Скачать или смотреть 8-Channel Arduino Synthesizer - Wind Chime Demo

Hi Everybody! This is my first public YouTube video in over a decade. It is a test of a software synthesizer project based around an Arduino MEGA2560, a pair of 8-bit R2R resistor DAC's, and some cheap speakers.

The software allows 8 independent sound channels, each with its own double-buffered 256-point waveform in RAM. Each channel has independent settings for pitch, left volume, and right volume. The pitch setting is 16-bits fixed-point, while everything else is 5-bits, including the waveform amplitudes. (This scheme is inspired by the sound of the PC Engine game console from late 1980's.) The ultimate goal of this project is to make a homebrew sound synthesizer card for a homebrew retro-computer.

For this chime demo, each channel is set to a note of a major chord spanning notes C-3 through B-4, and all waveforms are set to sine. At random times, a random channel is chosen, and if it happens to be quiet, its right/left volumes are set to random values. As channels play, their volumes are slowly decreased (linearly) to simulate vibration dampening.

You might notice a 'shimmering' noise to the sound. I believe it was caused by switching noise while DAC input bits are changed. I have since eliminated it using a couple RC lowpass filters, even though I think it's a cool sound.

Currently, the software isn't well optimized, so the output sample rate is set to 22.1 kHz. I intend to get it up to 44.1 kHz, even if I have to overclock the chip or use a faster one.

Eventually this chip will have a parallel data bus so it can be controlled by an 8-bit CPU, in my case, a Hitachi HD63C09P running at 3.58 MHz. ( I'm trying to ignore the fact that the processor in this sound card will be some orders of magnitude faster than the main CPU in my computer. haha! )

There's a serial port free on this chip, so I was thinking of having it as a bonus serial port function on the sound card, maybe specialized for MIDI. For other non-computer projects, it could instead be used as an alternate means of controlling the synthesizer.

The Arduino sketch is not much to look at yet, but if anyone is interested, I'll stick it on GitHub.

Thanks for watching!

PS: I didn't put much thought into the windchime note selection. If anybody has ever wanted to hear a chime with some particular notes, please let me know in the comments, and I'll make a video. (Unless overwhelmed by tons of requests. haha)