The Maximite Computer Is Now In Stock.

The Maximite Computer Is Now In Stock.

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The DonDuino Patch

The DonDuino Patch

On the Saturday, I spent a couple of hours on a project with Mick, all via email. I had an idea. We pushed it around. He designed the board artwork.

We should end up with a simple, low cost, Arduino shield addressing patch panel, that uses shunts and jumpers to cross configure all Maximite signals that drop into the Arduino shield format.

I have hunted the web, and found nothing even close to what we can achieve with "The DonDuino Patch". This isn't just for Maximite, it is also a new Arduino Shield product.

Mick completed the artwork on the Sunday,  and we submitted it to our PCB manufacturer on the Monday.

This idea was based on thoughts I had when I first saw Geoff Graham's Maximite Computer in Silicon Chip magazine, however I  imagined it for a parallel bus system using the 26 pin IDC cable principle.

I had spoken with Geoff about doing something like this, and he welcomed the idea, however we were not talking about Arduino shields, but about a parallel bus system.

When it came to applying it to the Arduino shield stack, it made even more sense, and was possibly easier to implement.

It is a little hard working from a B&W overlay, and not an actual picture of the board, complete with various examples of configurations of jumpers and shunts.

So here is a quick advanced no nonsense, no pictures summary:

Easiest way to explain this is, you populate the board with two sets of stacker header pins.

The J1 pins will insert into the board below the patch board and become the male pins of the patch board.

 The J2 pins will effectively be the sockets up to the board above. This means you may have to cut the male pins from these sockets, as they may foul with the board components below.

In the middle of the board, there are four R/A male headers. Two by 6 pin * 2, and two by 8 pin *2.

The lower pins are for the bottom board, and the top pins for the upper board.

All signals except the grounds, can be isolated.

To reconnect them together, you use shunts or test links to join common signals between the two boards, and either 50mm, or 100mm wire jumpers to cross patch your signal selection.

This will allow you to redirect and connect any signal of the bottom board, to any signal of the top board.

This can be either a permanent or temporary connection, it is up to you.

Boards are now available.

The DonDuino Patch will only be available as a bare board, or as a kit of parts.
Constructors should be able to build this in 5 or 10 minutes I would think.

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Maximite New Schematic and IDC I/O Connector Correction.

Maximite New Schematic and IDC I/O Connector Correction.

Click on the image below to open in a new window. Click on it to enlarge to your bowsers window size. If you then right click and save the image to a file, you should be able to print it from your file viewer.

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Maximite I/O R/A Male Header Pinout Correction Table.

From your Browser:

Right click on the corrected table below, select view image, and you can print it out in colour.

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The DonDuino Cross.

The DonDuino Cross.

Available from:

This is a Maximite 26 pin IDC I/O connector to Arduino Shield Converter Board.

Two weeks ago, I didn't know what an Arduino Shield was, now I love them. What a brilliant idea.

Any product that I produce based on this bus conversion, I will be calling the DonDuino range.

First one off the blocks, is a simple converter board, to assist users to get involved in the Arduino Shield range of products, without the hard work. They will simply plug together.

First a little piece of history:

My friend Mick Gulovsen reminded me about this.

25+ years ago, I designed an item I called The DB-Cross. This was used for RS-232 interfacing, and it was able to connect the full 25 pins of two females and two male DB-25 type connectors together.

It was a male to male gender bender, and a female to female gender bender. It also provided a point to connect  a tester, or monitor via one of the unused connectors. and it allows several similar devices to be connected together without additional wiring. It could be used with additional add-on modules such as the one pictured below, to show bus activity. We had little break out boxes, with DIP switches and jumper leads to reconfigure for typical RS-232 connections.

It was also stackable. You can see a strip of 25 pins at .1" centres on the unit on the left. This could be used to connect components, test equipment, or another module on top, so that you had eight connectors. You have six spare showing in the picture below. 

So you could plug them together like a Meccano set, or Lego blocks. This was the seed to make "The DonDuino Cross" in much the same manner and successful formula as the DB-Cross.


The DonDuino Cross

This is an all through hole design, so the user can build it easily themselves. Anyone who has done a little electronics work, should have very little trouble soldering this kit together.

Hardware and software will be the full responsibility of the user, as there are no guarantees on compatibility, or support of the Arduino Shields, so you are on your own.

Mick has completed the artwork, and the first production boards have been ordered.  All parts for the kit have also been ordered, and availability date should be around two weeks.

A table of pins for both the Maximite and the Arduino bus are at:

My first DonDuino I/O board has provision for two R/A Male, and two R/A Female connectors on it, as well as an Arduino foot print, a proto area, three LEDs and resistors for power monitors, a VIN and a diode for VIN input polarity protection.

Each of the R/A connectors carry the Maximite standard I/O bus.

You will be able to plug it into the Maximite in four different ways, using any of the male or female connectors. The females will plug straight in, pin for pin. The males will need a 10cm cable to allow it to plug into the Maximite.

To cater for all of these combinations, a twist in one cable is required. Two very tight 45 degree folds in the cable to allow the red wire to flip from one edge to the other.

What you end up with is:
Plug in via a twisted cable between the Maximite I/O connector and  . Boards end up 50mm (2") apart with the I/O board sitting at the back of the Maximite board.

Or you can plug in via a different male, so that the I/O board will sit on top of your Maximite case using again a 10cm cable with no twist.

Or you can plug in with no cable using either of the female connectors.

It is a design concept that is better explained in pictures than words. After all a word is only worth a milli-picture.

Note. I haven't done board artwork since the DOS Protel days, and my friend Mick possibly hasn't produced one this century.

Here is the dead set ugly 3.3 minute sketch that I threw at Mick to start this project:

The board:

The board measures 67mm x 68.6mm, 1.6mm thickness.
The holes in the corners are 3mm.

My initial specs:

(The J numbers have been changed since the first drawing).

A square chunk of PCB about 6cm square. An Arduino foot print in the middle. Call this J5

Along the bottom edge, provision for a R/A male connector. Call this J2
Along the top edge, provision for a R/A male connector. Call this J4

Four nice mounting holes in the corners.

Small sea of holes for prototyping.

Imagine you have the Maximite case sitting in front of you, and you want to run a cable out the back to the DonDuino board. You would normally run a cable from the back of your box, to J2 of the DonDuino board.

Say you wanted to sit the DonDuino board on top of the case, you would run a cable from the back of the box to the J4 connector.

This way the text on the any shield will line up with any text on the Maximite board. That is, they are facing the same way.

You now fit R/A female connectors to the left hand edge (J3), and the right hand edge, J1.

If you want to plug the two devices together without a cable, then you plug J3 straight into the back of the Maximite. This will tip the DD board 90 degrees sideways, so the text on the DD board is now pointing horizontally, instead of vertically.

By connecting them directly together, it means they have to be at the same height, else you will strain the connectors, so you may have to snip the legs off the stacker pins. I think the cable is the best way to go, as it will be awkward even if there were no pins. You may have to fit rubber feet, spacers, under the DD board, to make them the same height.

You could use standard straight female header pins that don't have the long tails like the stacker pins, then you wouldn't need to snip them off..

The connectors J3 and J1 can be used to extend the DonDuino bus, and don't need fitting unless the user wants to use them. If gives us heaps of flexibility from this little board. in fact the user only fits what he needs, and I think that will be possibly J2, (out the back of the case), J4 (on top of the case) and use standard female to female cables to connect it all together.

Boards can still be cascaded horizontally as you now have provision to plug boards together directly or via another cable.

You can use other manufacturers boards that have been designed on the flat ribbon cable expansion principle. Just plug them out the back.

As I found by using the same principles with SimmStick, you can build castles with these things. Just plug them together like a Lego or Meccano set.

You will have plenty of points to add CRO leads, logic analyzers, or in line testers, and break out boxes.

To say nothing of the potential of using the thousands of Arduino boards that are now around.

Click on the below schematic image to enlarge to full size:

Optional Items:

J6: VIN 2 pin R/A connector (bottom left)

D1 Diode in line to VIN signal.

L1 RED LED for +5V monitor.
R1 Resistor 330 ohms.

L2 YELLOW LED for +3.3V monitor.
R2 Resistor 120 ohms.

L3 Green LED for +9V monitor.
R3 Resistor 680 ohms.



J3 Female Connector:

If you plug the J3 Female connector of The DonDuino Cross straight into the back of the Maximite, you won't be able to fit a USB cable. However if you are using the Maximite board, and The DonDuino Cross in combination with an Arduino shield for a specific microcontroller application, then you more than likely won't need a USB connection to a PC. 

Stacker Pin Legs:

Do you snip off the legs off the Stacker pins on The DonDuino Cross, or do you fit short female headers? See:

Some time in the future there will be a DonDuino PIC32 board with the Arduino bus on it, and you may want to leave the legs intact. For very keen Maxiteers, you may build one with, and one without male pins out the bottom of the board.

This project is now 7 days old.

Cheers Don…

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DonDuino Bus Converter Lookup Table.

Conversion lookup table from the Maximite 26 PIN IDC bus, to the Arduino footprint that comprises 2 by 8 pin headers, and 2 by 6 pin headers.

Several products will be appearing in the future from Dontronics based on this conversion table, so I have named them the DonDuino range.

And the Arduino foot print with the tricky .16" step routine: PCB below shows .15", but have found on the official site that it is .16"

Last paragraph:

Note that the distance between digital pins 7 and 8 is 160 mil (0.16"), not an even multiple of the 100 mil spacing of the other pins.

                                           RED                      GREEN


Mauve               Blue


Picture below Added -2011-11-19  Dimensions are correct

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TRS-80 Level II Simulator.

TRS-80 Level II Basic Lessons.


Continue reading

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Maximite EV (SMD)

All Dontronics Maximite Computer products are located at:

Dontronics Shop:

The Maximite Computer. Embedded Version.
Fully Assembled

This version has no keyboard connector, and no VGA connector. It is designed as an end product for applications developed on the Maximite Computer.

It is called the EV (embedded version)
It is just the standard circuit minus the keyboard and video footprints.
It uses a  microSD card.
(There is no 'write protect' pin on the micro SD, so this signal is just connected the the Card detect CD line).
66mm x 68mm

Note **** This price includes a 26 Pin Female to Female IDC 10cm cable:



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Maximite Users: What Country do you live in?

Maximite Users: What Country do you live in?

It would be a big task to add every country to this poll, so I have grouped it into regions.
If you are having trouble with your region, check the link below:

Link to User Forum:

Continue reading

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Maximite Control:

Maximite Control:

This covers everything that is used to control the Maximite Computer, or the PIC32 micro, and has nothing to do with any 26 pin I/O connector devices that are connected to the rear of the unit.

So it covers Keyboard, Screen, and SD card at this stage.
It may cover an on board Real Time Clock, with battery Backup, in the near future.

Continue reading

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