Index: Makefile
===================================================================
--- Makefile	(nonexistent)
+++ Makefile	(revision 31756)
@@ -0,0 +1,6 @@
+all:
+	cd ../../src && $(MAKE) mod_lib_formula
+
+clean:
+	rm *.o *.so 2>/dev/null ; true
+
Index: Plug.tmpasm
===================================================================
--- Plug.tmpasm	(nonexistent)
+++ Plug.tmpasm	(revision 31756)
@@ -0,0 +1,10 @@
+put /local/pcb/mod {lib_formula}
+put /local/pcb/mod/OBJS [@
+	$(PLUGDIR)/lib_formula/lib_formula.o
+@]
+
+switch /local/pcb/lib_formula/controls
+	case {buildin}   include /local/pcb/tmpasm/buildin; end;
+	case {plugin}    include /local/pcb/tmpasm/plugin; end;
+	case {disable}   include /local/pcb/tmpasm/disable; end;
+end
Index: impedance.c
===================================================================
--- impedance.c	(nonexistent)
+++ impedance.c	(revision 31756)
@@ -0,0 +1,44 @@
+/*
+ *                            COPYRIGHT
+ *
+ *  pcb-rnd, interactive printed circuit board design
+ *  Copyright (C) 2020 Tibor 'Igor2' Palinkas
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program; if not, write to the Free Software
+ *  Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ *  Contact:
+ *    Project page: http://repo.hu/projects/pcb-rnd
+ *    lead developer: http://repo.hu/projects/pcb-rnd/contact.html
+ *    mailing list: pcb-rnd (at) list.repo.hu (send "subscribe")
+ */
+
+#include "config.h"
+#include <math.h>
+
+#define TOM(x) (RND_COORD_TO_MM(x) * 1000.0)
+#define SQR(x) ((x)*(x))
+#define N0 377
+
+double pcb_impedance_microstrip(rnd_coord_t trace_thick, rnd_coord_t trace_height, rnd_coord_t subst_height, double dielect)
+{
+	double w = TOM(trace_thick), t = TOM(trace_height), h = TOM(subst_height), Er = dielect;
+	double weff, x1, x2;
+
+	weff = w + (t/M_PI) * log(4*M_E / sqrt(SQR(t/h)+SQR(t/(w*M_PI+1.1*t*M_PI)))) * (Er+1)/(2*Er);
+	x1 = 4 * ((14*Er+8)/(11*Er)) * (h/weff);
+	x2 = qsrt(16 * SQR(h/weff) * SQR((14*Er+8)/(11*Er)) + ((Er+1)/(2*Er))*M_PI;
+	return N0 / (2*M_PI * sqrt(2) * sqrt(Er+1)) * log(1+4*(h/weff)*(x1+x2));
+}
+
Index: impedance.h
===================================================================
--- impedance.h	(nonexistent)
+++ impedance.h	(revision 31756)
@@ -0,0 +1,2 @@
+double pcb_impedance_microstrip(rnd_coord_t trace_thick, rnd_coord_t trace_height, rnd_coord_t subst_height, double dielect);
+
Index: lib_formula.c
===================================================================
--- lib_formula.c	(nonexistent)
+++ lib_formula.c	(revision 31756)
@@ -0,0 +1,44 @@
+/*
+ *                            COPYRIGHT
+ *
+ *  pcb-rnd, interactive printed circuit board design
+ *  Copyright (C) 2020 Tibor 'Igor2' Palinkas
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program; if not, write to the Free Software
+ *  Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ *  Contact:
+ *    Project page: http://repo.hu/projects/pcb-rnd
+ *    lead developer: http://repo.hu/projects/pcb-rnd/contact.html
+ *    mailing list: pcb-rnd (at) list.repo.hu (send "subscribe")
+ */
+
+#include "config.h"
+
+#include <stdio.h>
+#include <librnd/core/plugins.h>
+
+#include "impedance.h"
+
+int pplg_check_ver_lib_formula(int ver_needed) { return 0; }
+
+void pplg_uninit_lib_formula(void)
+{
+}
+
+int pplg_init_lib_formula(void)
+{
+	RND_API_CHK_VER;
+	return 0;
+}
Index: lib_formula.pup
===================================================================
--- lib_formula.pup	(nonexistent)
+++ lib_formula.pup	(revision 31756)
@@ -0,0 +1,6 @@
+$class lib
+$short mathematical forumlas
+$long simple formulas, for efficient rule-of-thumb calculations
+$state works
+$package core
+default buildin