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The clones are coming. . . The AlternatIVe Maximite M aximite World The Maximite world is growing. As we mentioned last month in our miniMaximite story, the Maximite has been cloned a number of times, so now there is a range of alternatives for you to choose from. To help you in this choice we gathered a number of these to test along with some expansion boards that might help you connect the Maximite to the rest of the world. W e start with the DuinoMite. It is a Maximite clone manufactured in Bulgaria by Olimex and sold in Australia by Dontronics. The idea was to make a Maximite-compatible computer that is also compatible with the Arduino connector format – quite a tall order. Olimex has managed to make it work, albeit with a number of compromises. The DuinoMite is actually a range of three boards consisting of a mini, standard and mega version with every option that you can think of. When we first saw them we mentally dubbed them baby bear, mother bear and father bear (of Goldilocks fame). The samples we reviewed were pre-production but we understand that the final products will be quite similar. The Maximite should be familiar to most SILICON CHIP readers but perhaps not the Arduino standard. The Arduino is a small single-board computer developed in Italy. It is generally based on an 8‑bit Atmel AVR microcontroller and is an open design that others can easily modify if they wish. The two standout features of the Arduino are an easyto-use development environment (based on the C language) and a universal connector that allows the board to be connected to a variety of interchangeable add-on modules. In Arduino-speak these are known as “shields”. siliconchip.com.au By Geoff Graham The success of the Arduino has caused an explosion in the number of available add-on shields. You can now purchase a shield with almost any function you care to imagine including networking, GPS, wireless, music and more. The DuinoMite range from Olimex seeks to capitalise on this wealth of products by providing the Maximite with an Arduino-compatible connector. All the boards in the range also implement a UEXT connector. UEXT is another standard for connecting pre-built, add-on boards. This standard was invented by Olimex who understandably have the widest range including an I/O board with relays, GPS, LCD, Ethernet and wireless networking. However, you do need to be careful when selecting a UEXT board as some require special software. For example, the WiFi board requires you to implement the TCP/IP protocol stack in software and that is simply not possible in MMBasic. These comments apply to the Arduino shields as well. This is because some of them require the Arduino development environment (based on the C programming language) to make them work. Also, many shields come with a demonstration program (again written in C) but that is not much help with the DuinoMite range which is programmed in MMBasic, the same as the Maximite. December 2011  61 DuinoMite-Mini The DuinoMite-Mini is the “baby bear” of the three and it is definitely diminutive at just 65mm x 75mm. The board is studded with connectors on all four sides and covered in small SMD components. It would be virtually impossible to hand-solder such a board, so it is fortunate that it comes fully assembled and tested as do all the boards in the range. This board is possibly the closest to the Maximite in its facilities. It has a VGA and keyboard connector, 26-pin external I/O connector, USB and an SD card socket. The last two are the miniature versions and for most people this means that they will have to purchase a micro SD card. These are cheap enough, so that is not a problem. The DuinoMite‑Mini does not have an Arduino-compatible connector but you can purchase the DuinoMite‑shield which adds this feature. Dontronics also have a number of other Maximite/Arduino conversion boards in their catalog which achieve the same purpose but come in a kit. Presumably any of these can also be used to add Arduino compatibility to the standard Maximite as well. One thing to watch out for when using the DuinoMite‑Mini is that its power must come from a 5V regulated power pack. Don’t use the more common unregulated type as the high unloaded voltage from these will overheat the onboard voltage regulator and may cause damage. Perhaps the greatest feature of the DuinoMite‑Mini is its price: fully assembled and tested for just over AU$40, including GST and delivery within Australia. It represents amazing value, especially when compared to the alternative Maximite kit of parts at almost $90 (to be fair, this does include a case). The DuinoMite range is certainly feature-packed. In addition to the Arduino and UEXT connectors, some models include battery backup (with an integrated battery charger), a realtime clock, RS-232 interface, CAN interface and proper connectors for sound and composite video. The actual features on offer vary from model to model so check the separate panels for details. To fit the additional features into the DuinoMite, the designers were forced to make a number of compromises compared to the Maximite. The first is that the DuinoMite will require a custom version of MMBasic with its own bootloader and serial port driver. This is not so bad as the MMBasic language is open source and can be modified by anyone (subject to conditions) but it does mean that this version will lag behind the “official” releases and is dependent on the supplier integrating their unique features into each new release. A more significant compromise in the design of these boards is that the signals on the I/O connectors share functions with many other areas of the board. For example, Maximite I/O pins 8, 9 and 10 (Arduino D11, D12 and D13) are also used to communicate with the SD card so they are unavailable if you plan to use the SD card for storage. Presumably Olimex will add commands to MMBasic to switch between 62  Silicon Chip the two uses for these pins but that does not help if you wish to simultaneously use the SD card and all of the I/O pins. Another example is Maximite pin 20 (Arduino D9) which is also used as the VGA vertical sync and to drive the yellow LED. This sharing means that this I/O pin will not available if you are planning to use the VGA output and by being connected to the LED, it means that it will be difficult to use that pin for other functions anyway. We counted nine I/O pins that are compromised in some way. This means that depending on how you intend to use the I/O pins and your technical expertise in getting around these complications, the DuinoMite will have much less than the normal twenty I/O pins to work with. In addition to this, the functions of the I/O pins have been mixed around from the Maximite standard. For example, pin 8 should be capable of measuring voltage but in the DuinoMite it cannot. However, you do get another counting input. The overall effect is that you will need to do a lot of research before you can use the I/O connectors in a project and if you change your mind (for example, to use the VGA display) your design and program might also have to change. You are also in a world of your own that is different from other Maximite users and you will not be able to easily exchange programs that use the I/O connectors. For users planning to use the Arduino connector, this mixup might be a little easier as the SD card signals on D11, D12 and D13 match the common use for these pins (SPI interface). However, you will still lose the use of the SD card and have difficulties with some of the other I/O pins. The main complication here is that many Arduino shields rely on special software modules written in C and they will not run on the DuinoMite. Because of the unusual features of the I/O connectors, the quality of the documentation supplied by the manufacturer will be paramount. Tracing the circuit diagrams is difficult and understanding the interactions with other parts of the DuinoMite is near impossible so a clear explanation will be a life saver. Great value The DuinoMite range is not a replacement for the Maximite. By design it is a different product with its own set of strengths and weaknesses. It is similar to the Maximite in some ways and different in many others The Mini version would make an excellent purchase if you were looking for a basic Maximite-like computer and did not want to do much with the . . . continued on P64 siliconchip.com.au DuinoMite (Standard) The DuinoMite (standard version) is the middle version of the three boards and is more orientated towards providing Arduino compatibility. Along with an Arduino connector it has a Maximite style 26 pin I/O connector and a 10-pin expansion connector. The board does not have VGA or keyboard connectors but you can add these using the DuinoMite-IO board which plugs into the 10-pin expansion connector. This expansion board provides connectors for VGA, composite video, sound (both RCA and 3.5mm socket) and a PS2 keyboard. Along with the others in the range this version has a UEXT connector, mini USB connector and a micro SD card socket. The power supply on this board is much more sophisticated. It will accept an external input of 9 to 30V and it uses a switching voltage regulator integrated onto the board to supply the lower voltages required without generating excessive heat. Switching between the power sources (external, USB etc) is automatic, so you can say goodbye to messing about with jumpers. As a bonus this board includes a charger for a Lithium Polymer battery and it will automatically switch to that on power failure. This means that adding battery backup to the DuinoMite simply involves plugging in a battery pack. You cannot get it much easier than that. The DuinoMite is priced the same as the DuinoMite-Mini but don’t forget that you will need to buy the expansion board if you want access to the video and keyboard interfaces. DuinoMite-Mega This is the “daddy bear” of the range. It does not attempt to keep a small footprint and it offers a veritable feast of features including all the attributes of the previous two boards. You have connectors for VGA and composite video, keyboard, sound (RCA and 3.5mm), Maximite-style I/O, Arduinostyle I/O, USB, micro SD card and two UEXT connectors. The DuinoMite-Mega adds a couple more features including a CAN networking connector and RS232 driver and connector. MMBasic already supports the serial protocol used by RS232 so that feature should work out of the box. However the CAN protocol is currently not supported and for this feature to be of use the manufacturer will need to add support for MMBasic. Olimex will sell you a laser-cut box for the DuinoMite-Mega so you can package it in a case to protect it and make it look more like a real computer. This is useful as it allows you to move it around and treat it like a normal gadget without fear of causing an accidental short on the PCB. All boards in the range (including the maxi version) have a 32,768Hz crystal connected to the PIC32 processor. This can be used to keep accurate time when the PIC32 chip is in one of its low power sleep modes. This feature does not have a battery backup so it will require an external Lithium Polymer battery (as described above) and modifications to MMBasic to be of any use. The value of this and other features will depend on the sensible integration of them into MMBasic and this is where we will have to wait and see – our pre-production samples were running a preliminary implementation of MMBasic which did not support these features. siliconchip.com.au December 2011  63 The standard DuinoMite does not have connections for video and keyboard. This accessory board provides both VGA and composite connectors along with sound and PS/2 compatible keyboard. I/O connectors. You can connect it to a VGA display, keyboard and power supply and be up and running with MMBasic straight away. For the price it is unbeatable in this role. To use these boards for more than this you will need to be technically orientated and prepared to dig through the circuit diagrams and technical details to put it to good use. If you do this you will find a powerful and versatile computer board with many handy features. We were impressed with the DuinoMite range. They are well made, offer exceptional value and they provide a host of additional features. But if you are a typical user who wants to build their own computer and experiment with programming in BASIC, don’t forget the standard Maximite. It is well documented and supported and it just works with far less complications. By the time you read this the DuinoMite range should be available for purchase from http://dontronics. com and other online shops. The manufacturer’s website is at www. olimex.com The UBW32 There are times where you will need a lot of external I/O pins, for example, building an automated centipede demonstration! Seriously, there are times where you will need more than 20 pins and also, perhaps, where you want a simple plug-in module like the mini Maximite described last month but you do not wish to build your own. For this reason we have created a version of MMBasic to run on the UBW32 64  Silicon Chip experimenter’s board. Running on this board MMBasic can control no less than fifty I/O pins. That is a lot and should satisfy almost any I/O hungry application. The UBW32 itself is a small, fully assembled and tested board which uses the 100-pin version of the PIC32 chip. At just 3cm wide and 11cm long it is more like a large IC than a computer board. You would normally solder header pins along the edges to make it into a general purpose plug-in module which can be used on a breadboard or motherboard. The main communication with the UBW32 is via a mini USB connector mounted on the board. Using this you can load firmware and interact with the running program. Other than this there are just a few components on the board – the PIC32, a couple of voltage regulators, some LEDs and three push buttons. The UBW32 makes a reasonably cost-effective embedded controller which is ideal for adding intelligence to your own creation, similar to the mini Maximite described last month. The version of MMBasic that we created for the UBW32 runs on the latest version of the board which is equipped with the PIC32MX795F512L chip. This chip has 128KB of RAM and speeds along at 80MHz, just like the chip used in the Maximite. The only difference is that it has 100 pins. The UBW32 is a small experimenters’ board with almost every pin of the 100-pin PIC32 chip available along its edges. Combined with MMBasic it makes a powerful embedded controller. Other than supporting the large number of I/O pins the UBW32 version of MMBasic is the same as the standard MMBasic running on the Maximite. You have the internal flash drive A:, the ability to attach a video monitor, keyboard, SD card and so on. We even wrote a full user manual describing how to use the UBW32 with MMBasic and that, along with the firmware can be downloaded from the SILICON CHIP website or the author’s website at http://geoffg.net/ ubw32.html You load MMBasic onto the UBW32 using the standard UBW32 bootloader which is provided by its creator - so you do not need a programmer or anything special. Then, when you cycle the power, it will start up running MMBasic, just like the Maximite. The UBW32 costs less than $50 and you can purchase it from http://dontronics.com and other on line shops. The developer has his own website where you can download the bootloader and other support material: www. schmalzhaus.com/UBW32 Updates to MMBasic for the UBW32 will be released at the same time as Maximite updates and can be downloaded from http://geoffg.net/ubw32.html Hamfield expansion boards Hamfield are a small company who were quick to realise the potential of the Maximite when it was introduced and have since built up a good range of expansion boards designed to plug into the Maximite’s 26 pin I/O connector. Their current range consists of seven boards which provide features such as isolation and input protection, output buffering and RS-232 outputs. A particularly neat product is one that provides a serial to Ethernet capability which, amongst other things, will siliconchip.com.au The Hamfield Prototyping Board makes it easy to test out circuits that can interface to the Maximite. The solderless breadboard allows you to assemble a small circuit and the built-in power supplies mean that you will not overload the Maximite. allow your Maximite to send emails. We reviewed three products – a prototyping board, a dual RS-232 interface board and a modular hub. These are supplied as a kit of parts for you to assemble. Commendably Hamfield will also sell you the bare board if you prefer, few suppliers will do that. The quality of the kits is excellent, the components are of high quality and are through-hole mounting, so the kits should go together easily in under an hour. Some documentation is included with the kit and they even provide a CD with high resolution circuit diagrams and other information. About the only issue is that due to a mix up in the early days of the Maximite the Hamfield 26-pin I/O connectors are reversed compared to that used on the Maximite. Their recommended solution is to unsolder the connector on the Maximite and replace it with a different one. This is something we definitely do not recommend as you will almost certainly damage the PCB while doing this. A much better solution is to make up an interconnecting cable that is reversed at one end. It has been over six months since this issue was discovered but Hamfield are still designing new boards with an incompatible connector. Their documentation includes a one page defence of this action but it ignores the plight of the user. It would much better if the boards were simply designed to match an unmodified Maximite or were supplied with a cable that corrected the issue. Prototyping board The Hamfield prototyping board is intended to help the user experiment with small circuits attached to the Maximite. It has three power supplies (12V, 5V and 3.3V) and a solderless breadboard with 30 rows capable of taking four 66  Silicon Chip the board there is no reason (other than cost) why you could not use that as the final circuit. The Prototyping Board costs $40 and is available from www.hamfield. com.au Dual RS-232 board 16-pin dual in line integrated circuits. The three power supplies are derived from an external 15V power supply. Each regulator has a substantial heatsink so you could use them to power devices such as relays and solenoids. This is preferable to using the Maximite’s internal power supply which has a limited capability. All 26 pins from the Maximite I/O are brought out onto a pin strip and can then be connected to the breadboard using standard jumpers, some of which are included in the kit. This arrangement allows you to quickly assemble and test a small circuit. When you have your circuit working it would be easy to transfer it to a PCB or prototyping stripboard and then use the prototyping board for something else. Due to the solid construction of This board takes the Maximite’s two serial interfaces and adds two RS-232 driver chips and DB9 female connectors. The Maximite’s serial output is at the TTL voltage level (0 to 3V) which is fine for talking to other chips or board mounted modules but for communicating with devices such as a printer or desktop computer the signal levels must be inverted and at a much higher voltage. This is what the Dual RS-232 Board does. It has a driver chip for each serial interface that inverts the signal and generates the required voltage levels (±12V) to match the RS-232 standard. A normal DB9 connector then enables you to connect to the external device. Jumpers allow you to select the power source (external or Maximite) and which signals are used. The board also includes LEDs for each signal line, which is handy as sorting out RS-232 communication problems can be a frustrating experience. A second 26 pin I/O connector allows you to daisy chain this board with another (for example the Prototyping Board). Other than dealing with the unfortunate problem of the incompatible I/O connectors the Dual RS-232 Board is easy to use and does its job without fuss. It costs $45 and is also available from www.hamfield.com.au This Dual RS-232 board makes it easy to use the Maximite serial interfaces with equipment that requires signals levels specified by the RS-232 standard. This board includes the drivers and the connectors that enable you to to connect the Maximite many devices including other computers, test equipment or a printer. siliconchip.com.au What Are Readers Using the Maximite For? In the months since the Maximite kit has become available many experimenters have been busy putting it to work and we thought that readers might take inspiration from some of these projects. In-car status display The photograph below was provided by John Gerrard who uses the Maximite to generate a status display for his car. The display panel was originally used with an in-car PC but with a press of a button, John can switch to the Maximite video output and check temperatures, pressures and more. Lest you are concerned, the manifold temperature is not correct – the sensor was not installed when this photo was taken. Other interesting projects Other Maximite projects that people have in progress include using it to control a Rohde and Schwartz ESMC communications receiver, a wind/solar power controller with data logging, a data logger recording the parameters of a Plasmatronics PL20 solar regulator and a super accurate GPS clock with LCD display and alarm outputs. And they are just the applications we’ve heard about – given the volume of sales, there are bount to be plenty more! Family affair: not one but three Maximites! When Leo Simpson and Ross Tester visited Mater Maria College recently, they were not overly surprised to find one of the year nine students, Alex, with a completed (and operational) Maximite. But they were somewhat taken aback when he told them that this was the second Maximite he had built – “the other one is at home controlling and monitoring things in the house”. He then went on to tell them that his year-eight sister had also successfully built her own Maximite, mainly because “she was always wanting to use mine, right when it was in the middle of doing things!” Maximite in Estonia This photograph was provided by SILICON CHIP reader John Gerrard, who uses the Maximite to generate a status display for his car, showing important temperatures and pressures. Boiler and heater control Peter Caffall-Davis of Hyder in Alaska has a project underway to use the Maximite to control his boiler and heating system. The system includes a state of the art wood fired boiler that uses forced air for complete combustion; the system is so efficient that it even burns the smoke from the wood! The hot water from the boiler is circulated to a radiator and a fan takes that heat and distributes it inside the house. Pete will use the Maximite to monitor the temperatures in the boiler’s water jacket and inside the house. Based on these readings his program will control the blowers, water circulation pumps and fans. Amongst other things this project gives readers from the hotter parts of our world an idea of the effort that goes into keeping comfortable in Alaska. If you want to see where Pete lives type 55°55’N 130°1’40”W into Google Earth and then tilt the view until you can see the horizon then rotate horizontally. The scenery is stunning. siliconchip.com.au The photo below shows what must be the smallest Maximite in the world. It was built by Antti Lukats in Estonia and is based on the CRUVI concept which includes a range of bolt on input/output modules which can connect to the legs of the Maximite. Don’t look too closely at the photograph as it is an early prototype but Antti is planning to start production of a more polished version soon. Unfortunately for the rest of us it will only be available in Estonia (initially anyway). Along with the rest of the CRUVI range the Maximite version will be used in nearly all Estonian schools to teach electronics and computer technology. The concept has also been entered in the country’s national Brainhunt competition and Antti is confident of winning a prize. You can see the CRUVI version of the Maximite in action on YouTube running a Morse code program written by Reg Gauci in Australia. Point your browser to: www. youtube.com/user/JukuJaJuhan#p/a/u/1/LUMnO5p-fjg It is tiny! SC December 2011  67