From a4cbbee0671ff20560c31a2f3945b6131496ab2b Mon Sep 17 00:00:00 2001
From: Trygve Laugstøl <trygvis@inamo.no>
Date: Wed, 13 Jun 2018 20:41:24 +0200
Subject: wip

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+# Assignment: MQTT with button
+
+## Goals
+
+* Get aquainted with MQTT.
+* Publish a message when a button is pressed.
+
+## Step 1
+
+Wire up this schematic on the bread board:
+
+![](schematic/mqtt-with-button_schem.pdf)
+
+![](schematic/mqtt-with-button_bb.pdf)
+
+# Step 2
+
+* Read button, print message on terminal
+
+# Step 3
+
+* Connect to the Wi-Fi network
+    * Use `WiFi.localIP()`
+
+* Connect to MQTT broker
+
+# Step 4
+
+* Publish a message on button press
+
+## Tips
+
+To generate a client id make something with `ESP.getChipId()`{.cpp}
+
+Creating a `String` from a number:
+
+* `String(123) => "123"`{.cpp}
+* Hex formatted: `String(0x123abc, HEX) => "123abc"`{.cpp}
+
+Some APIs require "plain C strings" aka a `char *`{.cpp}. They can be converted with `String::c_str()`:
+
+~~~.c++
+char *cStr = myString.c_str();
+~~~
+
+## Bonus
+
+**1:** Print the heap free size at regular intervals.
+
+**2:** Implement min, max and average temperature over configured interval.
+
+Suggested parameters:
+
+* Sample interval: 2 seconds
+* Publish interval: 10 seconds
+
+**3:** Make sure the values are calculated even if we're reconnecting to the Wi-Fi or MQTT server.
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