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Forum Index : Microcontroller and PC projects : Compact PCB for the uMite 28
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MicroBlocks Guru  Joined: 12/05/2012 Location: ThailandPosts: 2209 |
It is time to introduce the first module in a new series of modules that will make building projects more easy. The main idea is to have a module that can be used as part of a prototyping and development system and can be used in the final project. The concept is to have modules that are intelligent and do one thing very well. I have been waiting for the right moment to get this started and the Micromite made this possible as it exceeded my expectations early on. During the beta test it became clear that this is the right mix between simplicity and capabilities. Geoff did a fantastic job! I run a MakerSpace and i often see that people have trouble getting things done on an Arduino platform. The language being the biggest barrier, and the whole edit/compile/upload/test cycle is a big nuisance. I am sure that the MicroMite with its Basic Interpreter will be much easier to use and develop on by beginners and experienced people alike. This Saturday and Sunday we have a free workshop to introduce people to the MicroMite and our MakerSpace facebook page got 18000 hits when normally we have a few hundred at most. So there seems to be interest. :) Ok, enugh talk, this is what it looks like (47x37.5mm): 
It has four mounting holes for 3mm spacers/bolts to ensure a good rigid mount. It supports the 32MX1x0 and 32MX2x0 series of microcontrollers. In the case of 32MX1x0 chips the USB can be used as a power supply, with the 32MX2x0 series you have the choice to connect the USB directly to the microcontroller. This allows other uses then the MicroMite making the pcb more generic and versatile. It also has optional an crystal for when you need an accurate timebase (USB). On the top and bottom there are connectors to supply the module with power, a jumper can select between USB and an external +5v supply. All the connectors are on a 0.1" grid. The mounting holes are spaced 40mm and 30.5mm. On the left are several I/O pins and they all support PWM. This means you can have for instance five servos all connected on the left side. Also a power connection. On the bottom left there is a standard 6 pin ICSP connector allowing you to program the chip with a PicKit3 or other programming device. On the right there is the BUS. Here in more detail: 
This bus supports 2xSerial, 2xI2C, 2x SPI, 4 General purpose IO and has pins for +5v, 3.3v, GND and reset. The layout is chosen so that you can minimize the number of pins you need. For instance if you need only a serial port you can choose between the five top left pins (1,3,5,7,9,11) or the bottom five pins (26,24,22,20,18,16). The left side is 5v or 5v tolerant, the right side is 3.3v. When you look close you can see this layout is very symmetrical. The left is repeated on the right with a 180 degree turn. The same for the top half, it can be turned 180 degrees and you get the same pinout as the bottom half. This design allows for other modules to just use the left, the top, only half of the top etc. Just the pins that the specific module uses. That will allow modules to be small and use only pins and pcb space that is needed and nothing more. The idea behind this bus is that modules can be plugged into a backplane (think eurocard, s100 bus style but then much smaller), or modules can be connected through a strip board with a few connectors, allowing for rapid connections without wires. You can even choose to stack the boards on top of each other, or even at 90 degree angles if 90 degree connectors are used. You are free to choose which ones suit you best. If you like to use this together with a breadboard using all male or all female connectors is best. You can then use this module by placing it right next to the breadboard leaving the breadboard 100% available for your parts. A MCP2200 USB to UART module is being finalized right now and it will connect directly to the pins on the bottom. Alternatively you can use your own USB-Uart module. The choice to not have a MCP2200 on the board is that we like to keep the modules as compact and simple as possible. This will allow you to only use what you need. There are many circumstance where a USB-UART is unnecessary and placing one on this board would prevent you from ding that. Different carrier boards are in development. For example a UEXT board with six connectors, a Maximite compatible connector. A board that has room for 4 modules and one for eight modules. More will be developed over time once we get some feedback. And to be complete here is the schematic: Schematics PDF. The schematic is open source, the boards will be closed source to prevent outright copies. You are free to use the schematic and make your own boards of course. I would appreciate your thoughts about this board and suggestions are welcome. An order for a few boards will be made on Monday and by the time the boards arrive we will have all the parts in stock to have a final test. I hope this board will add another choice for you to consider. Thanks for reading! Microblocks. Build with logic. |
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panky Guru Joined: 02/10/2012 Location: AustraliaPosts: 1101 |
Wonderfull concept and implimentation TZ - put me down for a few when available(both bare boards and assembled modules). Well done, Doug. ... almost all of the Maximites, the MicromMites, the MM Extremes, the ArmMites, the PicoMite and loving it! |
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| WhiteWizzard Guru Joined: 05/04/2013 Location: United KingdomPosts: 2817 |
Great stuff TZA. Like Panky says, a wonderful implementation and I really like the connector layout. I would be interested in a few PCBs. Do you know roughly how much they could be per piece? And what shipping costs to UK. And the important question is how long before you think you're in a position to ship? Once again, well done! 
WW For everything Micromite visit micromite.org Direct Email: whitewizzard@micromite.o |
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Grogster Admin Group  Joined: 31/12/2012 Location: New ZealandPosts: 9308 |
Looks great - good luck. 18,000 interested people is very exciting numbers. Smoke makes things work. When the smoke gets out, it stops! |
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Lou Senior Member  Joined: 01/02/2014 Location: United StatesPosts: 229 |
TZA, The board looks great, very compact - looks like another winner. Am I missing something or is your oscillator circuit on the USB chip all grounded ?? Lou Microcontrollers - the other white meat |
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| paceman Guru Joined: 07/10/2011 Location: AustraliaPosts: 1329 |
Yes it looks a very versatile implementation TZ - congratulations. Between your 28 pin SOIC module/system, WWiz's 44 pin module and Mick's 28 pin DIP module we're looking pretty well covered. I like the way your schematic has been done too, I'll bet that took a few iterations. Comments: how about a quick explanation of the colour scheme on the boards above - it's not obvious to me. Greg |
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bigmik Guru Joined: 20/06/2011 Location: AustraliaPosts: 2914 |
TZ, Looks like an object of sheer beauty.. Very good work Regards, Mick PS. My PCBs are in customs in Melbourne at the moment (7 days since my order was placed). mik Mick's uMite Stuff can be found >>> HERE (Kindly hosted by Dontronics) <<< |
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| MicroBlocks Guru Joined: 12/05/2012 Location: ThailandPosts: 2209 |
@All: Thanks for the kind words. This has been a great learning experience. I use Diptrace for the schematics and pcb layout and i am now reasonably quick with it. @Panky: Doug, Thank you for interest. I will let you know when i have the boards available. @WW: Phil, The connector is the result of first idea, improve on it, let it rest for a while, then rethink it completely and then some iterations to get it 'right'. It is always a compromise, and i really had to think hard which signals are available on most mcu's and what is most useful to have on a bus. I am pretty happy with the current layout and find it easy to design modules that use the bus. I will probably use itead and put two designs next to each other (this pcb and the mcp2200 board) for a first limited run. Then get everything populated and tested before a larger order will be made. @Grogster: Those were views, i am curious how many will keep following it. But the first indication is that the McroMite has appeal. @Lou: Lou the crystals are directly connected to the pins of the mcu and each pin has a capacitor to ground. I agree it is not clear in the schematics. I will try to find a way to fix that. If you look carefully at the PCB you can see how the connections are. @Paceman: Greg, Yes that schematic took a while. I like to organize it in 'blocks' and easily see the connections between those 'blocks'. Best is when you can draw 'wires' between those blocks as looking all over a schematic to find the labels is not ideal. Using labels and wires is again a compromise and finding the right balance is not easy. Those 'blocks' were moved around often to make it as easy to follow as possible. Currently the colour scheme on the schematic and on the PCB do not match. Has to do with readability and i just forget to match them. :) Will do that soon. The colors you see on the PCB layout are added by hand in paint. They correspond with the colors on the BUS. It makes it more clear were certain signals are. In Diptrace pcb layout i use colored nets. A real handy feature. Only there is no back annotation for net colors yet, hence the differences with the schematic. @Bigmik, Thanks! Making it 'beautiful' is for me the extra step that i enjoy doing. Still some silkscreen markings can be better and more aesthetic. For now i want to boards to go out so that i can solder some and vigorously test them. Good that you get you boards soon. It is always special to see and feel something that was only on a computer screen before. I will keep you all updated on how it goes and will soon post some more modules like an usb-uart and i2c lcd (Thanks MOBI! for the firmware and testing). Microblocks. Build with logic. |
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