adds DISCRETE_RCFILTER_SW to discrete sound

* this implements multiple RC networks with CD4066 switches to connect/disconnect capacitor

src/emu/sound/disc_flt.c

@@ -91,6 +91,10 @@ struct dst_rcfilter_context
 	double	vCap;
 };
 
+struct dst_rcfilter_sw_context
+{
+	double	vCap[4];
+};
 
 /************************************************************************
  *
@@ -1076,6 +1080,67 @@ static void dst_rcfilter_reset(node_description *node)
 	node->output = 0;
 }
 
+/************************************************************************
+ *
+ * DST_RCFILTER_SW - Usage of node_description values for switchable RC filter
+ *
+ * input[0]    - Enable input value
+ * input[1]    - input value
+ * input[2]    - Resistor value (initialization only)
+ * input[3]    - Capacitor Value (initialization only)
+ * input[4]    - Voltage reference. Usually 0V.
+ *
+ ************************************************************************/
+#define DST_RCFILTER_SW__ENABLE		(*(node->input[0]))
+#define DST_RCFILTER_SW__VIN		(*(node->input[1]))
+#define DST_RCFILTER_SW__SWITCH		(*(node->input[2]))
+#define DST_RCFILTER_SW__R			(*(node->input[3]))
+#define DST_RCFILTER_SW__C(x)		(*(node->input[4+x]))
+
+#define CD4066_ON_RES  470
+
+static void dst_rcfilter_sw_step(node_description *node)
+{
+	struct dst_rcfilter_sw_context *context = node->context;
+	int i;
+	double rcexp;
+	double us=0, rs=0;
+
+	if(DST_RCFILTER_SW__ENABLE)
+	{
+		for (i=0;i<4;i++)
+		{
+			if ( ( (int)DST_RCFILTER_SW__SWITCH & (1<<i)) == 1)
+			{
+				us += context->vCap[i];
+				rs += DST_RCFILTER_SW__R;
+			}
+		}
+		node->output = CD4066_ON_RES / ( CD4066_ON_RES + rs) * DST_RCFILTER_SW__VIN + DST_RCFILTER_SW__R / (CD4066_ON_RES + rs)  * us;
+		for (i=0;i<4;i++)
+		{
+			if ( ( (int)DST_RCFILTER_SW__SWITCH & (1<<i)) == 1)
+			{
+				rcexp = 1.0 - exp(-1.0 / ( CD4066_ON_RES * DST_RCFILTER_SW__C(i)) * discrete_current_context->sample_rate);
+				context->vCap[i] += ((node->output - context->vCap[i]) * rcexp);
+			}
+		}
+	}
+	else
+	{
+		node->output=0;
+	}
+}
+
+static void dst_rcfilter_sw_reset(node_description *node)
+{
+	struct dst_rcfilter_sw_context *context = node->context;
+	int i;
+	
+	for (i=0;i<4;i++)
+		context->vCap[i] = 0;
+	node->output = 0;
+}
 
 /* !!!!!!!!!!! NEW FILTERS for testing !!!!!!!!!!!!!!!!!!!!! */
 

src/emu/sound/discrete.c

@@ -244,6 +244,7 @@ static const discrete_module module_list[] =
 	{ DST_RCINTEGRATE ,"DST_RCINTEGRATE" ,sizeof(struct dst_rcdisc_context)      ,dst_rcintegrate_reset ,dst_rcintegrate_step },
 	{ DST_RCDISC_MOD  ,"DST_RCDISC_MOD"  ,sizeof(struct dst_rcdisc_context)      ,dst_rcdisc_mod_reset  ,dst_rcdisc_mod_step  },
 	{ DST_RCFILTER    ,"DST_RCFILTER"    ,sizeof(struct dst_rcfilter_context)    ,dst_rcfilter_reset    ,dst_rcfilter_step    },
+	{ DST_RCFILTER_SW ,"DST_RCFILTER_SW" ,sizeof(struct dst_rcfilter_sw_context) ,dst_rcfilter_sw_reset ,dst_rcfilter_sw_step },
 	/* For testing - seem to be buggered.  Use versions not ending in N. */
 	{ DST_RCFILTERN   ,"DST_RCFILTERN"   ,sizeof(struct dss_filter1_context)     ,dst_rcfilterN_reset   ,dst_filter1_step     },
 	{ DST_RCDISCN     ,"DST_RCDISCN"     ,sizeof(struct dss_filter1_context)     ,dst_rcdiscN_reset     ,dst_rcdiscN_step     },

src/emu/sound/discrete.h

@@ -2585,6 +2585,43 @@
  * EXAMPLES: see Polaris
  *
  ***********************************************************************
+ *
+ * DISCRETE_RCFILTER_SW - Multiple switchable RC filters 
+ *
+ *                             R       
+ *    INPUT      >-----------ZZZZ-+-------+----......-----> Output  
+ *                                |       |    
+ *                               +-+     +-+
+ *    SWITCH     > Bit 0 ---->F1 | |  F2 | |
+ *                               '-'   ^ '-'
+ *                 Bit 1 ---------|----'  |
+ *                                |       |
+ *                 Bit ...       ---     ---
+ *                               --- C1  --- C2
+ *                                |       |
+ *                               GND     GND
+ *
+ * 
+ *  Declaration syntax
+ *
+ *     DISCRETE_RCFILTER_SW(name of node,
+ *                          enable,
+ *                          input node (or value),
+ *                          switch node (or value),
+ *                          R in Ohms,
+ *                          C1 in Farads,
+ *                          C2 in Farads,
+ *                          C3 in Farads,
+ *                          C4 in Farads)
+ *
+ *     This is a typical filter circuit in circusc or scramble. 
+ *     Switches are usually CD4066 with a "open" resistance of 
+ *     typical 470 Ohms at 5V.
+ *     This circuit supports up to 4 filters.
+ * 
+ * EXAMPLES: see circusc
+ *
+ ***********************************************************************
  =======================================================================
  * from from disc_flt.c
  * Component specific modules
@@ -3772,6 +3809,7 @@ enum
 	DST_RCINTEGRATE,	/* NPN RC charge/discharge network */
 	DST_RCDISC_MOD,		/* Two diode mixer with Transistor and charge/discharge network */
 	DST_RCFILTER,		/* Simple RC Filter network */
+	DST_RCFILTER_SW,	/* Switcheable RC Filter network */
 	/* For testing - seem to be buggered.  Use versions not ending in N. */
 	DST_RCFILTERN,		/* Simple RC Filter network */
 	DST_RCDISCN,		/* Simple RC discharge */
@@ -3927,6 +3965,7 @@ enum
 #define DISCRETE_RCINTEGRATE(NODE,ENAB,INP0,RVAL0,RVAL1,RVAL2,CVAL,vP,TYPE)		{ NODE, DST_RCINTEGRATE     , 8, { ENAB,INP0,NODE_NC,NODE_NC,NODE_NC,NODE_NC,NODE_NC,NODE_NC }, { ENAB,INP0,RVAL0,RVAL1,RVAL2,CVAL,vP,TYPE }, NULL, "RC Discharge 6" },
 #define DISCRETE_RCDISC_MODULATED(NODE,ENAB,INP0,INP1,RVAL0,RVAL1,RVAL2,RVAL3,CVAL,VP)			{ NODE, DST_RCDISC_MOD     , 9, { ENAB,INP0,INP1,RVAL0,RVAL1,RVAL2,RVAL3,CVAL,VP }, { ENAB,INP0,INP1,RVAL0,RVAL1,RVAL2,RVAL3,CVAL,VP }, NULL, "Modulated RC Discharge" },
 #define DISCRETE_RCFILTER(NODE,ENAB,INP0,RVAL,CVAL)                     { NODE, DST_RCFILTER    , 4, { ENAB,INP0,NODE_NC,NODE_NC }, { ENAB,INP0,RVAL,CVAL }, NULL, "RC Filter" },
+#define DISCRETE_RCFILTER_SW(NODE,ENAB,INP0,SW,RVAL,CVAL1,CVAL2,CVAL3,CVAL4) { NODE, DST_RCFILTER_SW, 8, { ENAB,INP0,SW,RVAL,CVAL1,CVAL2,CVAL3,CVAL4 }, { ENAB,INP0,SW,RVAL,CVAL1,CVAL2,CVAL3,CVAL4 }, NULL, "RC Filter Switch" },
 #define DISCRETE_RCFILTER_VREF(NODE,ENAB,INP0,RVAL,CVAL,VREF)           { NODE, DST_RCFILTER    , 5, { ENAB,INP0,NODE_NC,NODE_NC,NODE_NC }, { ENAB,INP0,RVAL,CVAL,VREF }, NULL, "RC Filter to VREF" },
 /* For testing - seem to be buggered.  Use versions not ending in N. */
 #define DISCRETE_RCDISCN(NODE,ENAB,INP0,RVAL,CVAL)                      { NODE, DST_RCDISCN     , 4, { ENAB,INP0,NODE_NC,NODE_NC }, { ENAB,INP0,RVAL,CVAL }, NULL, "RC Discharge (New Type)" },