[sdiy] Pots vs Encoders, was Re: [sdiy] dave smith *instruments*

[Jason Tribbeck]

Hi,

> The PIC will be an I/O controller, handling input from pots, encoders and
> various switches while also supporting output to the LCD.  There will be a
> serial interface for connecting the PIC board to the FPGA board, probably
> SPI.  The FPGA will do all of the synth internals, oscillators, filters or
> what have you.  I'm using a Xilinx FPGA, so I will use an embedded soft
> microcontroller (Picoblaze) for MIDI including sysex.  I've already
> developed the MIDI controller code for other FPGA synth projects and it is
> tiny.  The advantage I find in doing this is that the Picoblaze controller
> being right there in the FPGA makes it a matter of HDL to connect it's
> ports to the synth's registers and RAM.

I did look at the Picoblaze for mine, but I've got some fairly meaty calculations I want to do for the filters (the filters themselves are being done by the FPGA, but the coefficient calculations I want to be done in real-time (well, 100ths of a second). Since I'll have 288 oscillators on the FPGA, I'm not sure if the picoblaze could cope with this.

Although since it is my first FPGA synth project, I am trying to take it one step at a time!
-- 
Jason Tribbeck