At a Glance

Prerequisites

• Same as Module 2

Blinking LED

Now, let's modify the getting_started project to toggle an LED once a second. First, we'll use our Hardware Abstraction Library (HAL). As a refresher, the key purpose of a HAL is to abstract platform details into a common, portable API to allow developers to write high-level application code independently of the underlying hardware.

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# Move to the firmware folder (if you weren't already there)
cd ~/shared/firmware
# Checkout the wip_getting_started branch (just in case)
git checkout wip_getting_started
# Check what branch we're on and if we have any changes
# This should say something along the lines of "nothing to commit, working directory clean"
git status

Controlling an LED - HAL

Let's update getting_started for basic General Purpose Input/Output (GPIO) pin control. We'll assume that our LED is an active-low (turns on when output is 0) and connected to PC9 (port C, pin 9).

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Great! You should see a solid LED on the Discovery board. This is pretty simple.

Blinking an LED - HAL

Let's add a lot more code! Now, we'll use our soft timers to toggle the LED once a second.

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Woah, there's a lot going on here! Do you understand how everything works?

Code Breakdown - HAL

First, it really helps to have the firmware folder open in your editor so you can reference our source code.

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Try playing with the code - adjust the timeout, replace wait(), change the LED, add another LED at a different interval, etc.

Cleanup and Commit - HAL

You should know the drill:

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In all honesty, we should've committed our code when we first got a solid LED. The jump from a solid LED to blinking LED is definitely worth a commit.

Blinking LED - Registers

Just for fun, let's take a look at what something like this might look like when accessing registers directly. For this, the STM32F0 reference manual is indespensible. It will tell you everything you'll ever need to know about working with the STM32F0.

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