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Beginners advice from Dr. Paul (or Need help finding the right components for robots)
User Feedback
SimmStick Bus Concepts and SimmStick group Discussions
Scenix Micro on a SimmStick Contest99 Entry.
AT90S1200 Walking LED file, and programming SimmStick with MAC's
Has anyone ever asked for a 68HC11 SimmStick?
What about a 72 pin SimmStick?
The SimmStick Chat Group and a Typical Group Message
SimmStick Application:  by Peter Averill. I've just completed an interface from the Dalsemi Tini to a Simmstick mother board so I can use your peripheral cards.
An 8 channel serial servo controller . Prototyped on a DT101 SimmStick product. 
Have you ever seen a SimmStick Walking?

Subject:         dt006
   Date:         Sun, 7 Jul 2002 18:42:17 EDT
   From:        KBotB@

Hi Don,   This is Danny (dannynewp@)
I wanted to let you know I uploaded some pics of my dt006 board, relayboard and my expansion board that  I made.  I had to shrink all the files because my camera takes really big pictures, but they have a lot of detail though.  I may send a picture of the rs-232/485 terminal board pic once it is completed, I didn't see any built up units showing on your site and thought you may want a sample of a built one.  here are the links.....
thought you might be interested......Danny

fyi - KBotB is the name of a linux program I wrote that is also on my website under the other program section called (KDE Books of the Bible).

Subject:              RE: What is this board?
 Resent-Date:     Thu, 21 Jan 1999 00:02:49 -0500
 Resent-From:     sisuser@
        Date:           Thu, 21 Jan 1999 16:13:56 +1100
        From:          "Peter Homann" <>

I've just got my DT001 board constructed, Its a Rev A, that shows how long
I've been planning to build it up. It went together without any problems.

I'm planning to do some work with the PIC16C924, with the EPROM version in a 68 pin PLCC package. I'm using one of Dontronics 2" prototype boards in conjunction with the DT001 programmer. I've soldered a PLCC socket into the prototype board, and run wire links from the PLCC socket to the SIMM edge connector for the Gnd, RB6, RB7, VDD and VPP pins.

I'm using the PROPIC 2 software to do the programming. I changed the device config file for PROPIC 2, indicating that the 16C924 device has 18 pins. This causes the software to use the same parallel port pins for programming as it would for the 16F84 chip. The result is that the correct voltages and signals are presented to the SIMM socket on the DT001.

I've followed the development of both the SimmStick products and the PROPIC software for a number of years now and am very pleased with them both.

If anybody wants any more detail on what I've done, let me know, and I'll draw a diagram or take a photo.

Thanks, Peter

Subject:              Re: Need help finding the right components for robots.
 Resent-Date      Sat, 26 Sep 1998 22:49:46 +1000 (EST)
 Resent-From:     sisuser@
        Date:           Sat, 26 Sep 1998 21:51:58 +1000
        From:          "Paul B. Webster VK2BZC" <>
 Organization:      Webster Medical Pty. Ltd.
          To:            sisuser@

Rod wrote:
> I was looking for low cost alternatives to controller boards when I
> lucked on

  Yes, the simple PIC stuff is pretty "low-cost", but you must realise
it has limited memory and I/O capacity.  As you start to get to the
40-pin chips with plenty of I/O and more memory, costs start to escalate
toward the "other" controller boards.

> I found some terms that I didn't know, one of which was SimmSticks.

  At risk of repetition, as others have replied, these use the format of
30-pin SIMM memory cards.  The PCBs are small, fairly easily produced
(but not D-I-Y) and the SIMM sockets are dirt cheap from disposals
outlets.  It makes for a neat means of stacking modules; the
"motherboard" can even be Vero®.  (A fibreglass laminate version of Vero
would be **really* nice...)

> I get hit with the fact that I must pay for some sort of controller
> board, that needs either discontinued parts which are expensive & hard
> to find,

  Maybe, maybe not.  *Any* parts can be hard to find, and many old parts
such as the Z-80 are pretty cheap.  Most of the CMOS processors, which
are almost always the ones you want for economy of power, are still
current, but priced proportional to their capabilities.  The trick in
the Atmel AVR and PIC16F84 parts is that they are easily reprogrammable
*and* fairly cheap.

> or the STAMP module which is out of my price range.

  That very much depends on how many you want.  You can hack a single
Stamp module into a design much more cheaply and easily than building
Don's system; the module is complete and the software off the Web; you
need very little else.  You can cobble together a PIC'84 programmer
*much* cheaper than Don's however, but you won't have an application
board.  (Maybe you could use his DT-101s and cobble a version of the
DT-001, but I doubt it'd be worth the mess!)

  Once you've got the DT-001 up and running though, DT-101 modules *are*
going to be cheaper and more versatile than Stamps though and you get an
excellent base controller.  Neither contains interface as such (but Don
does those too).

> I guess what I'm asking is would someone please give me a little help
> in finding out if I can use the products offered by Dontronics as a
> contoller for a small mobile robot

  Done it? - not at this point.  I'd say though they are at worst, equal
to the Stamp (but you have to learn Assembler instead of Stamp "Basic")
and I'd advise you to go for it.

> a few small dc motors,

  You'll have to build drivers (whichever way you go) unless you can use
standard servos (worth considering; cost starts to mount).

> some simple sensors circuits,

  Pretty much processor-independent.  Pin count has to be monitored. A
clever trick is to have your sensor board contain a parallel-in, serial-
out shift register to clock in 8 or more inputs on only three lines.

> decent progamable memory size, expandable and upgradeable

  1K of PIC instructions goes a fair way; if you can learn to write the
interface to external serial EEPROM you can have 8K or so of token code
on the DT-101, or there is a form of Stamp-like "Basic" to do this.

> The controllers usually used by many robot buffs are STAMP's,
> Handyboard, and the Botboard. I can't afford any of these, but I could
> afford a low cost starter kit and then add on extras as I need them.

  I think you can better the Stamp with Don's stuff fairly well.  The
others you mention, particularly the Botboard however are not comparable
to my mind.  You are getting there to 68HC11 boards with major memory
resources (32K or more) and much more I/O, programmable in FORTH which
is still ace for robots.  They are almost certainly worth the money,
when you need them.
        Paul B.

User Feedback:

Subject:              RE: simm sockets and $500USD contest.
        Date:           Tue, 27 Apr 1999 16:33:05 -0700
        From:             BPuckett@ spam suppressed


About the contest - that's what prompted me to start getting serious about the SimmSticks.  When I read about it the first day I quickly jotted down notes for about a dozen projects.  All based on a common cool extension to the bus.  The little bus monitor board I wrote about this morning was just practice.  I hope to submit an entry in the next month (it takes me a while because I'm a software not hardware guy learning as I go).

The prize offering wasn't the hook - I just thrive on competition.  I figure someone has to win - someone has to lose.  I could be either one, but it's the thrill of the hunt.

I haven't really mentioned it here yet, but my web site is being updated with SimmStick and PIC stuff I am writing.  It's from a beginner's point of view, so it may not help a lot of people on this list, but I supposed some will benefit.

If interested, take a look at:

I am adding new material all the time.  Sections on choosing a programmer and a development platform are not done yet.  And, I plan a lot more on SimmSticks. Here is an excerpt from :

"You need to plug the PIC into something.  It's just a chip after all.  Many companies make prototyping boards.  You can wire up simple circuits on a solderless breadboard.  But, the coolest way to go is SimmSticks.  These are motherboards and plug in cards based on the 30 pin SIMM socket format.  A four slot motherboard with RS-232 port and power regulator on a 2.75" X 4" board."

I am having so much fun.  And, it's wild to write email at 2:45 and see it quoted on Don's web site at 4:00!

Bob Puckett

SimmStick Bus Concepts and Sisuser group Discussions

Please Note ***** Check the new SimmStick chat group at chat.html

Subject:  Re: SimmStick spec

             Wed, 09 Jun 1999 18:01:56 +1000
     Reply-To:   sisuser@

As I'm not sure if Mark is as yet on this list, I'll cc this to him and leave the message intact as I can only endorse what Rod is saying here. In fact he said it better than I would have come up with on short notice.

As an analogy, let me go back to when I was into design talks with Antti Lukats on the original SimmStick bus concept. We both have a previous love of Z80 hardware and software, where our micro roots are you might say.

Kicking around the idea of a Z80, a rom, a ram, and an interface to the outside world, and to be Simm Bus compatible, would mean an interface chip on the bus that would emulate the good things about the PIC and Atmel chips in their native I/O mode, meaning each and every pin is an I/O, not input only, not output only, but I/O.

This would mean any bus signal will cater for both directions. Have a look at the circuit of the dt102(.html) You will see that the same pins that are used to write to the LCD bus are also used for the DIP switch input readings.

OK Antti, how do we do this with a Z80?
With a PIC16C57/XT of course!!! was his answer.
After careful thought, I knew this was correct and have often wondered why I haven't done it by now.

It may mean a 3" SimmStick with a 40 pin Z80, 28 pin Ram, 28 pin Eprom, and a 28 pin PIC16C57, but you end up with a 3" SimmStick that is capable of running most of the Z80 and CPM software that has been available since 1976??, well with appropriate drivers anyway.

OK, this may well be an old dream for a couple of old-timers, but the theory remains the same for the SimmStick and the bus.

It's horses for courses as I would say. We don't really need to run CPM or a large data base, we just need some single chip control done cheaply.

I know what Mark is saying with the read/write/ale, as I have been there and done that many times, but I'm afraid it doesn't have much to do with where SimmStick is, or where it is heading.

Sure, users will make their own interpretation of the bus specs, and make it match their own requirements.
There are some very interesting developments that will unfold in this direction in the near future, but the concept of the I/O pin on, each and every data line basically remains the same.

Sage Telecommunications wrote:
> Unfortunately when the SimmStick bus was named it has brought with it
> numerous definitions of what a 'bus' is and/or should be.
> The original concept of a single chip micro with a 'bus' to allow easy
> access to i/o and simple addons was fine. It has some limitations but has
> been fairly well supported and allows for numerous add on cards. The biggest
> mistake was calling the I/O lines data lines! They are not they are I/O
> lines.
> There has been a number of proposals, including Mark's,  to change the
> definition of the bus to something along the lines of an ISA/PCI/S100( for
> those old enough ) bus. This kind of bus is also great. But it is a
> completely different concept.
> I am not quite sure how you could interface an 18 PIC or ATMEL to a 32k ram
> module and have any IO left to do anything with. You would need to create
> I/O cards with buffers/latches and separate connectors to interface to the
> outside world.
> My point is that what is being proposed is a different system all together.
> SimmStick as it stands is meant for developing single chip micro projects
> with one or two add on boards that connect directly to the I/O on the micro.
> There are a lot of generic micro bus specs out there. PC104 / ISA / EISA /
> PCI / S100 / VME / Multibus / STD etc. For most, if not all, of those
> busses(!) external interface to plug in boards requires separate connectors.
> The physical construction of the bus is quite robust. Simm sockets are not
> designed to be sufficiently robust. The physical size of a SimmStick board
> is limited, if the board is to big you will have a problem with physical
> integrity with the sockets.
> I really don't think that the SimmStick is the platform to use for a
> 'generic' bus product. There are a lot of applications that suit SimmStick
> very well and some that don't. YMMV
> That's my $0.02 + gst worth
> Rod Egan
> -----Original Message-----
> From: Don McKenzie <>
> To: Mark Dierolf <>; sisuser
> Date: Wednesday, 9 June 1999 10:29
> Subject: Re: SimmStick spec
> >Hi Mark,
> >See:
> >
> >which will point you to the subscribe sisuser info.
> >
> >Mark is thrashing out some SimmStick bus specs and I have suggested he
> >join, and air it on the sisuser list as others may have comments or be
> >interested, so here is our exchange so far.
> >
> >Mark Dierolf wrote:
> >>
> >> Thanks for the input don, i think it would be a good idea to report it to
> >> the group, however i am not on it! Could you forward me to a website so i
> >> can subscribe?
> >>
> >> I think i may have given you a slightly wrong impression. I think the
> >> standard should be revised and named differently, and at least the
> voltages
> >> on certain pins standardized, so that i/o pins cant get fried. I also
> think
> >> a databus should be standardized. While the ORIGINAL simmstick design can
> >> remain intact, there should be a definite way and pinout of communicating
> >> with add-on boards, which is documented as the recommended method or
> such.
> >> Anyways, if people want to use their own simmstick boards in a different
> >> pinout, with different voltages, they will do that no matter what the
> spec
> >> says. The big thing that i personally would like to see is modularity. It
> >> would be great if i could order a simmstick with an atmel 90s8515 from
> you,
> >> and then go and purchase a 32k sram board and just plug it right in,
> without
> >> having to look at pinout,voltages,etc..
> >>
> >> On a completely unrelated topic, if i were to create some simmstick
> PCB's,
> >> and sell them, can i legally call them "SimmStick"?
> >> The actual phrase, as an example, would be the following:
> >>
> >> 32k Sram
> >> SimmStick
> >> By Mark Dierolf 1999
> >>
> >> BTW The reason i came up with that databus is because it is physically
> >> compact, easy to implement, and can be directly connected to quite a few
> >> micros, especially the atmels, which have become popular as of late.
> >>
> >> Mark Dierolf
> >>
> >> > -----Original Message-----
> >> > From: Don McKenzie []
> >> > Sent: Sunday, June 06, 1999 8:51 PM
> >> > To: mud99
> >> > Subject: Re: SimmStick spec
> >> >
> >> >
> >> > > mud99 wrote:
> >> > >
> >> > > Dear Don,
> >> > > I have been interested for quite a while in trying out your simmstick
> >> > > products,
> >> > > and i have recently made up some PC Boards which fit into the sockets
> >> > > and use the same pinout as yours. I would like to release the PCB
> >> > > layouts
> >> > > to the public but i have found that while you have put a pinout for
> >> > > them on your site,
> >> > > the specification is very vague, for example, pin 3 can be special
> I/O
> >> > > or negative supply. The problem is that if someone were to plug their
> >> > > own card into one of your powered motherboards as an example,  they
> >> > > may recieve -5 or -12 volts to an I/O pin on their product, and the
> >> > > results would most likely not be good. This is the same with a number
> >> > > of other pins as well. Therefore i think it would be in the best
> >> > > interest of everyone to make the specification more clear, or come up
> >> > > with a revised spec and call it SimmStick-B or something like that.
> >> > > If you do decide to do this, my personal preference would be to
> >> > > implement some sort of actual data bus, here is how i have done it on
> >> > > my board:
> >> > > pin 1: RD(active Low)
> >> > > pin 2: WR(active Low)
> >> > > pin 3: Having at least a single interrupt would be nice, so i put it
> >> > > here
> >> > > pin 14:ALE(Active Low)
> >> > > pins 15-30:data and address bus, 8 or 16 bit data users choice
> >> > >
> >> > > I hope you will consider this as it would benefit all simmstick
> users,
> >> > > and
> >> > > i think it would be appreciated in the long run.
> >> > >
> >> > > Thanks,
> >> > > Mark Dierolf
> >> > >
> >> >
> >> > Hi Mark,
> >> > I thought the question may be better addressed to the sisuser group so
> >> > that others may be involved, in fact it still can of course.
> >> >
> >> > The problem of only having 30 pins, and allowing 3 for users means you
> >> > put there what you application needs.
> >> > If it needs 1V p/p video, then that's what you run on that signal, say
> >> > pin 1. If anyone else wants to use the same motherboard that has pin 1
> >> > common, they must be aware that this is used for video.
> >> >
> >> > To cater for every set of circumstances means a lot more pins than 30
> of
> >> > course.
> >> > If you wish, you or I could run the whole question and answer past the
> >> > sisusers for comment if you wish.
> >> >
> >> > BTW. It looks like you are aiming at a specific micro bus. :-)
> >> >
> >> > Cheers Don...

AT90S1200 Walking LED file, and programming SimmStick with MAC's
Subject:         Re: LEDTEST file
   Date:          Tue, 15 Jun 1999 19:39:46 +0000
   From:        "Ben Hitchcock" <>


I found this file out on the web, and it works really well.  It's a major achievement to get my simmstick programmed using my iMac and I'm pretty happy about it - the main reasons being:

a) no-one that I know of has done it before.
b) Lots of people told me it couldn't be done.
c) my Mac doesn't have any serial or parallel ports, apart from a USB port.

Well, I did it!  I'm going to improve the program a lot, write some html for it and then post it up on my web site.  If you're interested, I would be happy if you would 'mirror' it on your site so that other beginners like me could find it easier to get started.

Anyway, here is the LED test file.  This one is a bit better than the one you get with the ATMEL programs because you don't have to keep pressing 'reset' all the time.

; Bit rotation test program for Atmel AVR microcontrollers
; Ingeneering Inc.
; Jeff Holtzman
; 2/4/98

;Rotates a bit through LEDs using precise software time
;delay.  From 10/98 issue of Popular Electronics magazine.
;AUTHOR = Jeff Holtzman
;TARGET = AT90S1200

.device AT90S1200
.org 0

.equ    DDRB =  $17
.equ    PORTB = $18
.equ    OLC =   0               ; outer loop count for delay routine
.equ    ILC =   156             ; inner loop count for delay routine

RESET:  ldi     r16, 255

 out     DDRB, r16       ; set port B for all outputs

        ldi     r16, $FE        ; initially enable just the lowest bit
LOOP:   sec
        out     PORTB, r16      ; turn on one LED

        ldi     r17, 5          ; wait 0.5 sec
LP1:    rcall   DELAY
        dec    r17
        brne   LP1

        rol     r16             ; rotate the bit
        cpi     r16, $FF        ; if all bits not set
        brne    LOOP            ;   ... continue
        dec     r16             ; else set just the lowest bit
        rjmp    LOOP            ; loop forever

DELAY:  ldi     r22, OLC        ; delay for 1/10th second
DL1:    ldi     r23, ILC
DL2:    rcall   DUMMY           ; waste 7 cycles
        dec     r23
        brne    DL2
        dec     R22
        brne    DL1
DUMMY:  ret

Here's the compiled HEX file (compiled for a macintosh programmer - Yes,
they ARE different!):


And here's the compiled HEX file (compiled for a PC programmer):


Hope this helps!
Ben Hitchcock

Has anyone ever asked for a 68HC11 SimmStick?

From Robert Nansel's Amateur Robotics Notebook Column, Nuts & Volts magazine August-98:
There are currently no Motorola MCU chips such as the 68HC05 or 68HC11 supported by SimmSticks. This is a shame since these seem like naturals for SimmSticks, and they are certainly popular with us gearheads. If Don doesn't design an HC11 SimmStick, I may have to do one myself.

My response went something like this:
Around 1993, I was involved with Motorola micros and found that not only did I have to wait for parts, but the prices would increase two or three fold during this wait of sometimes up to 9 months before I could get my hands on parts. In fact, this was the reason I dropped off Motorola and got interested in PICmicros.

The feedback I get today indicates that unless you are into cell phones or auto manufacturing in a big way, the situation hasn't changed a lot since 1993.

If some one can convince me otherwise, and has a suitable working schematic that can be readily used on a SimmStick platform, then I may reconsider.

What about a 72 pin SimmStick?
When Antti first mapped out the bus achitecture of SimmStick, we spoke at length about a 72 pin version, so this has been an ongoing discussion for many years now.

A 30 pin bus such as SimmStick, suits 18 to 28 pin micros very nicely. 40 pin devices will fit with a bit of a push, however it still means some sort of additional header, like we have done with the dt106 .
Smaller pin counts such as the Atmel and PICmicro 8 pin devices, seem like a big overkill for SimmStick, however as the pin count is 8, it's not hard to jumper 8 wires on a dt201 proto board to interface to SimmStick for development.

For micros that have a greater pin count than this, it is felt a 72 pin or larger bus would be more suitable.

If there is to be a 72 pin version, then it will not be compatible with existing SimmStick designs, and will need a whole new range of not only Micro boards, but also I/O boards, so I don't see Dontronics moving into another bus standard in the near future, however this isn't in concrete..

I feel there is still a lot of scope for the advancement of 30 pin designs as well as surface mount in the 30 pin bus platform as it is currently setup.

The SimmStick Chat group:
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Typical Group Message

Subject:           Re: [simmstick] newbies:differences between simmstick and AVR?
     Date:          Mon, 4 Sep 2000 11:43:16 +0200
     From:          "Lars Wictorsson" <>

Hi Guy,
I will try to answer some of your questions...

> I just want to check if I got my big picture right.
> The Simmstick is a printed circuit board which has a PIC
> microprocessor on it and can be pushed in (like clipped) onto
> other boards made by DONtronics only.
> The AVR is from AMTEL and is a microcontroller which just push
> in a 20 or 40 pins sockets.

Well, the SimmStick platform has nothing to do with PIC or AVR etc. it is just the concept how the boards looks like in dimensions, signals etc. on the bus. A SimmStick board can be equipped with any microcontroller of your choice and today there are SimmStick boards that has a PICmicro controller, Atmel 8051, Atmel AVR and Scenix SX etc.

> The simmstick PIC xx877 can run at 20Mhz but the AVR will only run
> at 4 Mhz? is that correct?

Same here, the "SimmStick PIC xx877" as you refer to above is a simmstick board (DT106) with a PICmicro controller type 16F877. PICmicro's need to divide the chrystal speed by 4 when running, so 20Mhz gives you 5MIPS (5 miljon in instructions per second), while the AVR has 1MIPS/1Mhz and some AVR's has max speed of 4Mhz, some 6Mhz-10Mhz while the fastest (but not so usable IMO) has 12Mhz (=AT90S1200). So comparing the 16F877 running at 20Mhz and the AT90S8535 (which has ADC as the 877) runs at 8Mhz, gives the AVR a 8/5 more speed. The PICmicro has less code memory than the AVR, so you could fit more program into it. The PICmicro has also a strange memory bacnk switching that you have to think
of when using e.g. Assembler, the AVR has a straight memory, no hassles at all.

> The simmstick can be programmed in C, QBASIC and TASM
> The AVR can be programmed - I don't know...

Same here as well, the SimmStick has nothing to do with languages, it is the controller on the SimmStick that has to
do with that. So both a controller of PICmicro or an AVR on a SimmStick board can be programmed in either Assembler,
C, Basic etc. (any language that is supported for the controller).

> What is the main use of the simmstick and the AVR?

This is personal, but I prefer AVR before PICmicro, your question above should be written "What is the main use of
the PICmicro and the AVR" (since SimmStick has nothing to do with it).

> Can a simmstick programmer board be used to program also an AVR?

yes, check out the DT006 board that is an AVR platform and can be used as a base board for programming other SimmStick
boards with an AVR controller on it.

> The memory of a simmstick is a sort of EEPROM? is this correct?
> Is the memory of the AVR also an EEPROM?

Memory is 3 things:

Code Memory (where you store your program) is normally FLASH.
User RAM    (where you store variables) is RAM or registers.
User EEPROM (where you store parameters to be saved when power is off).

Both PICmicro and AVR has both of these memories depending on chip type, they have more or less of them.

> In both cases is it possible to add extra EEPROM to a simmstick or an
> AVR?

Yes, through either SPI or I2C busses.

> The PIC 16F877 is the latest in the line of PIC
> What about with AMTEL, what is the latest model number

AVR is a family, so you can't say there is any latest, new arrives when new perephials comes and more memory,
but the latest that will come in AVR is the ATmega163 (next year), which is an upgrade of AT90S8535, which has 8k code, 512bytes RAM & 512bytes EEPROM.

AVR's that are used today are:

AT90S2313: 2k Code, 128bytes RAM, 128bytes EEPROM, no ADC
AT90S8515: 8k Code, 512bytes RAM, 512bytes EEPROM, no ADC but
           possibility to add extra 64k SRAM.
AT90S8535: 8k Code, 512bytes RAM, 512bytes EEPROM, 8ch 10bit ADC but
           no possibility to add extra RAM (unless you make
           software support for it).

SimmStick boards for the above excists:

AT90S2313: DT104, DT006 or the new SIMM101 from us (availible in 2 weeks)
AT90S8515: DT103 or the new DT107 comming soon.
AT90S8535: SIMM100

> Most probably I am going to ask a question totally out of context and
>  be booted out by the moderator of this group. In all the electronics
> magazine I see the word BASIC STAMP. I can see roughly the difference
> between BASIC STAMP and PIC. BASIC STAMP is NOT as fast as PIC, but
> what are the other differences.

Don't be affraid to ask, the BASICstamp is a PICmicro, but it is running a BASIC interpreter, so the speed is low compared to
if you use the same controller as the BASICstamp is built upon, but program it in Assemlber or a BASIC compiler, you get *100 the speed (or so).
Regards /Lars
LAWICEL / SWEDEN           Phone  : +46 (0)451 - 598 77
Lars Wictorsson            Fax    : +46 (0)451 - 598 78
E-mail:   WWW    :

Embedded hardware/software together with 8051/C16x/AVR and
smart distributed I/O with CAN  (Controller Area Network).
See CANDIP at   AVR+SJA1000

Subject:          Fw: [simmstick] newbies:differences between simmstick and AVR?
     Date:          Mon, 4 Sep 2000 12:18:38 +0100
     From:          "Andy Howard" <>

----- Original Message -----
 From: "Guy North" <>
 > I just want to check if I got my big picture right.
> The Simmstick is a printed circuit board which has a PIC
> microprocessor on it and can be pushed in (like clipped) onto
> other boards made by DONtronics only.

 Not quite, basically the Simmstick is just a ready-etched PCB.

Simmstick is a standard way of making PCBs so that they can be plugged together on a bus made of standard 30pin SIMM sockets, the Simmstick itself can contain almost anything you want. Some carry microcontrollers (PIC or AVR), others just peripherals, e.g. Don's relay card. There are also ones consisting entirely of holes to prototype your own circuitry on. There are many kinds of Simmstick from several makers, though I believe Dontronics has the widest range.

You can make your own motherboards or fit a Simm socket to anything else you want to use Simmsticks with. You can also design your own Simmsticks and there is a prize competition to encourage people to do exactly this.

> The AVR is from AMTEL and is a microcontroller which just push
> in a 20 or 40 pins sockets.

Hmmm, I think you might be getting a little confused here, the 16F877 is also a microcontroller, one of a large range made by a company called Microchip, it isn't anything to do with Simmsticks in the way you suggest, it's just that it can be mounted on one type of Simmstick PCB. The AVR is ditto but made by Atmel. Either can be mounted on suitable Simmsticks. Both are available in standard IC type pinouts (DIP is the official name - Dual Inline Package). They are also available in various minature "surface mount" packages which are not really relevant to the beginning hobbyist. Most Simmsticks use the DIP type micros.

> The simmstick PIC xx877 can run at 20Mhz but the AVR will only run
> at 4 Mhz? is that correct?

In terms of speed, the Atmel AVR works differently to a PIC internally so for most commands a 4MHz AVR is roughly equivalent to a PIC running at 16MHz (this is an oversimplification but the principle holds good).

> The simmstick can be programmed in C, QBASIC and TASM
> The AVR can be programmed - I don't know...

There are a huge range of languages available for both PIC and AVR, including C, BASIC, Pascal, assembler and several that people have invented for the purpose e.g. JAL.

I'd *very strongly* recommend you start out by learning assembly language. Assembly language is simply instructions that work directly on the memory or pins of the chip and there are loads of good tutorials online.

Even if you plan to program in C, BASIC or whatever, you'll find that understanding assembler code makes programming in other languages a snap. Also there are some applications, e.g. when speed, timing or code size are critical, where assembler is your only option.

> What is the main use of the simmstick and the AVR?

I use Simmsticks for prototyping products, making custom one-off products and testing code. I make data collection, telemetry and remote control equipment. All my stuff is done with PICs but all of it could equally be done with AVRs.

> Can a simmstick programmer board be used to program also an AVR?

Yes, have a look at the Dontronics site for the AVR Simmsticks. The site is a bit confusing at first but all the info is there somewhere.

> The memory of a simmstick is a sort of EEPROM? is this correct?

A Simmstick is just a PCB, you can fit anything you like onto it, including micros with built in EEPROM and also standalone EEPROM chips. The serial type is normally used.

> Is the memory of the AVR also an EEPROM?

Both PIC and AVR have several different kinds of memory. Older ones have EPROM, which may be eraseable or One Time Programmable (OTP) which is used to hold the program you have written, they may also have smaller amounts of EEPROM and/or RAM to hold data. Both PIC and AVR have separate program and data memory, called Harvard architecture, unlike many earlier designs where data and program share the same memory areas.

PICs have different types of memory according to the model, all the ones with a C in the type number e.g. 12C671, 16C84, 17Cxxx, 18Cxxx have EPROM memory and are usually available in an expensive eraseable version for development and a cheaper OTP version for production. More recently they have introduced Flash EEPROM for the program memory on
some models and these have an F in the type number, e.g. 16F84, 16F877, they have pre-announced lots of future Flash versions of their chips but not many are available yet. These models can be reprogrammed very simply and are certainly the best bet for a beginner. I don't know enough about the AVR range to answer for them, but I'm sure Atmel's site has all the info.

> In both cases is it possible to add extra EEPROM to a simmstick or an
> AVR?


> The PIC 16F877 is the latest in the line of PIC

That's not quite true, the 17C series and 18C series of PICs have newer members andthere are new products arriving almost monthly.  In this context however, new doesn't automatically mean better, sometimes the newer model just adds (or removes) some of the on-chip peripherals. If you go to the microchip website and look at the Line Card you will get a good overview of all of the permutations available. For your first projects the 16F84 and 16F87x series are probably the best bet.

> Most probably I am going to ask a question totally out of context and
>  be booted out by the moderator of this group. In all the electronics
> magazine I see the word BASIC STAMP. I can see roughly the difference
> between BASIC STAMP and PIC. BASIC STAMP is NOT as fast as PIC, but
> what are the other differences.

The BASIC Stamp is a small PCB designed to plug into an IC socket which contains a surface-mount package PIC, an oscillator, power regulator and a few other components plus a built-in BASIC language interpreter. This last item is what makes it run so slowly. It's also a very expensive way to buy a $5 PIC in my opinion. For very little more you can buy a PIC and a copy of the PICBASIC compiler which you can then use to program any number of PICs in exactly the same BASIC language, and it will run 20 times faster at least. If you're tryng to decide whether to go for PIC or AVR I'd suggest to start
with PICs if only because there is so much support for them available online. It's easy to convert over to AVR if they have some feature not available on a PIC. The main advantage of AVRs is that they have larger memory, though I've not yet run out of space on the PICs that I use here. I don't know enough about AVR to give a full comparison here but I'm sure someone else will be able to help.

You can download the MPLAB development tools for the PIC, it's free from or even better, contact your local Microchip dealer and get the current CD which contains the tools and all the datasheet and application notes you could want.

> Moderator of this group, please remember I am NOT trying to be
> offensive to the group but trying to get a big picture in the scene
> of
> microcontrollers where I am going to spend a few of dollars inthe
> months to come.
> A very curious newbies.

Don't worry about asking questions Guy, we all had to start learning somewhere. Remember, the only stupid question is the one you _don't_ ask.

Spend some time browsing the DOntronics site, and as well as and (note that  Atmel sell two incompatible ranges of microcontroller, the AVR which we are  discussing here and which is broadly similar to the PIC range, and 8051 types). That should give you some background on all of this.

There are also webrings of sites that deal with PICs and AVRs, you can  probably find them via There is a huge amount of really  good info about these devices out there on the web.

But really I've saved the best bit until last.
Before you do any of the above go to and read that and follow all the links, you'll not find a better learning resource anywhere. It's a beginners guide compiled by one of the moderators of the PICList mailing list.

 The PICList is a quite high volume mailing list dealing with anything to do with the PIC processor. It's well worth subscribing to if you can handle the  volume of messages. As a complete beginner you may find some of it quite technical, but it is also a wealth of useful information and advice for newbies too. I'd suggest you sign up (full details at and read the list for a couple of weeks to get the flavour of it before attempting to post any questions. There is a very detailed FAQ about using the list, also at, which you should print out and keep.

 I hope this has made things a bit clearer for you. Do feel free to ask for anything above to be clarified if you're not sure. And keep on asking questions!
Cheers Andy.

Subject:         Re: DT203
   Date:         Fri, 8 Jun 2001 16:57:40 +1000
   From:        "Bart Pienaar" <bartp@
I received your bag of parts recently and assembled a DT006, simm100, DT107, DT104 and DT203. I quickly realised you won't be able to put a DT203 and another card together onto a DT006. If you put all the components onto the solder side of the DT203 and just the driver chips onto the component side you can plug both a CPU card and DT203 onto your DT006. If you wire an LCD to the DT203 with a short ribbon it makes a great little development tool. I hope this comment can be useful to someone. Kind regards Bart Pienaar

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