diff --git a/doc/PROTOCOL b/doc/PROTOCOL
index 32d4784..64173c7 100644
--- a/doc/PROTOCOL
+++ b/doc/PROTOCOL
@@ -31,6 +31,12 @@ Protocol
 
    9	n	0	Parameter ACK
 
+   10	0	0	Sample (64 bytes payload)
+
+   11	0	0	Sample ACK
+
+   13	n	0	Samples
+
 Unlock, firmware, image, and parameter packets all have a fixed-size
 64 bytes payload. Pings and acknowledgements have no payload. Pongs
 may have a variable-size payload.
@@ -45,3 +51,23 @@ Image format
 
 Two bytes per line. LSB of first byte is LED A1, MSB of last byte is B8.
 Unused lines must be set to zero.
+
+
+Sample format
+=============
+
+Each sample packet has the following structure:
+
+  Offset Size
+       0    2	Absolute time of X sample, high 16 bits
+       2  8*N	N samples
+
+Where each sample is
+
+  Offset Size
+       0    2	Absolute time of X sample, lower 16 bits
+       2    2	X sample (0-1023)
+       4    2	Absolute time of Y sample, lower 16 bits
+       6    2	Y sample (0-1023)
+
+Byte order TBD. (Defined by avr-gcc)
diff --git a/fw/Makefile b/fw/Makefile
index 084e9b2..9ef0e6f 100644
--- a/fw/Makefile
+++ b/fw/Makefile
@@ -30,7 +30,7 @@ OBJCOPY = $(AVR_PREFIX)objcopy
 #OBJDUMP = $(AVR_PREFIX)objdump
 SIZE = $(AVR_PREFIX)size
 
-OBJS = $(NAME).o accel.o dispatch.o hash.o image.o reset.o sweep.o \
+OBJS = $(NAME).o accel.o dispatch.o hash.o image.o reset.o sample.o sweep.o \
        $(COMMON_OBJS)
 BOOT_OBJS = boot.o flash.o fw.o $(COMMON_OBJS)
 COMMON_OBJS = rf.o spi.o
diff --git a/fw/antorcha.c b/fw/antorcha.c
index 0481ef9..ac8c3fd 100644
--- a/fw/antorcha.c
+++ b/fw/antorcha.c
@@ -33,6 +33,7 @@ static struct sweep sweep = {
 static const struct handler *protos[] = {
 	&image_handler,
 	&reset_handler,
+	&sample_handler,
 	NULL
 };
 
diff --git a/fw/dispatch.h b/fw/dispatch.h
index 7529743..1085220 100644
--- a/fw/dispatch.h
+++ b/fw/dispatch.h
@@ -28,6 +28,7 @@ struct handler {
 
 extern struct handler image_handler;
 extern struct handler reset_handler;
+extern struct handler sample_handler;
 
 
 bool dispatch(const uint8_t *buf, uint8_t len, const struct handler **protos);
diff --git a/fw/proto.h b/fw/proto.h
index 48a6813..675083d 100644
--- a/fw/proto.h
+++ b/fw/proto.h
@@ -28,6 +28,9 @@ enum pck_type {
 	IMAGE_ACK	= 7,	/* image upload acknowledgement */
 	PARAM		= 8,	/* parameter upload */
 	PARAM_ACK	= 9,	/* parameter upload acknowledgement */
+	SAMPLE		= 10,	/* start/stop sampling */
+	SAMPLE_ACK	= 11,	/* start/stop sampling acknowledgement */
+	SAMPLES		= 13,	/* samples */
 };
 
 
diff --git a/fw/sample.c b/fw/sample.c
new file mode 100644
index 0000000..7098f78
--- /dev/null
+++ b/fw/sample.c
@@ -0,0 +1,82 @@
+/*
+ * fw/sample.c - Acceleration sensor sample protocol
+ *
+ * Written 2012 by Werner Almesberger
+ * Copyright 2012 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 <stddef.h>
+#include <stdbool.h>
+#include <stdint.h>
+
+#include <avr/interrupt.h>
+
+#include "rf.h"
+#include "sweep.h"
+#include "accel.h"
+#include "proto.h"
+#include "dispatch.h"
+
+
+#define	MAX_PACKET	120	/* <- MAX_PSDU -3 (hdr) -2 (CRC) */
+
+static uint8_t buf[MAX_PACKET+3] = { SAMPLES, 0, 0 };
+static uint16_t *p;
+
+
+static void handler(bool x, uint16_t v)
+{
+	bool first;
+	uint32_t t;
+
+	first = p == (uint16_t *) (buf+3);
+	if (first && !x)
+		return;
+	t = uptime();
+	if (first)
+		*p++ = t >> 16; 
+	*p++ = t;
+	*p++ = v;
+	if (x)
+		return;
+	if ((uint8_t *) (p+4) <= buf+MAX_PACKET)
+		return;
+	rf_send(buf, (uint8_t *) p-buf);
+	p = (uint16_t *) (buf+3);
+}
+
+
+static bool sample_first(uint8_t limit, const uint8_t *payload)
+{
+	if (payload[0]) {
+		buf[1] = 0;
+		cli();
+		sample = handler;
+		p = (uint16_t *) (buf+3);
+		sei();
+	} else {
+		cli();
+		sample = NULL;
+		sei();
+	}
+	return 1;
+}
+
+
+static bool sample_more(uint8_t seq, uint8_t limit, const uint8_t *payload)
+{
+	return 0;
+}
+
+
+struct handler sample_handler = {
+        .type   = SAMPLE,
+        .first  = sample_first,
+        .more	= sample_more,
+};