forked from otomatalabs/ol_site
33 lines
1.8 KiB
Markdown
33 lines
1.8 KiB
Markdown
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---js
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const title = "Aerations - Hacking Furnace to do stuff";
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const description = "Some ramblings about timers";
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const date = "2025-09-17";
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const tags = ["atari st", "timer fx", "timers", "demoscene"];
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const draft = true;
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---
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[comment]: # (god the depresso is getting to me i'm going to write something to soothe the nerves, but well this is a hidden comment you're not supposed to see this in the final post - 09/17/2025 @ 8:57 pm)
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back in July this year, we released "Aerations" at the Sommarhack 2025 demoparty. with it, we
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demonstrated the ability to compose Atari ST music, with classic timer effects like PWM and
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SyncBuzzer, and the ability to export it under a format usable on real hardware (thanks Natt!)
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developing the tech required for it was a real pain in the arse... it turns out that the ST is
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janky, and therefore also has janky audio, and we needed to emulate this jankness in the tracker
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# timer effects: what?
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generally speaking, a timer is a mechanism that lets an action be done at a preset time. on
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computers, it lets the CPU do things periodically, and if it is able to interrupt the CPU, allows
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actions to be executed automatically at regular, periodic intervals.
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on every Atari ST ever made is a chip called the *MC68901: Multi-Function Peripheral (MFP)*,
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and this chip provides an USART, an interrupt controller, and most notably, 4 timers. these
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timers are at the heart of *timer effects* (hereby called *timer FX*).
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what is *timer FX*? on the Atari ST, it means any effect that messes with the YM2149 sound registers.
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this means it can be used to write to a register at regular intervals, producing
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audible effects (like frequency modulation, amplitude modulation, etc...). although there are a
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variety of effects that can be done with this, for Aerations in particular, we only used 2:
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- PWM (Pulse Width Modulation)
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- SyncBuzzer
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