diff --git a/tools/Makefile.common b/tools/Makefile.common
index c25dde6..272afd7 100644
--- a/tools/Makefile.common
+++ b/tools/Makefile.common
@@ -22,6 +22,8 @@ endif
 
 CC_host = gcc
 CC_ben = mipsel-openwrt-linux-gcc
+CFLAGS_host =
+CFLAGS_ben =
 LDLIBS_host = -lusb
 LDLIBS_ben =
 MACROS_host = -DHAVE_USB
@@ -40,5 +42,7 @@ else
     AR		= $(AR_quiet)
 endif
 
-CFLAGS += -I../../atusb/fw/include -I../include $(MACROS_$(TARGET))
+CFLAGS += $(CFLAGS_$(TARGET)) -I../../atusb/fw/include -I../include \
+          $(MACROS_$(TARGET))
 LDLIBS = $(LDLIBS_$(TARGET)) -L../lib -latspi
+OBJS += $(OBJS_$(TARGET))
diff --git a/tools/atspi-rssi/Makefile b/tools/atspi-rssi/Makefile
index a3365e1..268e837 100644
--- a/tools/atspi-rssi/Makefile
+++ b/tools/atspi-rssi/Makefile
@@ -14,3 +14,10 @@
 MAIN = atspi-rssi
 
 include ../Makefile.common
+
+CFLAGS_host += $(shell sdl-config --cflags)
+MACROS_host += -DHAVE_GFX
+LDLIBS_host += $(shell sdl-config --libs) -lSDL_gfx
+OBJS_host = gui.o zgrid.o digit.o
+
+$(MAIN):	$(OBJS_$(TARGET))
diff --git a/tools/atspi-rssi/atspi-rssi.c b/tools/atspi-rssi/atspi-rssi.c
index ae47732..cf2203c 100644
--- a/tools/atspi-rssi/atspi-rssi.c
+++ b/tools/atspi-rssi/atspi-rssi.c
@@ -21,6 +21,12 @@
 #include "atspi.h"
 #include "misctxrx.h"
 
+#ifdef HAVE_GFX
+#include "gui.h"
+#else
+#define	gui(dsc) abort()
+#endif
+
 
 static struct timeval t0;
 static volatile int run = 1;
@@ -59,6 +65,12 @@ static void usage(const char *name)
 {
 	fprintf(stderr,
 "usage: %s [-n] sweeps\n", name);
+
+#ifdef HAVE_GFX
+	fprintf(stderr,
+"%6s %s -g\n", "", name);
+#endif
+
 	exit(1);
 }
 
@@ -66,12 +78,19 @@ static void usage(const char *name)
 int main(int argc, char **argv)
 {
 	struct atspi_dsc *dsc;
-	unsigned long sweeps, i;
+	unsigned long arg = 0, i;
 	char *end;
 	int c;
+	int graphical = 0;
 
-	while ((c = getopt(argc, argv, "n")) != EOF)
+	while ((c = getopt(argc, argv, "gn")) != EOF)
 		switch (c) {
+#ifdef HAVE_GFX
+		case 'g':
+			graphical = 1;
+
+			break;
+#endif
 		case 'n':
 			break;
 		default:
@@ -79,8 +98,14 @@ int main(int argc, char **argv)
 		}
 
 	switch (argc-optind) {
+	case 0:
+		if (!graphical)
+			usage(*argv);
+		break;
 	case 1:
-		sweeps = strtoul(argv[optind], &end, 0);
+		if (graphical)
+			usage(*argv);
+		arg = strtoul(argv[optind], &end, 0);
 		if (*end)
 			usage(*argv);
 		break;
@@ -100,9 +125,13 @@ int main(int argc, char **argv)
 	 * We'll wait for the PLL lock after selecting the channel.
 	 */
 
-	gettimeofday(&t0, NULL);
-	for (i = 0; run && i != sweeps; i++)
-		sweep(dsc);
+	if (graphical)
+		gui(dsc);
+	else {
+		gettimeofday(&t0, NULL);
+		for (i = 0; run && i != arg; i++)
+			sweep(dsc);
+	}
 
 	atspi_reg_write(dsc, REG_TRX_STATE, TRX_CMD_TRX_OFF);
 
diff --git a/tools/atspi-rssi/digit.c b/tools/atspi-rssi/digit.c
new file mode 100644
index 0000000..101e355
--- /dev/null
+++ b/tools/atspi-rssi/digit.c
@@ -0,0 +1,87 @@
+/*
+ * atspi-rssi/digit.c - Draw 7 segment style digits
+ *
+ * Written 2010 by Werner Almesberger
+ * Copyright 2010 Werner Almesberger
+ *
+ * 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.
+ */
+
+
+#include <stdint.h>
+
+#include "SDL.h"
+#include "SDL_gfxPrimitives.h"
+
+#include "digit.h"
+
+
+static void hlines_3(SDL_Surface *s, int x0, int x1, int y0, int ym, int y1,
+    uint32_t fg)
+{
+	hlineColor(s, x0, x1, y0, fg);
+	hlineColor(s, x0, x1, ym, fg);
+	hlineColor(s, x0, x1, y1, fg);
+}
+
+
+void digit(SDL_Surface *s, int n, int x0, int x1, int y0, int ym, int y1,
+    uint32_t fg)
+{
+	switch (n) {
+	case 8:
+		hlineColor(s, x0, x1, ym, fg);
+		/* fall through */
+	case 0:
+		hlineColor(s, x0, x1, y0, fg);
+		vlineColor(s, x0, y0, y1, fg);
+		/* fall through */
+	case 7:
+		hlineColor(s, x0, x1, y1, fg);
+		vlineColor(s, x1, y0, y1, fg);
+		break;
+
+	case 1:
+		lineColor(s, x0, ym, x1, y1, fg);
+		vlineColor(s, x1, y0, y1, fg);
+		break;
+
+	case 2:
+		hlines_3(s, x0, x1, y0, ym, y1, fg);
+		vlineColor(s, x0, y0, ym, fg);
+		vlineColor(s, x1, ym, y1, fg);
+		break;
+
+	case 9:
+		vlineColor(s, x0, ym, y1, fg);
+		/* fall through */
+	case 3:
+		hlines_3(s, x0, x1, y0, ym, y1, fg);
+		vlineColor(s, x1, y0, y1, fg);
+		break;
+
+	case 4:
+		hlineColor(s, x0, x1, ym, fg);
+		vlineColor(s, x0, ym, y1, fg);
+		vlineColor(s, x1, y0, y1, fg);
+		break;
+
+	case 6:
+		hlines_3(s, x0, x1, y0, ym, y1, fg);
+		vlineColor(s, x0, y0, y1, fg);
+		vlineColor(s, x1, y0, ym, fg);
+		break;
+
+	case 5:
+		hlines_3(s, x0, x1, y0, ym, y1, fg);
+		vlineColor(s, x0, ym, y1, fg);
+		vlineColor(s, x1, y0, ym, fg);
+		break;
+
+	default:
+		abort();
+	}
+}
diff --git a/tools/atspi-rssi/digit.h b/tools/atspi-rssi/digit.h
new file mode 100644
index 0000000..a727547
--- /dev/null
+++ b/tools/atspi-rssi/digit.h
@@ -0,0 +1,25 @@
+/*
+ * atspi-rssi/digit.h - Draw 7 segment style digits
+ *
+ * Written 2010 by Werner Almesberger
+ * Copyright 2010 Werner Almesberger
+ *
+ * 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.
+ */
+
+
+#ifndef DIGIT_H
+#define DIGIT_H
+
+#include <stdint.h>
+
+#include "SDL.h"
+
+
+void digit(SDL_Surface *s, int n, int x0, int x1, int y0, int ym, int y1,
+    uint32_t fg);
+
+#endif /* !DIGIT_H */
diff --git a/tools/atspi-rssi/gui.c b/tools/atspi-rssi/gui.c
new file mode 100644
index 0000000..4191082
--- /dev/null
+++ b/tools/atspi-rssi/gui.c
@@ -0,0 +1,147 @@
+/*
+ * atspi-rssi/gui.c - Graphical output for atspi-rssi
+ *
+ * Written 2010 by Werner Almesberger
+ * Copyright 2010 Werner Almesberger
+ *
+ * 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.
+ */
+
+
+#include <stdlib.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <signal.h>
+#include <sys/time.h>
+
+#include "SDL.h"
+#include "SDL_gfxPrimitives.h"
+
+#include "at86rf230.h"
+#include "atspi.h"
+#include "misctxrx.h"
+
+#include "zgrid.h"
+#include "digit.h"
+#include "gui.h"
+
+
+#define	XRES	320
+#define	YRES	240
+
+#define	N_CHAN	16
+#define	N_TIME	64
+
+
+static struct timeval t0;
+
+
+static void shift_grid(int *z, int nx, int ny)
+{
+	int *p1, *p0, *s;
+	int x, y;
+
+	p1 = z+(ny-1)*nx;
+	for (y = 1; y != ny; y++) {
+		p0 = s = p1-nx;
+		for (x = 0; x != nx; x++)
+			*p1++ = *p0++;
+		p1 = s;
+	}
+}
+
+
+static void sweep(struct atspi_dsc *dsc, int *z)
+{
+	int chan;
+
+	for (chan = 11; chan <= 26; chan++) {
+		atspi_reg_write(dsc, REG_PHY_CC_CCA, chan);
+		/* 150 us, according to AVR2001 section 3.5 */
+		wait_for_interrupt(dsc, IRQ_PLL_LOCK, IRQ_PLL_LOCK, 10, 20);
+
+		*z++ = 3*atspi_reg_read(dsc, REG_PHY_RSSI) & RSSI_MASK;
+#if 0
+		if (chan >= 13 && chan <= 19 )
+			z[-1] = 3*28-(chan-16)*(chan-16)*(chan-16)*(chan-16);
+#endif
+	}
+}
+
+
+static void clear(SDL_Surface *s)
+{
+	SDL_FillRect(s, NULL, SDL_MapRGB(s->format, 0, 0, 0));
+}
+
+
+#define	CBIG(pos) \
+	x-5+(pos)*6, x-1+(pos)*6, y+8, y+4, y, 0xff4040ff
+#define	CSMALL(pos) \
+	x-7+(pos)*4, x-5+(pos)*4, y+15, y+13, y+11, 0x20ff00ff
+
+
+static void label_channels(SDL_Surface *s, int sx, int x0, int y0)
+{
+	int x, y, i, c, f;
+
+	x = x0;
+	y = s->h-y0+4;
+	for (i = 0; i != N_CHAN; i++) {
+		c = i+11;
+		digit(s, c/10, CBIG(0));
+		digit(s, c % 10, CBIG(1));
+		f = 2405+5*i;
+		if (i & 1)
+			y++;
+		digit(s, f/1000, CSMALL(0));
+		digit(s, (f/100) % 10, CSMALL(1));
+		digit(s, (f/10) % 10, CSMALL(2));
+		digit(s, f % 10, CSMALL(3));
+		if (i & 1)
+			y--;
+		x += sx;
+	}
+}
+
+
+void gui(struct atspi_dsc *dsc)
+{
+	SDL_Surface *surf;
+	int z[N_CHAN*N_TIME];
+
+	memset(z, 0, sizeof(z));
+	gettimeofday(&t0, NULL);
+	
+	if (SDL_Init(SDL_INIT_VIDEO) < 0) {
+		fprintf(stderr, "SDL_init: %s\n", SDL_GetError());
+		exit(1);
+	}
+	atexit(SDL_Quit);
+
+	surf = SDL_SetVideoMode(XRES, YRES, 0, SDL_SWSURFACE);
+	if (!surf) {
+		fprintf(stderr, "SDL_SetVideoMode: %s\n", SDL_GetError());
+		exit(1);
+	}
+
+	while (1) {
+		shift_grid(z, N_CHAN, N_TIME);
+		sweep(dsc, z);
+
+		SDL_LockSurface(surf);
+
+		clear(surf);
+		zgrid_draw(surf, z, N_CHAN, N_TIME,
+		    17, 2, 1,
+		    7, 40,
+		    0xffffff00, 0x00408080);
+		label_channels(surf, 17, 7, 40);
+
+		SDL_UnlockSurface(surf);
+		SDL_UpdateRect(surf, 0, 0, 0, 0);
+	}
+}
diff --git a/tools/atspi-rssi/gui.h b/tools/atspi-rssi/gui.h
new file mode 100644
index 0000000..cba2119
--- /dev/null
+++ b/tools/atspi-rssi/gui.h
@@ -0,0 +1,21 @@
+/*
+ * atspi-rssi/gui.h - Graphical output for atspi-rssi
+ *
+ * Written 2010 by Werner Almesberger
+ * Copyright 2010 Werner Almesberger
+ *
+ * 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.
+ */
+
+#ifndef GUI_H
+#define GUI_H
+
+#include "atspi.h"
+
+
+void gui(struct atspi_dsc *dsc);
+
+#endif /* !GUI_H */
diff --git a/tools/atspi-rssi/zgrid.c b/tools/atspi-rssi/zgrid.c
new file mode 100644
index 0000000..c9422f1
--- /dev/null
+++ b/tools/atspi-rssi/zgrid.c
@@ -0,0 +1,99 @@
+/*
+ * atspi-rssi/zgrid.c - Display a surface in faux 3D with SDL/SDL_gfx
+ *
+ * Written 2010 by Werner Almesberger
+ * Copyright 2010 Werner Almesberger
+ *
+ * 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.
+ */
+
+
+#include <stdint.h>
+#include <stdlib.h>
+#include <stdio.h>
+
+#include "SDL.h"
+#include "SDL_gfxPrimitives.h"
+
+#include "zgrid.h"
+
+
+#define	SWAP(x, y) 	\
+	do { typeof(x) swap_tmp = (x); (x) = (y); (y) = swap_tmp; } while (0)
+
+
+static int *alloc_row(int nx)
+{
+	int *p;
+
+	p = malloc(nx*sizeof(*p));
+	if (p)
+		return p;
+	perror("malloc");
+	exit(1);
+}
+
+
+static void draw_band(SDL_Surface *s, const int *ax, const int *ay,
+    const int *bx, const int *by, int n, uint32_t fg, uint32_t bg)
+{
+	Sint16 px[4], py[4];
+	int i;
+
+	for (i = n-2; i >= 0; i--) {
+		px[0] = ax[i];
+		px[1] = ax[i+1];
+		px[2] = bx[i+1];
+		px[3] = bx[i];
+		py[0] = ay[i];
+		py[1] = ay[i+1];
+		py[2] = by[i+1];
+		py[3] = by[i];
+		filledPolygonColor(s, px, py, 4, bg);
+		aalineColor(s, ax[i+1], ay[i+1], bx[i+1], by[i+1], fg);
+		aalineColor(s, bx[i], by[i], bx[i+1], by[i+1], fg);
+	}
+	aalineColor(s, ax[0], ay[0], bx[0], by[0], fg);
+}
+
+
+static void draw_polyline(SDL_Surface *s, const int *px, const int *py,
+    int n, uint32_t rgba)
+{
+	int i;
+
+	for (i = 0; i != n-1; i++)
+		aalineColor(s, px[i], py[i], px[i+1], py[i+1], rgba);
+}
+
+
+void zgrid_draw(SDL_Surface *s, const int *z, int nx, int ny,
+    int sx, int sy, int sxy, int x0, int y0, uint32_t fg, uint32_t bg)
+{
+	int *lx = alloc_row(nx);
+	int *ly = alloc_row(nx);
+	int *px = alloc_row(nx);
+	int *py = alloc_row(nx);
+	int x, y, yz0;
+	const int *zp;
+	uint8_t a;
+
+	for (y = ny-1; y >= 0; y--) {
+		a = (ny-1-y)*0xe0/(ny-1)+0x1f;
+		yz0 = s->h-y0-y*sy-1;
+		zp = z+y*nx;
+		for (x = 0; x != nx; x++) {
+			px[x] = x0+x*sx+y*sxy;
+			py[x] = yz0-zp[x];
+		}
+		if (y != ny-1) {
+			draw_band(s, px, py, lx, ly, nx, fg | a, bg);
+		}
+		SWAP(px, lx);
+		SWAP(py, ly);
+	}
+	draw_polyline(s, lx, ly, nx, fg | 0xff);
+}
diff --git a/tools/atspi-rssi/zgrid.h b/tools/atspi-rssi/zgrid.h
new file mode 100644
index 0000000..a5db289
--- /dev/null
+++ b/tools/atspi-rssi/zgrid.h
@@ -0,0 +1,24 @@
+/*
+ * atspi-rssi/zgrid.h - Display a surface in faux 3D with SDL/SDL_gfx
+ *
+ * Written 2010 by Werner Almesberger
+ * Copyright 2010 Werner Almesberger
+ *
+ * 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.
+ */
+
+#ifndef ZGRID_H
+#define ZGRID_H
+
+#include <stdint.h>
+
+#include "SDL.h"
+
+
+void zgrid_draw(SDL_Surface *s, const int *z, int nx, int ny,
+    int sx, int sy, int sxy, int x0, int y0, uint32_t fg, uint32_t bg);
+
+#endif /* !ZGRID_H */