From 09be8a0d1b07dc55a55fea52365c774398658d7d Mon Sep 17 00:00:00 2001
From: Trygve Laugstøl <trygvis@inamo.no>
Date: Thu, 26 Apr 2018 19:02:41 +0200
Subject: wip

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 assignments/mqtt/mqtt.md | 44 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 44 insertions(+)
 create mode 100644 assignments/mqtt/mqtt.md

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+# Assignment: MQTT
+
+## Goal
+
+Get aquainted with MQTT.
+
+## Steps
+
+1. Connect to the Wi-Fi network
+    * Use `WiFi.localIP()`
+
+1. Connect to MQTT broker
+1. Publish temperature
+1. Implement last will to indicate online status
+1. Implement subscription to reconfigure device
+    1. Change temperature report interval
+
+## 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 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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