A band-limited oscillator based on a resistor-capacitor timing scheme like the 555 timer IC.

 

svn path=/trunk/externals/mrpeach/; revision=13452

1 files changed, 117 insertions, 0 deletions

diff --git a/rcosc~/rcosc~.c b/rcosc~/rcosc~.c
new file mode 100644
index 0000000..0ab1c9d
--- /dev/null
+++ b/rcosc~/rcosc~.c
@@ -0,0 +1,117 @@
+/* rcosc~.c by Martin Peach 20100331 */
+/* Pd external emulating a resistor-capacitor-controlled oscillator */
+/* The first control parameter is a time constant in seconds (or resistance X capacitance) */
+/* The second control parameter is a threshold above which the cap is set to discharge */
+/* The third control parameter is a threshold below which the cap is set to charge */
+
+#include "m_pd.h"
+
+static t_class *rcosc_tilde_class;
+
+typedef struct _rcosc_tilde
+{
+    t_object    rc_obj;
+    t_float     rc_f;
+    t_float     rc_upper_threshold; /* if rc_dir is 1, charge to here */
+    t_float     rc_lower_threshold; /* if rc_dir is 0, discharge to here */
+    t_int       rc_dir;
+    double      rc_node;
+    double      rc_one;
+    double      rc_zero;
+    double      rc_sp;
+    double      rc_slewmax;
+} t_rcosc_tilde;
+
+static t_int *rcosc_tilde_perform(t_int *w);
+static void rcosc_tilde_dsp(t_rcosc_tilde *x, t_signal **sp);
+static void *rcosc_tilde_new(t_floatarg f);
+
+static t_int *rcosc_tilde_perform(t_int *w)
+{
+    t_rcosc_tilde   *x = (t_rcosc_tilde *)(w[1]);
+    t_sample        *in = (t_sample *)(w[2]);
+    t_sample        *out = (t_sample *)(w[3]);
+    int             n = (int)(w[4]);
+    double          slewrate, delta, node, overshoot;
+    int             i, n_oversamples = 64;
+
+//    if (x->rc_rc < x->rc_sp) slewrate = 1.0;    
+//    else slewrate = x->rc_sp/x->rc_rc;
+        
+    while (n--)
+    {
+        slewrate =  x->rc_one/(n_oversamples*(x->rc_sp*(*in++)));
+        if (slewrate < x->rc_zero) slewrate = x->rc_zero;
+        else if (slewrate > x->rc_one) slewrate = x->rc_one;
+        node = x->rc_node;
+        for (i = 0; i < n_oversamples; ++i)
+        {
+            if (x->rc_dir)
+            {
+                delta = slewrate*(x->rc_one - x->rc_node);
+                if (delta > x->rc_slewmax) delta = x->rc_slewmax;
+                x->rc_node += delta;
+                overshoot = x->rc_node - x->rc_upper_threshold;
+                if (overshoot > 0)
+                {
+                    x->rc_dir = 0;
+                    x->rc_node = x->rc_upper_threshold - overshoot; /* bounce */
+                }
+            }
+            else
+            {
+                delta = slewrate*(x->rc_zero - x->rc_node);
+                if (delta < -x->rc_slewmax) delta = -x->rc_slewmax;
+                x->rc_node += delta;
+                overshoot = x->rc_lower_threshold - x->rc_node;
+                if (overshoot > 0)
+                {
+                    x->rc_dir = 1;
+                    x->rc_node = x->rc_lower_threshold + overshoot; /* bounce */
+                }
+            }
+        }
+        *out++ = ((node + x->rc_node)*3)-3;
+    }
+    return (w+5);
+}
+
+static void rcosc_tilde_dsp(t_rcosc_tilde *x, t_signal **sp)
+{
+    x->rc_sp = sys_getsr();
+    dsp_add(rcosc_tilde_perform, 4, x, sp[0]->s_vec, sp[1]->s_vec, sp[0]->s_n);
+}
+
+static void *rcosc_tilde_new(t_floatarg f)
+{
+    t_rcosc_tilde *x = (t_rcosc_tilde *)pd_new(rcosc_tilde_class);
+
+    x->rc_f = f;
+    x->rc_node = 0.0;
+    x->rc_upper_threshold = 0.666; /* if rc_dir is 1, charge to here */
+    x->rc_lower_threshold = 0.333; /* if rc_dir is 0, discharge to here */
+    x->rc_slewmax = 0.003;/* arbitrary slew rate limit */
+    x->rc_dir = 1; /* start charging */
+    x->rc_one = 1;
+    x->rc_zero = 0;
+  
+    outlet_new(&x->rc_obj, &s_signal);
+
+    post("rcosc~ 20100331 Martin Peach");
+    return (void *)x;
+}
+
+void rcosc_tilde_setup(void)
+{
+    rcosc_tilde_class = class_new(gensym("rcosc~"),
+        (t_newmethod)rcosc_tilde_new,
+        0, sizeof(t_rcosc_tilde),
+        CLASS_DEFAULT, 
+        A_DEFFLOAT, 0);
+
+    class_addmethod(rcosc_tilde_class, (t_method)rcosc_tilde_dsp, gensym("dsp"), 0);
+    CLASS_MAINSIGNALIN(rcosc_tilde_class, t_rcosc_tilde, rc_f);
+}
+
+/* fin rcosc~.c */
+