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Table of Contents
what
A completely open design for a function/waveform generator: hardware, firmware, software
Notes & stuff
Waveform generation
Waveforms we want (in order of importance)
- Sine wave
- Square wave (with variable PWM)
- Triangle wave
- Sawtooth (possibly a modification of triangle wave???)
- arbitrary waveform (sync, envelopes, etc)
Frequency range:
- 1 Hz or lower
- 100 KHz or higher
- 1mHz → 10MHz is ideal
Generator tech
Two options for chip 'styles' is the all-in-one oscillator (ICL3038, etc) +PLL or DDS
Oscillators
All-in-one is nice, except that the MAX038 is completely unavailable. And the XR2206 kinda sucks. Also you'll need a PLL system to tune it.
DDS
Direct-Digital-Synthesis, currently popular. Basically: wavetable + 24 or 32 bit adder and sampling above nyquist to get precision waveforms.
Pros: digital, precise, no PLL needed Cons: hard to get high frequencies because of oversampling
Either roll your own or buy off the shelf (basically from AD)
Off the shelf, AD parts
They come with sync out, very very high speeds. But only sine and square out, and in small packages (TSSOP).
Roll your own
Idea #1: Get a chunk of SRAM (like, say, CY7C1399B-12VXC), fill it with your wavetable, then either clock it with a variable clock (LTC6903 1KHz→68MHz !!) and/or use the oversampling technique (a fast 32 bit adder)
