc, Littleton Massachusetts, (978) 742-9014.  #1 PIC
consultant in 2004 program year.  http://www.embedinc.com/products

2006\01\14@125911 by John Nall

picon face
Olin Lathrop wrote:
>
> > This is going to be difficult.  The dsPICs have a different pinout in the
> same packages as the 16 and 18 families.  For example, you couldn't plug a
> 30F3013 into a socket intended for a 16F876 or 18F2520.
>  
.
I don't see the difficulty, but since you usually know what you are
talking about I had best follow up to see if I am missing something.  I
do not propose to go pin 1 to pin 1, pin 2 to pin 2, right on down for
the first 28 pins.  Each pin of the 3013 would go to the appropriate
matching pin, which might or might not be the same physical number.  I
don't have the datasheet for the 3013 here in front of me, but just for
argument's sake let us say that Vdd on the 3013 consists of pins 8 and
13, whereas on the 452 Vdd consists of pins 11 and 32.  So pins 8 and 13
of the 28-pin socket would be wired to pins 11 and 32 of the 40-pin
socket.  There would be a lot of crossed wires, obviously, as well as
some unused pins on the 3013 which would not go to the 452 socket at all
(appropriate action would have to be taken for them, of course, so that
they're not left dangling).

There, with that explanation, do you still see a difficulty, other than
just physically how to get it done??

John


2006\01\14@142442 by olin piclist

face picon face
John Nall wrote:
> There would be a lot of crossed wires, obviously, as well as
> some unused pins on the 3013 which would not go to the 452 socket at
> all

Like which ones.  I think you can come with some 18F877 pin that is close
enough in purpose to all 30F3013 pins.

> There, with that explanation, do you still see a difficulty, other
> than just physically how to get it done??

It's the physical part I was referring to.  You can solder 20 wires from one
socket to another, but that is going to be an error prone process and the
result has 56 stress points for things to get undone.


******************************************************************
Embed Inc, Littleton Massachusetts, (978) 742-9014.  #1 PIC
consultant in 2004 program year.  http://www.embedinc.com/products

2006\01\14@150424 by John Nall

picon face
Olin Lathrop wrote:
> > Like which ones.  I think you can come with some 18F877 pin that is close
> enough in purpose to all 30F3013 pins.
>  
What does the 18F877 have to do with anything??  I think we are not
communicating here, Olin!  :-)  So far as "like which ones," the 3013
has 2 UART's and the 452 only has one, for example.  I think that
probably I did not describe the problem clearly enough.  I have a board,
which has instruments such as an RPG, an LCD, a pushbutton, some LED's,
a temperature sensor, etc., already in place.  I called it a prototype
board, but probably that was an ill-advised term.  The board has an
18F452 (in a socket) which is connected to the different instruments.  
Using exactly the same physical board, I want to substitute a 3013 for
the 452, converting the software which uses these things from 452
assembly language to 3013 assembly language.  Now you, as a practical
person who does practical things, might not see the value of this, I
will freely admit that.  But I want to do it for the same reason that
people purport to climb Mt. Everest (or so they say, anyway).
> > It's the physical part I was referring to.  You can solder 20 wires from one
> socket to another, but that is going to be an error prone process and the
> result has 56 stress points for things to get undone.
>  
Well, yeah, but keep in mind that there really are only two important
things in your life.  (a) You are born, and (b), you die.  In between
these  two important events is a bunch of  time that we need to somehow
kill.  :-)  Anyway, since no one has come up with a neat little
store-bought gadget that does this, guess I will just have to piggyback
a 28-pin socket on top of a 40-pin socket and start soldering.

Thanks for your help and suggestions, as always.

John

2006\01\14@154226 by olin piclist

face picon face
John Nall wrote:
> What does the 18F877 have to do with anything??

It's a generic example of a PIC with a 16/18 family 40 pin footprint.  I
couldn't remember what you were using at the time, but 18F452 has the same
footprint.

> So far as "like which ones," the 3013
> has 2 UART's and the 452 only has one, for example.

Yes, but your board doesn't expect two UARTS so the extra UART on the
30F3013 will be unused and you can use those pins as generic I/O pins.
Since your PIC has less pins than the board expects, I would think you'd
want to hook up all the ones you can.

Why 30F3013?  I would try something like 30F4011 which at least has the same
number of pins, although I think is has more power and ground pins and
therefore fewer usable pins than the 18F452.


******************************************************************
Embed Inc, Littleton Massachusetts, (978) 742-9014.  #1 PIC
consultant in 2004 program year.  http://www.embedinc.com/products

2006\01\14@160255 by John Nall

picon face
Olin Lathrop wrote:
> > Yes, but your board doesn't expect two UARTS so the extra UART on the
> 30F3013 will be unused and you can use those pins as generic I/O pins.
> Since your PIC has less pins than the board expects, I would think you'd
> want to hook up all the ones you can.
>  
.
Yes, I absolutely agree with you.  Thanks for pointing that out.  I was
a bit worried about the fewer I/O pins.
.
> > Why 30F3013?  I would try something like 30F4011 which at least has the same
> number of pins, although I think is has more power and ground pins and
> therefore fewer usable pins than the 18F452.
>  
Primarily because I have several 3013's in a drawer, and no 40-pin dip
dsPIC's.  But even if I did, it is not clear that the job would be any
easier, because the pins wouldn't match the way the existing socket is
connected.  It seems like it might even be harder.  There used to be an
old trick that us hobbyists used, that you professionals would turn up
your noses at.  :-)  It is called "dead bug soldering," and involves
turning an IC on it's back, so that the legs stick up in the air (thus
the name).  Makes it a lot easier to solder small wires.  Anyway, doing
that with a 28-pin socket in the middle of a 40-pin socket would be
easier than trying to use a 40-pin socket wired to a 40-pin socket (to
change the pins).  Or at least it seems that way to me.

2006\01\14@192741 by John Ferrell

face picon face
I tried something like that a while back.
I had a Channel Master Antenna rotator with a remote control that had a
toasted PIC in it that was only available in an OTP package. It seemed like
a simple task to adapt a ZIF to allow an F device to take advantage of the
PC board.

It took quite a bit of time just to plan it. then putting 40 (28 MIGHT be
easier) discrete wires in place between two sockets is very messy and error
prone.  I ran out of patience and shelved the project.

John Ferrell
http://DixieNC.US


> There, with that explanation, do you still see a difficulty, other than
> just physically how to get it done??
>
> John
>
>
> --

2006\01\14@202009 by John Nall

picon face
John Ferrell wrote:
> > It took quite a bit of time just to plan it. then putting 40 (28 MIGHT be
> easier) discrete wires in place between two sockets is very messy and error
> prone.  I ran out of patience and shelved the project.
>  

Hi, John:

Well, that is two of you (you and Olin) who are kind of down on the
project.  :-(  Since I have a lot of respect for the opinions of you
two, then most likely you are right and I am wasting my time.  But I'm
going to give it a try, anyway.  It will not cost me any money (I have
all the ingredients already) and I have lots of time.  And, of course,
if I succeed, then fame and fortune will be assured!  (Well, perhaps
not, but my grandson may possibly be impressed, anyway).

I figure that I can plan it (sketching out pin-to-pin) in an hour, and
wire it up in a couple of hours.  So three hours out of my lifetime
(which is admittedly getting shorter each day) is no big deal.

John

2006\01\14@202621 by Herbert Graf

flavicon
face
On Sat, 2006-01-14 at 20:20 -0500, John Nall wrote:
> Well, that is two of you (you and Olin) who are kind of down on the
> project.  :-(  Since I have a lot of respect for the opinions of you
> two, then most likely you are right and I am wasting my time.  But I'm
> going to give it a try, anyway.  It will not cost me any money (I have
> all the ingredients already) and I have lots of time.  And, of course,
> if I succeed, then fame and fortune will be assured!  (Well, perhaps
> not, but my grandson may possibly be impressed, anyway).
>
> I figure that I can plan it (sketching out pin-to-pin) in an hour, and
> wire it up in a couple of hours.  So three hours out of my lifetime
> (which is admittedly getting shorter each day) is no big deal.

FWIW I've done something similar (although it was mapping the pins of an
EPROM from TSSOP to DIP, the pinouts were different, and there were
quite a few wires, 32 I think). It took a while, but it worked fine for
at least a few years.

This is obviously not something I'd ever consider for anything beyond
the prototype stage, but for that stage there's nothing wrong with it.

For the record, the most I've done is hand wire two 100pin connectors to
each other to match differing pinouts. It wasn't an IC, but it sure was
alot of work! :)

TTYL

-----------------------------
Herbert's PIC Stuff:
http://repatch.dyndns.org:8383/pic_stuff/

2006\01\14@222333 by Peter Todd

picon face
On Sat, Jan 14, 2006 at 08:26:19PM -0500, Herbert Graf wrote:
> FWIW I've done something similar (although it was mapping the pins of an
> EPROM from TSSOP to DIP, the pinouts were different, and there were
> quite a few wires, 32 I think). It took a while, but it worked fine for
> at least a few years.
>
> This is obviously not something I'd ever consider for anything beyond
> the prototype stage, but for that stage there's nothing wrong with it.
>
> For the record, the most I've done is hand wire two 100pin connectors to
> each other to match differing pinouts. It wasn't an IC, but it sure was
> alot of work! :)

My uncle is a telephone repairman. Think a cable 6 inches thick filled
with 24gauge twisted pairs... that and a backhoe.

Fiberoptics is a wonderfull thing.

--
spam_OUTpeteTakeThisOuTspampetertodd.ca http://www.petertodd.ca

2006\01\15@094535 by John Ferrell

face picon face
Note that I 'shelved it' rather than trashed it!
If I get back to it I will plan it more carefully.
Your success will encourage me.

John Ferrell    
http://DixieNC.US

----- Original Message -----
From: "John Nall" <.....jwnallKILLspamspam@spam@gmail.com>
To: "Microcontroller discussion list - Public." <piclistspamKILLspammit.edu>
Sent: Saturday, January 14, 2006 8:20 PM
Subject: Re: [EE] Plugging a 28-pin dip into a 40-pin socket



2006\01\15@221510 by kravnus wolf

picon face
Perhaps you can use a ZIF for the rewiring?
Just place the dsPIC into a ZIF and use the adjacent
pin*snap off* to rewiring to the correct pin in the
demo board.


John

--- John Ferrell <.....johnferrellKILLspamspam.....earthlink.net> wrote:

{Quote hidden}

2006\01\16@063832 by Alan B. Pearce

face picon face
>Well, that is two of you (you and Olin) who are kind of
>down on the project.  :-(  Since I have a lot of respect
>for the opinions of you two, then most likely you are
>right and I am wasting my time.

Not necessarily. I suspect the problem is that Olin did not explain himself
too well, and you have a certain amount of hump with him, as IIRC you have
run-ins with him before.

I believe Olin was attempting to point out that if you take earlier family
pairs of chips where there is a 40 pin and a 28 pin in the same family, such
as 16F877/16F876 and 18F452/18F252 then the 28 pin chip will match the pin
out of the 40 pin chip reasonably well at some specific pin displacement.

Not only that but these two chip pairs have what Microchip has regarded as a
"standard pinout footprint" (or words to similar effect) such that it is
easy to upgrade to a higher performance chip. Unfortunately they have not
gone down the same route with the dsPic family, so attempting to do the pin
conversion you want is not as easy as with earlier chip families, which
means you will need to have a lot of jumper wires on your piggy back socket
to make everything connect how you need it too.

2006\01\16@081600 by John Nall

picon face
Alan B. Pearce wrote:
> > Not necessarily. I suspect the problem is that Olin did not explain himself
> too well, and you have a certain amount of hump with him, as IIRC you have
> run-ins with him before.
>  
.
Him referring to me as a "modern day hippy" you mean??  :-)  Nah.  So
far as I am aware Olin and I get along just fine.  I have exchanged
private emails with him (regarding purchasing stuff from Embed, Inc)
before and he is a pleasure to deal with.  He just has a low tolerance
for stupidity, that's all.


2006\01\16@085705 by alan smith

picon face
Even us "professionals" do that.  I used to also include on board layouts....back in the day....extra pads for plcc and soic parts.  Now, 80% of my parts are BGA, so hard to have extras for those.  IMHO, if you solder short wires, make sure you bypass the power pins (bypass with caps...) and carefull taking your time, you shouldn't have a problem adding in the other socket.  For a hobbyist, time is nothing.  For those who do this for a living, its more cost effective to layout a board, get it done bare bones or such and then populate it.  Less error prone, if you did the layout correct.  The other way is do like someone else suggested.....small adapter board.
  There used to be an
old trick that us hobbyists used, that you professionals would turn up
your noses at. :-) It is called "dead bug soldering," and involves
turning an IC on it's back, so that the legs stick up in the air (thus
the name).

               
---------------------------------
Yahoo! Photos – Showcase holiday pictures in hardcover
Photo Books. You design it and we’ll bind it!

2006\01\16@095333 by Alan B. Pearce

face picon face
>Him referring to me as a "modern day hippy" you mean??

No I referred to you as "you", the "him" was to refer to Olin.

> :-)  Nah.  So far as I am aware Olin and I get along just fine.

Oh, that's fine then, just the tone of the exchange seemed to me to be
getting a bit tetchy. Seems I was wrong.

2006\01\16@100408 by Bob Axtell

face picon face
John Nall wrote:

{Quote hidden}

I think it is even simpler than that. Olin genuinely wants to help
newbies, and he wants to
address as many Q's as possible, and in the process, he sometimes uses a
choice of
words that some folks are offended by due to speed of the answer..

Frankly, he's  an outstanding contributor to the PICLIST.

--Bob

--
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attachments must be sent to
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http://beam.to/azengineer

2006\01\16@115611 by M. Adam Davis

face picon face
I'd use perfboard and two sockets, one is a 40 pin wire wrap socket,
the other a regular 28 pin socket.

The wire wrap socket has long pins that will extend through the
perfboard into the existing 40 pin socket.  Then wire everything up.
Put bypass caps on the adaptor board.

Alternately, get a 40 pin ribbon cable <--> IC adaptor such as
Digikey's c2pxt-4006m-nd :
www.digikey.com/scripts/DkSearch/dksus.dll?PName?Name=C2PXT-4006M-ND
Then wire that cable to a PCB with the 28 pin chip.  Upside is that
you don't have a huge PCB hanging off the original 40 pin PCB,
downside is that you have issues with cable length affecting clock and
other signals (put the crystal on the PCB with the 28 pin chip).

There is a lot more you can do with ribbon cable in this area as well
(two socket connectors placed slight apart make a full IC socket, for
instance).

Good luck!

-Adam


On 1/14/06, John Nall <jwnallspamspam_OUTgmail.com> wrote:
{Quote hidden}

> -

2006\01\16@130230 by Larry G. Nelson Sr.

picon face

Many of us professionals do the dead bug trick in our rework or to add that 1 extra chip after the fact. Years ago I upgraded a TRS-80 model 1 computer memory by stacking the chips and bending the CS line out to the side with a wire wrap wire soldered on to connect the other banks of ram.
Larry


---- alan smith <@spam@micro_eng2KILLspamspamyahoo.com> wrote:
{Quote hidden}

> -

2006\01\16@133249 by Lintech

flavicon
face
On 16 Jan 2006, at 11:56, M. Adam Davis wrote:

On 16 Jan 2006, at 11:56, M. Adam Davis wrote:

> I'd use perfboard and two sockets, one is a 40 pin wire wrap socket,
> the other a regular 28 pin socket.

But I would add a sacrificial 40 way turned pin socket on the end of the wire
wrap pins since they are large and will make the original 40 pin unreliable for
any other normal IC (if that is likely in the future).



George Smith

2006\01\16@135750 by Mark Scoville

flavicon
face
> Larry G. Nelson Sr.
> Sent: Monday, January 16, 2006 1:02 PM
> To: Microcontroller discussion list - Public.
> Subject: Re: [EE] Plugging a 28-pin dip into a 40-pin socket
>
> to add that 1 extra chip after the fact. Years ago I upgraded a
> TRS-80 model 1 computer memory by stacking the chips and bending
> the CS line out to the side with a wire wrap wire soldered on to
> connect the other banks of ram.
> Larry

Ahhh... Brings back memories. I did that on a TRS-80 as well - I think that upped the memory from 16K to 32K. WooHoo.

-- Mark




2006\01\17@000321 by andrew kelley

picon face
On 1/16/06, M. Adam Davis <KILLspamstienmanKILLspamspamgmail.com> wrote:
> I'd use perfboard and two sockets, one is a 40 pin wire wrap socket,
> the other a regular 28 pin socket.

> The wire wrap socket has long pins that will extend through the
> perfboard into the existing 40 pin socket.  Then wire everything up.
> Put bypass caps on the adaptor board.

Or.. along similar lines

Get two WW sockets, one for the 40 pin and one for the 28.  WW pins
from the 40 to 28. Trim 28 pins. Check wiring. Plug and play.
--
andrew
(who has used wire wrapping and it is quite quick and easy to make circuits..
http://www.umassd.edu/engineering/ece/darpa/ used WW for motor[used a
pic of course] and also wheel sensor -> pc interface [i'm in the
groups list..])

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