Category Archives: Module

More Arrivals

Today, I’ve had an eventful day – not only have I received my small, test order from RS Components, I have also received the Nixie tubes and power supply boards. We chose to order 16 Nixie tubes – five for each 8-bit input register and six for the output register. Separate flyback boost converters are needed for the Nixie tubes as they operate at 120V which we are unable to supply directly.

I have yet to power up the tubes, but I’ll be sure to post some pictures when I do – they should give the TwitALU that vintage feel that we’ve been after. Continue reading


Here Come the Relays – Clickety Clickety Click…

1-Bit Relay Adder

1-Bit Relay Adder

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.

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SmartNixie Vacuum Tubes!

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.

SmartNixie IN12. Credit:

SmartNixie IN12. Credit:

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.

Monochrome 128x32 I2C OLED graphic display. Credit:

128×32 I2C OLED graphic display. Credit:

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The Beginning!

Welcome to the blog! This blog will be acting as a part project log – part project blog to document a project that aims to…

Design and construct a replica of the ALU found within the MOS Technology 6502 processor and interface it with the micro blogging service Twitter, allowing commands to be sent to it for arbitrary calculations and logical functions to be performed.

As the quote from the project specification says, the core goal is to internet connect the ALU from what is now an old but arguably very important processor in history that is still being used today. This will allow instructions that can be issued to either be as simple as integer additions, subtraction, multiplications and divisions or as complicated as we have time to allow the system to handle, with one of the eventual goals being to allow the (quite slow) execution of 6502 assembly instructions.

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