Following on from the last in this mini series, the giant 16 byte multiplexer is finished and tested – lots of head scratching due to shorts and wonky solder joints (it’s amazing how sensitive CMOS logic is, interference on accidental free pins causes strange effects) and I’ve replaced the breadboard with a new interface board between the Pi and the multiplexer.
Now it’s time to think more about the ‘front end’ – here are some prototype programming blocks made from the ‘holes’ from a hole saw (I’m chopping up bits of driftwood). These include a central drill hole, which we can use for an indicator LED.
This is the minimal circuitry needed for each programming block – it’s just a 4 bit identification code (reconfigurable via jumpers) and the LED, mounted around the 7 pin VGA style plug.
Here it’s mounted in the block after a bit of hollowing out. To be fully kid-proof I’ll probably eventually set the internals in epoxy glue.
Testing the plug/socket wiring on the breadboard. The plan is to paint the top surface of the programming block in blackboard paint so different instructions and languages can be tested and built with the same blocks. It also intriguingly makes abstraction possible, which is usually a problem with non-text based approaches, but this needs more thinking about.
Here it is with another unenclosed block attached to the main board, and via the new interface to the Raspberry Pi. The interface will need a bit more circuitry to drive the LEDs – which will be able to be lit in different ways depending on the needs of the language, perhaps sequential in some cases, more dependant on logic in others. Also, different shaped blocks or different coloured LEDs may have different meanings in a language too.