From: Martin Mares <mj@ucw.cz>
Date: Tue, 27 Dec 2011 13:45:19 +0000 (+0100)
Subject: Daemon mode
X-Git-Tag: v1.0~8
X-Git-Url: http://mj.ucw.cz/gitweb/?a=commitdiff_plain;h=0911a39b28f734a789cb87506b1307312ae31f66;p=arexx.git

Daemon mode
---

diff --git a/Makefile b/Makefile
index 04cfded..6d5a256 100644
--- a/Makefile
+++ b/Makefile
@@ -3,8 +3,8 @@ LD=gcc
 CFLAGS=-O2 -Wall -W -Wno-parentheses -Wstrict-prototypes -Wmissing-prototypes -Wundef -Wredundant-decls -std=gnu99
 LDLIBS=-lusb-1.0 -lm -lrrd
 
-all: arexx
+all: arexxd
 
 clean:
 	rm -f `find . -name "*~" -or -name "*.[oa]" -or -name "\#*\#" -or -name TAGS -or -name core -or -name .depend -or -name .#*`
-	rm -f arexx
+	rm -f arexxd
diff --git a/TODO b/TODO
index 1eef6b0..c5b8d9f 100644
--- a/TODO
+++ b/TODO
@@ -1,4 +1,2 @@
-- Print of messages -- use syslog?
-- Handle disconnect and reconnect of the receiver
-- Periodical synchronization of time
 - Multiple receivers?
+- Logging of min/max temperatures
diff --git a/arexx.c b/arexx.c
deleted file mode 100644
index 796d13a..0000000
--- a/arexx.c
+++ /dev/null
@@ -1,384 +0,0 @@
-/*
- *	Linux Interfece for Arexx Data Loggers
- *
- *	(c) 2011 Martin Mares <mj@ucw.cz>
- */
-
-#include <stdio.h>
-#include <stdarg.h>
-#include <stdlib.h>
-#include <string.h>
-#include <unistd.h>
-#include <math.h>
-#include <time.h>
-#include <sys/stat.h>
-#include <libusb-1.0/libusb.h>
-#include <rrd.h>
-
-typedef unsigned char byte;
-static libusb_context *usb_ctxt;
-static libusb_device_handle *devh;
-
-static int debug_packets = 0;
-static int debug_raw_data = 0;
-
-#define TIME_OFFSET 946681200		// Timestamp of 2000-01-01 00:00:00
-
-static void die(char *msg, ...)
-{
-	va_list args;
-	va_start(args, msg);
-	vfprintf(stderr, msg, args);
-	fputc('\n', stderr);
-	va_end(args);
-	exit(1);
-}
-
-/*** RRD interface ***/
-
-#define RRD_NAME "/tmp/power.rrd"
-#define SLOT_SIZE 10					// 10 seconds per averaging slot
-#define MAX_ARGS 20
-#define MAX_ARG_SIZE 1024
-
-static int arg_cnt;
-static char *arg_ptr[MAX_ARGS+1];
-static char arg_buf[MAX_ARG_SIZE];
-static int arg_pos;
-
-static void arg_new(void)
-{
-	arg_cnt = 1;
-	arg_pos = 0;
-	arg_ptr[0] = "rrdtool";
-}
-
-static void arg_push(const char *fmt, ...)
-{
-	if (arg_cnt >= MAX_ARGS)
-		die("MAX_ARGS exceeded");
-	va_list va;
-	va_start(va, fmt);
-	int len = 1 + vsnprintf(arg_buf + arg_pos, MAX_ARG_SIZE - arg_pos, fmt, va);
-	if (arg_pos + len > MAX_ARG_SIZE)
-		die("MAX_ARG_SIZE exceeded");
-	arg_ptr[arg_cnt++] = arg_buf + arg_pos;
-	arg_ptr[arg_cnt] = NULL;
-	arg_pos += len;
-}
-
-static void rrd_point(time_t t, int id, double val)
-{
-	char rr_name[256];
-	snprintf(rr_name, sizeof(rr_name), "sensor-%d.rrd", id);
-
-	struct stat st;
-	if (stat(rr_name, &st) < 0 || !st.st_size) {
-		// We have to create the RRD
-		printf("### Creating %s\n", rr_name);
-		arg_new();
-		arg_push(rr_name);
-		arg_push("--start");
-		arg_push("%d", (int) time(NULL) - 28*86400);
-		arg_push("--step");
-		arg_push("60");
-		arg_push("DS:temp:GAUGE:300:0:10000");		// Anything over 10 kW is considered a ghost
-		arg_push("RRA:AVERAGE:0.25:1:20160");		// Last 14 days with full resolution
-		arg_push("RRA:AVERAGE:0.25:60:88800");		// Last 10 years with 1h resolution
-		rrd_create(arg_cnt, arg_ptr);
-		if (rrd_test_error())
-			die("rrd_create failed: %s", rrd_get_error());
-	}
-
-	arg_new();
-	arg_push(rr_name);
-	arg_push("%d:%f", t, val);
-	rrd_update(arg_cnt, arg_ptr);
-	if (rrd_test_error())
-		printf("### rrd_update failed: %s\n", rrd_get_error());
-}
-
-/*** Transforms ***/
-
-static void cooked_point(time_t t, int id, double val, char *unit, int q)
-{
-	struct tm tm;
-	localtime_r(&t, &tm);
-
-	char tbuf[64];
-	strftime(tbuf, sizeof(tbuf), "%Y-%m-%d %H:%M:%S", &tm);
-
-	printf("== %s id=%d val=%.3f unit=%s q=%d\n", tbuf, id, val, unit, q);
-
-	rrd_point(t, id, val);
-}
-
-static void raw_point(int t, int id, int raw, int q)
-{
-	/*
-	 *  The binary blob provided by Arexx contains an embedded XML fragment
-	 *  with descriptions of all known sensor types. If you want to see it,
-	 *  grep the blob for "<deviceinfo>". The meanings of the parameters are
-	 *  as follows:
-	 *
-	 *	m1, m2		Device type matches if (raw_sensor_id & m1) == m2
-	 *	type		Unit measured by the sensor (1=Celsius, 2=RH%, 3=CO2 ppm)
-	 *	dm		User-visible sensor ID = raw_sensor_id & dm
-	 *	i		1 if the raw value is signed
-	 *	p[]		Coefficients of transformation polynomial (x^0 first)
-	 *	vLo, vUp	Upper and lower bound on the final value
-	 *	scale		Scaling function:
-	 *				0 = identity (default)
-	 *				1 = 10^x
-	 *				2 = exp(x)
-	 *				3 = (x < 0) ? 0 : log10(x)
-	 *				4 = (x < 0) ? 0 : log(x)
-	 *
-	 *  The raw values are transformed this way:
-	 *	- sign-extend if signed
-	 *	- apply the transformation polynomial
-	 *	- apply the scaling function
-	 *	- drop if outside the interval [vLo,vUp]
-	 *
-	 *  This function applies the necessary transform for sensors we've
-	 *  seen in the wild. We deliberately ignore the "dm" parameter as we want
-	 *  to report different channels of a single sensor as multiple sensors.
-	 */
-
-	double z = raw;
-	double hi, lo;
-	char *unit;
-	int idhi = id & 0xf000;
-
-	if (idhi == 0x1000) {
-		z = 0.02*z - 273.15;
-		lo = -200;
-		hi = 600;
-		unit = "C";
-	} else if (idhi == 0x2000) {
-		if (raw >= 0x8000)
-			z -= 0x10000;
-		z /= 128;
-		lo = -60;
-		hi = 125;
-		unit = "C";
-	} else if (idhi == 0x4000) {
-		if (!(id & 1)) {
-			z = z/100 - 39.6;
-			lo = -60;
-			hi = 125;
-			unit = "C";
-		} else {
-			z = -2.8e-6*z*z + 0.0405*z - 4;
-			lo = 0;
-			hi = 100.1;
-			unit = "%RH";
-		}
-	} else if (idhi == 0x6000) {
-		if (!(id & 1)) {
-			if (raw >= 0x8000)
-				z -= 0x10000;
-			z /= 128;
-			lo = -60;
-			hi = 125;
-			unit = "C";
-		} else {
-			z = -3.8123e-11*z;
-			z = (z + 1.9184e-7) * z;
-			z = (z - 1.0998e-3) * z;
-			z += 6.56;
-			z = pow(10, z);
-			lo = 0;
-			hi = 1e6;
-			unit = "ppm";
-		}
-	} else {
-		printf("### Unknown sensor type 0x%04x\n", id);
-		return;
-	}
-
-	if (z < lo || z > hi) {
-		printf("### Sensor %d: value %f out of range\n", id, z);
-		return;
-	}
-
-	cooked_point(t + TIME_OFFSET, id, z, unit, q);
-}
-
-/*** USB interface ***/
-
-static void find_device(void)
-{
-	libusb_device **devlist;
-	ssize_t devn = libusb_get_device_list(usb_ctxt, &devlist);
-	if (devn < 0)
-		die("Cannot enumerate USB devices: error %d\n", (int) devn);
-
-	for (ssize_t i=0; i<devn; i++) {
-		struct libusb_device_descriptor desc;
-		libusb_device *dev = devlist[i];
-		if (!libusb_get_device_descriptor(dev, &desc)) {
-			if (desc.idVendor == 0x0451 && desc.idProduct == 0x3211) {
-				printf("Arexx USB receiver found at usb%d.%d\n", libusb_get_bus_number(dev), libusb_get_device_address(dev));
-				int err;
-				if (err = libusb_open(dev, &devh))
-					die("libusb_open() failed: error %d\n", err);
-				if (err = libusb_claim_interface(devh, 0))
-					die("libusb_claim_interface() failed: error %d\n", err);
-				libusb_free_device_list(devlist, 1);
-				return;
-			}
-		}
-	}
-
-	die("No Arexx USB receiver found");
-}
-
-static void dump_packet(byte *pkt)
-{
-	for (int i=0; i<64; i++) {
-		if (!(i % 16))
-			printf("\t%02x:", i);
-		printf(" %02x", pkt[i]);
-		if (i % 16 == 15)
-			printf("\n");
-	}
-}
-
-static int send_and_receive(byte *req, byte *reply)
-{
-	int err, transferred;
-	if (err = libusb_bulk_transfer(devh, 0x01, req, 64, &transferred, 200)) {
-		fprintf(stderr, "Transmit error: %d\n", err);
-		return 0;
-	}
-	if (debug_packets) {
-		printf(">> xmit %d bytes\n", transferred);
-		dump_packet(req);
-	}
-	if (err = libusb_bulk_transfer(devh, 0x81, reply, 64, &transferred, 200)) {
-		fprintf(stderr, "Receive error: %d\n", err);
-		return 0;
-	}
-	if (debug_packets)
-		printf("<< recv %d bytes\n", transferred);
-	while (transferred < 64)
-		reply[transferred++] = 0xff;
-	if (debug_packets)
-		dump_packet(reply);
-	return 1;
-}
-
-static unsigned int get_be16(byte *p)
-{
-	return p[1] | (p[0] << 8);
-}
-
-static unsigned int get_le16(byte *p)
-{
-	return p[0] | (p[1] << 8);
-}
-
-static unsigned int get_le32(byte *p)
-{
-	return get_le16(p) | (get_le16(p+2) << 16);
-}
-
-static void put_le16(byte *p, unsigned int x)
-{
-	p[0] = x;
-	p[1] = x >> 8;
-}
-
-static void put_le32(byte *p, unsigned int x)
-{
-	put_le16(p, x);
-	put_le16(p+2, x>>16);
-}
-
-static int parse_packet(byte *reply)
-{
-	if (reply[0]) {
-		printf("### Unknown packet type %02x\n", reply[0]);
-		return 0;
-	}
-
-	int pos = 1;
-	int points = 0;
-	while (pos < 64) {
-		byte *p = reply + pos;
-		int len = p[0];
-		if (!len || len == 0xff)
-			break;
-		if (len < 9 || len > 10) {
-			printf("### Unknown tuple length %02x\n", len);
-			break;
-		}
-		if (pos + len > 64) {
-			printf("### Tuple truncated\n");
-			break;
-		}
-		int id = get_le16(p+1);
-		int raw = get_be16(p+3);
-		int t = get_le32(p+5);
-		int q = (len > 9) ? p[9] : -1;
-		if (debug_raw_data) {
-			printf("... %02x: id=%d raw=%d t=%d", len, id, raw, t);
-			if (len > 9)
-				printf(" q=%d", q);
-			printf("\n");
-		}
-		raw_point(t, id, raw, q);
-		pos += len;
-		points++;
-	}
-
-	return points;
-}
-
-static void set_clock(void)
-{
-	puts("### Syncing time");
-
-	byte req[64], reply[64];
-	memset(req, 0, 64);
-	req[0] = 4;
-	time_t t = time(NULL);
-	put_le32(req+1, t-TIME_OFFSET);
-	send_and_receive(req, reply);
-
-#if 0
-	/*
-	 *  Original software also sends a packet with type 3 and the timestamp,
-	 *  but it does not make any sense, especially as they ignore the sensor
-	 *  readings in the answer.
-	 */
-	req[0] = 3;
-	send_and_receive(req, reply);
-	parse_packet(reply);
-#endif
-}
-
-int main(void)
-{
-	int err;
-	if (err = libusb_init(&usb_ctxt))
-		die("Cannot initialize libusb: error %d", err);
-	libusb_set_debug(usb_ctxt, 3);
-
-	find_device();
-	set_clock();
-
-	for (;;) {
-		byte req[64], reply[64];
-		memset(req, 0, sizeof(req));
-		req[0] = 3;
-		if (send_and_receive(req, reply)) {
-			if (parse_packet(reply))
-				continue;
-		}
-		sleep(4);
-	}
-
-	return 0;
-}
diff --git a/arexxd.c b/arexxd.c
new file mode 100644
index 0000000..6e301a0
--- /dev/null
+++ b/arexxd.c
@@ -0,0 +1,528 @@
+/*
+ *	Linux Interfece for Arexx Data Loggers
+ *
+ *	(c) 2011 Martin Mares <mj@ucw.cz>
+ */
+
+#include <stdio.h>
+#include <stdarg.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <math.h>
+#include <time.h>
+#include <getopt.h>
+#include <syslog.h>
+#include <pwd.h>
+#include <grp.h>
+#include <sys/stat.h>
+#include <libusb-1.0/libusb.h>
+#include <rrd.h>
+
+#define LOG_PATH "/var/log/arexxd"
+
+typedef unsigned char byte;
+static libusb_context *usb_ctxt;
+static libusb_device_handle *devh;
+
+static int use_syslog;
+static int debug_mode;
+static int debug_packets;
+static int debug_raw_data;
+
+static void die(char *fmt, ...)
+{
+	va_list args;
+	va_start(args, fmt);
+	if (use_syslog)
+		vsyslog(LOG_CRIT, fmt, args);
+	else {
+		vfprintf(stderr, fmt, args);
+		fprintf(stderr, "\n");
+	}
+	va_end(args);
+	exit(1);
+}
+
+static void log_error(char *fmt, ...)
+{
+	va_list args;
+	va_start(args, fmt);
+	if (use_syslog)
+		vsyslog(LOG_ERR, fmt, args);
+	else {
+		vfprintf(stderr, fmt, args);
+		fprintf(stderr, "\n");
+	}
+	va_end(args);
+}
+
+static void log_info(char *fmt, ...)
+{
+	va_list args;
+	va_start(args, fmt);
+	if (use_syslog)
+		vsyslog(LOG_INFO, fmt, args);
+	else {
+		vfprintf(stderr, fmt, args);
+		fprintf(stderr, "\n");
+	}
+	va_end(args);
+}
+
+static void log_pkt(char *fmt, ...)
+{
+	if (!debug_packets)
+		return;
+	va_list args;
+	va_start(args, fmt);
+	vprintf(fmt, args);
+	va_end(args);
+}
+
+/*** RRD interface ***/
+
+#define SLOT_SIZE 10					// 10 seconds per averaging slot
+#define MAX_ARGS 20
+#define MAX_ARG_SIZE 1024
+
+static int arg_cnt;
+static char *arg_ptr[MAX_ARGS+1];
+static char arg_buf[MAX_ARG_SIZE];
+static int arg_pos;
+
+static void arg_new(void)
+{
+	arg_cnt = 1;
+	arg_pos = 0;
+	arg_ptr[0] = "rrdtool";
+}
+
+static void arg_push(const char *fmt, ...)
+{
+	if (arg_cnt >= MAX_ARGS)
+		die("MAX_ARGS exceeded");
+	va_list va;
+	va_start(va, fmt);
+	int len = 1 + vsnprintf(arg_buf + arg_pos, MAX_ARG_SIZE - arg_pos, fmt, va);
+	if (arg_pos + len > MAX_ARG_SIZE)
+		die("MAX_ARG_SIZE exceeded");
+	arg_ptr[arg_cnt++] = arg_buf + arg_pos;
+	arg_ptr[arg_cnt] = NULL;
+	arg_pos += len;
+}
+
+static void rrd_point(time_t t, int id, double val)
+{
+	char rr_name[256];
+	snprintf(rr_name, sizeof(rr_name), "sensor-%d.rrd", id);
+
+	struct stat st;
+	if (stat(rr_name, &st) < 0 || !st.st_size) {
+		// We have to create the RRD
+		log_info("Creating %s", rr_name);
+		arg_new();
+		arg_push(rr_name);
+		arg_push("--start");
+		arg_push("%d", (int) time(NULL) - 28*86400);
+		arg_push("--step");
+		arg_push("60");
+		arg_push("DS:temp:GAUGE:300:0:10000");		// Anything over 10 kW is considered a ghost
+		arg_push("RRA:AVERAGE:0.25:1:20160");		// Last 14 days with full resolution
+		arg_push("RRA:AVERAGE:0.25:60:88800");		// Last 10 years with 1h resolution
+		rrd_create(arg_cnt, arg_ptr);
+		if (rrd_test_error()) {
+			log_error("rrd_create on %s failed: %s", rr_name, rrd_get_error());
+			return;
+		}
+	}
+
+	arg_new();
+	arg_push(rr_name);
+	arg_push("%d:%f", t, val);
+	rrd_update(arg_cnt, arg_ptr);
+	if (rrd_test_error())
+		log_error("rrd_update on %s failed: %s", rr_name, rrd_get_error());
+}
+
+/*** Transforms ***/
+
+#define TIME_OFFSET 946681200		// Timestamp of 2000-01-01 00:00:00
+
+static void cooked_point(time_t t, int id, double val, char *unit, int q)
+{
+	struct tm tm;
+	localtime_r(&t, &tm);
+
+	char tbuf[64];
+	strftime(tbuf, sizeof(tbuf), "%Y-%m-%d %H:%M:%S", &tm);
+
+	if (debug_raw_data)
+		printf("== %s id=%d val=%.3f unit=%s q=%d\n", tbuf, id, val, unit, q);
+
+	rrd_point(t, id, val);
+}
+
+static void raw_point(int t, int id, int raw, int q)
+{
+	/*
+	 *  The binary blob provided by Arexx contains an embedded XML fragment
+	 *  with descriptions of all known sensor types. If you want to see it,
+	 *  grep the blob for "<deviceinfo>". The meanings of the parameters are
+	 *  as follows:
+	 *
+	 *	m1, m2		Device type matches if (raw_sensor_id & m1) == m2
+	 *	type		Unit measured by the sensor (1=Celsius, 2=RH%, 3=CO2 ppm)
+	 *	dm		User-visible sensor ID = raw_sensor_id & dm
+	 *	i		1 if the raw value is signed
+	 *	p[]		Coefficients of transformation polynomial (x^0 first)
+	 *	vLo, vUp	Upper and lower bound on the final value
+	 *	scale		Scaling function:
+	 *				0 = identity (default)
+	 *				1 = 10^x
+	 *				2 = exp(x)
+	 *				3 = (x < 0) ? 0 : log10(x)
+	 *				4 = (x < 0) ? 0 : log(x)
+	 *
+	 *  The raw values are transformed this way:
+	 *	- sign-extend if signed
+	 *	- apply the transformation polynomial
+	 *	- apply the scaling function
+	 *	- drop if outside the interval [vLo,vUp]
+	 *
+	 *  This function applies the necessary transform for sensors we've
+	 *  seen in the wild. We deliberately ignore the "dm" parameter as we want
+	 *  to report different channels of a single sensor as multiple sensors.
+	 */
+
+	double z = raw;
+	double hi, lo;
+	char *unit;
+	int idhi = id & 0xf000;
+
+	if (idhi == 0x1000) {
+		z = 0.02*z - 273.15;
+		lo = -200;
+		hi = 600;
+		unit = "C";
+	} else if (idhi == 0x2000) {
+		if (raw >= 0x8000)
+			z -= 0x10000;
+		z /= 128;
+		lo = -60;
+		hi = 125;
+		unit = "C";
+	} else if (idhi == 0x4000) {
+		if (!(id & 1)) {
+			z = z/100 - 39.6;
+			lo = -60;
+			hi = 125;
+			unit = "C";
+		} else {
+			z = -2.8e-6*z*z + 0.0405*z - 4;
+			lo = 0;
+			hi = 100.1;
+			unit = "%RH";
+		}
+	} else if (idhi == 0x6000) {
+		if (!(id & 1)) {
+			if (raw >= 0x8000)
+				z -= 0x10000;
+			z /= 128;
+			lo = -60;
+			hi = 125;
+			unit = "C";
+		} else {
+			z = -3.8123e-11*z;
+			z = (z + 1.9184e-7) * z;
+			z = (z - 1.0998e-3) * z;
+			z += 6.56;
+			z = pow(10, z);
+			lo = 0;
+			hi = 1e6;
+			unit = "ppm";
+		}
+	} else {
+		log_error("Unknown sensor type 0x%04x", id);
+		return;
+	}
+
+	if (z < lo || z > hi) {
+		log_error("Sensor %d: value %f out of range", id, z);
+		return;
+	}
+
+	cooked_point(t + TIME_OFFSET, id, z, unit, q);
+}
+
+/*** USB interface ***/
+
+static int find_device(void)
+{
+	libusb_device **devlist;
+	ssize_t devn = libusb_get_device_list(usb_ctxt, &devlist);
+	if (devn < 0) {
+		log_error("Cannot enumerate USB devices: error %d", (int) devn);
+		return 0;
+	}
+
+	for (ssize_t i=0; i<devn; i++) {
+		struct libusb_device_descriptor desc;
+		libusb_device *dev = devlist[i];
+		if (!libusb_get_device_descriptor(dev, &desc)) {
+			if (desc.idVendor == 0x0451 && desc.idProduct == 0x3211) {
+				log_info("Arexx USB receiver found at usb%d.%d", libusb_get_bus_number(dev), libusb_get_device_address(dev));
+				int err;
+				if (err = libusb_open(dev, &devh)) {
+					log_error("libusb_open() failed: error %d", err);
+					goto failed;
+				}
+				if (err = libusb_claim_interface(devh, 0)) {
+					log_error("libusb_claim_interface() failed: error %d", err);
+					libusb_close(devh);
+					goto failed;
+				}
+				libusb_free_device_list(devlist, 1);
+				return 1;
+			}
+		}
+	}
+
+failed:
+	libusb_free_device_list(devlist, 1);
+	return 0;
+}
+
+static void release_device(void)
+{
+	libusb_close(devh);
+	devh = NULL;
+}
+
+static void dump_packet(byte *pkt)
+{
+	for (int i=0; i<64; i++) {
+		if (!(i % 16))
+			log_pkt("\t%02x:", i);
+		log_pkt(" %02x", pkt[i]);
+		if (i % 16 == 15)
+			log_pkt("\n");
+	}
+}
+
+static int send_and_receive(byte *req, byte *reply)
+{
+	int err, transferred;
+	if (err = libusb_bulk_transfer(devh, 0x01, req, 64, &transferred, 200)) {
+		if (err == LIBUSB_ERROR_TIMEOUT) {
+			log_pkt(">> xmit timed out\n");
+			return 0;
+		}
+		log_error("Transmit error: %d", err);
+		return err;
+	}
+	if (debug_packets) {
+		log_pkt(">> xmit %d bytes\n", transferred);
+		dump_packet(req);
+	}
+	if (err = libusb_bulk_transfer(devh, 0x81, reply, 64, &transferred, 200)) {
+		if (err == LIBUSB_ERROR_TIMEOUT) {
+			log_pkt(">> recv timed out\n");
+			return 0;
+		}
+		log_error("Receive error: %d", err);
+		return err;
+	}
+	if (debug_packets)
+		log_pkt("<< recv %d bytes\n", transferred);
+	while (transferred < 64)
+		reply[transferred++] = 0xff;
+	if (debug_packets)
+		dump_packet(reply);
+	return 1;
+}
+
+static unsigned int get_be16(byte *p)
+{
+	return p[1] | (p[0] << 8);
+}
+
+static unsigned int get_le16(byte *p)
+{
+	return p[0] | (p[1] << 8);
+}
+
+static unsigned int get_le32(byte *p)
+{
+	return get_le16(p) | (get_le16(p+2) << 16);
+}
+
+static void put_le16(byte *p, unsigned int x)
+{
+	p[0] = x;
+	p[1] = x >> 8;
+}
+
+static void put_le32(byte *p, unsigned int x)
+{
+	put_le16(p, x);
+	put_le16(p+2, x>>16);
+}
+
+static int parse_packet(byte *reply)
+{
+	if (reply[0]) {
+		log_error("Unknown packet type %02x", reply[0]);
+		return 0;
+	}
+
+	int pos = 1;
+	int points = 0;
+	while (pos < 64) {
+		byte *p = reply + pos;
+		int len = p[0];
+		if (!len || len == 0xff)
+			break;
+		if (len < 9 || len > 10) {
+			log_error("Unknown tuple length %02x", len);
+			break;
+		}
+		if (pos + len > 64) {
+			log_error("Tuple truncated");
+			break;
+		}
+		int id = get_le16(p+1);
+		int raw = get_be16(p+3);
+		int t = get_le32(p+5);
+		int q = (len > 9) ? p[9] : -1;
+		if (debug_raw_data) {
+			printf("... %02x: id=%d raw=%d t=%d", len, id, raw, t);
+			if (len > 9)
+				printf(" q=%d", q);
+			printf("\n");
+		}
+		raw_point(t, id, raw, q);
+		pos += len;
+		points++;
+	}
+
+	return points;
+}
+
+static void set_clock(void)
+{
+	log_info("Synchronizing receiver time");
+
+	byte req[64], reply[64];
+	memset(req, 0, 64);
+	req[0] = 4;
+	time_t t = time(NULL);
+	put_le32(req+1, t-TIME_OFFSET);
+	send_and_receive(req, reply);
+
+#if 0
+	/*
+	 *  Original software also sends a packet with type 3 and the timestamp,
+	 *  but it does not make any sense, especially as they ignore the sensor
+	 *  readings in the answer.
+	 */
+	req[0] = 3;
+	send_and_receive(req, reply);
+	parse_packet(reply);
+#endif
+}
+
+/*** Main ***/
+
+static const struct option long_options[] = {
+	{ "debug",		0, NULL, 'd' },
+	{ "log-packets",	0, NULL, 'p' },
+	{ NULL,			0, NULL, 0 },
+};
+
+static void usage(void)
+{
+	fprintf(stderr, "Usage: arexxd [--debug] [--log-packets]\n");
+	exit(1);
+}
+
+int main(int argc, char **argv)
+{
+	int opt;
+	while ((opt = getopt_long(argc, argv, "dp", long_options, NULL)) >= 0)
+		switch (opt) {
+			case 'd':
+				debug_mode++;
+				break;
+			case 'p':
+				debug_packets++;
+				debug_raw_data++;
+				break;
+			default:
+				usage();
+		}
+	if (optind < argc)
+		usage();
+
+	int err;
+	if (err = libusb_init(&usb_ctxt))
+		die("Cannot initialize libusb: error %d", err);
+	// libusb_set_debug(usb_ctxt, 3);
+
+	if (!debug_mode) {
+		if (chdir(LOG_PATH) < 0)
+			die("Cannot change directory to %s: %m", LOG_PATH);
+		if (debug_packets || debug_raw_data) {
+			close(1);
+			if (open("debug", O_WRONLY | O_CREAT | O_APPEND, 0666) < 0)
+				die("Cannot open debug log: %m");
+			setlinebuf(stdout);
+		}
+		openlog("arexxd", LOG_NDELAY, LOG_DAEMON);
+		pid_t pid = fork();
+		if (pid < 0)
+			die("fork() failed: %m");
+		if (pid)
+			return 0;
+		setsid();
+		use_syslog = 1;
+	}
+
+	int inited = 0;
+	for (;;) {
+		if (!find_device()) {
+			if (!inited) {
+				inited = 1;
+				log_error("Receiver not connected, waiting until it appears");
+			}
+			sleep(30);
+			continue;
+		}
+
+		inited = 1;
+
+		int sync_in = 0;
+		for (;;) {
+			if (!sync_in) {
+				set_clock();
+				sync_in = 100;
+			}
+			byte req[64], reply[64];
+			memset(req, 0, sizeof(req));
+			req[0] = 3;
+			err = send_and_receive(req, reply);
+			if (err < 0)
+				break;
+			if (err > 0 && parse_packet(reply))
+				continue;
+			sleep(4);
+			sync_in--;
+		}
+
+		log_info("Disconnecting receiver");
+		release_device();
+	}
+
+	return 0;
+}