This is a flexible, compact and beautiful modular prototyping framework

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I think that many readers, in one way or another, have used microcontroller-based debug boards to prototype devices under development and to start debugging embedded software at a stage when a full-fledged device board is not yet ready. You can connect all the necessary peripherals to such boards with wires and start developing the firmware. But often such debug stands are terribly inconvenient, they take up a lot of space on the table, they are flimsy and not so easy to move from place to place, and the connections between the boards are unreliable.

In this project, I'm trying to solve these problems by developing my own flexible, compact and beautiful modular desktop prototyping framework.

Modules design

I have always wanted to use small modules. As much as possible and reasonable in terms of placing the components of a complete functional assembly on them. Ideally 50x50mm or even smaller.

The electrical connections between the modules must be reliable, the modules must be securely fastened together so that the structure does not fall apart from another careless movement at the table and the contacts should not fail.
As a result, I came to this format of the printed circuit board of the module.

Expanding the assembly vertically is, of course, good. But expansion in the horizontal plane is still necessary, otherwise, with a large number of modules, we will get a narrow and unstable rack of modules. Horizontal expansion is also possible using hub boards. Those. in one of the tiers, a larger hub board is placed, which is a multiple of the module dimensions (for example, 2x1, 1x2, 2x2, 3x2, etc.). It has all the same inter-module connectors at the top and bottom and mounting holes as conventional modules. Such hubs allow you to parallelize modules from several racks and connect them mechanically.

The obvious disadvantages of this solution are: the hub board consumes 1 tier in the assembly, and the mechanical connection between the racks is much lower than in one rack without hubs.


  • For inter-module connection, 2 connectors 2x10 with a pitch of 2.54 mm are used. Surface mount connectors. Mothers above, fathers below.
  • Inter-module connectors determine the distance between the boards of two adjacent tiers - 12 mm. Brass stands of this height are common and inexpensive. Stands are optional, though, because the inter-module connectors hold the modules together quite well.
  • Module board size - 40x40 mm. The corners of the board are rounded with a radius of 6 mm, which allows you to make a similar rounding in
  • Connectors for external connections, as well as means of control and indication can be output from the front or rear (the sides are covered with intermodule connectors).
  • The distance between the pins of the two inter-module connectors is a multiple of 2.54 mm pitch, so the bottom module can be inserted into an arbitrary size breadboard and soldered there. Or solder 2-row connectors on the breadboard and insert the bottom module into them. This allows you to neatly expand the assembly of modules using standard breadboards:

Modules placement in the case

Connectors for external connections are located with a 2 mm protrusion beyond the board. This is necessary so that the connectors of the device are not recessed into the case and do not stick out of it. A case with a wall of 1.6 mm can be printed on a 3D printer, the remaining 0.4 mm is the gap between the board and the wall of the case.

Brass stands used for fastening the modules to each other can also be used to fasten the assembly of modules in the case. The M3 screw can be used to fasten the module rack to the chassis. Another option is to use M3 injection nuts:

then the first level module is applied, the first level stands are screwed in, the second level module is applied, etc. In a cut it looks like this:

Pinout of intermodule connectors

The task of choosing the pinout of a common bus in a modular design is very non-trivial. If you forget to distribute some important signals among the pins, then in the future you will either have to put up with it, or redesign some of the modules (or even everything!).

But let's take it step by step...

Inter-module connectors are located symmetrically and mechanically nothing prevents connecting the next module by turning it 180 degrees. This, in my opinion, is more bad than good. I've tried using this feature when designing modules, but it's confusing most of the time.

However, if connected incorrectly, nothing should definitely burn out. Therefore, the pins responsible for supplying power are located so that, in any orientation of the module, power is supplied correctly.

Also, as you can see from...

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Schematic for the RTC_PCF8563 module board

Adobe Portable Document Format - 76.52 kB - 02/06/2023 at 20:05



Schematic for the PSU_DC module board

Adobe Portable Document Format - 78.81 kB - 02/06/2023 at 20:05



Schematic for the ETH_W5500 module board

Adobe Portable Document Format - 127.42 kB - 02/06/2023 at 20:05



Schematic for the PSU_AC module board

Adobe Portable Document Format - 67.84 kB - 02/06/2023 at 20:05



Schematic for the CPU_ESP32S3 module board (based on ESP32-S3-WROOM-1)

Adobe Portable Document Format - 122.57 kB - 02/06/2023 at 20:02


  • next.module: CPU modules

    Ruslan2 days ago 3 comments

    next.module CPU modules*

    * All specifications are preliminary

  • New hardware revision!

    Ruslan5 days ago 0 comments

    The new hardware revision is nearly ready for the production of prototypes!

    There were many sleepless nights and now I am approaching the order of the first prototypes.

    Module specification:

    • A module is a 42x42 mm square PCB with rounded corners
    • Modules can be stacked in a rack and racks can be combined with HUB PCBs (more on those in one of our upcoming posts)
    • Inter-module connections provide two 2 x 10-pin connectors. The connectors are all-through, with the top connector being female and the bottom connector being male
    • The spacing between the pins of each module connector and the pins of the adjacent modules is equal to a multiple of 2.54 mm (100 mils) for compatibility with common breadboards.

    And, by the way, the project is now called next.module

View all 2 project logs

Enjoy this project?



Samuk wrote 09/05/2023 at 23:45 point

For my part I'm currently interested in the v7 version of the Mikroe system:*=7th-generation,7th-generation

I might do an adaptor so the Micromod cards can drop into them.

  Are you sure? yes | no

VASILIS VORRIAS wrote 09/03/2023 at 10:25 point

Hi ,Ruslan  

I found this space after a Samuk made a post in my Git-lab space  by pointing out your project

Excellent idea.

I used this ESP32 pin out on our M10CUBE sensor module some years ago.

Here is what we came up after years of experience in Automation Industry

We believe that this footprint is the golden rule in dimension

Your idea is fine and applicable but I believe M10CUBE drive project building to another level.

These are  (among others):

- Raspberry Pi bus

- 90X90 mm real estate for embedding a lot of sensors and other stuff.

- 100x100 mm Final box outside dimensions  (That is very convenient volume). DIN RAIL or wall mounted. Some models already build.

- Stuck-able or freestanding using 40 pin flat cable (find it everywhere left from old IDE HD)

- Robust platform to build Industrial IOT prototypes but at the same time to be a production module ready as well

- Already working many Industrial I/Os . A lot is comming on (BLE mesh, CM4 board, LTE-M, NB-IOT, DECT NR+ and more...)

Can you join us on a similar idea? You have skills we believe will give M10CUBE project a boost and every body can benefit..

We need fresh ides to drive it sky high.

Thank you


  Are you sure? yes | no

Ruslan wrote 09/15/2023 at 19:58 point

Hi, Vasilis. Sorry for late answer

Thank you for your interest!

It's amazing how similar ideas are born in different people's heads)
I liked your project. I don’t know yet what could be improved, but I will follow it and participate whenever possible

  Are you sure? yes | no

nigel wrote 06/07/2023 at 11:28 point

This is very interesting. It reminds me of Digilent PMods with a lot more options.

  Are you sure? yes | no

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