lc-oscillator-finder.ngjs

#!/usr/bin/env ngspicejs
// Find LC oscillators with random topology
// linter: ngspicejs-lint
"use strict";

// configuration
var config = file_read_json('config.json');

// use random seed
if (config.seed > 0) {
    echo('seed', config.seed);
    mersenne_twister(config.seed).replace_math_random();
}

dir_create('candidates');

var nets = {}; // Object (key is net name) with all devices connected to this net, e.g. nets['net1'] = [r1, c3];

function create_random_topology() {
    // Add battery, decoupling cap and random parts and nets

    // battery
    var bat = battery('U1', 'bat', 0, config.battery_voltage).rs(config.battery_rs);
    // decoupling capacitor
    var cd = capacitor('Cd', 'bat', 0, '10u');
    nets.bat = [bat.attr.name, cd.attr.name];
    nets[0] = [bat.attr.name, cd.attr.name];

    // add random nets
    var i, net_names = ['bat', 0], a, b, r, c, n, internal_nets = [];
    for (i = 0; i < config.counts.net; i++) {
        n = 'net' + (i + 1).toString();
        net_names.push(n);
        internal_nets.push(n);
    }
    //echo('net_names:');
    //echo_json(net_names);

    function two_nets() {
        // pick 2 distinct nets
        var na = '';
        var nb = '';
        while (na === nb) {
            na = net_names.randomItem();
            nb = net_names.randomItem();
        }
        return [na, nb]; //{a: na, b: nb};
    }

    function three_distinct_nets() {
        // pick 3 distinct nets (all 3 must be different)
        var na = '';
        var nb = '';
        var nc = '';
        while (na === nb || na === nc || nb === nc) {
            na = net_names.randomItem();
            nb = net_names.randomItem();
            nc = net_names.randomItem();
        }
        return [na, nb, nc];
    }

    // add exactly one inductor
    [a, b] = two_nets();
    inductor('L1', a, b, config.inductor_l).rs(config.inductor_rs);

    // add npn transistors
    for (i = 0; i < config.counts.npn; i++) {
        [a, b, c] = three_distinct_nets();
        npn('T' + (i + 1), a, b, c, config.npn_model);
    }

    // add resistors between 2 random nets
    for (i = 0; i < config.counts.resistor; i++) {
        [a, b] = two_nets();
        r = resistor('R' + (i + 1), a, b, series_e12(10, '10M').randomItem());
        nets[a] = nets[a] || [];
        nets[a].push(r.attr.name);
        nets[b] = nets[b] || [];
        nets[b].push(r.attr.name);
    }

    // add capacitors between 2 random nets
    var cap_nets = {
        'bat_0': true
    };
    for (i = 0; i < config.counts.capacitor; i++) {
        var stuck = 0;
        while (true) {
            stuck++;
            if (stuck > 1000) {
                hint("Lower the amount of capacitors or increase the amount of nets, for example:");
                hint("config.counts.net = " + config.counts.net + ";");
                hint("config.counts.resistor = " + config.counts.resistor + ';');
                hint("config.counts.capacitor = " + config.counts.capacitor - 1 + ';');
                throw new Exception("Cannot place capacitor C" + (i + 1) + " because all other net pairs already have a cap, this would create parallel caps!");
            }
            [a, b] = two_nets();
            // do not create parallel caps
            if (cap_nets[a + '_' + b] || cap_nets[b + '_' + a]) {
                //warn('parallel cap ' + a + ' ' + b);
                continue;
            }
            break;
        }
        cap_nets[a + '_' + b] = true;
        c = capacitor('C' + (i + 1), a, b, i === 0 ? config.capacitor : series_e12('10p', '10u').randomItem());
        nets[a] = nets[a] || [];
        nets[a].push(r.attr.name);
        nets[b] = nets[b] || [];
        nets[b].push(r.attr.name);
        //echo('c', i + 1, 'a', a, 'b', b);
    }

    return {
        internal_nets
    };
}

function has_oscillation(aCoilCurrentData) {
    // Return true if data contains oscillation
    // second half of coil current must contain current larger than min amplitude
    var second_half = aCoilCurrentData.slice(Math.floor(aCoilCurrentData.length / 2));
    var avg = second_half.avg();
    second_half = second_half.addScalar(-avg);
    return second_half.range() > config.min_amplitude;
}

function find_oscillator() {
    // Keep generating random nets until valid oscillator is found
    var t;
    var attempt = 0;
    while (true) {
        attempt++;
        echo_progress();
        if (attempt % 100 === 0) {
            echo('tested ' + attempt + ' topologies...');
        }

        // clear netlist
        netlist_clear();
        nets = {};

        // add battery and decoupling cap and random components
        var r = create_random_topology();

        // check if all internal nets have path to ground and battery
        var edges = topology_edges(netlist_devices);
        var issues = false;
        // jshint -W083
        r.internal_nets.filter((n) => edges[n]).every((n) => {
            // Net must have path to ground
            if (!topology_path_exists(edges, n, '0', ['0', 'bat'])) {
                issues = true;
                return false;
            }
            // Net must have path to battery
            if (!topology_path_exists(edges, n, 'bat', ['0', 'bat'])) {
                issues = true;
                return false;
            }
            return true;
        });
        if (issues) {
            //echo('No path to bat/ground, starting over');
            continue;
        }

        // check for singular matrix
        if (singular_matrix()) {
            //echo('Singular matrix, trying new topology');
            continue;
        }
        if (!tran_ok()) {
            //echo('Simulation failed, trying new topology');
            continue;
        }
        // run transient analysis
        t = tran().step('20u').interval('25m').run();
        if (!has_oscillation(t.data['I(L1.L0)'])) {
            continue;
        }
        // all checks passed
        break;
    }

    // get timestamp
    var ts = Date.now();

    // show chart and save it
    t.chart('I(L1.L0)');
    t.last_chart.gif('candidates/' + ts + '.gif');

    // save url with schematic
    echo(netlist_export_schematic_url());
    file_write('candidates/' + ts + '.url', netlist_export_schematic_url());

    // save netlist as ngjs script
    var sn = 'candidates/' + ts + '.ngjs';
    file_write_ngspicejs(sn);
    file_write(sn, file_read(sn) + '\n' + "tran().step('1u').interval('20m').run().chart('I(L1.L0)');");
    file_mode(sn, parseInt('0755', 8));
}

echo('Finding novel LC oscillators, typical rate is one per minute, be patient...');
var found = 0;
while (true) {
    find_oscillator();
    found++;
    echo(found, 'oscillator found');
    beep();
    //break;
}