Retro!

Preamble

After watching The Gigatron TTL Computer without a Microprocessor, I got to thinking about building an Apple I (or II). After a quick search I found the Wikipedia entry for the Replica 1 (see this Apple 1 kit page), and from there the Apple II section of ReactiveMicro’s site, and the apple-ii-rev-0 board.

Then I came across loads of retro teardowns from EEVblog

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Noisey chips

Preamble

Following on from Banging noises…, I attempted to recreate the Noise Chip (U4) depicted in the LDB-1 schematic, from the article Anatomy of a drum machine. The noise chip creates both a white noise signal as well as four tuned square waves at different (unknown) frequencies. I have attempted to contact the author for more details but have not had a reply as yet.

It is using either PIC (which is likely seeing as the author states a preference for the PIC microcontrollers), or an ATtiny.  I will attempt to use a ATtiny/ATmega microcontroller (specifically ATmega48P/88P/168P/328P but the code should compile for most Arduinos).

Note that parts of this are a work in progress.

Note: The phase-correct 50% trick is possible with Timer0 on an ATtiny85, but it is not clear if it is possible with Timer1 (although Timer0 does have two channels). Atmel AVR ATtiny comparison chart

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Messrs. Schmitt, Trigger and APC (and other stories)

Preamble

Just for the hell of it, I wondered if it was possible to substitute the 555 timers in an Atari Punk Console (APC) with some other component, or components.

After seeing some Schmitt-trigger inverters (CD40106) used in oscillator circuits, see Swingers, I thought that I would come up with an alternative design.

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555 Noisemusick kit

Preamble

A friend of mine sent me details of the 555 Noisemusick kit, which, while it looks like an Atari Punk Console (APC) – see Atari Punx… – it is essentially two astable multivibrators, with the first providing a CV input to the second, and with additional IR sensors and touch pads (rather than an astable followed by a monostable, which is what the APC is).

It is also available as an iOS app, source code is available on github:Noisemusick.

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