Reflection Technology

SimmStick Bus Specification

SimmStick(tm) started with a PIC 16F84 Single Board Computer designed by Antti Lukats from Estonia based around the 30pin SIMM socket used on PC motherboards. The initial bus design was versatile enough that in addition to the PIC16F84-based design, there are now boards for 20 & 40 pin Atmel AVR and non-AVR micros. 

Boards are re-usable and reconfigurable for many different applications. You can prototype a design on a breadboard with a 30 pin Simm Socket for your PIC16Cxx or Atmel micro, then a final board design can include or exclude the SimmStick module.

The best part is the price - about $6USD per bare printed circuit board for single quantities. This is for a 3.5" by 1" double-sided, plated-through, solder-masked board.

Many boards are available including large and small proto boards, CPU boards, Motherboards, and many I/O boards. These include Relay modules, LEDs and Switches I/O boards.

The DT001 8 slot Development Platform also contains an inexpensive PIC programmer for the SimmStick bus.

A SimmStick bus structure isn't a definite requirement as these modules can also be connected together with straight or right angle 30 pin male and female pins, as a set of header pin holes are provided just behind the edge connector pads.


  SimmStick Bus Definition

PIN # Name Funct Pin # Name Function
1 A1 Special 16 D1 I/O
2 A2 Special 17 D2 I/O
3 A3 Special 18 D3 I/O
4 PWR Unregulated DC in or +12V or VPP 19 D4 I/O
5 CI Clock Input or OSC1 20 D5 I/O
6 CO Clock Output or OSC2 21 D6 I/O
7 VDD +5V In or Out 22 D7 I/O
8 RES Reset In or Out 23 D8 I/O
9 GND Digital Ground 24 D9 I/O
10 SCL I2C Clock or 25 D10 I/O
11 SDA I2C Data or 26 D11 I/O
12 SI Serial In or 27 D12 I/O
13 SO Serial Out or 28 D13 I/O
14 I/O General purpose 29 D14 I/O
15 D0 I/O 30 D15 I/O

 SimmStick Dimensions.

A DT Series Board 2 Inch Simmstick is 2.025" high and has the top holes .175" from the top edge.
The spacing is the same from each edge, that is .13"

A DT Series Board 2.5 Inch Simmstick is 2.65" high and has the top holes .175" from the top edge.
The spacing is the same from each edge, that is .13"

FAQ - Questions and Answers

What are the 3 special I/O lines used for?
A1, A2, and A3 are User defined. They can be a card select, Video In/Out, whatever you care to make it for your project.
We have used it for alternative RS-232 on some boards.

Why connect D0 to D15 together on the motherboards?
Most small applications may only have 2, 3, or 4 boards connected together. In these cases, the I/O will no doubt be common.

On larger applications, or where multi-processors are used, you may need to custom design or jumper a motherboard to suit.
The idea is to change the mother board platform to configure your SimmSticks. The most common hobby PCB board you can purchase appears to be a simple parallel tracked PCB that matches 30 pin Simm sockets nicely.

If you need to design and manufacture a custom motherboard and use off the shelf SimmSticks, then future design is easy. You don't need to cut tracks and run jumpers on SimmSticks if you do all your configuration on the motherboard.

More info can be found at:


Simm Socket Mating Cycle Endurance

Subject:Re: simm sockets, etc.
Date:   Fri, 11 Sep 1998 10:32:34 +0900 ("EDT)
From:  Ron Kreymborg

I have used the DT101 and DT001/DT003/004 for a number of projects.  One I remember had a DT003 connected to a number of peripherals with a 16F84 on a DT101 simmstick. I continually modified and expanded on what it could do d display, and in so doing must have moved the DT101 from the DT003 based product to the DT001 programmer board hundreds of times.

Never a hickup and examination of the sockets/contacts shows no appreciable wear. The advantage of the DT101 socket is that it is pressed together with no sliding (read scraping) motion.


Simm Socket Footprint


 Subject:Re: Need help finding the right components for robots 
 Date:   Sat, 26 Sep 1998 21:51:58 +1000 
 From: "Paul B. Webster VK2BZC" <>

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.


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