20060303a

20 files changed, 6274 insertions, 0 deletions

diff --git a/appl/demo/lego/clockface.b b/appl/demo/lego/clockface.b
new file mode 100644
index 00000000..1f2aa105
--- /dev/null
+++ b/appl/demo/lego/clockface.b
@@ -0,0 +1,367 @@
+# Model 1
+implement Clockface;
+
+include "sys.m";
+include "draw.m";
+
+Clockface : module {
+	init : fn (ctxt : ref Draw->Context, argv : list of string);
+};
+
+sys : Sys;
+
+hmpath : con "motor/0";		# hour-hand motor
+mmpath : con "motor/2";		# minute-hand motor
+allmpath : con "motor/012";	# all motors (for stopall msg)
+
+hbpath : con "sensor/0";		# hour-hand sensor
+mbpath : con "sensor/2";		# minute-hand sensor
+lspath: con "sensor/1";		# light sensor;
+
+ONTHRESH : con 780;		# light sensor thresholds
+OFFTHRESH : con 740;
+NCLICKS : con 120;
+MINCLICKS : con 2;			# min number of clicks required to stop a motor
+
+Hand : adt {
+	motor : ref Sys->FD;
+	sensor : ref Sys->FD;
+	fwd : array of byte;
+	rev : array of byte;
+	stop : array of byte;
+	pos : int;
+};
+
+lightsensor : ref Sys->FD;
+allmotors : ref Sys->FD;
+hourhand : ref Hand;
+minutehand : ref Hand;
+
+reqch: chan of (string, chan of int);
+
+init(nil : ref Draw->Context, argv : list of string)
+{
+	sys = load Sys Sys->PATH;
+	sys->pctl(Sys->NEWPGRP, nil);
+
+	argv = tl argv;
+	if (len argv != 1) {
+		sys->print("usage: lego_dir\n");
+		raise("fail:usage");
+	}
+
+	# set up our control file
+	if (sys->bind("#s", ".", Sys->MBEFORE) == -1) {
+		sys->print("failed to bind srv device: %r\n");
+		return;
+	}
+	f2c := sys->file2chan(".", "clockface");
+	if (f2c == nil) {
+		sys->print("cannot create legolink channel: %r\n");
+		return;
+	}
+
+	legodir := hd argv;
+	if (legodir[len legodir -1] != '/')
+		legodir[len legodir] = '/';
+
+	# get the motor files
+	sys->print("opening motor files\n");
+	hm := sys->open(legodir + hmpath, Sys->OWRITE);
+	mm := sys->open(legodir +mmpath, Sys->OWRITE);
+	allmotors = sys->open(legodir + allmpath, Sys->OWRITE);
+	if (hm == nil || mm == nil || allmotors == nil) {
+		sys->print("cannot open motor files\n");
+		raise("fail:error");
+	}
+
+	# get the sensor files
+	sys->print("opening sensor files\n");
+	hb := sys->open(legodir + hbpath, Sys->ORDWR);
+	mb := sys->open(legodir + mbpath, Sys->ORDWR);
+	lightsensor = sys->open(legodir + lspath, Sys->ORDWR);
+
+	if (hb == nil || mb == nil) {
+		sys->print("cannot open sensor files\n");
+		raise("fail:error");
+	}
+
+	hourhand = ref Hand(hm, hb, array of byte "f7", array of byte "r7", array of byte "s7", 0);
+	minutehand = ref Hand(mm, mb, array of byte "f7", array of byte "r7", array of byte "s7", 0);
+
+	sys->print("setting sensor types\n");
+	setsensortypes(hourhand, minutehand, lightsensor);
+
+	reqch = chan of (string, chan of int);
+	spawn sethands();
+#	reqch <-= ("reset", nil);
+	spawn srvlink(f2c);
+}
+
+srvlink(f2c : ref Sys->FileIO)
+{
+	for (;;) alt {
+	(offset, count, fid, rc) := <- f2c.read =>
+		if (rc == nil)
+			continue;
+		if (offset != 0) {
+			rc <-= (nil, nil);
+			continue;
+		}
+		rc <- = (array of byte gettime(), nil);
+
+	(offset, data, fid, wc) := <- f2c.write =>
+		if (wc == nil)
+			continue;
+		if (offset != 0) {
+			wc <-= (0, "bad offset");
+			continue;
+		}
+		spawn settime(wc, string data, len data);
+	}
+}
+
+gettime(): string
+{
+	hpos := hourhand.pos;
+	mpos := minutehand.pos;
+
+	h := 12 * hpos / NCLICKS;
+	m := 60 * mpos / NCLICKS;
+
+	time := "??:??";
+	for (hadj := -1; hadj <= 1; hadj++) {
+		hpos2 := (((h+hadj) * NCLICKS) / 12) + ((m * NCLICKS) / (12 * 60));
+		dhpos := hpos - hpos2;
+		if (dhpos >= -2 && dhpos <= 2) {
+			# allow 2 clicks of imprecision either way
+			time = sys->sprint("%.2d:%.2d", h+hadj, m);
+			break;
+		}	
+	}
+	return sys->sprint("%s %d %d", time, hpos*360/NCLICKS, mpos*360/NCLICKS);
+}
+
+settime(wc: Sys->Rwrite, time: string, wn: int)
+{
+	done := chan of int;
+	reqch <-= (time, done);
+	<- done;
+	wc <-= (wn, nil);
+}
+
+str2clicks(s : string) : (int, int)
+{
+	h, m : int = 0;
+	(n, toks) := sys->tokenize(s, ":");
+	if (n > 1) {
+		h = int hd toks;
+		toks = tl toks;
+		n--;
+	}
+	if (n > 0) {
+		m = int hd toks;
+	}
+	h = ((h * NCLICKS) / 12) + ((m * NCLICKS) / (12 * 60));
+	m = (m * NCLICKS)/60;
+	return (h, m);
+}
+
+sethands()
+{
+	for (;;) {
+		(time, rc) := <- reqch;
+		if (time == "reset" || time == "reset\n") {
+			reset();
+			time = "12:00";
+		}
+		(hclk, mclk) := str2clicks(time);
+		for (i := 0; i < 6; i++) {
+			hdelta := clickdistance(hourhand.pos, hclk, NCLICKS);
+			mdelta := clickdistance(minutehand.pos, mclk, NCLICKS);
+			if (hdelta == 0 && mdelta == 0)
+				break;
+			if (hdelta != 0)
+				sethand(hourhand, hdelta);
+			if (mdelta != 0)
+				sethand(minutehand, mdelta);
+		}
+		releaseall();
+		if (rc != nil)
+			rc <- = 1;
+	}
+}
+
+clickdistance(start, stop, mod : int) : int
+{
+	if (start > stop)
+		stop += mod;
+	d := (stop - start) % mod;
+	if (d > mod/2)
+		d -= mod;
+	return d;
+}
+
+setsensortypes(h1, h2 : ref Hand, ls : ref Sys->FD)
+{
+	button := array of byte "b0";
+	light := array of byte "l0";
+
+	sys->seek(h1.sensor, big 0, Sys->SEEKSTART);
+	sys->write(h1.sensor, button, len button);
+	sys->seek(h2.sensor, big 0, Sys->SEEKSTART);
+	sys->write(h2.sensor, button, len button);
+	sys->seek(ls, big 0, Sys->SEEKSTART);
+	sys->write(ls, light, len light);
+}
+
+HOUR_ADJUST : con 1;
+MINUTE_ADJUST : con 3;
+reset()
+{
+	# run the motors until hands are well away from 12 o'clock (below threshold)
+	setsensortypes(hourhand, minutehand, lightsensor);
+	val := readsensor(lightsensor);
+	if (val > OFFTHRESH) {
+		triggered := chan of int;
+		sys->print("wait for hands clear of light sensor\n");
+		spawn lightwait(triggered, lightsensor, 0);
+		forward(minutehand);
+		reverse(hourhand);
+		val = <- triggered;
+		stopall();
+		sys->print("sensor %d\n", val);
+	}
+
+	resethand(hourhand);
+	hourhand.pos += HOUR_ADJUST;
+	resethand(minutehand);
+	minutehand.pos += MINUTE_ADJUST;
+}
+
+sethand(hand : ref Hand, delta : int)
+{
+	triggered := chan of int;
+	dir := 1;
+	if (delta < 0) {
+		dir = -1;
+		delta = -delta;
+	}
+	if (delta > MINCLICKS) {
+		spawn handwait(triggered, hand, delta - MINCLICKS);
+		if (dir > 0)
+			forward(hand);
+		else
+			reverse(hand);
+		<- triggered;
+		stop(hand);
+	hand.pos += dir * readsensor(hand.sensor);
+	} else {
+		startval := readsensor(hand.sensor);
+		if (dir > 0)
+			forward(hand);
+		else
+			reverse(hand);
+		stop(hand);
+		hand.pos += dir * (readsensor(hand.sensor) - startval);
+	}
+	if (hand.pos < 0)
+		hand.pos += NCLICKS;
+	hand.pos %= NCLICKS;
+}
+
+resethand(hand : ref Hand)
+{
+	triggered := chan of int;
+	val : int;
+
+	# run the hand until the light sensor is above threshold
+	sys->print("running hand until light sensor activated\n");
+	spawn lightwait(triggered, lightsensor, 1);
+	forward(hand);
+	val = <- triggered;
+	stop(hand);
+	sys->print("sensor %d\n", val);
+
+	startclick := readsensor(hand.sensor);
+
+	# advance until light sensor drops below threshold
+	sys->print("running hand until light sensor clear\n");
+	spawn lightwait(triggered, lightsensor, 0);
+	forward(hand);
+	val = <- triggered;
+	stop(hand);
+	sys->print("sensor %d\n", val);
+	
+	stopclick := readsensor(hand.sensor);
+	nclicks := stopclick - startclick;
+	sys->print("startpos %d, endpos %d (nclicks %d)\n", startclick, stopclick, nclicks);
+
+	hand.pos = nclicks/2;
+}
+
+stop(hand : ref Hand)
+{
+	sys->seek(hand.motor, big 0, Sys->SEEKSTART);
+	sys->write(hand.motor, hand.stop, len hand.stop);
+}
+
+stopall()
+{
+	msg := array of byte "s0s0s0";
+	sys->seek(allmotors, big 0, Sys->SEEKSTART);
+	sys->write(allmotors, msg, len msg);
+}
+
+releaseall()
+{
+	msg := array of byte "F0F0F0";
+	sys->seek(allmotors, big 0, Sys->SEEKSTART);
+	sys->write(allmotors, msg, len msg);
+}
+
+forward(hand : ref Hand)
+{
+	sys->seek(hand.motor, big 0, Sys->SEEKSTART);
+	sys->write(hand.motor, hand.fwd, len hand.fwd);
+}
+
+reverse(hand : ref Hand)
+{
+	sys->seek(hand.motor, big 0, Sys->SEEKSTART);
+	sys->write(hand.motor, hand.rev, len hand.rev);
+}
+
+readsensor(fd : ref Sys->FD) : int
+{
+	buf := array [4] of byte;
+	sys->seek(fd, big 0, Sys->SEEKSTART);
+	n := sys->read(fd, buf, len buf);
+	if (n <= 0)
+		return -1;
+	return int string buf[0:n];
+}
+
+handwait(reply : chan of int, hand : ref Hand, clicks : int)
+{
+	blk := array of byte ("b" + string clicks);
+	sys->seek(hand.sensor, big 0, Sys->SEEKSTART);
+	sys->print("handwait(%s)\n", string blk);
+	if (sys->write(hand.sensor, blk, len blk) != len blk)
+	sys->print("handwait write error: %r\n");
+	reply <- = readsensor(hand.sensor);
+}
+
+lightwait(reply : chan of int, fd : ref Sys->FD, on : int)
+{
+	thresh := "";
+	if (on)
+		thresh = "l>" + string ONTHRESH;
+	else
+		thresh = "l<" + string OFFTHRESH;
+	blk := array of byte (thresh);
+	sys->print("lightwait(%s)\n", string blk);
+	sys->seek(fd, big 0, Sys->SEEKSTART);
+	sys->write(fd, blk, len blk);
+	reply <- = readsensor(fd);
+}
\ No newline at end of file
diff --git a/appl/demo/lego/clockface.dis b/appl/demo/lego/clockface.dis
new file mode 100644
index 00000000..27ef856a
--- /dev/null
+++ b/appl/demo/lego/clockface.dis
diff --git a/appl/demo/lego/clockface.sbl b/appl/demo/lego/clockface.sbl
new file mode 100644
index 00000000..f8e4dfb9
--- /dev/null
+++ b/appl/demo/lego/clockface.sbl
@@ -0,0 +1,998 @@
+limbo .sbl 2.1
+Clockface
+3
+clockface.b
+sys.m
+draw.m
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+
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+3
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+
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+
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+0:t0:15,21 s
+4:t1:15,21 Ct8.2
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+4:t1:32,38 R@9
+
+
+
+aDraw->Display 201.1,230.2 20
+5
+0:image:203.2,7 R@5
+
+4:white:204.2,7 R@5
+
+8:black:205.2,7 R@5
+
+12:opaque:206.2,8 R@5
+
+16:transparent:207.2,13 R@5
+
+aDraw->Image 142.1,198.2 56
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+
+16:clipr:147.2,7 @6
+
+32:depth:148.2,7 i
+36:chans:149.2,7 @2
+
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+
+48:screen:152.2,8 R@8
+
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+aDraw->Rect 116.1,139.2 16
+2
+0:min:118.2,5 @7
+
+8:max:119.2,5 @7
+
+aDraw->Point 99.1,113.2 8
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+4:y:102.2,3 i
+aDraw->Screen 249.1,263.2 16
+4
+0:id:251.2,4 i
+4:image:252.2,7 R@5
+
+8:fill:253.2,6 R@5
+
+12:display:254.2,9 R@4
+
+aDraw->Wmcontext 282.1,291.2 28
+7
+0:kbd:284.2,5 Ci
+4:ptr:285.2,5 CR@10
+
+8:ctl:286.2,5 Cs
+12:wctl:287.2,6 Cs
+16:images:288.2,8 CR@5
+
+20:connfd:289.2,8 R@11
+
+24:ctxt:290.2,6 R@3
+
+aDraw->Pointer 266.1,271.2 16
+3
+0:buttons:268.2,9 i
+4:xy:269.2,4 @7
+
+12:msec:270.2,6 i
+aSys->FD 1:45.1,48.2 4
+1
+0:fd:47.2,4 i
+aSys->FileIO 65.1,69.2 8
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+0:read:67.2,6 Ct16.4
+0:t0:17,20 i
+4:t1:17,20 i
+8:t2:17,20 i
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+
+
+4:write:68.2,7 Ct16.4
+0:t0:18,21 i
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+8:t2:18,21 i
+12:t3:18,21 @14
+
+
+Ct8.2
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+4:t1:22,35 s
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+4:t1:23,26 s
+aHand 0:26.0,33.1 24
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+
+4:sensor:28.1,7 R@11
+
+8:fwd:29.1,4 Ab
+12:rev:30.1,4 Ab
+16:stop:31.1,5 Ab
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+6
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+
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+
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+
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+
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+
+n131:srvlink
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+
+8
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+
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+64:wc:21,23 @14
+
+n195:gettime
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+s232:settime
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+
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+40:hdelta:180.3,9 i
+44:mdelta:181.3,9 i
+48:i:179.7,8 i
+52:hclk:178.3,7 i
+56:mclk:9,13 i
+n318:clickdistance
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+36:stop:21,25 i
+40:mod:27,30 i
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+i327:setsensortypes
+3
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+
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+
+40:ls:34,36 R@11
+
+2
+44:button:207.1,7 Ab
+48:light:208.1,6 Ab
+n366:reset
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+36:triggered:226.2,11 Ci
+n410:sethand
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+
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+
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+
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+
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+
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+40:n:339.1,2 i
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+36:hand:30,34 R@15
+
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+n649:lightwait
+3
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+36:fd:31,33 R@11
+
+40:on:49,51 i
+2
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+48:thresh:357.1,7 s
+n6
+60:allmotors:36.0,9 R@11
+
+116:hourhand:37.0,8 R@15
+
+132:lightsensor:35.0,11 R@11
+
+140:minutehand:38.0,10 R@15
+
+172:reqch:40.0,5 Ct8.2
+0:t0:16,22 s
+4:t1:16,22 Ci
+
+224:sys:11.0,3 mSys
+1:4.0,160.1 0
+
diff --git a/appl/demo/lego/clockreg.sh b/appl/demo/lego/clockreg.sh
new file mode 100644
index 00000000..9c0c6447
--- /dev/null
+++ b/appl/demo/lego/clockreg.sh
@@ -0,0 +1,17 @@
+#!/dis/sh.dis
+load std
+
+port=$1
+DIR=/dis/demo/lego
+pctl forkns newpgrp
+
+cd $DIR
+if { firmdl $port /dis/demo/lego/styx.srec } {
+	legolink $port
+	memfs /tmp
+	cd /tmp
+	mount -o -A /net/legolink /n/remote
+	$DIR/clockface /n/remote
+	echo reset > clockface
+	grid/register -a resource Robot -a name 'Lego Clock' {export /tmp}
+}
diff --git a/appl/demo/lego/firmdl.b b/appl/demo/lego/firmdl.b
new file mode 100644
index 00000000..1cc94e7b
--- /dev/null
+++ b/appl/demo/lego/firmdl.b
@@ -0,0 +1,294 @@
+implement RcxFirmdl;
+
+include "sys.m";
+include "draw.m";
+include "bufio.m";
+include "rcxsend.m";
+
+RcxFirmdl : module {
+	init : fn (ctxt : ref Draw->Context, argv : list of string);
+};
+
+sys : Sys;
+bufio : Bufio;
+rcx : RcxSend;
+me : int;
+
+Iobuf : import bufio;
+
+Image : adt {
+	start : int;
+	offset : int;
+	length : int;
+	data : array of byte;
+};
+
+DL_HDR : con 5;			# download packet hdr size
+DL_DATA : con 16rc8;		# download packet payload size
+
+init(nil : ref Draw->Context, argv : list of string)
+{
+	sys = load Sys Sys->PATH;
+	me = sys->pctl(Sys->NEWPGRP, nil);
+
+	bufio = load Bufio Bufio->PATH;
+	if (bufio == nil)
+		error(sys->sprint("cannot load bufio module: %r"));
+	rcx = load RcxSend "rcxsend.dis";
+	if (rcx == nil)
+		error(sys->sprint("cannot load rcx module: %r"));
+
+	argv = tl argv;
+	if (len argv != 2)
+		error("usage: portnum file");
+
+	portnum := int hd argv;
+	file := hd tl argv;
+
+	img := getimage(file);
+	cksum := sum(img.data[0:img.length]);
+	sys->print("length %.4x start %.4x \n", img.length, img.start);
+
+	err := rcx->init(portnum, 1);
+	if (err != nil)
+		error(err);
+
+	# delete firmware
+	sys->print("delete firmware\n");
+	reply : array of byte;
+	rmfirm := array [] of {byte 16r65, byte 1, byte 3, byte 5, byte 7, byte 11};
+	reply = rcx->send(rmfirm, len rmfirm, 1);
+	if (reply == nil)
+		error("delete firmware failed");
+	chkreply(reply, array [] of {byte 16r92}, "delete firmware");
+
+	# start download
+	sys->print("start download\n");
+	dlstart := array [] of {byte 16r75,
+					byte (img.start & 16rff),
+					byte ((img.start>>8) & 16rff),
+					byte (cksum & 16rff),
+					byte ((cksum>>8) & 16rff),
+					byte 0,
+	};
+	reply = rcx->send(dlstart, len dlstart, 2);
+	chkreply(reply,array [] of {byte 16r82, byte 0}, "start download");
+
+	# send the image
+	data := array [DL_HDR+DL_DATA+1] of byte;	# hdr + data + 1 byte cksum
+	seqnum := 1;
+	step := DL_DATA;
+	for (i := 0; i < img.length; i += step) {
+		data[0] = byte 16r45;
+		if (seqnum & 1)
+			# alternate ops have bit 4 set
+			data[0] |= byte 16r08;
+		if (i + step > img.length) {
+			step = img.length - i;
+			seqnum = 0;
+		}
+		sys->print(".");
+		data[1] = byte (seqnum & 16rff);
+		data[2] = byte ((seqnum >> 8) & 16rff);
+		data[3] = byte (step & 16rff);
+		data[4] = byte ((step >> 8) & 16rff);
+		data[5:] = img.data[i:i+step];
+		data[5+step] = byte (sum(img.data[i:i+step]) & 16rff);
+		reply = rcx->send(data, DL_HDR+step+1, 2);
+		chkreply(reply, array [] of {byte 16rb2, byte 0}, "tx data");
+		seqnum++;
+	}
+
+	# unlock firmware
+	sys->print("\nunlock firmware\n");
+	ulfirm := array [] of {byte 16ra5, byte 'L', byte 'E', byte 'G', byte 'O', byte 174};
+	reply = rcx->send(ulfirm, len ulfirm, 26);
+	chkreply(reply, array [] of {byte 16r52}, "unlock firmware");
+	sys->print("result: %s\n", string reply[1:]);
+
+	# all done, tidy up
+	killgrp(me);
+}
+
+chkreply(got, expect : array of byte, err : string)
+{
+	if (got == nil || len got < len expect)
+		error(err + ": short reply");
+	# RCX sometimes sets bit 3 of 'opcode' byte to prevent
+	# headers with same opcode having exactly same value - mask out
+	got[0] &= byte 16rf7;
+
+	for (i := 0; i < len expect; i++)
+		if (got[i] != expect[i]) {
+			hexdump(got);
+			error(sys->sprint("%s: reply mismatch at %d", err, i));
+		}
+}
+	
+error(msg : string)
+{
+	sys->print("%s\n", msg);
+	killgrp(me);
+	raise "fail:error" ;
+}
+
+killgrp(pid : int)
+{
+	pctl := sys->open("/prog/" + string pid + "/ctl", Sys->OWRITE);
+	if (pctl != nil) {
+		poison := array of byte "killgrp";
+		sys->write(pctl, poison, len poison);
+	}
+}
+
+sum(data : array of byte) : int
+{
+	t := 0;
+	for (i := 0; i < len data; i++)
+		t += int data[i];
+	return t;
+}
+
+hexdump(data : array of byte)
+{
+	for (i := 0; i < len data; i++)
+		sys->print("%.2x ", int data[i]);
+	sys->print("\n");
+}
+
+IMGSTART : con 16r8000;
+IMGLEN : con 16r4c00;
+getimage(path : string) : ref Image
+{
+	img := ref Image (IMGSTART, IMGSTART, 0, array [IMGLEN] of {* => byte 0});
+	iob := bufio->open(path, Sys->OREAD);
+	if (iob == nil)
+		error(sys->sprint("cannot open %s: %r", path));
+
+	lnum := 0;
+	while ((s := iob.gets('\n')) != nil) {
+		lnum++;
+		slen := len s;
+		# trim trailing space
+		while (slen > 0) {
+			ch := s[slen -1];
+			if (ch == ' ' || ch == '\r' || ch == '\n') {
+				slen--;
+				continue;
+			}
+			break;
+		}
+		# ignore blank lines
+		if (slen == 0)
+			continue;
+
+		if (slen < 10)
+			# STNNAAAACC
+			error("short S-record: line " + string lnum);
+
+		s = s[0:slen];
+		t := s[1];
+		if (s[0] != 'S' || t < '0' || t > '9')
+			error("bad S-record format: line " + string lnum);
+
+		data := hex2bytes(s[2:]);
+		if (data == nil)
+			error("bad chars in S-record:  line " + string lnum);
+
+		count := int data[0];
+		cksum := int data[len data - 1];
+		if (count != len data -1)
+			error("S-record length mis-match:  line " + string lnum);
+
+		if (sum(data[0:len data -1]) & 16rff != 16rff)
+			error("bad S-record checksum:  line " + string lnum);
+
+		alen : int;
+		case t {
+		'0' =>
+			# addr[2] mname[10] ver rev desc[18] cksum
+			continue;
+		'1' =>
+			# 16-bit address, data
+			alen = 2;
+		'2' =>
+			# 24-bit address, data
+			alen = 3;
+		'3' =>
+			# 32-bit address, data
+			alen = 4;
+		'4' =>
+			# extension record
+			error("bad S-record type: line " + string lnum);
+		'5' =>
+			# data record count - ignore
+			continue;
+		'6' =>
+			# unused - ignore
+			continue;
+		'7' =>
+			img.start = wordval(data, 1, 4);
+			continue;
+		'8' =>
+			img.start = wordval(data, 1, 3);
+			continue;
+		'9' =>
+			img.start = wordval(data, 1, 2);
+			continue;
+		}
+		addr := wordval(data, 1, alen) - img.offset;
+		if (addr < 0 || addr > len img.data)
+			error("S-record address out of range: line " + string lnum);
+		img.data[addr:] = data[1+alen:1+count];
+		img.length = max(img.length, addr + count -(alen +1));
+	}
+	iob.close();
+	return img;
+}
+
+wordval(src : array of byte, s, l : int) : int
+{
+	r := 0;
+	for (i := 0; i < l; i++) {
+		r <<= 8;
+		r += int src[s+i];
+	}
+	return r;
+}
+
+max(a, b : int) : int
+{
+	if (a > b)
+		return a;
+	return b;
+}
+
+hex2bytes(s : string) : array of byte
+{
+	slen := len s;
+	if (slen & 1)
+		# should be even
+		return nil;
+	data := array [slen/2] of byte;
+	six := 0;
+	dix := 0;
+	while (six < slen) {
+		d1 := hexdigit(s[six++]);
+		d2 := hexdigit(s[six++]);
+		if (d1 == -1 || d2 == -1)
+			return nil;
+		data[dix++] = byte ((d1 << 4) + d2);
+	}
+	return data;
+}
+
+hexdigit(h : int) : int
+{
+	if (h >= '0' && h <= '9')
+		return h - '0';
+	if (h >= 'A' && h <= 'F')
+		return 10 + h - 'A';
+	if (h >= 'a' && h <= 'f')
+		return 10 + h - 'a';
+	return -1;
+}
diff --git a/appl/demo/lego/firmdl.dis b/appl/demo/lego/firmdl.dis
new file mode 100644
index 00000000..de04fdbb
--- /dev/null
+++ b/appl/demo/lego/firmdl.dis
diff --git a/appl/demo/lego/firmdl.sbl b/appl/demo/lego/firmdl.sbl
new file mode 100644
index 00000000..2fd58677
--- /dev/null
+++ b/appl/demo/lego/firmdl.sbl
@@ -0,0 +1,819 @@
+limbo .sbl 2.1
+RcxFirmdl
+5
+firmdl.b
+sys.m
+draw.m
+bufio.m
+rcxsend.m
+587
+31.1,25 0
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diff --git a/appl/demo/lego/legolink.b b/appl/demo/lego/legolink.b
new file mode 100644
index 00000000..ea29efd6
--- /dev/null
+++ b/appl/demo/lego/legolink.b
@@ -0,0 +1,601 @@
+implement LegoLink;
+
+include "sys.m";
+include "draw.m";
+include "timers.m";
+include "rcxsend.m";
+
+LegoLink : module {
+	init : fn (ctxt : ref Draw->Context, argv : list of string);
+};
+
+POLLDONT : con 0;
+POLLNOW : con 16r02;
+POLLDO : con 16r04;
+
+sys : Sys;
+timers : Timers;
+Timer : import timers;
+datain : chan of array of byte;
+errormsg : string;
+
+error(msg: string)
+{
+	sys->fprint(sys->fildes(2), "%s\n", msg);
+	raise "fail:error";
+}
+
+init(nil : ref Draw->Context, argv : list of string)
+{
+	sys = load Sys Sys->PATH;
+	sys->pctl(Sys->NEWPGRP, nil);
+
+	argv = tl argv;
+	if (len argv != 1)
+		error("usage: legolink portnum");
+
+	timers = load Timers "timers.dis";
+	if (timers == nil)
+		error(sys->sprint("cannot load timers module: %r"));
+
+	portnum := int hd argv;
+	(rdfd, wrfd, err) := serialport(portnum);
+	if (err != nil)
+		error(err);
+
+	# set up our mount file
+	if (sys->bind("#s", "/net", Sys->MBEFORE) == -1)
+		error(sys->sprint("failed to bind srv device: %r"));
+
+	f2c := sys->file2chan("/net", "legolink");
+	if (f2c == nil)
+		error(sys->sprint("cannot create legolink channel: %r"));
+
+	datain = chan of array of byte;
+	send := chan of array of byte;
+	recv := chan of array of byte;
+	timers->init(50);
+	spawn reader(rdfd, datain);
+	consume();
+	spawn protocol(wrfd, send, recv);
+	spawn srvlink(f2c, send, recv);
+}
+
+srvlink(f2c : ref Sys->FileIO, send, recv : chan of array of byte)
+{
+	me := sys->pctl(0, nil);
+	rdfid := -1;
+	wrfid := -1;
+	buffer := array [256] of byte;
+	bix := 0;
+
+	rdblk := chan of (int, int, int, Sys->Rread);
+	readreq := rdblk;
+	wrblk := chan of (int, array of byte, int, Sys->Rwrite);
+	writereq := f2c.write;
+	wrreply : Sys->Rwrite;
+	sendblk := chan of array of byte;
+	sendchan := sendblk;
+	senddata : array of byte;
+
+	for (;;) alt {
+	data := <- recv =>
+		# got some data from brick, nil for error
+		if (data == nil) {
+			# some sort of error
+			if (wrreply != nil) {
+				wrreply <- = (0, errormsg);
+			}
+			killgrp(me);
+		}
+		if (bix + len data > len buffer) {
+			newb := array [bix + len data + 256] of byte;
+			newb[0:] = buffer;
+			buffer = newb;
+		}
+		buffer[bix:] = data;
+		bix += len data;
+		readreq = f2c.read;
+
+	(offset, count, fid, rc) := <- readreq =>
+		if (rdfid == -1)
+			rdfid = fid;
+		if (fid != rdfid) {
+			if (rc != nil)
+				rc <- = (nil, "file in use");
+			continue;
+		}
+		if (rc == nil) {
+			rdfid = -1;
+			continue;
+		}
+		if (errormsg != nil) {
+			rc <- = (nil, errormsg);
+			killgrp(me);
+		}
+		# reply with what we've got
+		if (count > bix)
+			count = bix;
+		rdata := array [count] of byte;
+		rdata[0:] = buffer[0:count];
+		buffer[0:] = buffer[count:bix];
+		bix -= count;
+		if (bix == 0)
+			readreq = rdblk;
+		alt {
+		rc <- = (rdata, nil)=>
+			;
+		* =>
+			;
+		}
+
+	(offset, data, fid, wc) := <- writereq =>
+		if (wrfid == -1)
+			wrfid = fid;
+		if (fid != wrfid) {
+			if (wc != nil)
+				wc <- = (0, "file in use");
+			continue;
+		}
+		if (wc == nil) {
+			wrfid = -1;
+			continue;
+		}
+		if (errormsg != nil) {
+			wc <- = (0, errormsg);
+			killgrp(me);
+		}
+		senddata = data;
+		sendchan = send;
+		wrreply = wc;
+		writereq = wrblk;
+
+	sendchan <- = senddata =>
+		alt {
+		wrreply <- = (len senddata, nil) =>
+			;
+		* =>
+			;
+		}
+		wrreply = nil;
+		sendchan = sendblk;
+		writereq = f2c.write;
+	}
+}
+
+killgrp(pid : int)
+{
+	pctl := sys->open("/prog/" + string pid + "/ctl", Sys->OWRITE);
+	if (pctl != nil) {
+		poison := array of byte "killgrp";
+		sys->write(pctl, poison, len poison);
+	}
+	exit;
+}
+
+serialport(port : int) : (ref Sys->FD, ref Sys->FD, string)
+{
+	serport := "/dev/eia" + string port;
+	serctl := serport + "ctl";
+
+	rfd := sys->open(serport, Sys->OREAD);
+	if (rfd == nil)
+		return (nil, nil, sys->sprint("cannot read %s: %r", serport));
+	wfd := sys->open(serport, Sys->OWRITE);
+	if (wfd == nil)
+		return (nil, nil, sys->sprint("cannot write %s: %r", serport));
+	ctlfd := sys->open(serctl, Sys->OWRITE);
+	if (ctlfd == nil)
+		return (nil, nil, sys->sprint("cannot open %s: %r", serctl));
+
+	config := array [] of {
+		"b2400",
+		"l8",
+		"po",
+		"m0",
+		"s1",
+		"d1",
+		"r1",
+	};
+
+	for (i := 0; i < len config; i++) {
+		cmd := array of byte config[i];
+		if (sys->write(ctlfd, cmd, len cmd) <= 0)
+			return (nil, nil, sys->sprint("serial config (%s): %r", config[i]));
+	}
+	return (rfd, wfd, nil);
+}
+
+# reader and nbread as in rcxsend.b
+reader(fd : ref Sys->FD, out : chan of array of byte)
+{
+	# with buf size of 1 there is no need
+	# for overrun code in nbread()
+
+	buf := array [1] of byte;
+	for (;;) {
+		n := sys->read(fd, buf, len buf);
+		if (n <= 0)
+			break;
+		data := array [n] of byte;
+		data[0:] = buf[0:n];
+		out <- = data;
+	}
+	out <- = nil;
+}
+
+overrun : array of byte;
+
+nbread(ms, n : int) : array of byte
+{
+	ret := array[n] of byte;
+	tot := 0;
+	if (overrun != nil) {
+		if (n < len overrun) {
+			ret[0:] = overrun[0:n];
+			overrun = overrun[n:];
+			return ret;
+		}
+		ret[0:] = overrun;
+		tot += len overrun;
+		overrun = nil;
+	}
+	tmr := timers->new(ms, 0);
+loop:
+	while (tot < n) {
+		tmr.reset();
+		alt {
+			data := <- datain =>
+				if (data == nil)
+					break loop;
+				dlen := len data;
+				if (dlen > n - tot) {
+					dlen = n - tot;
+					overrun = data[dlen:];
+				}
+				ret[tot:] = data[0:dlen];
+				tot += dlen;
+			<- tmr.tick =>
+				# reply timeout;
+				break loop;
+		}
+	}
+	tmr.destroy();
+	if (tot == 0)
+		return nil;
+	return ret[0:tot];
+}
+
+consume()
+{
+	while (nbread(300, 1024) != nil)
+		;
+}
+
+# fd: connection to remote client
+# send: from local to remote
+# recv: from remote to local
+protocol(fd : ref Sys->FD, send, recv : chan of array of byte)
+{
+	seqnum := 0;
+	towerdown := timers->new(1500, 0);
+	starttower := 1;
+	tmr := timers->new(250, 0);
+
+	for (;;) {
+		data : array of byte = nil;
+		# get data to send
+		alt {
+		data = <- send =>
+			;
+		<- tmr.tick =>
+			data = nil;
+		<- towerdown.tick =>
+			starttower = 1;
+			continue;
+		}
+			
+		poll := POLLNOW;
+		while (poll == POLLNOW) {
+			reply : array of byte;
+			(reply, poll, errormsg) = datasend(fd, seqnum++, data, starttower);
+			starttower = 0;
+			towerdown.reset();
+			if (errormsg != nil) {
+sys->print("protocol: send error: %s\n", errormsg);
+				tmr.destroy();
+				recv <- = nil;
+				return;
+			}
+			if (reply != nil) {
+				recv <- = reply;
+			}
+			if (poll == POLLNOW) {
+				# quick check to see if we have any more data
+				alt {
+				data = <- send =>
+						;
+				* =>
+						data = nil;
+				}
+			}
+		}
+		if (poll == POLLDO)
+			tmr.reset();
+		else
+			tmr.cancel();
+	}
+}
+
+TX_HDR : con 3;
+DL_HDR : con 5;	# 16r45 seqLSB seqMSB lenLSB lenMSB
+DL_CKSM : con 1;
+LN_HDR : con 1;
+LN_JUNK : con 2;
+LN_LEN : con 2;
+LN_RXLEN : con 2;
+LN_POLLMASK : con 16r06;
+LN_COMPMASK : con 16r08;
+
+
+# send a message (may be empty)
+# wait for the reply
+# returns (data, poll request, error)
+
+datasend(wrfd : ref Sys->FD, seqnum : int, data : array of byte, startup : int) : (array of byte, int, string)
+{
+if (startup) {
+	dummy := array [] of { byte 255, byte 0, byte 255, byte 0};
+	sys->write(wrfd, dummy, len dummy);
+	nbread(100, 100);
+}
+	seqnum = seqnum & 1;
+	docomp := 0;
+	if (data != nil) {
+		comp := rlencode(data);
+		if (len comp < len data) {
+			docomp = 1;
+			data = comp;
+		}
+	}
+
+	# construct the link-level data packet
+	# DL_HDR LN_HDR data cksum
+	# last byte of data is stored in cksum byte
+	llen := LN_HDR + len data;
+	blklen := LN_LEN + llen - 1;	# llen includes cksum
+	ldata := array [DL_HDR + blklen + 1] of byte;
+
+	# DL_HDR
+	if (seqnum == 0)
+		ldata[0] = byte 16r45;
+	else
+		ldata[0] = byte 16r4d;
+	ldata[1] = byte 0;				# blk number LSB
+	ldata[2] = byte 0;				# blk number MSB
+	ldata[3] = byte (blklen & 16rff);		# blk length LSB
+	ldata[4] = byte ((blklen >> 8) & 16rff);	# blk length MSB
+
+	# LN_LEN
+	ldata[5] = byte (llen & 16rff);
+	ldata[6] = byte ((llen>>8) & 16rff);
+	# LN_HDR
+	lhval := byte 0;
+	if (seqnum == 1)
+		lhval |= byte 16r01;
+	if (docomp)
+		lhval |= byte 16r08;
+	
+	ldata[7] = lhval;
+
+	# data (+cksum)
+	ldata[8:] = data;
+
+	# construct the rcx data packet
+	# TX_HDR (dn ~dn) cksum ~cksum
+	rcxlen := TX_HDR + 2*(len ldata + 1);
+	rcxdata := array [rcxlen] of byte;
+
+	rcxdata[0] = byte 16r55;
+	rcxdata[1] = byte 16rff;
+	rcxdata[2] = byte 16r00;
+	rcix := TX_HDR;
+	cksum := 0;
+	for (i := 0; i < len ldata; i++) {
+		b := ldata[i];
+		rcxdata[rcix++] = b;
+		rcxdata[rcix++] = ~b;
+		cksum += int b;
+	}
+	rcxdata[rcix++] = byte (cksum & 16rff);
+	rcxdata[rcix++] = byte (~cksum & 16rff);
+
+	# send it
+	err : string;
+	reply : array of byte;
+	for (try := 0; try < 8; try++) {
+		if (err != nil)
+			sys->print("Try %d (lasterr %s)\n", try, err);
+		err = "";
+		step := 8;
+		for (i = 0; err == nil && i < rcxlen; i += step) {
+			if (i + step > rcxlen)
+				step = rcxlen -i;
+			if (sys->write(wrfd, rcxdata[i:i+step], step) != step) {
+				return (nil, 0, "hangup");
+			}
+
+			# get the echo
+			reply = nbread(300, step);
+			if (reply == nil || len reply != step)
+				# short echo
+				err = "tower not responding";
+
+			# check the echo
+			for (ei := 0; err == nil && ei < step; ei++) {
+				if (reply[ei] != rcxdata[i+ei])
+					# echo mis-match
+					err = "serial comms error";
+			}
+		}
+		if (err != nil) {
+			consume();
+			continue;
+		}
+
+		# wait for a reply
+		replen := TX_HDR + LN_JUNK + 2*LN_RXLEN;
+		reply = nbread(300, replen);
+		if (reply == nil || len reply != replen) {
+			err = "brick not responding";
+			consume();
+			continue;
+		}
+		if (reply[0] != byte 16r55 || reply[1] != byte 16rff || reply[2] != byte 0
+		|| reply[5] != ~reply[6] || reply[7] != ~reply[8]) {
+			err = "bad reply from brick";
+			consume();
+			continue;
+		}
+		# reply[3] and reply [4] are junk, ~junk
+		# put on front of msg by rcx rom
+		replen = int reply[5] + ((int reply[7]) << 8) + 1;
+		cksum = int reply[3] + int reply[5] + int reply[7];
+		reply = nbread(200, replen * 2);
+		if (reply == nil || len reply != replen * 2) {
+			err = "short reply from brick";
+			consume();
+			continue;
+		}
+		cksum += int reply[0];
+		for (i = 1; i < replen; i++) {
+			reply[i] = reply[2*i];
+			cksum += int reply[i];
+		}
+		cksum -= int reply[replen-1];
+		if (reply[replen-1] != byte (cksum & 16rff)) {
+			err = "bad checksum from brick";
+			consume();
+			continue;
+		}
+		if ((reply[0] & byte 1) != byte (seqnum & 1)) {
+			# seqnum error
+			# we have read everything, don't bother with consume()
+			err = "bad seqnum from brick";
+			continue;
+		}
+
+		# TADA! we have a valid message
+		mdata : array of byte;
+		lnhdr := int reply[0];
+		poll := lnhdr & LN_POLLMASK;
+		if (replen > 2) {
+			# more than just hdr and cksum
+			if (lnhdr & LN_COMPMASK) {
+				mdata = rldecode(reply[1:replen-1]);
+				if (mdata == nil) {
+					err = "bad brick msg compression";
+					continue;
+				}
+			} else {
+				mdata = array [replen - 2] of byte;
+				mdata[0:] = reply[1:replen-1];
+			}
+		}
+		return (mdata, poll, nil);
+	}
+	return (nil, 0, err);
+}
+
+
+rlencode(data : array of byte) : array of byte
+{
+	srcix := 0;
+	outix := 0;
+	out := array [64] of byte;
+	val := 0;
+	nextval := -1;
+	n0 := 0;
+
+	while (srcix < len data || nextval != -1) {
+		if (nextval != -1) {
+			val = nextval;
+			nextval = -1;
+		} else {
+			val = int data[srcix];
+			if (val == 16r88)
+				nextval = 0;
+			if (val == 0) {
+				n0++;
+				srcix++;
+				if (srcix < len data && n0 < 16rff + 2)
+					continue;
+			}
+			case n0 {
+			0 =>
+				srcix++;
+			1 =>
+				val = 0;
+				nextval = -1;
+				n0 = 0;
+			2 =>
+				val = 0;
+				nextval = 0;
+				n0 = 0;
+			* =>
+				val = 16r88;
+				nextval = (n0-2);
+				n0 = 0;
+			}
+		}
+		if (outix >= len out) {
+			newout := array [2 * len out] of byte;
+			newout[0:] = out;
+			out = newout;
+		}
+		out[outix++] = byte val;
+	}
+	return out[0:outix];
+}
+
+rldecode(data : array of byte) : array of byte
+{
+	srcix := 0;
+	outix := 0;
+	out := array [64] of byte;
+
+	n0 := 0;
+	val := 0;
+	while (srcix < len data || n0 > 0) {
+		if (n0 > 0)
+			n0--;
+		else {
+			val = int data[srcix++];
+			if (val == 16r88) {
+				if (srcix >= len data)
+					# bad encoding
+					return nil;
+				n0 = int data[srcix++];
+				if (n0 > 0) {
+					n0 += 2;
+					val = 0;
+					continue;
+				}
+			}
+		}
+		if (outix >= len out) {
+			newout := array [2 * len out] of byte;
+			newout[0:] = out;
+			out = newout;
+		}
+		out[outix++] = byte val;
+	}
+	return out[0:outix];
+}
+
+hexdump(data : array of byte)
+{
+	for (i := 0; i < len data; i++)
+		sys->print("%.2x ", int data[i]);
+	sys->print("\n");
+}
diff --git a/appl/demo/lego/legolink.dis b/appl/demo/lego/legolink.dis
new file mode 100644
index 00000000..77f5573f
--- /dev/null
+++ b/appl/demo/lego/legolink.dis
diff --git a/appl/demo/lego/legolink.sbl b/appl/demo/lego/legolink.sbl
new file mode 100644
index 00000000..11de96e7
--- /dev/null
+++ b/appl/demo/lego/legolink.sbl
@@ -0,0 +1,1298 @@
+limbo .sbl 2.1
+LegoLink
+5
+legolink.b
+sys.m
+draw.m
+timers.m
+rcxsend.m
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+56:newout:587.3,9 Ab
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+200:errormsg:20.0,8 s
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diff --git a/appl/demo/lego/mkfile b/appl/demo/lego/mkfile
new file mode 100644
index 00000000..3ae4e898
--- /dev/null
+++ b/appl/demo/lego/mkfile
@@ -0,0 +1,36 @@
+<../../../mkconfig
+
+TARG=\
+		clockface.dis\
+		firmdl.dis\
+		legolink.dis\
+		rcxsend.dis\
+		timers.dis\
+		styx.srec\
+
+SHTARG=\
+		clockreg.sh\
+
+MODULES=\
+	rcxsend.m\
+
+SYSMODULES= \
+	bufio.m\
+	draw.m\
+	sys.m\
+	timers.m\
+
+DISBIN=$ROOT/dis/demo/lego
+
+<$ROOT/mkfiles/mkdis
+
+$DISBIN/%.srec:	%.srec
+	rm -f $target && cp $stem.srec $target
+
+SHFILES=${SHTARG:%.sh=$DISBIN/%}
+install:V:	$SHFILES
+%.install:V:	$DISBIN/%
+%.installall:V:	$DISBIN/%
+
+$DISBIN/%:	%.sh
+	cp $stem.sh $target && chmod a+rx $target
diff --git a/appl/demo/lego/rcxsend.b b/appl/demo/lego/rcxsend.b
new file mode 100644
index 00000000..5896f09b
--- /dev/null
+++ b/appl/demo/lego/rcxsend.b
@@ -0,0 +1,240 @@
+implement RcxSend;
+
+include "sys.m";
+include "timers.m";
+include "rcxsend.m";
+
+sys : Sys;
+timers : Timers;
+Timer : import timers;
+datain : chan of array of byte;
+debug : int;
+rpid : int;
+wrfd : ref Sys->FD;
+
+TX_HDR : con 3;
+TX_CKSM : con 2;
+
+init(portnum, dbg : int) : string
+{
+	debug = dbg;
+	sys = load Sys Sys->PATH;
+	timers = load Timers "timers.dis";
+	if (timers == nil)
+		 return sys->sprint("cannot load timer module: %r");
+
+	rdfd : ref Sys->FD;
+	err : string;
+	(rdfd, wrfd, err) = serialport(portnum);
+	if (err != nil)
+		return err;
+
+	timers->init(50);
+	pidc := chan of int;
+	datain = chan of array of byte;
+	spawn reader(pidc, rdfd, datain);
+	rpid = <- pidc;
+	consume();
+	return nil;
+}
+
+reader(pidc : chan of int, fd : ref Sys->FD, out : chan of array of byte)
+{
+	pidc <- = sys->pctl(0, nil);
+
+	# with buf size of 1 there is no need
+	# for overrun code in nbread()
+
+	buf := array [1] of byte;
+	for (;;) {
+		n := sys->read(fd, buf, len buf);
+		if (n <= 0)
+			break;
+		data := array [n] of byte;
+		data[0:] = buf[0:n];
+		out <- = data;
+	}
+	if (debug)
+		sys->print("Reader error\n");
+}
+
+send(data : array of byte, n, rlen: int) : array of byte
+{
+	# 16r55 16rff 16r00 (d[i] ~d[i])*n cksum ~cksum
+	obuf := array [TX_HDR + (2*n ) + TX_CKSM] of byte;
+	olen := 0;
+	obuf[olen++] = byte 16r55;
+	obuf[olen++] = byte 16rff;
+	obuf[olen++] = byte 16r00;
+	cksum := 0;
+	for (i := 0; i < n; i++) {
+		obuf[olen++] = data[i];
+		obuf[olen++] = ~data[i];
+		cksum += int data[i];
+	}
+	obuf[olen++] = byte (cksum & 16rff);
+	obuf[olen++] = byte (~cksum & 16rff);
+
+	needr := rlen;
+	if (rlen > 0)
+		needr = TX_HDR + (2 * rlen) + TX_CKSM;
+	for (try := 0; try < 5; try++) {
+		ok := 1;
+		err := "";
+		reply : array of byte;
+
+		step := 8;
+		for (i = 0; ok && i < olen; i += step) {
+			if (i + step > olen)
+				step = olen -i;
+			if (sys->write(wrfd, obuf[i:i+step], step) != step) {
+				if (debug)
+					sys->print("serial tx error: %r\n");
+				return nil;
+			}
+
+			# get the echo
+			reply = nbread(200, step);
+			if (reply == nil || len reply != step) {
+				err = "short echo";
+				ok = 0;
+			}
+
+			# check the echo
+			for (ei := 0; ok && ei < step; ei++) {
+				if (reply[ei] != obuf[i+ei]) {
+					err = "bad echo";
+					ok = 0;
+				}
+			}
+		}
+
+		# get the reply
+		if (ok) {
+			if (needr == 0)
+				return nil;
+			if (needr == -1) {
+				# just get what we can
+				needr = TX_HDR + TX_CKSM;
+				reply = nbread(300, 1024);
+			} else {
+				reply = nbread(200, needr);
+			}
+			if (len reply < needr) {
+				err = "short reply";
+				ok = 0;
+			}
+		}
+		# check the reply
+		if (ok && reply[0] == byte 16r55 && reply[1] == byte 16rff && reply[2] == byte 0) {
+			cksum := int reply[len reply -TX_CKSM];
+			val := reply[TX_HDR:len reply -TX_CKSM];
+			r := array [len val / 2] of byte;
+			sum := 0;
+			for (i = 0; i < len r; i++) {
+				r[i] = val[i*2];
+				sum += int r[i];
+			}
+			if (cksum == (sum & 16rff)) {
+				return r;
+			}
+			ok = 0;
+			err = "bad cksum";
+		} else if (ok) {
+			ok = 0;
+			err = "reply header error";
+		}
+		if (debug && ok == 0 && err != nil) {
+			sys->print("try %d %s: ", try, err);
+			hexdump(reply);
+		}
+		consume();
+	}
+	return nil;
+}
+
+overrun : array of byte;
+
+nbread(ms, n : int) : array of byte
+{
+	ret := array[n] of byte;
+	tot := 0;
+	if (overrun != nil) {
+		if (n < len overrun) {
+			ret[0:] = overrun[0:n];
+			overrun = overrun[n:];
+			return ret;
+		}
+		ret[0:] = overrun;
+		tot += len overrun;
+		overrun = nil;
+	}
+	tmr := timers->new(ms, 0);
+loop:
+	while (tot < n) {
+		tmr.reset();
+		alt {
+			data := <- datain =>
+				dlen := len data;
+				if (dlen > n - tot) {
+					dlen = n - tot;
+					overrun = data[dlen:];
+				}
+				ret[tot:] = data[0:dlen];
+				tot += dlen;
+			<- tmr.tick =>
+				# reply timeout;
+				break loop;
+		}
+	}
+	tmr.destroy();
+	if (tot == 0)
+		return nil;
+	return ret[0:tot];
+}
+
+consume()
+{
+	while (nbread(300, 1024) != nil)
+		;
+}
+
+serialport(port : int) : (ref Sys->FD, ref Sys->FD, string)
+{
+	serport := "/dev/eia" + string port;
+	serctl := serport + "ctl";
+
+	rfd := sys->open(serport, Sys->OREAD);
+	if (rfd == nil)
+		return (nil, nil, sys->sprint("cannot read %s: %r", serport));
+	wfd := sys->open(serport, Sys->OWRITE);
+	if (wfd == nil)
+		return (nil, nil, sys->sprint("cannot write %s: %r", serport));
+	ctlfd := sys->open(serctl, Sys->OWRITE);
+	if (ctlfd == nil)
+		return (nil, nil, sys->sprint("cannot open %s: %r", serctl));
+
+	config := array [] of {
+		"b2400",
+		"l8",
+		"po",
+		"m0",
+		"s1",
+		"d1",
+		"r1",
+	};
+
+	for (i := 0; i < len config; i++) {
+		cmd := array of byte config[i];
+		if (sys->write(ctlfd, cmd, len cmd) <= 0)
+			return (nil, nil, sys->sprint("serial config (%s): %r", config[i]));
+	}
+	return (rfd, wfd, nil);
+}
+hexdump(data : array of byte)
+{
+	for (i := 0; i < len data; i++)
+		sys->print("%.2x ", int data[i]);
+	sys->print("\n");
+}
+
diff --git a/appl/demo/lego/rcxsend.dis b/appl/demo/lego/rcxsend.dis
new file mode 100644
index 00000000..cf718cce
--- /dev/null
+++ b/appl/demo/lego/rcxsend.dis
diff --git a/appl/demo/lego/rcxsend.m b/appl/demo/lego/rcxsend.m
new file mode 100644
index 00000000..f597ea1f
--- /dev/null
+++ b/appl/demo/lego/rcxsend.m
@@ -0,0 +1,4 @@
+RcxSend : module {
+	init: fn (pnum, dbg : int) : string;
+	send : fn (data : array of byte, slen, rlen : int) : array of byte;
+};
\ No newline at end of file
diff --git a/appl/demo/lego/rcxsend.sbl b/appl/demo/lego/rcxsend.sbl
new file mode 100644
index 00000000..34d1dc97
--- /dev/null
+++ b/appl/demo/lego/rcxsend.sbl
@@ -0,0 +1,552 @@
+limbo .sbl 2.1
+RcxSend
+4
+rcxsend.b
+sys.m
+timers.m
+rcxsend.m
+423
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+48:ret:160.1,4 Ab
+52:data:177.3,7 Ab
+56:tmr:172.1,4 R@3
+
+Ab309:consume
+0
+0
+n318:serialport
+1
+32:port:202.11,15 i
+8
+36:serport:204.1,8 s
+40:i:227.6,7 i
+44:config:217.1,7 As
+48:cmd:228.2,5 Ab
+52:ctlfd:213.1,6 R@2
+
+56:rfd:207.1,4 R@2
+
+60:serctl:205.1,7 s
+64:wfd:210.1,4 R@2
+
+t12.3
+0:t0:202.26,37 R@2
+
+4:t1:26,37 R@2
+
+8:t2:26,37 s
+407:hexdump
+1
+32:data:234.8,12 Ab
+1
+36:i:236.6,7 i
+n7
+72:datain:10.0,6 CAb
+76:debug:11.0,5 i
+92:overrun:156.0,7 Ab
+108:rpid:12.0,4 i
+132:sys:7.0,3 mSys
+1:4.0,160.1 0
+
+136:timers:0:8.0,6 mTimers
+2:1.0,13.1 0
+
+148:wrfd:0:0,4 R@2
+
diff --git a/appl/demo/lego/styx.srec b/appl/demo/lego/styx.srec
new file mode 100755
index 00000000..687a50aa
--- /dev/null
+++ b/appl/demo/lego/styx.srec
@@ -0,0 +1,329 @@
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diff --git a/appl/demo/lego/timers.b b/appl/demo/lego/timers.b
new file mode 100644
index 00000000..67e08dec
--- /dev/null
+++ b/appl/demo/lego/timers.b
@@ -0,0 +1,263 @@
+# Chris Locke. June 2000
+
+# TODO: for auto-repeat timers don't set up a new sender
+# if there is already a pending sender for that timer.
+
+implement Timers;
+
+include "sys.m";
+include "timers.m";
+
+RealTimer : adt {
+	t : ref Timer;
+	nticks : int;
+	rep : int;
+	nexttick: big;
+	tick : chan of int;
+	sender : int;
+};
+
+Sender : adt {
+	tid : int;
+	idle : int;		# set by sender() when done, reset by main when about to assign work
+	ctl : chan of chan of int;
+};
+
+sys : Sys;
+acquire : chan of int;
+timers := array [4] of ref RealTimer;
+senders := array [4] of ref Sender;
+curtick := big 0;
+tickres : int;
+
+init(res : int)
+{
+	sys = load Sys Sys->PATH;
+	acquire = chan of int;
+	tickres = res;
+	spawn main();
+}
+
+new(ms, rep : int) : ref Timer
+{
+	acquire <- = 1;
+	t := do_new(ms, rep);
+	<- acquire;
+	return t;
+}
+
+Timer.destroy(t : self ref Timer)
+{
+	acquire <- = 1;
+	do_destroy(t);
+	<- acquire;
+}
+
+Timer.reset(t : self ref Timer)
+{
+	acquire <- = 1;
+	do_reset(t);
+	<- acquire;
+}
+
+Timer.cancel(t : self ref Timer)
+{
+	acquire <- = 1;
+	do_cancel(t);
+	<- acquire;
+}
+
+# only call under lock
+#
+realtimer(t : ref Timer) : ref RealTimer
+{
+	if (t.id < 0 || t.id >= len timers)
+		return nil;
+	if (timers[t.id] == nil)
+		return nil;
+	if (timers[t.id].t != t)
+		return nil;
+	return timers[t.id];
+}
+
+
+# called under lock
+#
+do_destroy(t : ref Timer)
+{
+	rt := realtimer(t);
+	if (rt == nil)
+		return;
+	clearsender(rt, t.id);
+	timers[t.id] = nil;
+}
+
+# called under lock
+#
+do_reset(t : ref Timer)
+{
+	rt := realtimer(t);
+	if (rt == nil)
+		return;
+	clearsender(rt, t.id);
+	rt.nexttick = curtick + big (rt.nticks);
+	startclk = 1;
+}
+
+# called under lock
+#
+do_cancel(t : ref Timer)
+{
+	rt := realtimer(t);
+	if (rt == nil)
+		return;
+	clearsender(rt, t.id);
+	rt.nexttick = big 0;
+}
+
+# only call under lock
+#
+clearsender(rt : ref RealTimer, tid : int)
+{
+	# check to see if there is a sender trying to deliver tick
+	if (rt.sender != -1) {
+		sender := senders[rt.sender];
+		rt.sender = -1;
+		if (sender.tid == tid && !sender.idle) {
+			# receive the tick to clear the busy state
+			alt {
+				<- rt.tick =>
+					;
+				* =>
+					;
+			}
+		}
+	}
+}
+
+# called under lock
+do_new(ms, rep : int) : ref Timer
+{
+	# find free slot
+	for (i := 0; i < len timers; i++)
+		if (timers[i] == nil)
+			break;
+	if (i == len timers) {
+		# grow the array
+		newtimers := array [len timers * 2] of ref RealTimer;
+		newtimers[0:] = timers;
+		timers = newtimers;
+	}
+	tick := chan of int;
+	t := ref Timer(i, tick);
+	nticks := ms / tickres;
+	if (nticks == 0)
+		nticks = 1;
+	rt := ref RealTimer(t, nticks, rep, big 0, tick, -1);
+	timers[i] = rt;
+	return t;
+}
+
+startclk : int;
+stopclk : int;
+
+main()
+{
+	clktick := chan of int;
+	clkctl := chan of int;
+	clkstopped := 1;
+	spawn ticker(tickres, clkctl, clktick);
+
+	for (;;) alt {
+	<- acquire =>
+		# Locking
+		acquire <- = 1;
+
+		if (clkstopped && startclk) {
+			clkstopped = 0;
+			startclk = 0;
+			clkctl <- = 1;
+		}
+
+	t := <- clktick =>
+		if (t == 0) {
+			stopclk = 0;
+			if (startclk) {
+				startclk = 0;
+				clkctl <- = 1;
+			} else {
+				clkstopped = 1;
+				continue;
+			}
+		}
+		curtick++;
+		npend := 0;
+		for (i := 0; i < len timers; i++) {
+			rt := timers[i];
+			if (rt == nil)
+				continue;
+			if (rt.nexttick == big 0)
+				continue;
+			if (rt.nexttick > curtick) {
+				npend++;
+				continue;
+			}
+			# Timeout - arrange to send the tick
+			if (rt.rep) {
+				rt.nexttick = curtick + big rt.nticks;
+				npend++;
+			} else
+				rt.nexttick = big 0;
+			si := getsender();
+			s := senders[si];
+			s.tid = i;
+			s.idle = 0;
+			rt.sender = si;
+			s.ctl <- = rt.tick;
+
+		}
+		if (!npend)
+			stopclk = 1;
+	}
+}
+
+getsender() : int
+{
+	for (i := 0; i < len senders; i++) {
+		s := senders[i];
+		if (s == nil || s.idle == 1)
+			break;
+	}
+	if (i == len senders) {
+		newsenders := array [len senders * 2] of ref Sender;
+		newsenders[0:] = senders;
+		senders = newsenders;
+	}
+	if (senders[i] == nil) {
+		s := ref Sender (-1, 1, chan of chan of int);
+		spawn sender(s);
+		senders[i] = s;
+	}
+	return i;
+}
+
+sender(me : ref Sender)
+{
+	for (;;) {
+		tickch := <- me.ctl;
+		tickch <- = 1;
+		me.idle = 1;
+	}
+}
+
+ticker(ms : int, start, tick : chan of int)
+{
+	for (;;) {
+		<- start;
+		while (!stopclk) {
+			sys->sleep(ms);
+			tick <- = 1;
+		}
+		tick <- = 0;
+	}
+}
diff --git a/appl/demo/lego/timers.dis b/appl/demo/lego/timers.dis
new file mode 100644
index 00000000..f5b2613e
--- /dev/null
+++ b/appl/demo/lego/timers.dis
diff --git a/appl/demo/lego/timers.m b/appl/demo/lego/timers.m
new file mode 100644
index 00000000..55c97b5f
--- /dev/null
+++ b/appl/demo/lego/timers.m
@@ -0,0 +1,15 @@
+Timers : module{
+	Timer : adt {
+		id : int;
+		tick : chan of int;
+
+		reset : fn (t : self ref Timer);
+		cancel : fn (t : self ref Timer);
+		destroy : fn (t : self ref Timer);
+	};
+
+	init : fn (res : int);
+	new : fn(ms, rep : int) : ref Timer;
+};
+
+
diff --git a/appl/demo/lego/timers.sbl b/appl/demo/lego/timers.sbl
new file mode 100644
index 00000000..59751a86
--- /dev/null
+++ b/appl/demo/lego/timers.sbl
@@ -0,0 +1,441 @@
+limbo .sbl 2.1
+Timers
+3
+timers.b
+sys.m
+timers.m
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