This shows you the differences between two versions of the page.
Both sides previous revision Previous revision Next revision | Previous revision | ||
openbench:fgen [2007/11/09 17:31] geekabit idea #4: simple proc + chunk of ram |
openbench:fgen [2016/01/28 18:05] (current) |
||
---|---|---|---|
Line 2: | Line 2: | ||
A completely open design for a function/waveform generator: hardware, firmware, software | A completely open design for a function/waveform generator: hardware, firmware, software | ||
- | for more info, read about [[about|openbench]] | + | for more info, read about [[start|openbench]] |
For collected links, try [[http://del.icio.us/ladyada/dds|DDS link on delicious]] and [[http://del.icio.us/ladyada/fgen|Function Gen link on delicious]] | For collected links, try [[http://del.icio.us/ladyada/dds|DDS link on delicious]] and [[http://del.icio.us/ladyada/fgen|Function Gen link on delicious]] | ||
====== Notes & stuff ====== | ====== Notes & stuff ====== | ||
- | |||
===== Design constraints ===== | ===== Design constraints ===== | ||
- | |||
One or two designs: Low cost, high cost. | One or two designs: Low cost, high cost. | ||
* Low cost is ~$50-75 | * Low cost is ~$50-75 | ||
Line 21: | Line 19: | ||
* Sawtooth (possibly a modification of triangle wave???) | * Sawtooth (possibly a modification of triangle wave???) | ||
* Arbitrary waveform (sync, envelopes, etc) | * Arbitrary waveform (sync, envelopes, etc) | ||
+ | * Noise (white noise, pink noise, brown noise, etc) | ||
+ | |||
+ | Modulation (in order of importance) | ||
+ | * Sweep (actually is FM) | ||
+ | * AM | ||
+ | * FM | ||
Frequency range: | Frequency range: | ||
- | * 1 Hz -> 100 KHz required (must cover audio ranges) | + | * 1Hz to 100KHz required (must cover audio ranges) |
- | * 1mHz -> 10MHz is ideal (digital/analog ranges) | + | * DC to 10MHz is ideal (digital/analog ranges) |
Output capabilities: | Output capabilities: | ||
- | * 50 ohm/inf impedance | + | * 50ohm/inf impedance |
- | * 1mv -> 10V amplitude | + | * 1mv to 10V amplitude |
- | * 0 -> 10V DC offset | + | * 0 to 10V DC offset |
* trigger output | * trigger output | ||
- | USB control? Panel control? Both? | + | USB control? Serial control? Panel control? All of the above? |
Vpp? (+-12V is pretty 'standard') | Vpp? (+-12V is pretty 'standard') | ||
Line 43: | Line 47: | ||
===== Waveform generation ===== | ===== Waveform generation ===== | ||
- | |||
Waveforms we want (in order of importance) | Waveforms we want (in order of importance) | ||
* Sine wave | * Sine wave | ||
* Square wave (with variable PWM) | * Square wave (with variable PWM) | ||
- | * Triangle wave | + | * Triangle wave (with variable PWM?) |
* Sawtooth (possibly a modification of triangle wave???) | * Sawtooth (possibly a modification of triangle wave???) | ||
- | * arbitrary waveform (sync, envelopes, etc) | + | * Arbitrary waveform (sync, envelopes, etc) |
+ | * Noise (white noise, pink noise, brown noise, etc) | ||
Frequency range: | Frequency range: | ||
- | * 1 Hz or lower | + | * 1Hz to 100KHz required (must cover audio ranges) |
- | * 100 KHz or higher (must cover audio ranges) | + | * DC to 10MHz is ideal (digital/analog ranges) |
- | * 1mHz -> 10MHz is ideal (digital/analog ranges) | + | |
- | + | ||
- | + | ||
- | + | ||
- | + | ||
- | + | ||
==== Generator tech ==== | ==== Generator tech ==== | ||
- | |||
Two options for chip 'styles' is the all-in-one oscillator (ICL3038, etc) +PLL or DDS | Two options for chip 'styles' is the all-in-one oscillator (ICL3038, etc) +PLL or DDS | ||
=== Oscillators === | === Oscillators === | ||
- | |||
All-in-one is nice, although not very stable w/o PLL. Two options available, MAX038 & XR220. | All-in-one is nice, although not very stable w/o PLL. Two options available, MAX038 & XR220. | ||
Line 75: | Line 70: | ||
Pros: easy, cheap, simple | Pros: easy, cheap, simple | ||
Cons: unavailable, PLL required | Cons: unavailable, PLL required | ||
- | |||
=== DDS === | === DDS === | ||
- | |||
Direct-Digital-Synthesis, currently popular. Basically: wavetable + 24 or 32 bit adder and sampling above nyquist to get precision waveforms. | 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 | * Pros: digital, precise, no PLL needed | ||
Line 86: | Line 79: | ||
== Off the shelf, AD parts == | == 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). | They come with sync out, very very high speeds. But only sine and square out, and in small packages (TSSOP). | ||
== Roll your own == | == Roll your own == | ||
- | |||
**Idea #1**: Get a chunk of SRAM (like, say, CY7C1399B-12VXC), fill it with your wavetable, then clock it with a variable clock ([[http://www.linear.com/pc/productDetail.do?navId=H0,C1,C1010,C1096,P2415|LTC6903]] 1KHz->68MHz !!) maybe use along with adder/scaler to provide more range at high/low freq. We could get up to 4MHz, nice! | **Idea #1**: Get a chunk of SRAM (like, say, CY7C1399B-12VXC), fill it with your wavetable, then clock it with a variable clock ([[http://www.linear.com/pc/productDetail.do?navId=H0,C1,C1010,C1096,P2415|LTC6903]] 1KHz->68MHz !!) maybe use along with adder/scaler to provide more range at high/low freq. We could get up to 4MHz, nice! | ||
* Pros: high frequency range | * Pros: high frequency range | ||
Line 113: | Line 104: | ||
===== Power supply ===== | ===== Power supply ===== | ||
- | |||
Need 3.3V (probably), 5V, +-12V (@100mA) | Need 3.3V (probably), 5V, +-12V (@100mA) | ||
Line 120: | Line 110: | ||
* Cons: need to load down 5V - should look into this | * Cons: need to load down 5V - should look into this | ||
- | **Idea #2** Use 78xx's with 120V transformer. | + | **Idea #2** Use 78xx's with mains transformer. |
* Pros: well understood, cheap, safe (isolated), clean power, huge | * Pros: well understood, cheap, safe (isolated), clean power, huge | ||
- | * Cons: Transformers kind of a pain, unsafe (to build, wiring 120V yuk) | + | * Cons: Transformers kind of a pain, unsafe (to build, wiring mains yuk) |
**Idea #3** Use a regulated power supply/wall wart with multiple outputs (see [[http://www.jameco.com/webapp/wcs/stores/servlet/ProductDisplay?langId=-1&storeId=10001&catalogId=10001&productId=154624|Jameco#154624]] 5V @0.5A +-12V @0.13A each $13) | **Idea #3** Use a regulated power supply/wall wart with multiple outputs (see [[http://www.jameco.com/webapp/wcs/stores/servlet/ProductDisplay?langId=-1&storeId=10001&catalogId=10001&productId=154624|Jameco#154624]] 5V @0.5A +-12V @0.13A each $13) | ||
Line 131: | Line 121: | ||
* Pros: simple, regulated, ultra compact | * Pros: simple, regulated, ultra compact | ||
* Cons: expensive, noisy | * Cons: expensive, noisy | ||
+ | **Idea #4b** Build your own DC/DC converter, a bit like [[http://spritesmods.com/?art=ucboost&page=2|sprite_tm]] did. Have the processor generate the PWM needed for the converter. | ||
+ | * Pros: cheap, same as idea #4 | ||
+ | * Cons: noisy | ||
====== Planned versions ====== | ====== Planned versions ====== | ||
- | |||
===== Inexpensive kit ===== | ===== Inexpensive kit ===== | ||
Line 149: | Line 141: | ||
2x16 LCD and some buttons & rotary encoders for UI. | 2x16 LCD and some buttons & rotary encoders for UI. | ||
Maybe an 'm88? at 12MHz does the UI work and USB nonsense. (USB "serial" (or raw) interface using USBtiny.) and sends just raw serial/spi commands to DDS chipset | Maybe an 'm88? at 12MHz does the UI work and USB nonsense. (USB "serial" (or raw) interface using USBtiny.) and sends just raw serial/spi commands to DDS chipset | ||
- | |||
==== Chipset ==== | ==== Chipset ==== |