Introduction
Welcome to the firmware team! We’re glad to have you.
In this lesson we’ll be covering:
What firmware is
An overview of our firmware system
How we’re working remotely
What our process for writing firmware is
Just a quick note before we jump into the content. All of our modules assume that you have some familiarity with programming, specifically the C language. You unfortunately won’t be able to do much until you have some familiarity with the language (specifically pointers, functions and structures).
C Language Resources:
Midnight sun specific Intro to C programming (Shoutout Arshan Khanifar)
Interactive tutorial - Learn-C.org. If you’ve programmed before in other languages before, the most important parts for our team are listed below:
With that out of the way, let’s get started!
What’s firmware?
Software vs. Firmware
Software is a set of instructions that you run on a computer. For example, your favourite video game or code editor is software. It’s normally stored on your hard drive, then when you want to execute it, your operating system (Windows or Mac OS or Linux) will grab those instructions, put them into working memory (RAM), and execute those instructions.
Firmware is also a set of instructions, but instead of being stored on your hard drive, they’re stored forever in memory. As soon as the computer is powered on, it’ll start executing the instructions it has in firmware.
In our firmware team, we work mainly on writing code for microcontrollers (think Arduino) that control electrical signals or monitor the solar car. Microcontrollers are essentially just computers but much smaller, and directly connected to hardware components.
Why does it matter?
Firmware generally has a lot more restrictions than software. Firstly, the processor isn’t very fast and there isn’t much memory available, so our code needs to be simple and not too demanding. We partially get around this restriction by breaking the firmware into small projects and running it on different boards, each responsible for controlling a different part of the car. Breaking it down also helps us work on different parts at the same time.
Systems overview
Here’s a diagram of the car’s electrical system:
If this scares you, don’t worry! It scares us too. Thankfully, implementing what’s in this diagram is the hardware team’s job, not ours!
Firmware system overview
See, we don’t even need to worry about wires. Much cleaner and easier to understand.
Each non-bolded line in the diagram represents a firmware project that controls a part of the car’s electrical system, grouped under the headings in bold. Here’s a quick rundown of what each firmware project does:
Battery: Ensures the battery doesn’t explode.
Driver controls: Takes input from the driver and passes it on to the rest of the system.
Power distribution: Turns other boards on and off (controls which boards are powered).
Drivetrain: Converts the angle that the pedal is at to the current levels for the motors (so if you floor it the car will go faster).
Charging: Manages charging of the battery from an off-the-shelf wall electric car wall charger or from the solar array.
Your PC vs a Microcontroller
We write all the code on our personal computers, but we need it to build it differently so that we can flash it over to run on our microcontrollers in a way that they understand. There are a few differences between the two that we need to consider.
Quick disclaimer: if this section doesn’t really make sense to you, that’s ok! You can still write code without it. But, this should help you understand what the difference is between working remotely and working directly with hardware.
First, let’s talk about compiling code.
Compiling code
As you may or may not know, to run C code, first you have to compile it. This means turning the higher level instructions you write as code into simpler instructions for the computer to understand.
An important caveat here is that not all computers understand the same instructions. For example, the processor in your laptop understands instructions called x86 (instruction set for Intel processors), while the computer chips we run our firmware on understands instructions called ARM.
Compiling our code
To do things like turn headlights on or off and read voltages from our hardware components on the BMS (battery management system) through code, we use pieces of code that are called libraries. Our firmware projects implement the logic parts we need, like determining when and how often we want an LED to blink and then we use the library to actually talk to the LED to turn it on or off. What this allows us to do is have different versions of the libraries for different types of computers:
This is the key to letting us work remotely! We can write all our C code and run it on our laptops, and never worry about actually touching the hardware, right?
Unfortunately, it’s not quite that simple. Some things are really hard to emulate on x86, especially things that are time-sensitive since you don’t know what else your laptop might be doing while you’re running the code. Microcontrollers have internal clocks which may differ from the one on your computer. However, it still gives us enough capability to write code and test our main logic.
Also, the hardware is still around, we’re just not close to it anymore. Good thing zoom, discord, and slack all exist! If we want to run our code on real hardware, we just have to call up the hardware member with the board and ask them to run it for us. Yes, this is more inconvenient, but it’s better than showing up a month later without having tested anything at all on hardware.
Our Process
Writing Code
Our firmware runs in safety critical situations, and as such it can be dangerous if it goes wrong. To help prevent this we have a structure for creating and testing our firmware.
High-level design: We come up with a high-level structure of the project that fulfils the requirement.
Detail design: we sort out the specifics, like what events or messages need to be passed between modules of the project
Implementation: we write the code.
Unit testing: we write tests that test specific parts of the code to make sure our logic works the way we think it does.
IO testing/Hardware validation: input/output testing. We run the project on hardware, and make sure the hardware works the way we expect it to.
Integration testing: we connect multiple boards together and make sure they work together the way we expect them to.
Notice how much testing we go through! This is really important. In firmware, writing the code is often only half the battle, and there can be many unforeseen delays when you actually start interacting with hardware.
Tools
GitHub:
Git is a version control system that lets us have a master version of our firmware code as well as “branches”. GitHub allows you to use git to Each branch can have modifications made to it in an isolated environment, then once the changes are checked and verified, they can be “merged” back into master. We use this as a way to give each member an isolated environment to work on their changes.
JIRA:
A project tracking tool that lets us easily keep track of all the tasks people are assigned to and their progress.
We put “tickets” on the board, which include the task, the assignee, and some other information about the task.
Conclusion
Thanks for sticking through! In conclusion, here’s what you should come away from reading this with an understanding of:
What firmware is
What our firmware systems do at a high level
How we’re able to work on firmware without direct access to the hardware
Our process for completing firmware projects
Next in firmware 102, we’ll go into more depth on our firmware system, controller boards, our project structure, testing and validation, and our collaboration platforms. We hope to see you there!
FW 101 Tasks
Each of these modules comes with some tasks or projects that should be completed before moving onto the next part. There will usually be a deliverable so that we can check off that you’ve completed the homework.
*One important thing: as you are working through your tasks, you will encounter errors. The leads are happy to answer questions about any of these issues, but most of the time it can be solved by a quick google. 90% of the errors you will encounter can usually be solved with answers from Stack Overflow, and a little bit of thinking.
FW 101 Tasks
There are several tasks that need to be completed as part of this module:
Get your environment set up by following the instructions listed at Setup
Learn about Git and the Command Line by watching/reading the following tutorials
Git Tutorial Videos (part 1 and 2) and branching lesson
Command Line Tutorials (Part 1 and 2)
Final Steps
Once you’ve got your box set up and have pulled the fwxv repository, build the can_communication project, and run it on the x86 platform with the command (fill in the blank
make run PROJECT=... PLATFORM=...
Once it’s started, take a screenshot and send it to the firmware lead. It should look something like this:
Don’t worry about what anything means, this is just to make sure you’ve got things up and running. You can find other information on make commands here: https://github.com/uw-midsun/firmware_xiv#usage
Tip: press ctrl+C to exit.