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| <p>Mita is a programming language that is focused on making Internet-Of-Things things easier to program, especially for developers without embedded development background. |
| Its language design and feature-set are meant to make anyone coming from a world of Javascript, Typescript, Java, Swift or Go feel right at home. |
| Compared to C you do not have to care about allocating memory, strings behave naturally, as do arrays. |
| Featuring powerful abstractions and a model-driven system configuration approach we can often tell at compile time if something will not work. |
| At the core of Mita is a platform model which describes what resources (think connectivity, sensors or low-level hardware interfaces) you have to work with.</p> |
| |
| <p>All Mita code compiles to C code. This is a very powerful feature. |
| It allows developers to inspect the generated code, learn from it and when they hit that inevitable glass ceiling continue where they left off, but in C. |
| Further, once you leave the prototyping phase or feel that you need more control over your system, you can always fall back to the C level and go from there.</p> |
| |
| <h2 id="anatomy-of-an-mita-program">Anatomy of an Mita program</h2> |
| |
| <p>Mita programs live in files ending with <code>.x</code>, for example <code>application.x</code>. Let’s have a look at an example which implements a simple Bluetooth enabled shock detector:</p> |
| <div class="highlight"><pre class="chroma"><code class="language-TypeScript" data-lang="TypeScript"><span class="kr">package</span> <span class="nx">main</span><span class="p">;</span> |
| |
| <span class="kr">import</span> <span class="nx">platforms</span><span class="p">.</span><span class="nx">xdk110</span><span class="p">;</span> |
| |
| <span class="nx">setup</span> <span class="nx">smartphone</span> : <span class="kt">BLE</span> <span class="p">{</span> |
| <span class="nx">deviceName</span> <span class="o">=</span> <span class="s2">"HelloWorld"</span><span class="p">;</span> |
| <span class="kd">var</span> <span class="nx">shockDetected</span> <span class="o">=</span> <span class="nx">bool_characteristic</span><span class="p">(</span><span class="nx">UUID</span><span class="o">=</span><span class="mh">0xCAFE</span><span class="p">);</span> |
| <span class="p">}</span> |
| |
| <span class="nx">every</span> <span class="nx">accelerometer</span><span class="p">.</span><span class="nx">activity</span> <span class="p">{</span> |
| <span class="k">if</span><span class="p">(</span><span class="nx">accelerometer</span><span class="p">.</span><span class="nx">magnitude</span><span class="p">.</span><span class="nx">read</span><span class="p">()</span> <span class="o">></span> <span class="mi">5000</span><span class="p">)</span> <span class="p">{</span> |
| <span class="nx">smartphone</span><span class="p">.</span><span class="nx">shockDetected</span><span class="p">.</span><span class="nx">write</span><span class="p">(</span><span class="kc">true</span><span class="p">);</span> |
| <span class="p">}</span> |
| <span class="p">}</span></code></pre></div> |
| <p>Now let’s go over this code and understand it bit by bit.</p> |
| <div class="highlight"><pre class="chroma"><code class="language-TypeScript" data-lang="TypeScript"><span class="kr">package</span> <span class="nx">main</span><span class="p">;</span></code></pre></div> |
| <p>All Mita code has a package associated with it, which means that the first line of any <code>.x</code> file is always a <em>package</em> statement which tells the compiler to which package the subsequent code belongs to. |
| There is no fixed naming that you would need to adhere to, merely conventions. For example, the main application logic is typically located in a package named <em>main</em>. More details about packages can be found in the [language section].</p> |
| <div class="highlight"><pre class="chroma"><code class="language-TypeScript" data-lang="TypeScript"><span class="kr">import</span> <span class="nx">platforms</span><span class="p">.</span><span class="nx">xdk110</span><span class="p">;</span></code></pre></div> |
| <p>Much like packages are defined, they need to be imported so that they can be used. This import is a special one, and the only import that every <code>.x</code> file needs to have. It imports the platform for which we are writing our program. |
| By convention platforms are located in the <em>platforms</em> package.</p> |
| <div class="highlight"><pre class="chroma"><code class="language-TypeScript" data-lang="TypeScript"><span class="nx">setup</span> <span class="nx">smartphone</span> : <span class="kt">BLE</span> <span class="p">{</span> |
| <span class="p">...</span> |
| <span class="p">}</span></code></pre></div> |
| <p>Setup blocks configure the resources we have at our disposal, in this case a Bluetooth Low Energy connectivity. Which resources exist depends on the platform you have previously imported - not every hardware has the same radio or sensors installed, for example. The content of the setup block depends on the resource being set up. Whenever you are inside a setup block, you can use auto-complete (<code>Ctrl+Space</code>) |
| to find out what you can configure or do next.</p> |
| <div class="highlight"><pre class="chroma"><code class="language-TypeScript" data-lang="TypeScript"><span class="nx">every</span> <span class="nx">accelerometer</span><span class="p">.</span><span class="nx">activity</span> <span class="p">{</span> |
| <span class="p">...</span> |
| <span class="p">}</span></code></pre></div> |
| <p>Most of their time IoT devices spend sleeping in some low-power mode. Every now and then, triggered by time or some external event, they wake up do some sensing, computation and send data using wireless connectivity. |
| Mita is an event based language which maps nicely to the way such IoT devices work. Using the <em>every</em> keyword we can react to events or time. Instead of <code>every accelerometer.activity { ... }</code> we could also write <code>every 100 milliseconds { ... }</code> which would simply execute every 100 milliseconds.</p> |
| <div class="highlight"><pre class="chroma"><code class="language-TypeScript" data-lang="TypeScript"><span class="k">if</span><span class="p">(</span><span class="nx">accelerometer</span><span class="p">.</span><span class="nx">magnitude</span><span class="p">.</span><span class="nx">read</span><span class="p">()</span> <span class="o">></span> <span class="mi">5000</span><span class="p">)</span> <span class="p">{</span> |
| <span class="p">...</span> |
| <span class="p">}</span></code></pre></div> |
| <p>Sensor data and other resources providing data at runtime (we call them <em>modalities</em>) can be read at any time. We did not have to set up the accelerometer, the platform told the compiler that such a sensor exists and has a magnitude that can be read. Should you want to change the default values of the accelerometer after all, you can always use a <code>setup accelerometer { ... }</code> block to do that.</p> |
| <div class="highlight"><pre class="chroma"><code class="language-TypeScript" data-lang="TypeScript"><span class="nx">smartphone</span><span class="p">.</span><span class="nx">shockDetected</span><span class="p">.</span><span class="nx">write</span><span class="p">(</span><span class="kc">true</span><span class="p">);</span></code></pre></div> |
| <p>Earlier in the setup block for the Bluetooth Low Energy resource we configured a <a href="https://en.wikipedia.org/wiki/Bluetooth_Low_Energy#Software_model">BLE GATT characteristic</a>, which we named <code>shockDetected</code>. To send out data using Bluetooth all we need to do is to write to this characteristic using the built-in <code>write</code> function. All the nitty details of how to use the underlying Bluetooth stack are handled by the platform, not by you, the developer.</p> |
| |
| <p>That concludes our first tour of an Mita program. There is a lot more to learn though. The following sections give an overview of the basic concepts, followed by more in-depth chapters of specific language elements.</p> |
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