SimLogue

SimLogue is an analogue circuit simulator. The goal is to simulate modular synths in real-time.

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Features

• Currently supports these components:
  • voltage (single and double pin, ac/dc) and current sources
  • linear inductors, capacitors and resistors
  • switches
• Voltage and current scopes
• Rendering scope graphs and exporting the data to csv
• Loading circuits from .simlog files

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Usage

simlogue [options] circuit_file duration Options:

• -v, --version - Show version information
• -h, --help - Show the help message
• -r, --samplerate <freq> - Sets the sample rate in Hz (default: 44100)
• -e, --export-tables - Exports the scope tables
• -t, --tables <path> - Path to generated CSV tables (default: ./tables/)
• -g, --show-graphs - Displays the scope graphs after run

duration is in seconds, and it represents the simulation time. So when the duration is 5 and the sample rate is 1000, the simulation will produce 5000 samples.

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Requirements

• You need to have gnuplot installed to render the graphs

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Build

On Linux

Using cmake in the CLI

git clone https://github.com/Myshaak-Jr/SimLogue.git
cd SimLogue

cmake --preset linux-release
cmake --build --preset build-linux-release

Resulting executable will be ./out/build/linux-release/simlogue.

On Windows

Using Visual Studio, open it as a CMake project, select Release and build all. Resulting executable will be ./out/build/windows-vs/Release/simlogue.exe

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The simlog Language

A simple scripting language to build the circuits.

Features:

Comments: Comment using C-style comments // this will be commented, /* this is a comment */

Components: Create a new component by writing: <component> <name>[: <value>, ...]

Each component has a constructor footprint consisting of quantity values. Different values can be listed in any order and the interpreter will match them to the correct quantity, only exception are values of the same quantity, these have to be listed in the correct order.

List of available components with their constructors:

• capacitor: capacity
• current_source: current
• inductor: inductance
• resistor: resistance
• switch - off by default
• voltage_source: voltage - single pin version
• voltage_source_2P: voltage - two pin version
• ac_voltage_source: amplitude (voltage), frequency, phase (time) = 0s - single pin version
• ac_voltage_source_2P: amplitude (voltage), frequency, phase (time) = 0s - two pin version
• op_amp: low saturation voltage, high saturation voltage, amplification (none) = 100000 - operational amplifier

Names: All names must be in the format: [A-Za-z_][A-Za-z0-9_]* Examples: V1, R5, VSource_25V

Values: All values consist of a value and a unit, like 5V, 6.3m_Am, 68_uF, etc. The cannot be a space between the value and the unit, you can use an underscore.

Units:

• Current - A, Am
• Voltage - V
• Resistance - Ohm, Ω
• Capacitance - F
• Inductance - H
• Time - s, min
• Frequency - Hz
• Angle - rad, deg, grad, °
• None - ""

You can use multipliers like E, P, T, G, M, k, m, u, n, p, f, a between the value and unit, \micro instead of u is also supported.

When using mutlipliers you can put '_' between them and the unit itself for readability: k_Ohm or in the future when for example units of length get added to differentiate between milli inches and minutes: m_in vs min.

That being said, when no underscore is present in the unit name, the parser will first try to parse as a whole unit name, and if it fails to do so it will proceed to parse the first letter as a multiplier.

Units such as mdeg or Grad (giga radian) are technically supported although not recommended, Grad can be especially confusing with grad being a real unit.

The "none" quantity cannot have modifiers;

Connections: Parts can be connected by simply writing: V1 - R1 This will connect V1 to R1, since V1 is a single-pin part, the parser will automatically select that pin. And since the R1 is a two-pin part and you are connecting from the left, it will connect to the .a pin. You can also chain them V1 - S1 - R1 - C1 - GND. This is the same as:

V1.a - S1.a
S1.b - R1.a
R1.b - C1.a
C1.b - GND.a

Unless the parts are single- or two- pin, the names between the - must be pin names.

Pin names: Pin names consist of a part name and the pin name itself separated by a dot. For basic parts the pin names are indexed by letters: a for the first pin, b for the second one, etc. Single-pin part names can be used directly as their pin name.

Scopes: Scopes can be added by writing: scope <quantity> (of <two-pin-part> | between <pin-name> and <pin-name>)

Quantity can be either voltage and current. When using of, the part name must have two exactly pins. When using scope current between, the two pins must belong to the same part.

Scheduling switches: Switched can be scheduled by writing: turn (on|off) <switch-name> at <time>

The corresponding switch will then set its state to the specified one when the simulation time reaches <time>. The time is specified using the <value> format with the unit being s.

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Examples

Some example circuit can be found in the ./examples/ directory.

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Technology

• The simulator uses the MNA approach.
• Currently I use gaussian elimination to solve the system
• The graphs are rendered using Sciplot

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Future plans

• Use sparse matrices and LU factorization with precalculated pivoting, the method Part::gen_matrix_entries is prepared to generate the entries for the sparse matrix.
• Create a multi-circuit system, that can be connected using buffered voltage inputs and outputs, every circuit will have its own matrix and thread.
• Make it real-time and export directly to the audio buffer.

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Known issues

• The gaussian elimination doesn't work with modulo integers, because it uses comparison.
• The gnuplot errors when having a number of scopes that can't be put into a 16:9 grid.