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authorMitja Felicijan <mitja.felicijan@gmail.com>2023-11-01 22:54:27 +0100
committerMitja Felicijan <mitja.felicijan@gmail.com>2023-11-01 22:54:27 +0100
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1<!doctype html><html lang=en-us><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=generator content="JBMAFP - github.com/mitjafelicijan/jbmafp"><link href="data:image/x-icon;base64,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" rel=icon type=image/x-icon><title>Simple IOT application supported by real-time monitoring and data history</title><meta name=description content="Initial thoughtsI have been developing these kind of application for the better part of my last5 years and people keep asking me how to approach developing such applicationand I will give a try explaining it here."><meta name=author content="Mitja Felicijan"><link rel=alternate type=application/rss+xml title="Mitja Felicijan's posts" href=https://mitjafelicijan.com/index.xml><link rel=alternate type=application/rss+xml title="Mitja Felicijan's notes" href=https://mitjafelicijan.com/notes.xml><style>:root{--border-color:gainsboro;--border-size:2px;--link-color:blue;--bg-color:#eee}*::selection{background:var(--link-color);color:#fff}*::-moz-selection{background:var(--link-color);color:#fff}*::-webkit-selection{background:var(--link-color);color:#fff}body{padding:2.5rem;max-width:1900px;background:#fff;font-family:sans-serif;line-height:1.35rem;font-size:16px}hr{border:0;border-bottom:var(--border-size)solid var(--border-color);margin-block-start:1.5rem}a{color:var(--link-color);text-decoration:none}h1,h2,h3{line-height:initial}h1{font-size:xx-large}footer{margin-block-start:2rem}cap{text-transform:capitalize}blockquote{font-style:italic}table{max-width:100%;border:var(--border-size)solid var(--border-color);border-collapse:separate;border-spacing:0}table thead tr th{border-bottom:var(--border-size)solid var(--border-color);text-align:left}table th,table td{padding:.5em .8em}ul.list li{padding:.2em 0}ul{line-height:1.35em}pre{text-wrap:nowrap;overflow-x:auto;padding:0 1em;border:var(--border-size)solid var(--border-color)}code{padding:0 3px;font-size:14px;border:0;background:var(--bg-color)}pre code{line-height:1.3em;background:#fff}pre,code,pre *,code *{font-family:monospace}figure{margin-inline-start:0;margin-inline-end:0}figcaption{width:800px;max-width:100%;text-align:center}figcaption p{margin:.3em 0 1.5em;font-style:italic}img,video,audio{width:800px;max-width:100%;border:var(--border-size)solid var(--border-color);padding:.5em}header nav{display:flex;gap:.9rem}article iframe{margin:0!important}audio::-webkit-media-controls-enclosure{border-radius:0}@media only screen and (max-width:600px){body{padding:.5em;word-wrap:break-word}header nav{gap:.7rem}header nav .hob{display:none}a{word-wrap:break-word}img,video,audio{padding:0}}</style><header><nav class=main itemscope itemtype=http://schema.org/SiteNavigationElement role=navigation aria-label="Main navigation"><a href=/>Home</a>
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9<a href=/index.xml target=_blank class=hob>RSS</a></nav></header><main role=main><article itemtype=http://schema.org/Article><h1 itemtype=headline>Simple IOT application supported by real-time monitoring and data history</h1><p><cap>post</cap>, Aug 11, 2017 on <a href=https://mitjafelicijan.com>Mitja Felicijan's blog</a><div><h2 id=initial-thoughts>Initial thoughts</h2><p>I have been developing these kind of application for the better part of my last
105 years and people keep asking me how to approach developing such application
11and I will give a try explaining it here.<p>IOT applications are really no different than any other kind of applications.
12We have data that needs to be collected and visualized in some form of tables or
13charts. The main difference here is that most of the times these data is
14collected by some kind of device foreign to developer that mainly operates in
15web domain. But fear not, it's not that different than writing some JavaScript.<p>There are many devices able to transmit data via wireless or wired network by
16default but for the sake of example we will be using commonly known Arduino with
17wireless module already on the board → <a href=https://store.arduino.cc/arduino-mkr1000>Arduino
18MKR1000</a>.<p>In order to make this little project as accessible to others as possible I will
19try to make it as inexpensive as possible. And by this I mean that I will avoid
20using hosted virtual servers and will be using my own laptop as a server. But
21you must buy Arduino MKR1000 to follow steps below. But if you would want to
22deploy this software I would suggest using
23<a href=https://www.digitalocean.com>DigitalOcean</a> → smallest VPS is only per month
24making this one of the most affordable option out there. Please notice that this
25software will not run on stock web hosting that only supports LAMP (Linux,
26Apache, MySQL, and PHP).<p>But before we begin please take notice that this is strictly experimental code
27and not well optimized and there are much better ways in handling some aspects
28of the application but that requires much deeper knowledge of technology that is
29not needed for an example like this.<p><strong>Development steps</strong><ol><li>Simple Python API that will receive and store incoming data.<li>Prototype C++ code that will read "sensor data" and transmit it to API.<li>Data visualization with charts → extends Python web application.</ol><p>Step 1. and 3. will share the same web application. One route will be dedicated
30to API and another to serving HTML with chart.<p>Schema below represents what we will try to achieve and how different parts
31correlates to each other.<figure><img src=/posts/iot-application/simple-iot-application-overview.svg alt=Overview></figure><h2 id=simple-python-api>Simple Python API</h2><p>I have always been a fan of simplicity so we will be using <a href=https://bottlepy.org/docs/dev/>Bottle: Python Web
32Framework</a>. It is a single file web framework
33that seriously simplifies working with routes, templating and has built-in web
34server that satisfies our need in this case.<p>First we need to install bottle package. This can be done by downloading
35<code>bottle.py</code> and placing it in the root of your application or by using pip
36software <code>pip install bottle --user</code>.<p>If you are using Linux or MacOS then Python is already installed. If you will
37try to test this on Windows please install <a href=https://www.python.org/downloads/windows/>Python for
38Windows</a>. There may be some problems
39with path when you will try to launch <code>python webapp.py</code> so please take care
40of this before you continue.<h3 id=basic-web-application>Basic web application</h3><p>Most basic bottle application is quite simple. Paste code below in
41<code>webapp.py</code> file and save.<pre tabindex=0 style=background-color:#fff><code><span style=display:flex><span><span style=color:green># -*- coding: utf-8 -*-</span>
42</span></span><span style=display:flex><span>
43</span></span><span style=display:flex><span><span style=color:#00f>import</span> bottle
44</span></span><span style=display:flex><span>
45</span></span><span style=display:flex><span><span style=color:green># initializing bottle app</span>
46</span></span><span style=display:flex><span>app = bottle.Bottle()
47</span></span><span style=display:flex><span>
48</span></span><span style=display:flex><span><span style=color:green># triggered when / is accessed from browser</span>
49</span></span><span style=display:flex><span><span style=color:green># only accepts GET → no POST allowed</span>
50</span></span><span style=display:flex><span>@app.route(<span style=color:#a31515>&#34;/&#34;</span>, method=[<span style=color:#a31515>&#34;GET&#34;</span>])
51</span></span><span style=display:flex><span><span style=color:#00f>def</span> route_default():
52</span></span><span style=display:flex><span> <span style=color:#00f>return</span> <span style=color:#a31515>&#34;howdy from python&#34;</span>
53</span></span><span style=display:flex><span>
54</span></span><span style=display:flex><span><span style=color:green># starting server on http://0.0.0.0:5000</span>
55</span></span><span style=display:flex><span><span style=color:#00f>if</span> __name__ == <span style=color:#a31515>&#34;__main__&#34;</span>:
56</span></span><span style=display:flex><span> bottle.run(
57</span></span><span style=display:flex><span> app = app,
58</span></span><span style=display:flex><span> host = <span style=color:#a31515>&#34;0.0.0.0&#34;</span>,
59</span></span><span style=display:flex><span> port = 5000,
60</span></span><span style=display:flex><span> debug = <span style=color:#00f>True</span>,
61</span></span><span style=display:flex><span> reloader = <span style=color:#00f>True</span>,
62</span></span><span style=display:flex><span> catchall = <span style=color:#00f>True</span>,
63</span></span><span style=display:flex><span> )
64</span></span></code></pre><p>To run this simple application you should open command prompt or terminal on
65your machine and go to the folder containing your file and type <code>python webapp.py</code>. If everything goes ok then open your web browser and point it to
66<code>http://0.0.0.0:5000</code>.<p>If you would like change the port of your application (like port 80) and not use
67root to run your app this will present a problem. The TCP/IP port numbers below
681024 are privileged ports → this is a security feature. So in order of
69simplicity and security use a port number above 1024 like I have used port 5000.<p>If this fails at any time please fix it before you continue, because nothing
70below will work otherwise.<p>We use 0.0.0.0 as default host so that this app is available over your local
71network. If you find your local ip <code>ifconfig</code> and try accessing this site
72with your phone (if on same network/router as your machine) this should work as
73well (example of such ip <code>http://192.168.1.15:5000</code>). This is a must have
74because Arduino will be accessing this application to send it's data.<h3 id=web-application-security>Web application security</h3><p>There is a lot to be said about security and is a topic of many books. Of course
75all this can not be written here but to just establish some basic security → you
76should always use SSL with your application. Some fantastic free certificates
77are available by <a href=https://letsencrypt.org>Let's Encrypt - Free SSL/TLS
78Certificates</a>. With SSL certificate installed you
79should then make use of HTTP headers and send your "API key" via a header. If
80your key is send via header then this key is encrypted by SSL and send encrypted
81over the network. Never send your api keys by GET parameter like
82<code>http://example.com/?api_key=somekeyvalue</code>. The problem that this kind of
83sending presents is that this key is visible in logs and by network sniffers.<p>There is a fantastic article describing some aspects about security: <a href=https://www.keycdn.com/blog/web-application-security-best-practices/>11 Web
84Application Security Best
85Practices</a>. Please
86check it out.<h3 id=simple-api-for-writing-data-points>Simple API for writing data-points</h3><p>We will now be using boilerplate code from example above and extend it to be
87SQLite3 because it plays well with Python and can store quite large amount of
88able to write data received by API to local storage. For example use I will use
89data. I have been using it to collect gigabytes of data in a single database
90without any corruption or problems → your experience may vary.<p>To avoid learning SQLite I will be using <a href=https://dataset.readthedocs.io/en/latest/index.html>Dataset: databases for lazy
91people</a>. This package
92abstracts SQL and simplifies writing and reading data from database. You should
93install this package with pip software <code>pip install dataset --user</code>.<p>Because API will use POST method I will be testing if code works correctly by
94using <a href=https://chrome.google.com/webstore/detail/restlet-client-rest-api-t/aejoelaoggembcahagimdiliamlcdmfm>Restlet Client for Google
95Chrome</a>.
96This software also allows you to set headers → for basic security with API_KEY.<p>To quickly generate passwords or API keys I usually use this nifty website
97<a href=https://randomkeygen.com/>RandomKeygen</a>.<p>Copy and paste code below over your previous code in file <code>webapp.py</code>.<pre tabindex=0 style=background-color:#fff><code><span style=display:flex><span><span style=color:green># -*- coding: utf-8 -*-</span>
98</span></span><span style=display:flex><span>
99</span></span><span style=display:flex><span><span style=color:#00f>import</span> time
100</span></span><span style=display:flex><span><span style=color:#00f>import</span> bottle
101</span></span><span style=display:flex><span><span style=color:#00f>import</span> random
102</span></span><span style=display:flex><span><span style=color:#00f>import</span> dataset
103</span></span><span style=display:flex><span>
104</span></span><span style=display:flex><span><span style=color:green># initializing bottle app</span>
105</span></span><span style=display:flex><span>app = bottle.Bottle()
106</span></span><span style=display:flex><span>
107</span></span><span style=display:flex><span><span style=color:green># connects to sqlite database</span>
108</span></span><span style=display:flex><span><span style=color:green># check_same_thread=False allows using it in multi-threaded mode</span>
109</span></span><span style=display:flex><span>app.config[<span style=color:#a31515>&#34;dsn&#34;</span>] = dataset.connect(<span style=color:#a31515>&#34;sqlite:///data.db?check_same_thread=False&#34;</span>)
110</span></span><span style=display:flex><span>
111</span></span><span style=display:flex><span><span style=color:green># api key that will be used in Arduino code</span>
112</span></span><span style=display:flex><span>app.config[<span style=color:#a31515>&#34;api_key&#34;</span>] = <span style=color:#a31515>&#34;JtF2aUE5SGHfVJBCG5SH&#34;</span>
113</span></span><span style=display:flex><span>
114</span></span><span style=display:flex><span><span style=color:green># triggered when /api is accessed from browser</span>
115</span></span><span style=display:flex><span><span style=color:green># only accepts POST → no GET allowed</span>
116</span></span><span style=display:flex><span>@app.route(<span style=color:#a31515>&#34;/api&#34;</span>, method=[<span style=color:#a31515>&#34;POST&#34;</span>])
117</span></span><span style=display:flex><span><span style=color:#00f>def</span> route_default():
118</span></span><span style=display:flex><span> status = 400
119</span></span><span style=display:flex><span> ts = int(time.time()) <span style=color:green># current timestamp</span>
120</span></span><span style=display:flex><span> value = bottle.request.body.read() <span style=color:green># data from device</span>
121</span></span><span style=display:flex><span> api_key = bottle.request.get_header(<span style=color:#a31515>&#34;Api_Key&#34;</span>) <span style=color:green># api key from header</span>
122</span></span><span style=display:flex><span>
123</span></span><span style=display:flex><span> <span style=color:green># outputs to console received data for debug reason</span>
124</span></span><span style=display:flex><span> print <span style=color:#a31515>&#34;&gt;&gt;&gt; </span><span style=color:#a31515>{}</span><span style=color:#a31515> :: </span><span style=color:#a31515>{}</span><span style=color:#a31515>&#34;</span>.format(value, api_key)
125</span></span><span style=display:flex><span>
126</span></span><span style=display:flex><span> <span style=color:green># if api_key is correct and value is present</span>
127</span></span><span style=display:flex><span> <span style=color:green># then writes attribute to point table</span>
128</span></span><span style=display:flex><span> <span style=color:#00f>if</span> api_key == app.config[<span style=color:#a31515>&#34;api_key&#34;</span>] <span style=color:#00f>and</span> value:
129</span></span><span style=display:flex><span> app.config[<span style=color:#a31515>&#34;dsn&#34;</span>][<span style=color:#a31515>&#34;point&#34;</span>].insert(dict(ts=ts, value=value))
130</span></span><span style=display:flex><span> status = 200
131</span></span><span style=display:flex><span>
132</span></span><span style=display:flex><span> <span style=color:green># we only need to return status</span>
133</span></span><span style=display:flex><span> <span style=color:#00f>return</span> bottle.HTTPResponse(status=status, body=<span style=color:#a31515>&#34;&#34;</span>)
134</span></span><span style=display:flex><span>
135</span></span><span style=display:flex><span><span style=color:green># starting server on http://0.0.0.0:5000</span>
136</span></span><span style=display:flex><span><span style=color:#00f>if</span> __name__ == <span style=color:#a31515>&#34;__main__&#34;</span>:
137</span></span><span style=display:flex><span> bottle.run(
138</span></span><span style=display:flex><span> app = app,
139</span></span><span style=display:flex><span> host = <span style=color:#a31515>&#34;0.0.0.0&#34;</span>,
140</span></span><span style=display:flex><span> port = 5000,
141</span></span><span style=display:flex><span> debug = <span style=color:#00f>True</span>,
142</span></span><span style=display:flex><span> reloader = <span style=color:#00f>True</span>,
143</span></span><span style=display:flex><span> catchall = <span style=color:#00f>True</span>,
144</span></span><span style=display:flex><span> )
145</span></span></code></pre><p>To run this simply go to folder containing python file and run <code>python webapp.py</code> from terminal. If everything goes ok you should have simple API
146available via POST method on /api route.<p>After testing the service with Restlet Client you should be able to view your
147data in a database file <code>data.db</code>.<figure><img src=/posts/iot-application/iot-rest-example.png alt="REST settings example"></figure><p>You can also check the contents of new database file by using desktop client
148for SQLite → <a href=http://sqlitebrowser.org/>DB Browser for SQLite</a>.<figure><img src=/posts/iot-application/iot-sqlite-db.png alt="SQLite database example"></figure><p>Table structure is as simple as it can be. We have ts (timestamp) and value
149(value from Arduino). As you can see timestamp is generated on API side. If you
150would happen to have atomic clock on Arduino it would be then better to generate
151and send timestamp with the value. This would be particularity useful if we
152would be collecting sensor data at a higher frequency and then sending this data
153in bulk to API.<p>If you will deploy this app with uWSGI and multi-threaded, use DSN (Data Source
154Name) url with <code>?check_same_thread=False</code>.<p>Ok, now that we have some sort of a working API with some basic security so
155unwanted people can not post data to your database can we proceed further and
156try to program Arduino to send data to API.<h2 id=sending-data-to-api-with-arduino-mkr1000>Sending data to API with Arduino MKR1000</h2><p>First of all you should have MKR1000 module and microUSB cable to proceed. If
157you have ever done any work with Arduino you should know that you also need
158<a href=https://www.arduino.cc/en/Main/Software>Arduino IDE</a>. On provided link you
159should be able to download and install IDE. Once that task is completed and you
160have successfully run blink example you should proceed to the next step.<p>In order to use wireless capabilities of MKR1000 you need to first install
161<a href=https://www.arduino.cc/en/Reference/WiFi101>WiFi101 library</a> in Arduino IDE.
162Please check before you install, you may already have it installed.<p>Code below is a working example that sends data to API. Before you try to test
163your code make sure you have run Python web application. Then change settings
164for wifi, api endpoint and api_key. If by some reason code bellow doesn't work
165for you please leave a comment and I'll try to help.<p>Once you have opened IDE and copied this code try to compile and upload it.
166Then open "Serial monitor" to see if any output is presented by Arduino.<pre tabindex=0 style=background-color:#fff><code><span style=display:flex><span><span style=color:#00f>#include</span> <span style=color:#00f>&lt;WiFi101.h&gt;</span><span style=color:#00f>
167</span></span></span><span style=display:flex><span><span style=color:#00f></span>
168</span></span><span style=display:flex><span><span style=color:green>// wifi settings
169</span></span></span><span style=display:flex><span><span style=color:green></span><span style=color:#2b91af>char</span> ssid[] = <span style=color:#a31515>&#34;ssid-name&#34;</span>;
170</span></span><span style=display:flex><span><span style=color:#2b91af>char</span> pass[] = <span style=color:#a31515>&#34;ssid-password&#34;</span>;
171</span></span><span style=display:flex><span>
172</span></span><span style=display:flex><span><span style=color:green>// api server enpoint
173</span></span></span><span style=display:flex><span><span style=color:green></span><span style=color:#2b91af>char</span> server[] = <span style=color:#a31515>&#34;192.168.6.22&#34;</span>;
174</span></span><span style=display:flex><span><span style=color:#2b91af>int</span> port = 5000;
175</span></span><span style=display:flex><span>
176</span></span><span style=display:flex><span><span style=color:green>// api key that must be the same as the one in Python code
177</span></span></span><span style=display:flex><span><span style=color:green></span>String api_key = <span style=color:#a31515>&#34;JtF2aUE5SGHfVJBCG5SH&#34;</span>;
178</span></span><span style=display:flex><span>
179</span></span><span style=display:flex><span><span style=color:green>// frequency data is sent in ms - every 5 seconds
180</span></span></span><span style=display:flex><span><span style=color:green></span><span style=color:#2b91af>int</span> timeout = 1000 * 5;
181</span></span><span style=display:flex><span>
182</span></span><span style=display:flex><span><span style=color:#2b91af>int</span> status = WL_IDLE_STATUS;
183</span></span><span style=display:flex><span>
184</span></span><span style=display:flex><span><span style=color:#2b91af>void</span> setup() {
185</span></span><span style=display:flex><span>
186</span></span><span style=display:flex><span> <span style=color:green>// initialize serial and wait for port to open:
187</span></span></span><span style=display:flex><span><span style=color:green></span> Serial.begin(9600);
188</span></span><span style=display:flex><span> delay(1000);
189</span></span><span style=display:flex><span>
190</span></span><span style=display:flex><span> <span style=color:green>// check for the presence of the shield
191</span></span></span><span style=display:flex><span><span style=color:green></span> <span style=color:#00f>if</span> (WiFi.status() == WL_NO_SHIELD) {
192</span></span><span style=display:flex><span> Serial.println(<span style=color:#a31515>&#34;WiFi shield not present&#34;</span>);
193</span></span><span style=display:flex><span> <span style=color:#00f>while</span> (true);
194</span></span><span style=display:flex><span> }
195</span></span><span style=display:flex><span>
196</span></span><span style=display:flex><span> <span style=color:green>// attempt to connect to wifi network
197</span></span></span><span style=display:flex><span><span style=color:green></span> <span style=color:#00f>while</span> (status != WL_CONNECTED) {
198</span></span><span style=display:flex><span> Serial.print(<span style=color:#a31515>&#34;Attempting to connect to SSID: &#34;</span>);
199</span></span><span style=display:flex><span> Serial.println(ssid);
200</span></span><span style=display:flex><span> status = WiFi.begin(ssid, pass);
201</span></span><span style=display:flex><span> <span style=color:green>// wait 10 seconds for connection
202</span></span></span><span style=display:flex><span><span style=color:green></span> delay(10000);
203</span></span><span style=display:flex><span> }
204</span></span><span style=display:flex><span>
205</span></span><span style=display:flex><span> <span style=color:green>// output wifi status to serial monitor
206</span></span></span><span style=display:flex><span><span style=color:green></span> Serial.print(<span style=color:#a31515>&#34;SSID: &#34;</span>);
207</span></span><span style=display:flex><span> Serial.println(WiFi.SSID());
208</span></span><span style=display:flex><span>
209</span></span><span style=display:flex><span> IPAddress ip = WiFi.localIP();
210</span></span><span style=display:flex><span> Serial.print(<span style=color:#a31515>&#34;IP Address: &#34;</span>);
211</span></span><span style=display:flex><span> Serial.println(ip);
212</span></span><span style=display:flex><span>
213</span></span><span style=display:flex><span> <span style=color:#2b91af>long</span> rssi = WiFi.RSSI();
214</span></span><span style=display:flex><span> Serial.print(<span style=color:#a31515>&#34;signal strength (RSSI):&#34;</span>);
215</span></span><span style=display:flex><span> Serial.print(rssi);
216</span></span><span style=display:flex><span> Serial.println(<span style=color:#a31515>&#34; dBm&#34;</span>);
217</span></span><span style=display:flex><span>}
218</span></span><span style=display:flex><span>
219</span></span><span style=display:flex><span><span style=color:#2b91af>void</span> loop() {
220</span></span><span style=display:flex><span> WiFiClient client;
221</span></span><span style=display:flex><span>
222</span></span><span style=display:flex><span> <span style=color:#00f>if</span> (client.connect(server, port)) {
223</span></span><span style=display:flex><span>
224</span></span><span style=display:flex><span> <span style=color:green>// I use random number generator for this example
225</span></span></span><span style=display:flex><span><span style=color:green></span> <span style=color:green>// but you can use analog or digital inputs from arduino
226</span></span></span><span style=display:flex><span><span style=color:green></span> String content = String(random(1000));
227</span></span><span style=display:flex><span>
228</span></span><span style=display:flex><span> client.println(<span style=color:#a31515>&#34;POST /api HTTP/1.1&#34;</span>);
229</span></span><span style=display:flex><span> client.println(<span style=color:#a31515>&#34;Connection: close&#34;</span>);
230</span></span><span style=display:flex><span> client.println(<span style=color:#a31515>&#34;Api-Key: &#34;</span> + api_key);
231</span></span><span style=display:flex><span> client.println(<span style=color:#a31515>&#34;Content-Length: &#34;</span> + String(content.length()));
232</span></span><span style=display:flex><span> client.println();
233</span></span><span style=display:flex><span> client.println(content);
234</span></span><span style=display:flex><span>
235</span></span><span style=display:flex><span> delay(100);
236</span></span><span style=display:flex><span> client.stop();
237</span></span><span style=display:flex><span> Serial.println(<span style=color:#a31515>&#34;Data sent successfully ...&#34;</span>);
238</span></span><span style=display:flex><span>
239</span></span><span style=display:flex><span> } <span style=color:#00f>else</span> {
240</span></span><span style=display:flex><span> Serial.println(<span style=color:#a31515>&#34;Problem sending data ...&#34;</span>);
241</span></span><span style=display:flex><span> }
242</span></span><span style=display:flex><span>
243</span></span><span style=display:flex><span> <span style=color:green>// waits for x seconds and continue looping
244</span></span></span><span style=display:flex><span><span style=color:green></span> delay(timeout);
245</span></span><span style=display:flex><span>}
246</span></span></code></pre><p>As seen from example you can notice that Arduino is generating random integer
247between [ 0 .. 1000 ]. You can easily replace this with a temperature sensor or
248any other kind of sensor.<p>Now that we have API under the hood and Arduino is sending demo data we can now
249focus on data visualization.<h2 id=data-visualization>Data visualization</h2><p>Before we continue we should examine our project folder structure. Currently we
250only have two files in our project:<p><em>simple-iot-app/</em><ul><li><em>webapp.py</em><li><em>data.db</em></ul><p>We will now add HTML template that will contain CSS and JavaScript code inline
251for the simplicity reason. And for the bottle framework to be able to scan root
252application folder for templates we will add <code>bottle.TEMPLATE_PATH.insert(0, "./")</code> in <code>webapp.py</code>. By default bottle framework uses <code>views/</code>
253subfolder to store templates. This is not the ideal situation and if you will
254use bottle to develop web applications you should use native behavior and store
255templates in it's predefined folder. But for the sake of example we will
256over-ride this. Be careful to fully replace your code with new code that is
257provided below. Avoid partially replacing code in file :) Also new code for
258reading data-points is provided in Python example below.<p>First we add new route to our web application. It should be trigger when browser
259hits root of application <code>http://0.0.0.0:5000/</code>. This route will do nothing
260more than render <code>frontend.html</code> template. This is done by <code>return bottle.template("frontend.html")</code>. Check code below to further examine how
261exactly this is done.<p>Now we will expand <code>/api</code> route and use different methods to write or read
262data-points. For writing data-point we will use POST method and for reading
263points we will use GET method. GET method will return JSON object with latest
264readings and historical data.<p>There is a fantastic JavaScript library for plotting time-series charts called
265<a href=https://www.metricsgraphicsjs.org>MetricsGraphics.js</a> that is based on
266<a href=https://d3js.org/>D3.js</a> library for visualizing data.<p>Data schema required by MetricsGraphics.js → to achieve this we need to
267transform data from database into this format:<pre tabindex=0 style=background-color:#fff><code><span style=display:flex><span>[
268</span></span><span style=display:flex><span> {
269</span></span><span style=display:flex><span> &#34;date&#34;: <span style=color:#a31515>&#34;2017-08-11 01:07:20&#34;</span>,
270</span></span><span style=display:flex><span> &#34;value&#34;: 933
271</span></span><span style=display:flex><span> },
272</span></span><span style=display:flex><span> {
273</span></span><span style=display:flex><span> &#34;date&#34;: <span style=color:#a31515>&#34;2017-08-11 01:07:30&#34;</span>,
274</span></span><span style=display:flex><span> &#34;value&#34;: 743
275</span></span><span style=display:flex><span> }
276</span></span><span style=display:flex><span>]
277</span></span></code></pre><p>Web application is now complete and we only need <code>frontend.html</code> that we
278will develop now. If you would try to start web app now and go to root app this
279will return error because we don't have frontend.html yet.<pre tabindex=0 style=background-color:#fff><code><span style=display:flex><span><span style=color:green># -*- coding: utf-8 -*-</span>
280</span></span><span style=display:flex><span>
281</span></span><span style=display:flex><span><span style=color:#00f>import</span> time
282</span></span><span style=display:flex><span><span style=color:#00f>import</span> bottle
283</span></span><span style=display:flex><span><span style=color:#00f>import</span> json
284</span></span><span style=display:flex><span><span style=color:#00f>import</span> datetime
285</span></span><span style=display:flex><span><span style=color:#00f>import</span> random
286</span></span><span style=display:flex><span><span style=color:#00f>import</span> dataset
287</span></span><span style=display:flex><span>
288</span></span><span style=display:flex><span><span style=color:green># initializing bottle app</span>
289</span></span><span style=display:flex><span>app = bottle.Bottle()
290</span></span><span style=display:flex><span>
291</span></span><span style=display:flex><span><span style=color:green># adds root directory as template folder</span>
292</span></span><span style=display:flex><span>bottle.TEMPLATE_PATH.insert(0, <span style=color:#a31515>&#34;./&#34;</span>)
293</span></span><span style=display:flex><span>
294</span></span><span style=display:flex><span><span style=color:green># connects to sqlite database</span>
295</span></span><span style=display:flex><span><span style=color:green># check_same_thread=False allows using it in multi-threaded mode</span>
296</span></span><span style=display:flex><span>app.config[<span style=color:#a31515>&#34;db&#34;</span>] = dataset.connect(<span style=color:#a31515>&#34;sqlite:///data.db?check_same_thread=False&#34;</span>)
297</span></span><span style=display:flex><span>
298</span></span><span style=display:flex><span><span style=color:green># api key that will be used in Arduino code</span>
299</span></span><span style=display:flex><span>app.config[<span style=color:#a31515>&#34;api_key&#34;</span>] = <span style=color:#a31515>&#34;JtF2aUE5SGHfVJBCG5SH&#34;</span>
300</span></span><span style=display:flex><span>
301</span></span><span style=display:flex><span><span style=color:green># triggered when / is accessed from browser</span>
302</span></span><span style=display:flex><span><span style=color:green># only accepts GET → no POST allowed</span>
303</span></span><span style=display:flex><span>@app.route(<span style=color:#a31515>&#34;/&#34;</span>, method=[<span style=color:#a31515>&#34;GET&#34;</span>])
304</span></span><span style=display:flex><span><span style=color:#00f>def</span> route_default():
305</span></span><span style=display:flex><span> <span style=color:#00f>return</span> bottle.template(<span style=color:#a31515>&#34;frontend.html&#34;</span>)
306</span></span><span style=display:flex><span>
307</span></span><span style=display:flex><span><span style=color:green># triggered when /api is accessed from browser</span>
308</span></span><span style=display:flex><span><span style=color:green># accepts POST and GET</span>
309</span></span><span style=display:flex><span>@app.route(<span style=color:#a31515>&#34;/api&#34;</span>, method=[<span style=color:#a31515>&#34;GET&#34;</span>, <span style=color:#a31515>&#34;POST&#34;</span>])
310</span></span><span style=display:flex><span><span style=color:#00f>def</span> route_default():
311</span></span><span style=display:flex><span>
312</span></span><span style=display:flex><span> <span style=color:green># if method is POST then we write datapoint</span>
313</span></span><span style=display:flex><span> <span style=color:#00f>if</span> bottle.request.method == <span style=color:#a31515>&#34;POST&#34;</span>:
314</span></span><span style=display:flex><span> status = 400
315</span></span><span style=display:flex><span> ts = int(time.time()) <span style=color:green># current timestamp</span>
316</span></span><span style=display:flex><span> value = bottle.request.body.read() <span style=color:green># data from device</span>
317</span></span><span style=display:flex><span> api_key = bottle.request.get_header(<span style=color:#a31515>&#34;Api-Key&#34;</span>) <span style=color:green># api key from header</span>
318</span></span><span style=display:flex><span>
319</span></span><span style=display:flex><span> <span style=color:green># outputs to console recieved data for debug reason</span>
320</span></span><span style=display:flex><span> print <span style=color:#a31515>&#34;&gt;&gt;&gt; </span><span style=color:#a31515>{}</span><span style=color:#a31515> :: </span><span style=color:#a31515>{}</span><span style=color:#a31515>&#34;</span>.format(value, api_key)
321</span></span><span style=display:flex><span>
322</span></span><span style=display:flex><span> <span style=color:green># if api_key is correct and value is present</span>
323</span></span><span style=display:flex><span> <span style=color:green># then writes attribute to point table</span>
324</span></span><span style=display:flex><span> <span style=color:#00f>if</span> api_key == app.config[<span style=color:#a31515>&#34;api_key&#34;</span>] <span style=color:#00f>and</span> value:
325</span></span><span style=display:flex><span> app.config[<span style=color:#a31515>&#34;db&#34;</span>][<span style=color:#a31515>&#34;point&#34;</span>].insert(dict(ts=ts, value=value))
326</span></span><span style=display:flex><span> status = 200
327</span></span><span style=display:flex><span>
328</span></span><span style=display:flex><span> <span style=color:green># we only need to return status</span>
329</span></span><span style=display:flex><span> <span style=color:#00f>return</span> bottle.HTTPResponse(status=status, body=<span style=color:#a31515>&#34;&#34;</span>)
330</span></span><span style=display:flex><span>
331</span></span><span style=display:flex><span> <span style=color:green># if method is GET then we read datapoint</span>
332</span></span><span style=display:flex><span> <span style=color:#00f>else</span>:
333</span></span><span style=display:flex><span> response = []
334</span></span><span style=display:flex><span> datapoints = app.config[<span style=color:#a31515>&#34;db&#34;</span>][<span style=color:#a31515>&#34;point&#34;</span>].all()
335</span></span><span style=display:flex><span>
336</span></span><span style=display:flex><span> <span style=color:#00f>for</span> point <span style=color:#00f>in</span> datapoints:
337</span></span><span style=display:flex><span> response.append({
338</span></span><span style=display:flex><span> <span style=color:#a31515>&#34;date&#34;</span>: datetime.datetime.fromtimestamp(int(point[<span style=color:#a31515>&#34;ts&#34;</span>])).strftime(<span style=color:#a31515>&#34;%Y-%m-</span><span style=color:#a31515>%d</span><span style=color:#a31515> %H:%M:%S&#34;</span>),
339</span></span><span style=display:flex><span> <span style=color:#a31515>&#34;value&#34;</span>: point[<span style=color:#a31515>&#34;value&#34;</span>]
340</span></span><span style=display:flex><span> })
341</span></span><span style=display:flex><span>
342</span></span><span style=display:flex><span> bottle.response.content_type = <span style=color:#a31515>&#34;application/json&#34;</span>
343</span></span><span style=display:flex><span> <span style=color:#00f>return</span> json.dumps(response)
344</span></span><span style=display:flex><span>
345</span></span><span style=display:flex><span><span style=color:green># starting server on http://0.0.0.0:5000</span>
346</span></span><span style=display:flex><span><span style=color:#00f>if</span> __name__ == <span style=color:#a31515>&#34;__main__&#34;</span>:
347</span></span><span style=display:flex><span> bottle.run(
348</span></span><span style=display:flex><span> app = app,
349</span></span><span style=display:flex><span> host = <span style=color:#a31515>&#34;0.0.0.0&#34;</span>,
350</span></span><span style=display:flex><span> port = 5000,
351</span></span><span style=display:flex><span> debug = <span style=color:#00f>True</span>,
352</span></span><span style=display:flex><span> reloader = <span style=color:#00f>True</span>,
353</span></span><span style=display:flex><span> catchall = <span style=color:#00f>True</span>,
354</span></span><span style=display:flex><span> )
355</span></span></code></pre><p>And now finally we can implement <code>frontend.html</code>. Create file with this name
356and copy code below. When you are done you can start web application. Steps for
357this part are listed below the code.<pre tabindex=0 style=background-color:#fff><code><span style=display:flex><span><span style=color:#00f>&lt;!DOCTYPE html&gt;</span>
358</span></span><span style=display:flex><span>&lt;html&gt;
359</span></span><span style=display:flex><span>
360</span></span><span style=display:flex><span> &lt;head&gt;
361</span></span><span style=display:flex><span> &lt;meta charset=<span style=color:#a31515>&#34;utf-8&#34;</span>&gt;
362</span></span><span style=display:flex><span> &lt;title&gt;Simple IOT application&lt;/title&gt;
363</span></span><span style=display:flex><span> &lt;/head&gt;
364</span></span><span style=display:flex><span>
365</span></span><span style=display:flex><span> &lt;body&gt;
366</span></span><span style=display:flex><span>
367</span></span><span style=display:flex><span> &lt;h1&gt;Simple IOT application&lt;/h1&gt;
368</span></span><span style=display:flex><span>
369</span></span><span style=display:flex><span> &lt;div class=<span style=color:#a31515>&#34;chart-placeholder&#34;</span>&gt;
370</span></span><span style=display:flex><span> &lt;div id=<span style=color:#a31515>&#34;chart&#34;</span>&gt;&lt;/div&gt;
371</span></span><span style=display:flex><span> &lt;/div&gt;
372</span></span><span style=display:flex><span>
373</span></span><span style=display:flex><span> <span style=color:green>&lt;!-- application main script --&gt;</span>
374</span></span><span style=display:flex><span> &lt;script src=<span style=color:#a31515>&#34;https://cdnjs.cloudflare.com/ajax/libs/jquery/3.2.1/jquery.min.js&#34;</span>&gt;&lt;/script&gt;
375</span></span><span style=display:flex><span> &lt;script src=<span style=color:#a31515>&#34;https://cdnjs.cloudflare.com/ajax/libs/d3/4.10.0/d3.min.js&#34;</span>&gt;&lt;/script&gt;
376</span></span><span style=display:flex><span> &lt;script src=<span style=color:#a31515>&#34;https://cdnjs.cloudflare.com/ajax/libs/metrics-graphics/2.11.0/metricsgraphics.min.js&#34;</span>&gt;&lt;/script&gt;
377</span></span><span style=display:flex><span> &lt;script&gt;
378</span></span><span style=display:flex><span> <span style=color:#00f>function</span> fetch_and_render() {
379</span></span><span style=display:flex><span> d3.json(<span style=color:#a31515>&#34;/api&#34;</span>, <span style=color:#00f>function</span>(data) {
380</span></span><span style=display:flex><span> data = MG.convert.date(data, <span style=color:#a31515>&#34;date&#34;</span>, <span style=color:#a31515>&#34;%Y-%m-%d %H:%M:%S&#34;</span>);
381</span></span><span style=display:flex><span> MG.data_graphic({
382</span></span><span style=display:flex><span> data: data,
383</span></span><span style=display:flex><span> chart_type: <span style=color:#a31515>&#34;line&#34;</span>,
384</span></span><span style=display:flex><span> full_width: <span style=color:#00f>true</span>,
385</span></span><span style=display:flex><span> height: 270,
386</span></span><span style=display:flex><span> target: document.getElementById(<span style=color:#a31515>&#34;chart&#34;</span>),
387</span></span><span style=display:flex><span> x_accessor: <span style=color:#a31515>&#34;date&#34;</span>,
388</span></span><span style=display:flex><span> y_accessor: <span style=color:#a31515>&#34;value&#34;</span>
389</span></span><span style=display:flex><span> });
390</span></span><span style=display:flex><span> });
391</span></span><span style=display:flex><span> }
392</span></span><span style=display:flex><span> window.onload = <span style=color:#00f>function</span>() {
393</span></span><span style=display:flex><span> <span style=color:green>// initial call for rendering
394</span></span></span><span style=display:flex><span><span style=color:green></span> fetch_and_render();
395</span></span><span style=display:flex><span>
396</span></span><span style=display:flex><span> <span style=color:green>// updates chart every 5 seconds
397</span></span></span><span style=display:flex><span><span style=color:green></span> setInterval(<span style=color:#00f>function</span>() {
398</span></span><span style=display:flex><span> fetch_and_render();
399</span></span><span style=display:flex><span> }, 5000);
400</span></span><span style=display:flex><span> }
401</span></span><span style=display:flex><span> &lt;/script&gt;
402</span></span><span style=display:flex><span>
403</span></span><span style=display:flex><span> <span style=color:green>&lt;!-- application styles --&gt;</span>
404</span></span><span style=display:flex><span> &lt;style&gt;
405</span></span><span style=display:flex><span> body {
406</span></span><span style=display:flex><span> <span style=color:#00f>font</span>: 13<span style=color:#2b91af>px</span> <span style=color:#00f>sans-serif</span>;
407</span></span><span style=display:flex><span> <span style=color:#00f>padding</span>: 20<span style=color:#2b91af>px</span> 50<span style=color:#2b91af>px</span>;
408</span></span><span style=display:flex><span> }
409</span></span><span style=display:flex><span> .<span style=color:#2b91af>chart-placeholder</span> {
410</span></span><span style=display:flex><span> <span style=color:#00f>border</span>: 2<span style=color:#2b91af>px</span> <span style=color:#00f>solid</span> #ccc;
411</span></span><span style=display:flex><span> <span style=color:#00f>width</span>: 100<span style=color:#2b91af>%</span>;
412</span></span><span style=display:flex><span> <span style=color:#00f>user-select</span>: <span style=color:#00f>none</span>;
413</span></span><span style=display:flex><span> }
414</span></span><span style=display:flex><span> <span style=color:green>/* chart styles */</span>
415</span></span><span style=display:flex><span> .<span style=color:#2b91af>mg-line1-color</span> {
416</span></span><span style=display:flex><span> stroke: <span style=color:#00f>red</span>;
417</span></span><span style=display:flex><span> stroke-width: 2;
418</span></span><span style=display:flex><span> }
419</span></span><span style=display:flex><span> .<span style=color:#2b91af>mg-main-area</span>, .<span style=color:#2b91af>mg-main-line</span> {
420</span></span><span style=display:flex><span> fill: #fff;
421</span></span><span style=display:flex><span> }
422</span></span><span style=display:flex><span> .<span style=color:#2b91af>mg-x-axis</span> line, .<span style=color:#2b91af>mg-y-axis</span> line {
423</span></span><span style=display:flex><span> stroke: #b3b2b2;
424</span></span><span style=display:flex><span> stroke-width: 1<span style=color:#2b91af>px</span>;
425</span></span><span style=display:flex><span> }
426</span></span><span style=display:flex><span> &lt;/style&gt;
427</span></span><span style=display:flex><span>
428</span></span><span style=display:flex><span> &lt;/body&gt;
429</span></span><span style=display:flex><span>
430</span></span><span style=display:flex><span>&lt;/html&gt;
431</span></span></code></pre><p>Now the folder structure should look like:<p><em>simple-iot-app/</em><ul><li><em>webapp.py</em><li><em>data.db</em><li><em>frontend.html</em></ul><p>Ok, lets now start application and start feeding it data.<ol><li><code>python webapp.py</code><li>connect Arduino MKR1000 to power source<li>open browser and go to <code>http://0.0.0.0:5000</code></ol><p>If everything goes well you should be seeing new data-points rendered on chart
432every 5 seconds.<p>If you navigate to <code>http://0.0.0.0:5000</code> you should see rendered chart as
433shown on picture below.<figure><img src=/posts/iot-application/iot-app-output.png alt="Application output"></figure><p>Complete application with all the code is available for
434<a href=/posts/iot-application/simple-iot-application.zip>download</a>.<h2 id=conclusion>Conclusion</h2><p>I hope this clarifies some aspects of IOT application development. Of course
435this is a minimal example and is far from what can be done in real life with
436some further dive into other technologies.<p>If you would like to continue exploring IOT world here are some interesting
437resources for you to examine:<ul><li><a href=https://www.allaboutcircuits.com/projects/reading-sensors-with-an-arduino/>Reading Sensors with an Arduino</a><li><a href=http://www.hivemq.com/blog/how-to-get-started-with-mqtt>MQTT 101 – How to Get Started with the lightweight IoT Protocol</a><li><a href=https://www.html5rocks.com/en/tutorials/eventsource/basics/>Stream Updates with Server-Sent Events</a><li><a href=http://www.tutorialspoint.com/internet_of_things/>Internet of Things (IoT) Tutorials</a></ul><p>Any comment or additional ideas are welcomed in comments below.</div></article></main><section><hr><h2>Posts from blogs I follow around the net</h2><ul><li><a href=https://utcc.utoronto.ca/~cks/space/blog/linux/NFSv4ServerLockClients target=_blank rel=noopener>Finding which NFSv4 client owns a lock on a Linux NFS(v4) server</a> — <a href=https://utcc.utoronto.ca/~cks/space/blog/>Chris's Wiki :: blog</a><div>A while back I wrote an entry about finding which NFS client owns
438a lock on a Linux NFS server, which turned
439out to be specific to NFS v3 (which I really should have seen coming,
440since it involved NLM and lockd). Finding the NFS v4 client that
441owns a lock is, depending on your perspective, either simpl…<li><a href=http://www.landley.net/notes-2023.html#28-10-2023 target=_blank rel=noopener>October 28, 2023</a> — <a href=http://www.landley.net/notes-2023.html>Rob Landley's Blog Thing for 2023</a><div>Oh good grief, two of my least favorite licensing people, Larry Rosen
442and Bradley Kuhn, are interacting on the OSI's license-discuss
443list where the're doing
444bad computer history and insisting that a guy Larry Rosen
445coincidentally interviewed for a book years ago is clearly the origin of
446somethin…<li><a href="http://offbeatpursuit.com:80/blog/?id=25" target=_blank rel=noopener>A fix by any other name</a> — <a href=http://offbeatpursuit.com:80/blog/>WLOG - blog</a><div>tags:
447i2c, plan9
448Another month, another file system.
449Well, if you can’t fix it in software, fix it in hardware (looking at
450you, bme680, we’re not
451done yet). The show must go on, as they say, and I would like my
452experiments to go on.
453So a “new” addition to the environmental sensor family connected to
454the h…<li><a href=https://mirzapandzo.com/next-image-url-parameter-is-valid-but-upstream-response-is-invalid target=_blank rel=noopener>Next/Image "url" parameter is valid but upstream response is invalid</a> — <a href=https://mirzapandzo.com/>Mirza Pandzo's Blog</a><div>Getting "url" parameter is valid but upstream response is invalid error with Next/Image on WSL2<li><a href=https://drewdevault.com/2023/10/13/Going-off-script.html target=_blank rel=noopener>Going off-script</a> — <a href=https://drewdevault.com>Drew DeVault's blog</a><div>There is a phenomenon in society which I find quite bizarre. Upon our entry to
455this mortal coil, we are endowed with self-awareness, agency, and free will.
456Each of the 8 billion members of this human race represents a unique person, a
457unique worldview, and a unique agency. Yet, many of us have the sam…<li><a href=https://szymonkaliski.com/writing/2023-10-02-building-a-diy-pen-plotter/ target=_blank rel=noopener>Building a DIY Pen Plotter</a> — <a href=http://github.com/dylang/node-rss>Szymon Kaliski</a><div>This article documents my learnings from designing and building a DIY Pen Plotter during the summer of 2023.
458My ultimate goal is to build my…<li><a href=https://neil.computer/notes/chart-of-accounts-for-startups-and-saas-companies/ target=_blank rel=noopener>Chart of Accounts for Startups and SaaS Companies</a> — <a href=https://neil.computer/>Neil Panchal</a><div>Accounting is fundamental to starting a business. You need to have a basic understanding of accounting principles and essential bookkeeping. I had to learn it. There was no choice. For filing taxes, your CPA is going to ask you for an Income Statement (also known as P/L statement). If<li><a href=https://journal.valeriansaliou.name/deploy-a-nomad-cluster-on-alpine-linux-with-vultr/ target=_blank rel=noopener>Deploy a Nomad Cluster on Alpine Linux with Vultr</a> — <a href=https://journal.valeriansaliou.name/>Valerian Saliou</a><div>After spending countless hours trying to understand how to deploy my apps on Kubernetes for the first time to host Mirage, an AI API service that I run, I ended up making myself a promise that the next app I work on would be using a more productive & simpler<li><a href=https://jcs.org/2023/10/25/wifi_da target=_blank rel=noopener>BlueSCSI Wi-Fi Desk Accessory 1.0 Released</a> — <a href=https://jcs.org/>joshua stein</a><div>BlueSCSI Wi-Fi Desk Accessory
4591.0 has been released:
460wifi_da-1.0.sit
461(StuffIt 3 archive)
462SHA256: ccfc9d27dd5da7412d10cef73b81119a1fec3848e4d1d88ff652a07ffdc6a69aSHA1: ff124972f202ceda6d7fa4788110a67ccda6a13a
463This is the initial public release of my BlueSCSI Wi-Fi Desk Accessory for
464classic MacOS.<li><a href=https://michael.stapelberg.ch/posts/2023-10-25-my-all-flash-zfs-network-storage-build/ target=_blank rel=noopener>My 2023 all-flash ZFS NAS (Network Storage) build</a> — <a href=https://michael.stapelberg.ch/>Michael Stapelbergs Website</a><div>For over 10 years now, I run two self-built NAS (Network Storage) devices which serve media (currently via Jellyfin) and run daily backups of all my PCs and servers.
465In this article, I describe my goals, which hardware I picked for my new build (and why) and how I set it up.
466Design Goals
467I use my netw…</ul><p>Generated with <a href=https://git.sr.ht/~sircmpwn/openring target=_blank rel=noopener>openring</a>.</section><footer><hr><p><big><strong>Want to comment or have something to add?</strong></big><p>You can write me an email
468at <a href=mailto:mitja.felicijan@gmail.com>mitja.felicijan@gmail.com</a> or
469catch up with me <a href=https://telegram.me/mitjafelicijan target=_blank>on Telegram</a>.<hr><p>This website does not track you. Content is made available under the <a href=https://creativecommons.org/licenses/by/4.0/ target=_blank rel=noreferrer>CC BY 4.0 license</a> unless
470specified otherwise. Blog is also available as <a href=/index.xml target=_blank>RSS feed</a>.</footer><script>
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