I'm about to start work on designing the next iteration of the blocks and modules. I have some (mostly vague) plans for this redesign:

Integrate a value module into some blocks

Variables, Loops, If, Output and some other block types all require at least one value, if not a whole expression to work properly. I think it makes sense to integrate a value module into a program block, which will reduce the number of parts needed to write a program. In order to do this, I think the combined block + value will need to use a microcontroller with more free GPIOs than the ATTiny841.

I really like the '841, but to incorporate a value module I need more GPIOs than are available. I could get around this by including an I2C GPIO extender chip (such as the MCP23008) but that adds complexity and cost. It is probably best to just jump straight to a larger MCU. I'm leaning toward the ATMega328P, or even the ATMega328PB (which has two serial ports instead of one). I have samples of both, so I will do some prototypes to see which works out best...

Revisit the interconnections

Currently the blocks connect to one another using a 4-pin make and female connectors. I think this is fine for prototyping, but it might not be the best solution for a finished product. I need to do some research into other connectors to find something that is cheap and robust enough to be practical. For now I will probably stick with the connectors I am using, but I should start looking sooner rather than later.

The pinout of my connectors is also something I need to look at. The block connections I am happy with - they have VCC, Gnd, Tx, Rx. For block to module connections I have used SDA, SCL, Gnd, and VCC. Grove connectors use SCL, SDA, VCC, Gnd which is quite a different layout. I think it might make sense to standardise on the Grove connector to allow for a wider variety of add-ons.

Finally, I need to look at the value connectors. I am using a modified 6-pin connector, with pin two removed to make the connector polarised. This works, but can be a bit awkward to plug the numeric, variable and operator dongles in at times. So I need to find a better way of plugging values into a block or module.

Form factor

The form factor for the blocks and modules was decreed by the size of the original tiny breadboards I used for my first prototype and the size of the Arduino Pro Mini modules I was using to control the blocks. Now I am using bare chips instead of pre-built devices, I can resize the blocks and modules.

However, I do find the size quite pleasing so far. 30x50mm for the blocks seems like a nice size. The blocks are not too big and not too small for my clumsy hands to manipulate. The variable and value dongles on the other hand are a bit small. 8^/

These blocks and modules will eventually be housed in cases of some description. I would like the cases to be colourful and sturdy, with different functions have a specific colour and shape to allow for quick and easy identification. Smaller PCBs can fit in large cases without problems, but large PCBs limit the smallest size the case can be. I think making the PCBs larger just for sake of making them larger might be a mistake.

The case layout and design may actually inform the layout of the PCBs to an extent. The placement of the connectors, LEDs and value connections all need to be consistent and work with the eventual case design. I should consider mocking up some cases just to get a feel for what I might be working with here.

What else should I consider when designing the next rev?