Let's Design and Build a (mostly) Digital Theremin!

Wow!  It's like there's some kind of contest to make the smallest possible FPGA board.
-- Dewster

Yet another board for contest (PSOC module) is announced in Sipeed twitter, not as small as previous one (50x70 or 50x50mm), but has 138K LUTs and a dual hardcore RiscV.

#FPGA Tang MEGA 138K coming soon~
138K Luts, 7Mbits SRAM, ~300 Multiplier, 8lane hardcore MIPI, 8lane 12.5G Serdes,  Dual hardcore #RISCV at 800MHz,
Dual Flash, Dual DDR3(2x512MByte),  3x120pin BTB breakout~
All of them in 5x7 or 5x5 cm module, 60~80$ !

"Yet another board for contest (PSOC module) is announced in Sipeed twitter, not as small as previous one (50x70 or 50x50mm), but has 138K LUTs and a dual hardcore RiscV."  - Buggins

RISC-V is really taking off!  It's probably a good fit for the FPGA world too, even as hardcore.

I've found that there is Xilinx based Colorlight i9+ SODIMM module, pinout compatible with Lattice based SODIMM-200 modules.

Extension board (which provides breakout for USB, HDMI and a lot of PMODs) is compatible with all three of them.
Open source toolchain is working for all three of them as well.

Colorlight i9 Plus - 65 EUR
Xilinx Artix 7
XC7A50T 52K logic cells (actually, 32600 LUT6s or 65200 LUT5s + 65200 FFs)
Module contains 8MB sdram and 16MB spi flash.

Colorlight i9 - 53 EUR
Lattice ECP5
FPGA LFE5U-45F-6BG381C 44K LUT
Module contains 8MB sdram and 8MB spi flash.

Colorlight i5 - 15 EUR
Lattice ECP5
LFE5U-25F-6BG381C 24K LUT
Module contains 8MB sdram and 2MB spi flash.

All three boards have dual ethernet PHI. Useless for theremins?
Each phi has two differential inputs and two outputs (transformers?)
Cannot we connect AFE here?

These three boards are competing to similar form factor Ice Sugar Pro board.
Ice Sugar Pro - 55 EUR
Lattice ECP5
LFE5U-25F-6BG256C 24K LUTs
Module contains 32MB sdram and 32MB spi flash.
Unlike Colorlight, has on-board USB connector and IceLink programmer (CDC serial port and JTAG) and SD card.

Connector pinout looks pretty similar to Colorlight - probably they are compatible.

Github link for IceSugar Pro

IceSugar is fully open source. Colorlight have only pinouts reverse engineered.
I think, if SODIMM200 form factor of FPGA module is selected for the project it's possible to use ICESugar Pro for development, and then cheap Colorlight i5 for production...

Artix XC7A50T FPGA has actually a lot of resources, enough for any crazy digital theremin design.

Buns In The Oven

Working on another small wave of D-Lev kits, doing 6 at a time instead of the usual 12 to try to keep it from feeling too much like work. All the boards are stuffed except for the AFEs, which are only lacking the decoupling capacitors (should be arriving today) and plugging in the ICs. Tuners are tested, FPGA boards pumped, LCDs and encoders arrived yesterday. Now concentrating on all the 3D printing, coil boxes and tuner plates are done, doing logos and control panels.

Buggins, thanks for doing all of this FPGA board research!  FPGAs with only a single PLL inside it may be a problem generating 48kHz and higher powers of 2 needed for PCM audio?  I do wish they would use oscillators with base frequencies that could offer broader options here.

Two-Way Street

Not saying I'm all that hot at synthesis or anything, but I wonder if acoustic instrument builders could learn anything from those who synthesize them?  Normally it's a one-way street, they build them and we struggle to emulate them.  The resonances of a violin comes to mind as a possible candidate, perhaps there are sweet sounding distributions just waiting to be discovered and then embodied in the real thing?

An acoustic theremin.
No hassle to find a mains outlet, no batteries, no amp, no speaker, no wires.
Waaaaoh !

"An acoustic theremin."  - Andre

https://en.wikipedia.org/wiki/Musical_saw

Good point !

But it's not a touchless instrument !

"But it's not a touchless instrument !"  - Andre

Maybe blow on a wind chime?