After a very exciting unboxing of the first ever PCBs that Jeremy and I have ever ordered, I started the task of constructing and populating the boards.
The first task was to break the tabs that we had created to avoid PCBTrain’s pricing. This proved to be really easy with a guillotine. The edges of each board were then sanded down on a belt sander to smooth out the tabs. Continue reading →
Now that we have a Twitter Arithmetic Logic Unit, we can begin the fun stuff! Although 7400 logic is a classic platform for logic circuits, there is still an air of mystery about what goes on inside those little black chips. The advantage of 7400 logic is that it’s incredibly easy to use and the variant that we’ve chosen (74HCT) is super speedy.
But don’t worry, the Twittithmetic Logic Unit (TLU) isn’t just a PCB with a few black boxes. The core aim of the TwitALU project is to make computing rhythmically audible and visually entertaining. This is where the adder module comes into its own.
Here we go everyone, as promised, a video of the prototype system working from start to finish! I can recommend viewing it in HD at full screen with a bit of volume for effect. Obviously theres still the final system to create but this is the big turning point in functionality. Let us know what you think in the comments here or on YouTube we’re interested to know what you think of the system as much as the video at this stage.
We’ve had great fun using the Raspberry Pi’s I2C bus and Port Expanders to talk to all the registers in the system and to control the ALU. It’s such an easy to use protocol – writing to 8 pins of a Port Expander is as selecting the Port Expander and sending it a byte of data.
However, Port Expanders aren’t the only I2C device around. You can find all sorts of devices like LED dimmers, LCD drivers, Data Converters (DAC/ADC), Memories, Clocks and Audio synthesisers to name just a few.