LE Audio, Engineered
Build a private LE Audio link, then flip the same two boards into an Auracast broadcast: an nRF5340 Audio DK transmitter taking USB audio in, and its twin receiver putting music on a headphone jack. Auracast is the climax: the broadcast architecture behind the public venue audio Bluetooth is rolling out to airports, gyms and theatres, built on your desk, from the same firmware you just made unicast work with.
LE Audio is where Bluetooth stops being polite
The usual way
- LE Audio explained as a feature list: LC3, isochronous channels, Auracast, with no path from the words to a working link
- A reference application treated as a black box: flash it, hope, and learn nothing when it stutters
- Unicast and broadcast taught as separate worlds, on separate examples, so the flip between them stays abstract
- Failures named in documentation but never diagnosed in front of you
This course
- The real reference application, taken apart role by role, so what you learn transfers to any product built on it
- Unicast first, because a private CIS link is where every LE Audio concept is easiest to see clearly; broadcast second, on hardware you already trust
- Diagnosis is a chapter, not an afterthought: log forensics, planted faults, and a real field case worked end to end
- A sniffer chapter that puts a third radio on your own pair and teaches you to read what the air actually carried
The Auracast pair, in two acts
Act 1: a private unicast pair. The transmitter takes audio from your computer over USB; the receiver decodes LC3 and plays it to a headphone jack, with a real CIS link, negotiated QoS, and a microphone path back. Act 2: the same pair, reflashed into an Auracast broadcast. The transmitter becomes a source anyone can join; the receiver syncs to the broadcast by periodic advertising and listens, no connection, no pairing. You finish with both firmwares, release builds of each, and a product card that documents your pair like a product.
CIS establishment, step by step
Discovery, ASE states, QoS, the first frame on time. (Chapter 5)
A broadcast is born
BIG and BIS, periodic advertising, the BASE. (Chapter 8)
Reading Act 2 on the air
The sniffer's view of your own broadcast. (Chapter 12)
Real animations from inside the lessons
LE Audio is timing: streams established step by step, a sink hunting for its broadcast, a BIG coming alive. The lessons animate those flows and hand you the controls. These three are the actual chapter animations, untouched.
CIS establishment, step by step
The sink finds its broadcast
A broadcast is born
Chapter by chapter
Thirteen chapters and a troubleshooting appendix. Total: about 39 to 45 hours of follow-along work, depending on your pace. Labs repo, public: github.com/learnbittoboard/le-audio-engineered.
Why audio needed a second Bluetooth
Classic audio’s limits, the isochronous idea, LC3, and CIS vs BIS. Meet the Auracast pair and the Audio DK.
The reference application, taken apart
Two cores, four roles, one application. Build all four role images and learn to read a build tree.
The transmitter: USB audio in
The gateway role, USB audio as the source, and the set identity (SIRK) that makes two boards one product.
The receiver: LC3 to the headphone jack
The headset’s decode path: ISO in, LC3 decoded, the CS47L63 hardware codec, sound out. Plus the mic path back.
CIS under the microscope
Discovery, ASE states, QoS negotiation, and CIS establishment, step by step. Act 1 becomes a link you can defend.
Tuning the stream
QoS presets as deliberate trades: frame duration, sample rate, retransmission, presentation delay. Change, rebuild, diff.
When it stutters: diagnosis
Log forensics module by module: no stream, dropping stream, drifting stream. Three planted faults, diagnosed from evidence.
Act 2: the Auracast source
The connectionless flip: BIG and BIS, periodic advertising, the BASE, Broadcast ID, and encrypted broadcasts.
The Auracast sink: sync and receive
PA sync from the sink’s side: find your broadcast among strangers, select the stream, listen. The assistant story, honestly scoped.
One pair, two personalities
Release builds, role switching without confusion, identity that survives reflashing, and buildable firmware-update images.
Capstone: ship the pair
The cold bring-up protocol, a structured listening test, and a product card. Plus an honest map of what comes next.
Reading the air: the sniffer chapter
The third radio that settles arguments: nRF Sniffer and Wireshark on your own pair, the encryption boundary, and your own keys.
Case File: the sync that died on a schedule
One real Auracast field failure, worked end to end: the log’s metronome, the two images that disagreed about a clock, the one line fix.
The sniffer, and the case file
Chapter 12 adds the third radio that settles arguments: an nRF Sniffer and Wireshark on your own pair, reading a CIS coming up and an Auracast broadcast being synced to, up to the exact line where encryption closes the payload to anyone without the keys, your keys, your devices.
Chapter 13 closes the course the way the job actually works: one real Auracast field failure from a public support thread, worked end to end from its log to its confirmed one line fix: a broadcast headset that lost sync every 0.800 seconds, on a schedule, because two firmware images disagreed about a clock.
What you will be able to do
- Build all four LE Audio roles (unicast client and server, broadcast source and sink) and prove from the build that each image is the role you intended
- Explain a CIS establishment and an Auracast PA sync step by step, and point at the log line family that proves each step
- Choose a QoS preset for a product and defend the trade in numbers
- Diagnose the three classic failure shapes (no stream, dropping stream, drifting stream) from logs instead of folklore
- Put a sniffer on your own pair and read its traffic, and work a real field failure to its confirmed root cause
The hardware, stated plainly
Hardware is not included. This project has one non-negotiable line: it takes two Audio DKs.
nRF5340 Audio DK ×2 (required)
Two, not one: an Auracast pair is a transmitter and a receiver, and a one board setup cannot do this project. (PCA10121)
A computer
Running the pinned stack, nRF Connect SDK v3.4.1, the exact SDK this project is built and verified against.
For Chapter 12 only: a third Nordic board
The sniffer chapter needs one board that can run the nRF Sniffer firmware as the witness: an nRF52840 Dongle is the usual, cheap choice; an nRF52840 DK works too. The chapter is fully readable without it.
Headphones
Any wired pair with a 3.5 mm plug, for the receiver's headphone jack.
USB cables
One per board, plus the transmitter's USB audio connection to your computer.
Everything is a deliverable
- 13 chapters of labs: the reference application taken apart role by role, every build step compile-verified on the pinned stack; listening checks written as explicit bench protocols
- 110 quiz questions with full answer keys: self-check cards, graded as you go
- 46 diagrams, plus an animated diagram in every chapter: CIS establishment, the tuning trade space, PA sync, the 0.800 second loop
- A public labs repo, step by step: github.com/learnbittoboard/le-audio-engineered
- The sniffer chapter: nRF Sniffer and Wireshark on your own pair, and the encryption boundary taught honestly
- A real case file: one documented field failure, its log, its diagnosis, its confirmed fix
- Stretch exercises. Break the stream on purpose, retune it, prove you understood
- All 13 chapters, labs, quizzes and diagrams
- Lifetime access in the online player, nothing to install, read anywhere
- The full labs repo, step by step
- Email support from the instructor
- Free updates to the course
Placeholder price for this preview build. Secure checkout opens at launch; the refund policy (7 days, no questions) will apply from day one.
Before you start
Prerequisites, honestly: intermediate BLE fluency. You know what a GATT service is, you have built and flashed a Zephyr application before, and reading a Kconfig tree does not scare you. The free BLE, Project Zero course on this site (the macro pad project) is the on ramp; equivalent experience works. And the boards: two nRF5340 Audio DKs. There is no one board track for this project.
What owners get
Buying the course is the start, not the whole deal. This is what's included with it, and the headline is a human being on the other end of an email.
Lifetime email support
Stream will not establish, or a sync that dies on a schedule? Email your question about the course to [email protected] and a working engineer answers, within 1 to 2 working days. Support covers questions about the course material and its labs. It is not general consulting, and it does not extend to debugging projects unrelated to the course. For as long as you own the course: no support tiers, no expiry, no ticket bot.
Animated diagrams
The moving parts (a CIS being established, a broadcast being born, a sink finding its PA, the metronome failure loop), taught as animations you play, pause and step through.
110 quiz questions, with answer keys
Every chapter ends in a self-check quiz with full answers, so you find the gaps while they're still cheap to fix.
The troubleshooting appendix
When it breaks. The failure table for this course's builds and boards: symptom, cause, fix. Kept open beside the labs, it earns its place in the first week.
Exercise-by-exercise code
The pair grows one verified step at a time, unicast first, broadcast second, every exercise a buildable checkpoint in a public repo.
A certificate you have to earn
Finish every chapter, then pass the final exam: 30 questions, 70% to pass, graded on our server, retakes allowed. Passing earns a certificate of completion with its own public verification page, so anyone can check that it is real, and see its status if that ever changes.
More perks on the way
Owning a course here will keep getting better. More owner perks are in the works, and when they land, owners get them, free.
Two ways to take this course
Hardware is the recommended route, not an admission ticket. Start with the path that fits your desk today, and you can return to the bench later without starting over.
With hardware: build it for real
Use two nRF5340 Audio DKs (plus the third witness board for Chapter 12). You build all four roles, establish the CIS link, tune the stream, flip the pair to Auracast and finish with a working broadcast pair on your bench.
Read-along: no board required
Follow every chapter with the full code, the exact commands, and the expected outputs in the text, so the theory, the labs, the quizzes, the exam, and the certificate all work with no hardware at all.
What read along cannot give you is the bench feel of a real RF link: hearing the stream lock, and chasing a stutter with your own logs. That part stays worth coming back for.
Before you ask
Do I really need two Audio DKs?
Yes. LE Audio is a link, and Auracast is a broadcast with a listener; a single board cannot do either act of this project. Two boards is the whole bill of materials for hardware.
I have never used LE Audio. Is this for me?
If your BLE basics are solid (GATT, advertising, connections, one Zephyr build under your belt), yes: Chapter 1 rebuilds the audio specific ideas from the ground up. If BLE itself is new, start with the free BLE, Project Zero course on this site (the macro pad project).
Can I follow along without the boards?
Yes. Every chapter carries the full code, commands, and expected outputs; the quizzes, exam, and certificate all work read along. You will miss the listening checks, which are written as bench protocols for when the boards arrive.
Why not just read Nordic's documentation?
You should; Chapter 2 uses it as a primary source. What the course adds is the path: which of the four roles to build first, what each build proves, how the concepts connect, and how to diagnose the failures the docs only name.