NESSY 4-bit 4-channel MIDI NES sound module - introduction

Short intro for the NESSY box - a simple MCU soundbox which began as a sound module for a Roland S-10 sampler keyboard which has a busted QuickDisk drive. The sample memory is horribly small, too, but the MIDI IO is fine. Serves as a good platform for MIDI experiments although its command set is rather outdated.

It's got 4 channels, ie. all the channels of a NES without the DPCM. Two squares, one triangle, one noise - all output with a single 6bit R2R DAC. With the low bit depth processing needs to be rapid and without dedicated hardware for each channel there is slight interrupt dependent intermodulation. It's minimal with a little attention to ISR smoothness but it's still there. The hardware oddities such as slight triangle volume scaling aren't modeled, although a few external BJTs would have sufficed. Perhaps in the next model.

Questions are welcome although the schematic is all there in the video, nothing unusual. I won't be posting the source code anywhere since it's a poorly commented heap based on a couple test functions. Atmel's own AVR Studio was used along with AVR-GCC.

I apologize for my lack of keyboard lessons, need to train a while before recorcing more material!

(That's my skippy beat-drifting rendition of the NES Metroid intro playing in the background...)

Category:

Science & Technology

Tags:

• midi
• lofi
• atmel
• avr
• nes
• 4bit
• synth
• green
• thing

[ODMSys]

@SgtThom The DPCM channel is by itself a bit useless without a sample memory or generator to accompany it. Also, I'd have run further out of processing time in using that channel as well which would have increased artifacts. Maybe with a 16bit DAC and bandllimited sampling it'd be easier to pull off.

I guess the lack of effort by remodelers and the difficulty of interface in NES-mods makes DPCM a less attractive channel. It does sound great, though, especially in Sunsoft games!

[SgtThom]

You people don't like the differential pulse-code modulation  channel do you?