analog-filter-designer: cutoff frequency output

dist/tools/general/analog-filter-designer/index.html

@@ -139,6 +139,16 @@ <h1 class="text-center mb-4">Analog Filter Designer</h1>
 
                 <hr />
 
+
+                <div class="input-group mb-3">
+                    <span class="input-group-text bg-dark text-white" data-toggle="tooltip"
+                        title="Output Cutoff Frequency">$f_c$</span>
+                    <input required type="text" class="form-control"
+                        id="out_fc" readonly value="">
+                </div>
+
+                <hr />
+
                 <div id="plot">
                 </div>
 
@@ -183,6 +193,7 @@ <h1 class="text-center mb-4">Analog Filter Designer</h1>
     <script src="js/ngrp.js"></script>
     <script src="js/ngspice.js"></script>
     <script src="js/models.js"></script>
+    <script src="js/eng2num.js"></script>
     <script src="js/main.js"></script>
 
 </body>

dist/tools/general/analog-filter-designer/js/eng2num.js

@@ -0,0 +1,47 @@
+spiceUnitsMap = {
+    'f': 1e-15,
+    'p': 1e-12,
+    'n': 1e-9,
+    'u': 1e-6,
+    'm': 1e-3,
+    '': 1,
+    'k': 1e3,
+    'meg': 1e6,
+    'g': 1e9,
+    't': 1e12
+}
+
+unitsMapInverted = Object.create(null)
+unitsMapInverted[-15] = 'f'
+unitsMapInverted[-12] = 'p'
+unitsMapInverted[-9] = 'n'
+unitsMapInverted[-6] = 'u'
+unitsMapInverted[-3] = 'm'
+unitsMapInverted[0] = ''
+unitsMapInverted[3] = 'k'
+unitsMapInverted[6] = 'M'
+unitsMapInverted[9] = 'G'
+unitsMapInverted[12] = 'T'
+
+function eng2num(eng) {
+    eng = eng.toLowerCase()
+
+    result = eng.match(/\d+/g)
+    num = result[0]
+    dec = result.length == 2 ? result[1] : 0
+
+    units = eng.match(/[a-z]+/)
+    units = units == null ? '' : units[0]
+    multiplier = spiceUnitsMap[units]
+
+    return parseFloat(num + '.' + dec) * multiplier
+}
+
+function num2eng(num) {
+    const toOptionalFixed = (num, digits) =>
+        `${Number.parseFloat(num.toFixed(digits))}`;
+
+    scale = Math.floor(Math.log10(num) / 3) * 3
+    unit = unitsMapInverted[scale]
+    return `${toOptionalFixed(num / 10**scale, 3)} ${unit}`
+}

dist/tools/general/analog-filter-designer/js/main.js

@@ -105,10 +105,14 @@ function update() {
     if (!args_elem.every(x => x.validity.valid)) return
 
     args = args_elem.map(x => x.value)
+    args_num = args.map(x => eng2num(x))
 
     sim_model = createFormattedString(sim_models[sim_name], args)
     document.getElementById('spice-input').textContent = sim_model
 
+    freq = freq_models[sim_name](args_num)
+    document.getElementById("out_fc").value = num2eng(freq) + 'Hz'
+
     processSimulation()
 }
 

dist/tools/general/analog-filter-designer/js/models.js

@@ -30,6 +30,13 @@ downloadURL = function(data, fileName) {
 
 const sim_command = `.ac dec 500 1 {0}`
 
+const freq_models = {
+    'se_rc': (args) => 1/(2*Math.PI*args[1]*args[2]),
+    'se_rc_hpf': (args) => 1/(2*Math.PI*args[1]*args[2]),
+    'diff_rc': (args) => 1/(2*2*Math.PI*args[1]*args[2]),
+    'lrc_lpf': (args) => 1/(2*Math.PI*Math.sqrt(args[1]*args[3])),
+}
+
 const sim_models = {
     // ----------------------------------------
     'se_rc': `Single Ended RC LPF