openbench:fgen
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openbench:fgen [2007/11/09 17:21] geekabit + amplitude, DC offset |
openbench:fgen [2007/12/03 16:36] geekabit |
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| 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]] | ||
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| * 100 KHz or higher (must cover audio ranges) | * 100 KHz or higher (must cover audio ranges) | ||
| * 1mHz -> 10MHz is ideal (digital/analog ranges) | * 1mHz -> 10MHz is ideal (digital/analog ranges) | ||
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| 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 | ||
| * Cons: hard to get high frequencies because of oversampling | * Cons: hard to get high frequencies because of oversampling | ||
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| * Cons: 8 @ 20MHz -> low frequency output (20M/16samples/8cycles = ~150KHz), 8bit resolution | * Cons: 8 @ 20MHz -> low frequency output (20M/16samples/8cycles = ~150KHz), 8bit resolution | ||
| Other possibilities include going with an SX instead of AVR: SX28 can be clocked up to 75MIPS (maybe give us 500KHz...but will draw an insane 100mA from 5V. jesus!) | Other possibilities include going with an SX instead of AVR: SX28 can be clocked up to 75MIPS (maybe give us 500KHz...but will draw an insane 100mA from 5V. jesus!) | ||
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| + | **Idea #4**: A combination of idea #1 and idea #3. Take a simple AVR that is able to calculate waveforms, but not in realtime. Load the wavetable in some external RAM, and clock it at the desired speed. | ||
| + | * Pros: high frequency, adjustable waveform | ||
| + | * Cons: complex | ||
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| * 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 ====== | ||
/home/ladyada/public_html/wiki/data/pages/openbench/fgen.txt · Last modified: 2016/01/28 18:05 (external edit)
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