Adding requirements page

docs/requirements.md

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+# Specifying Requirements
+
+In this addendum to the tutorial, you will learn a bit about specifying requirements. Software requirements are derived from higher-level system requirements and represent the detail needed to implement the software.
+
+## System Requirements
+
+For this tutorial we have severl higher-level system requirements. These requirements would be defined by requirements specified by the electronics subsystem which are themselves derived by requirements defined at the full system level.
+
+| Requirement     | Description                                              |
+|-----------------|----------------------------------------------------------|
+| ELECTRONICS-001 | The system shall blink an LED in response to a command.  |
+| ELECTRONICS-002 | The blink rate of the LED shall be changeable in-flight. |
+
+## Software Requirements
+
+These are the requirements that the software team cares about. These dictate how the software should operate and trace to the higher-level system requirements. These also come with a verification method to ensure the softare meets these requirements.
+
+Ideally, the software engineer would be handed these requirements, however; in-practice this is often a discussion between the software engineer and their system engineers. A sample requirement is provided below.
+
+| Requirement     | Description                                                     | Derives From    | Verification |
+|-----------------|-----------------------------------------------------------------|-----------------|--------------|
+| LED-BLINKER-001 | The software shall start LED blinking in response to a command. | ELECTRONICS-001 | Unit Test    |
+
+> Take a moment to identify some other requirements you might derive from the above electronics requirements. Do this before moving on to the next section.
+
+## LED Blinker
+
+Here we list a number of requirements for our led software to implement.
+
+| Requirement     | Description                                                     | Derived From    | Verification |
+|-----------------|-----------------------------------------------------------------|-----------------|--------------|
+| LED-BLINKER-001 | The software shall start LED blinking in response to a command. | ELECTRONICS-001 | Unit Test    |
+| LED-BLINKER-002 | The software shall stop LED blinking in response to a command.  | ELECTRONICS-001 | Unit Test    |
+| LED-BLINKER-003 | The software shall telemeter the current LED blinking state.    | ELECTRONICS-001 | Unit Test    |
+| LED-BLINKER-004 | The software shall emit events when the blinking state changes. | ELECTRONICS-001 | Unit Test    |
+| LED-BLINKER-005 | The software shall store the blink interval as a parameter.     | ELECTRONICS-002 | Unit Test    |
+| LED-BLINKER-006 | The software shall blink the LED using GPIO pin 13              | Electrical ICD  | Unit Test    |
+
+> Notice how the software also includes a requirement that derived from the Electrical Interface Control Document. This captures the details of the software/hardware interface and is captured here as a requirement.