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144 lines
5.6 KiB
Markdown
144 lines
5.6 KiB
Markdown
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[](https://github.com/marketplace/actions/arduino_ci)
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[](https://github.com/RobTillaart/FunctionGenerator/actions/workflows/arduino-lint.yml)
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[](https://github.com/RobTillaart/FunctionGenerator/actions/workflows/jsoncheck.yml)
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[](https://github.com/RobTillaart/FunctionGenerator/blob/master/LICENSE)
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[](https://github.com/RobTillaart/FunctionGenerator/releases)
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# FunctionGenerator
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Arduino library to generate (numeric) wave forms for a DAC.
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## Description
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This library presents a class for a function generator in software.
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It is typical used to control one or more DAC's.
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To maximize signal quality one has to apply all (or most) processor power
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to calculate new values over and over again to get enough resolution.
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In practice the generator is useful for low frequencies,
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0.01 - 25 Hz, depending on waveform and processor and number of DAC's.
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(see indication below).
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Note: this class generates float values, performance wise this can be optimized,
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to achieve higher speeds at cost of accuracy / precision.
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## Performance
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Indication of what performance can be expected (based upon 0.2.1 version).
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Note that the values need to be transported to a DAC or serial port too.
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Numbers based on performance example, for one single signal.
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| Processor | Clock | Waveform | usec/calls | max freq |
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|:-------------|---------:|:---------|-----------:|---------:|
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| Arduino UNO | 16 MHz | sawtooth | 62 | 60 Hz |
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| Arduino UNO | 16 MHz | triangle | 74 | 50 Hz |
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| Arduino UNO | 16 MHz | square | 53 | 1000 Hz |
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| Arduino UNO | 16 MHz | sinus | 164 | 25 Hz |
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| Arduino UNO | 16 MHz | stair | 81 | 50 Hz |
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| Arduino UNO | 16 MHz | random | 37 | 1000 Hz |
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| | | | | |
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| ESP32 | 240 MHz | sawtooth | 3.8 | 1000 Hz |
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| ESP32 | 240 MHz | triangle | 3.9 | 1000 Hz |
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| ESP32 | 240 MHz | square | 2.8 | 1000 Hz |
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| ESP32 | 240 MHz | sinus | 13.6 | 250 Hz |
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| ESP32 | 240 MHz | stair | 4.8 | 800 Hz |
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| ESP32 | 240 MHz | random | 1.3 | 1000 Hz |
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- assumption minimal 250 samples per period to get a smooth signal.
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if a rougher signal is OK, higher frequencies are possible.
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- ESP32 can do more calculations however 1000 Hz seems to be a nice
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upper limit for a software based function generator.
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- if one wants to control multiple DAC's one need to divide the numbers
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and round down.
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Note: hardware function generator https://github.com/RobTillaart/AD985X
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## Interface
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### Constructor
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- **funcgen(float period = 1.0, float amplitude = 1.0, float phase = 0.0, float yShift = 0.0)**
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All parameters can be set in the constructor but also later in configuration.
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### Configuration
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- **void setPeriod(float period = 1.0)** set the period of the wave in seconds.
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- **float getPeriod()** returns the set period.
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- **void setFrequency(float frequency = 1.0)** set the frequency of the wave in Hertz (1/s).
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- **float getFrequency()** returns the set frequency in Hertz.
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- **void setAmplitude(float amplitude = 1.0)** sets the amplitude of the wave. TODO point to point?
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Setting the amplitude to 0 gives ?what?
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- **float getAmplitude()** returns the set amplitude.
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- **void setPhase(float phase = 0.0)** shifts the phase of the wave. Will only be noticeable when
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compared with other waves.
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- **float getPhase()** returns the set phase.
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- **void setYShift(float yShift = 0.0)** sets an Y-shift in amplitude, allows to set some zero point.
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- **float getYShift()** returns the set Y-shift.
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### Wave forms
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t is time in seconds
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- **float sawtooth(float t, uint8_t mode = 0)** mode == 0 (default) ==> sawtooth /|. mode == 1 ==> sawtooth |\.
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- **float triangle(float t)** triangle form, duty cycle 50%.
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- **float square(float t)** square wave with duty cycle 50%.
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- **float sinus(float t)** sinus wave, has no duty cycle.
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- **float stair(float t, uint16_t steps = 8, uint8_t mode = 0)** mode = 0 ==> steps up, mode = 1 steps down.
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- **float random()** noise generation.
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- **float line()** constant voltage line. Depends on the set YShift and amplitude.
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- **float zero()** constant zero.
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Line() and zero() are functions that can be used to drive a constant voltage from a DAC
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and can be used to calibrate the generator / DAC combination.
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## Operational
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See examples.
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## Future
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#### waveforms
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- square duty-cycle (will be slower!)
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- triangle duty-cycle (makes sawtooth a special triangle)
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- trapezium wave (would merge square and triangle and sawtooth)
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- Bezier curve?
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#### investigate
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- duty-cycle for sinus what does it mean. move peak.
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- white noise, pink noise etc.
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- investigate algorithms for performance gains (DAC specific values 10-12-16 bit)
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- Amplitude modulation ?
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- external clock to synchronize two or more sw function generators.
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- RC function curve.
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- heartbeat curve?
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- record a signal and play back
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#### misc
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- stand-alone functions in separate .h?
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- mapping to voltage function.
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- check for synergy with https://github.com/RobTillaart/AD985X
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#### examples
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- example ESP32 version as separate task...
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- example with DAC. 8 12 16 bit.
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- example with potentiometers for 4 parameters
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