arekinath/Makefile

## README.md

      
    Raw
  

              README.md
            
          
    Ascot AA2-WS-15 weather station

This is an implementation of an SDR receiver to listen for weather updates (temperature + humidity) from an Ascot AA2-WS-15 weather station transmitter, and put it into an rrdtool database. It uses an RTL-SDR and librtlsdr (http://sdr.osmocom.org/trac/wiki/rtl-sdr)
Setup/using etc


download everything
run 'make'
then sh z_create_rrd.sh && ./z_daemon.rb start
now set up a cronjob to run z_graph_rrd.sh every minute or so

Encoding/modulation


pulse gap modulation


pulses are about 1ms long, spacing between them determines the data


first gap of a frame is always 4ms (I call this the X bit)


then 2ms gap for a 1, and 1ms gap for a 0


frames consist of 3 12-bit words


first word = preamble


second word = 10 * temperature


third word = low 7 (?) bits are rel. humidity in percent... high 5 bits always 30?


transmission of data occurs once every ~60sec, and consists of 10+ identical frames (to allow for receiver clock drift)


Examples

32.0 / 27%    X  1 0 1 0 1 1 1 0 1 0 0 0  0 0 0 1 0 1 0 0 0 0 0 0  1 1 1 1 0  0 0 1 1 0 1 1
33.0 / 29%    X  1 0 1 0 1 1 1 0 1 0 0 0  0 0 0 1 0 1 0 0 1 0 1 0  1 1 1 1 0  0 0 1 1 1 0 1
33.3 / 29%    X  1 0 1 0 1 1 1 0 1 0 0 0  0 0 0 1 0 1 0 0 1 1 0 1  1 1 1 1 0  0 0 1 1 1 0 1
33.1 / 29%    X  1 0 1 0 1 1 1 0 1 0 0 0  0 0 0 1 0 1 0 0 1 0 1 1  1 1 1 1 0  0 0 1 1 1 0 1
32.7 / 29%    X  1 0 1 0 1 1 1 0 1 0 0 0  0 0 0 1 0 1 0 0 0 1 1 1  1 1 1 1 0  0 0 1 1 1 0 1


## Makefile
weather: weather.c
	gcc -O2 -msse2 -ftree-vectorize -I/opt/local/include -L/opt/local/lib -lrtlsdr -lm -std=c99 weather.c -o weather

## weather.c
/*
 * weather.c -- receiver for ascot weather station
 *
 * Copyright (c) 2012, Alex Wilson (arekinath)
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *     * Redistributions of source code must retain the above copyright
 *       notice, this list of conditions and the following disclaimer.
 *     * Redistributions in binary form must reproduce the above copyright
 *       notice, this list of conditions and the following disclaimer in the
 *       documentation and/or other materials provided with the distribution.
 *     * Neither the name of the <organization> nor the
 *       names of its contributors may be used to endorse or promote products
 *       derived from this software without specific prior written permission.
 *
 * See the standard BSD license disclaimer for details about warranty, liability,
 * fitness for purpose, etc.
 */

#include <rtl-sdr.h>
#include <stdio.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <math.h>

int
main(int argc, char *argv[])
{
	rtlsdr_dev_t *dev;
	int ret;

	if (rtlsdr_open(&dev, 0)) {
		fprintf(stderr, "failed to open rtlsdr\n");
		return 1;
	}

	/* 433.798 MHz is the channel 1 freq (approximately) */
	const int32_t freq = 433798000;

	/* tune 100kHz above the target */
	if (rtlsdr_set_center_freq(dev, freq - 100000)) {
		fprintf(stderr, "failed to set centre\n");
		return 1;
	}

	/* ask for it back so we know the actual centre */
	int32_t rfreq = rtlsdr_get_center_freq(dev);
	int32_t devn = freq - rfreq;

	uint32_t samprate = 1048576;
	if (rtlsdr_set_sample_rate(dev, samprate)) {
		fprintf(stderr, "failed set sample rate\n");
		return 1;
	}

	samprate = rtlsdr_get_sample_rate(dev);
	const uint32_t centre = rtlsdr_get_center_freq(dev);

	/* xxx: sort out what tuner gain to use */
	rtlsdr_set_tuner_gain(dev, 490);

	const int readsize = 1024;

	uint8_t *buf = malloc(readsize);
	memset(buf, 0, readsize);

	/* generate the ~100kHz oscillator to mix the incoming signal with */
	double *wave = malloc(sizeof(double)*readsize);
	for (int i = 0; i < (readsize / 2); ++i) {
		double t = (devn * (double)i) / (double)samprate;
		wave[i*2] = cos(2*3.14159*t);
		wave[i*2+1] = sin(2*3.14159*t);
	}

	double *demod = malloc(sizeof(double)*readsize);
	double *demod_smooth = malloc(sizeof(double)*readsize);

	int lenout;

	/* always have to call reset_buffer before reading */
	if (rtlsdr_reset_buffer(dev)) {
		fprintf(stderr, "failed reset buffer\n");
		return 1;
	}

	/* number of reads we've been 'high' for */
	uint64_t highfor = 0;
	uint64_t lowfor = 0;

	/* was there a pulse before the last change? */
	uint8_t pulse = 0;

	/* frame state */
	uint64_t last_last_frame = 1;
	uint64_t last_frame = 1;
	uint64_t frame = 0;
	uint8_t bitno = 0;

	while (1) {
		/* fill up the buffer with incoming I/Q samples */
		ret = rtlsdr_read_sync(dev, buf, readsize, &lenout);
		if (ret || lenout < readsize) {
			fprintf(stderr, "short read! (=%d) %d/%d\n", ret, lenout, readsize);
			return 1;
		}

		/* mix with the local oscillator to downconvert it. also rectify at the same time */
		for (int i = 0; i < readsize; ++i) {
			demod[i] = ((((double)buf[i]) / 256.0) - 0.5) * wave[i];
			if (demod[i] < 0) demod[i] = 0;
		}

		/* now do a moving average filter to smooth the resulting waveform */
		for (int i = 0; i < 20; ++i)
			demod_smooth[i] = demod[i];

		for (int i = 20; i < readsize; ++i)
			demod_smooth[i] = (demod[i] + demod[i-2] + demod[i-4] + demod[i-6] + demod[i-8] + demod[i-10] + demod[i-12] + demod[i-14] + demod[i-16] + demod[i-18] + demod[i-20]) / 11;

		/* sum the mags of the samples (don't bother squaring, since we rectified it) */
		double magsum = 0;
		for (int i = 0; i < readsize; i+=2) {
			double mag = demod_smooth[i] + demod_smooth[i+1];
			magsum += mag * mag;
		}

		/* xxx: arbitrary constant warning! somewhere from 0.5 - 1.5 seems to work */
		if (magsum > 0.7) {
			/* this is a 'high' sample, as in during a pulse */

			/* is this the first 'high' sample? ie, did we just end a gap? */
			if (highfor == 0) {
				const uint64_t one64 = 1;

				/* zeros take 1-2 samples */
				if (pulse && lowfor >= 1 && lowfor <= 2) {
					bitno--;
					frame &= ~(one64<<bitno);

				/* ones take 3-5 samples */
				} else if (pulse && lowfor >= 3 && lowfor <= 5) {
					bitno--;
					frame |= (one64<<bitno);

				/* and 6-8 samples is an 'X' */
				} else if (pulse && lowfor >= 6 && lowfor <= 8) {

					if (last_frame == frame && last_last_frame == frame && bitno == 0) {
						const uint64_t mask12 = 0xfff;
						const uint64_t mask7 = 0x7f;
						uint64_t preamble = (frame >> 24) & mask12;
						if (preamble == 0xae8) {
							uint64_t temp = (frame >> 12) & mask12;
							uint16_t tempwhole = temp / 10;
							uint16_t tempfrac = temp % 10;
							uint64_t humid = frame & mask7;
							printf("N:%hu.%hu:%llu\n", tempwhole, tempfrac, humid);
							break;
						}
					}

					last_last_frame = last_frame;
					last_frame = frame;
					frame = 0;
					bitno = 36;
				}

				pulse = 0;
				lowfor = 0;
			}

			/* increment the counter for high samples in a row */
			highfor++;

		} else {
			/* this is a low sample */

			/* is this the first? did we just end a pulse? */
			if (lowfor == 0) {
				if (highfor >= 1 && highfor <= 3) {
					pulse = 1;
				} else {
					pulse = 0;
				}
				highfor = 0;
			}
			lowfor++;
		}

	}

	/* xxx: todo: cleanup other stuff */
	rtlsdr_close(dev);
}

## z_create_rrd.sh
rrdtool create weather.rrd -s 60 \
	DS:temperature:GAUGE:300:-10:60 \
	DS:humidity:GAUGE:300:0:100 \
	RRA:AVERAGE:0.5:1:1440 \
	RRA:AVERAGE:0.5:5:2016 \
	RRA:AVERAGE:0.5:30:1488 \
	RRA:AVERAGE:0.5:240:2190 \
	RRA:MIN:0.5:1:1440 \
	RRA:MIN:0.5:5:2016 \
	RRA:MIN:0.5:30:1488 \
	RRA:MAX:0.5:1:1440 \
	RRA:MAX:0.5:5:2016 \
	RRA:MAX:0.5:30:1488 \
	RRA:LAST:0.5:1:1440 \
	RRA:LAST:0.5:5:2016 \
	RRA:LAST:0.5:30:1488

## z_daemon.rb
#!/usr/bin/env ruby

require 'daemons'

Daemons.run_proc('weatherd') do
	Dir.chdir("/home/alex/weather")
	loop do
		data = `./weather`
		`rrdtool update weather.rrd #{data}`
		sleep(54)
	end
end

## z_graph_rrd.sh
#!/bin/bash

cd /home/alex/weather

function tempgraph {
	rrdtool graph htdocs/temperature-$1.png \
		-s $2 \
		-t "Temperature ($1)" \
		--vertical-label="degrees C" \
		-w 400 -h 150 \
		DEF:temp=weather.rrd:temperature:AVERAGE \
		LINE4:temp#dd4444 \
		AREA:temp#eebbbb:temperature \
		GPRINT:temp:LAST:" Now\:%4.1lf %s" \
		GPRINT:temp:MIN:" Min\:%4.1lf %s" \
		GPRINT:temp:MAX:" Max\:%4.1lf %s" \
		GPRINT:temp:AVERAGE:" Avg\:%4.1lf\n"
}

tempgraph 12hr -12h
tempgraph 2day -2d
tempgraph 1week -1w
tempgraph 1month -31d

function humgraph {
	rrdtool graph htdocs/humidity-$1.png \
		-s $2 \
		-t "Rel. humidity ($1)" \
		--vertical-label="percent rel humidity" \
		-w 400 -h 150 \
		DEF:hum=weather.rrd:humidity:AVERAGE \
		LINE4:hum#4444dd \
		AREA:hum#bbbbee:humidity \
		GPRINT:hum:LAST:" Now\:%4.0lf%% %s" \
		GPRINT:hum:MIN:" Min\:%4.0lf%% %s" \
		GPRINT:hum:MAX:" Max\:%4.0lf%% %s" \
		GPRINT:hum:AVERAGE:" Avg\:%4.0lf%%\n"
}

humgraph 12hr -12h
humgraph 2day -2d
humgraph 1week -1w
humgraph 1month -31d

function dpgraph {
	A="6.1121"
	B="18.678"
	C="257.14"
	D="234.5"

	rrdtool graph htdocs/dewpoint-$1.png \
		-s $2 \
		-t "Dew point ($1)" \
		--vertical-label="degrees C" \
		-w 400 -h 150 \
		DEF:T=weather.rrd:temperature:AVERAGE \
		DEF:RH=weather.rrd:humidity:AVERAGE \
		CDEF:gamma=T,$C,T,+,/,$B,T,$D,/,-,*,EXP,RH,100,/,*,LOG \
		CDEF:Tdp=$C,gamma,*,$B,gamma,-,/ \
		LINE4:Tdp#44dd44 \
		AREA:Tdp#bbeebb:"dew point" \
		GPRINT:Tdp:LAST:" Now\:%4.1lf %s" \
		GPRINT:Tdp:MIN:" Min\:%4.1lf %s" \
		GPRINT:Tdp:MAX:" Max\:%4.1lf %s" \
		GPRINT:Tdp:AVERAGE:" Avg\:%4.1lf\n"
}

dpgraph 12hr -12h
dpgraph 2day -2d
dpgraph 1week -1w
dpgraph 1month -31d
	weather: weather.c
	gcc -O2 -msse2 -ftree-vectorize -I/opt/local/include -L/opt/local/lib -lrtlsdr -lm -std=c99 weather.c -o weather
	/*
	* weather.c -- receiver for ascot weather station
	*
	* Copyright (c) 2012, Alex Wilson (arekinath)
	* All rights reserved.
	*
	* Redistribution and use in source and binary forms, with or without
	* modification, are permitted provided that the following conditions are met:
	* * Redistributions of source code must retain the above copyright
	* notice, this list of conditions and the following disclaimer.
	* * Redistributions in binary form must reproduce the above copyright
	* notice, this list of conditions and the following disclaimer in the
	* documentation and/or other materials provided with the distribution.
	* * Neither the name of the <organization> nor the
	* names of its contributors may be used to endorse or promote products
	* derived from this software without specific prior written permission.
	*
	* See the standard BSD license disclaimer for details about warranty, liability,
	* fitness for purpose, etc.
	*/

	#include <rtl-sdr.h>
	#include <stdio.h>
	#include <stdint.h>
	#include <stdlib.h>
	#include <string.h>
	#include <unistd.h>
	#include <math.h>

	int
	main(int argc, char *argv[])
	{
	rtlsdr_dev_t *dev;
	int ret;

	if (rtlsdr_open(&dev, 0)) {
	fprintf(stderr, "failed to open rtlsdr\n");
	return 1;
	}

	/* 433.798 MHz is the channel 1 freq (approximately) */
	const int32_t freq = 433798000;

	/* tune 100kHz above the target */
	if (rtlsdr_set_center_freq(dev, freq - 100000)) {
	fprintf(stderr, "failed to set centre\n");
	return 1;
	}

	/* ask for it back so we know the actual centre */
	int32_t rfreq = rtlsdr_get_center_freq(dev);
	int32_t devn = freq - rfreq;

	uint32_t samprate = 1048576;
	if (rtlsdr_set_sample_rate(dev, samprate)) {
	fprintf(stderr, "failed set sample rate\n");
	return 1;
	}

	samprate = rtlsdr_get_sample_rate(dev);
	const uint32_t centre = rtlsdr_get_center_freq(dev);

	/* xxx: sort out what tuner gain to use */
	rtlsdr_set_tuner_gain(dev, 490);

	const int readsize = 1024;

	uint8_t *buf = malloc(readsize);
	memset(buf, 0, readsize);

	/* generate the ~100kHz oscillator to mix the incoming signal with */
	double wave = malloc(sizeof(double)readsize);
	for (int i = 0; i < (readsize / 2); ++i) {
	double t = (devn * (double)i) / (double)samprate;
	wave[i2] = cos(23.14159*t);
	wave[i2+1] = sin(23.14159*t);
	}

	double demod = malloc(sizeof(double)readsize);
	double demod_smooth = malloc(sizeof(double)readsize);

	int lenout;

	/* always have to call reset_buffer before reading */
	if (rtlsdr_reset_buffer(dev)) {
	fprintf(stderr, "failed reset buffer\n");
	return 1;
	}

	/* number of reads we've been 'high' for */
	uint64_t highfor = 0;
	uint64_t lowfor = 0;

	/* was there a pulse before the last change? */
	uint8_t pulse = 0;

	/* frame state */
	uint64_t last_last_frame = 1;
	uint64_t last_frame = 1;
	uint64_t frame = 0;
	uint8_t bitno = 0;

	while (1) {
	/* fill up the buffer with incoming I/Q samples */
	ret = rtlsdr_read_sync(dev, buf, readsize, &lenout);
	if (ret \|\| lenout < readsize) {
	fprintf(stderr, "short read! (=%d) %d/%d\n", ret, lenout, readsize);
	return 1;
	}

	/* mix with the local oscillator to downconvert it. also rectify at the same time */
	for (int i = 0; i < readsize; ++i) {
	demod[i] = ((((double)buf[i]) / 256.0) - 0.5) * wave[i];
	if (demod[i] < 0) demod[i] = 0;
	}

	/* now do a moving average filter to smooth the resulting waveform */
	for (int i = 0; i < 20; ++i)
	demod_smooth[i] = demod[i];

	for (int i = 20; i < readsize; ++i)
	demod_smooth[i] = (demod[i] + demod[i-2] + demod[i-4] + demod[i-6] + demod[i-8] + demod[i-10] + demod[i-12] + demod[i-14] + demod[i-16] + demod[i-18] + demod[i-20]) / 11;

	/* sum the mags of the samples (don't bother squaring, since we rectified it) */
	double magsum = 0;
	for (int i = 0; i < readsize; i+=2) {
	double mag = demod_smooth[i] + demod_smooth[i+1];
	magsum += mag * mag;
	}

	/* xxx: arbitrary constant warning! somewhere from 0.5 - 1.5 seems to work */
	if (magsum > 0.7) {
	/* this is a 'high' sample, as in during a pulse */

	/* is this the first 'high' sample? ie, did we just end a gap? */
	if (highfor == 0) {
	const uint64_t one64 = 1;

	/* zeros take 1-2 samples */
	if (pulse && lowfor >= 1 && lowfor <= 2) {
	bitno--;
	frame &= ~(one64<<bitno);

	/* ones take 3-5 samples */
	} else if (pulse && lowfor >= 3 && lowfor <= 5) {
	bitno--;
	frame \|= (one64<<bitno);

	/* and 6-8 samples is an 'X' */
	} else if (pulse && lowfor >= 6 && lowfor <= 8) {

	if (last_frame == frame && last_last_frame == frame && bitno == 0) {
	const uint64_t mask12 = 0xfff;
	const uint64_t mask7 = 0x7f;
	uint64_t preamble = (frame >> 24) & mask12;
	if (preamble == 0xae8) {
	uint64_t temp = (frame >> 12) & mask12;
	uint16_t tempwhole = temp / 10;
	uint16_t tempfrac = temp % 10;
	uint64_t humid = frame & mask7;
	printf("N:%hu.%hu:%llu\n", tempwhole, tempfrac, humid);
	break;
	}
	}

	last_last_frame = last_frame;
	last_frame = frame;
	frame = 0;
	bitno = 36;
	}

	pulse = 0;
	lowfor = 0;
	}

	/* increment the counter for high samples in a row */
	highfor++;

	} else {
	/* this is a low sample */

	/* is this the first? did we just end a pulse? */
	if (lowfor == 0) {
	if (highfor >= 1 && highfor <= 3) {
	pulse = 1;
	} else {
	pulse = 0;
	}
	highfor = 0;
	}
	lowfor++;
	}

	}

	/* xxx: todo: cleanup other stuff */
	rtlsdr_close(dev);
	}
	rrdtool create weather.rrd -s 60 \
	DS:temperature:GAUGE:300:-10:60 \
	DS:humidity:GAUGE:300:0:100 \
	RRA:AVERAGE:0.5:1:1440 \
	RRA:AVERAGE:0.5:5:2016 \
	RRA:AVERAGE:0.5:30:1488 \
	RRA:AVERAGE:0.5:240:2190 \
	RRA:MIN:0.5:1:1440 \
	RRA:MIN:0.5:5:2016 \
	RRA:MIN:0.5:30:1488 \
	RRA:MAX:0.5:1:1440 \
	RRA:MAX:0.5:5:2016 \
	RRA:MAX:0.5:30:1488 \
	RRA:LAST:0.5:1:1440 \
	RRA:LAST:0.5:5:2016 \
	RRA:LAST:0.5:30:1488
	#!/usr/bin/env ruby

	require 'daemons'

	Daemons.run_proc('weatherd') do
	Dir.chdir("/home/alex/weather")
	loop do
	data = `./weather`
	`rrdtool update weather.rrd #{data}`
	sleep(54)
	end
	end
	#!/bin/bash

	cd /home/alex/weather

	function tempgraph {
	rrdtool graph htdocs/temperature-$1.png \
	-s $2 \
	-t "Temperature ($1)" \
	--vertical-label="degrees C" \
	-w 400 -h 150 \
	DEF:temp=weather.rrd:temperature:AVERAGE \
	LINE4:temp#dd4444 \
	AREA:temp#eebbbb:temperature \
	GPRINT:temp:LAST:" Now\:%4.1lf %s" \
	GPRINT:temp:MIN:" Min\:%4.1lf %s" \
	GPRINT:temp:MAX:" Max\:%4.1lf %s" \
	GPRINT:temp:AVERAGE:" Avg\:%4.1lf\n"
	}

	tempgraph 12hr -12h
	tempgraph 2day -2d
	tempgraph 1week -1w
	tempgraph 1month -31d

	function humgraph {
	rrdtool graph htdocs/humidity-$1.png \
	-s $2 \
	-t "Rel. humidity ($1)" \
	--vertical-label="percent rel humidity" \
	-w 400 -h 150 \
	DEF:hum=weather.rrd:humidity:AVERAGE \
	LINE4:hum#4444dd \
	AREA:hum#bbbbee:humidity \
	GPRINT:hum:LAST:" Now\:%4.0lf%% %s" \
	GPRINT:hum:MIN:" Min\:%4.0lf%% %s" \
	GPRINT:hum:MAX:" Max\:%4.0lf%% %s" \
	GPRINT:hum:AVERAGE:" Avg\:%4.0lf%%\n"
	}

	humgraph 12hr -12h
	humgraph 2day -2d
	humgraph 1week -1w
	humgraph 1month -31d

	function dpgraph {
	A="6.1121"
	B="18.678"
	C="257.14"
	D="234.5"

	rrdtool graph htdocs/dewpoint-$1.png \
	-s $2 \
	-t "Dew point ($1)" \
	--vertical-label="degrees C" \
	-w 400 -h 150 \
	DEF:T=weather.rrd:temperature:AVERAGE \
	DEF:RH=weather.rrd:humidity:AVERAGE \
	CDEF:gamma=T,$C,T,+,/,$B,T,$D,/,-,,EXP,RH,100,/,,LOG \
	CDEF:Tdp=$C,gamma,*,$B,gamma,-,/ \
	LINE4:Tdp#44dd44 \
	AREA:Tdp#bbeebb:"dew point" \
	GPRINT:Tdp:LAST:" Now\:%4.1lf %s" \
	GPRINT:Tdp:MIN:" Min\:%4.1lf %s" \
	GPRINT:Tdp:MAX:" Max\:%4.1lf %s" \
	GPRINT:Tdp:AVERAGE:" Avg\:%4.1lf\n"
	}

	dpgraph 12hr -12h
	dpgraph 2day -2d
	dpgraph 1week -1w
	dpgraph 1month -31d