BLE, Project Zero
The free beginner BLE course, and it starts the way every course here starts: with a product. Build a real Bluetooth macro pad: four buttons that type, pairing and bonding done properly, a hand-wired switch matrix with scanning firmware you write yourself, keymaps and media keys, and an optional battery finale. You learn BLE by shipping the pad.
Free means free: every chapter, no card, no trial clock.
BLE vocabulary is not a BLE product
The usual way
- Advertising, GATT and pairing explained as vocabulary, then a demo that stops at "connected"
- A vendor sample you flash once and learn nothing from taking apart
- Bonding, debounce and ghosting left as mysteries for your first real project to solve painfully
- Nothing on your desk at the end that you would show anyone
This course
- Every concept arrives when the pad needs it: the report map when the buttons must type, bonding when the host demands an encrypted link
- You write the scanning and debounce firmware yourself, and hit the six-key rollover wall on purpose to learn why diodes exist
- Pairing and bonding done the way shipped keyboards do them, with the two shell commands every product needs
- You finish with a working macro pad, and the optional finale turns it into a battery product on a XIAO
One pad, built in stages
On the nRF52840 DK: four buttons that type real letters over HID over GATT, then pairing and bonding, then a hand-wired 3 by 4 switch matrix (12 switches, 12 diodes, seven wires) scanned by firmware you wrote, then keymaps, a momentary layer and media keys on a second report. Chapter 8 is the optional finale: the same firmware ported to a Seeed XIAO nRF52840 with a LiPo cell, reporting its battery to the host.
Be seen, then connect
Advertising, connection events, and the restart nobody tells you about. (Chapter 3)
The report map is the contract
HID over GATT, byte by byte. (Chapter 4)
Twelve keys on seven wires
The switch matrix: scanning, debounce, ghosting. (Chapter 6)
Real animations from inside the lessons
The flows that matter in BLE (advertising that restarts itself, one keystroke becoming two reports, a grid being scanned) are taught as animations you control. These three are lifted straight out of the chapters, untouched.
Advertise, connect, advertise again
One keystroke, two reports
Scanning the grid
Chapter by chapter
Eight chapters and a troubleshooting appendix, 18 to 22½ hours of follow-along building. The course completes on Chapters 1 to 7 plus the appendix; Chapter 8 is the optional finale for readers who want the standalone battery product.
Setup the pinned way, and your first debug session
Install the pinned toolchain, build and flash your first apps, and drive the board from its own shell.
Buttons that behave: interrupts, work, and debounce
Interrupts announce, threads work, and a timestamp filter tells a real press from switch bounce.
Be seen: advertising, connections, and the two roles
The board advertises, a phone finds it, a connection forms, and advertising learns to restart itself.
The board becomes a keyboard
HID over GATT end to end: the report map byte by byte, and the DK’s four buttons type real letters.
Pairing and bonding: the keyboard grows up
Encrypted links required, bonds stored in flash, and the two shell commands every shipped keyboard needs.
Twelve keys on seven wires: the switch matrix
Hand-wire a 3 by 4 switch matrix with diodes, scan and debounce the grid, and hit the six-key wall on purpose.
Make it yours: keymaps, layers, and media keys
Keymaps as data, a momentary layer, media keys on a second report, and a name the host can read.
Chapter 8 (finale): Off the dev kit: the XIAO pad Optional finale
Optional finale: port the pad to a Seeed XIAO with a LiPo cell, a battery gauge the host can see, and honest runtime arithmetic.
Everything is a deliverable
- 8 chapters of labs: every lab a numbered procedure with checkpoints and expected outputs, each step build-verified on the pinned stack (NCS v3.4.1, Zephyr 4.4.2)
- 40 quiz questions with full answer keys: a self-check in every chapter
- 17 diagrams, plus an animated diagram in every chapter: the build loop, the interrupt rule, the pairing sequence, the scan
- The complete companion repo, public on GitHub: 11 step-by-step applications, each building on the last (github.com/learnbittoboard/ble-project-zero)
- Two exercises per chapter: a core exercise and a labeled stretch
- The troubleshooting appendix: When it breaks, 15 symptoms from this exact project, cause and fix
- Deliberately scoped: custom GATT profile design, connection privacy in depth, throughput tuning, OTA updates and sniffing are the advanced ladder's syllabus, and the course says so. Project Zero teaches exactly what a keyboard needs, at full depth
- All 8 chapters, labs, quizzes and diagrams
- The optional XIAO battery finale included
- The full companion repo on GitHub
- Read anywhere in the online player
- Free updates to the course
Free means free: no card, no trial, no expiry.
Before you start
You need basic C and a first microcontroller behind you; no Bluetooth experience is assumed. The board path needs an nRF52840 DK. Chapter 6 adds 12 keyboard switches, 12 1N4148 diodes, a breadboard and wire (a few dollars). The optional finale adds a Seeed XIAO nRF52840 and a small LiPo cell. Or read along with no hardware at all: the next section explains how that works.
Free, in full
This is the complete course, not a teaser for one. The same format, the same standard, the same desk as the paid shelf.
The whole course, no card
Every chapter, every lab, every quiz and the appendix. Nothing is held back behind a paywall, and there is no trial clock. If it teaches you BLE the way it is meant to, the paid shelf is there when you want the advanced ladder.
Animated diagrams
The flows (the build and flash loop, announce-in-the-interrupt, advertising that restarts itself, the pairing sequence), taught as animations you play, pause and step through at your own pace.
40 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. Fifteen symptoms from this exact project: the advertising that never restarts, the phantom key, the bond the host forgot. Symptom, cause, fix.
Exercise-by-exercise code
The pad grows one verified step at a time in a public repo, every exercise a buildable checkpoint, nothing dropped on you all at once.
A product on your desk
A working macro pad you wired and programmed yourself, and with the optional finale, a battery product that reports its own charge. That is the artifact this course leaves you with.
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 an nRF52840 DK, then the switches and diodes from Chapter 6, and the XIAO plus LiPo if you take the finale. You wire the matrix, scan it, pair the pad with your own computer and finish with a macro pad that works on your desk.
Read-along: no board required
Follow every chapter with the full code and the expected output at each checkpoint: every step's code and results are in the lessons, so the course can be followed with no hardware purchase. The chapter quizzes work the same.
What does not transfer is the bench feel: wiring a matrix that ghosts, watching a scanner find your pad, fixing a setup that misbehaves only in the room. That part stays worth coming back for.
Before you ask
Is it really free?
Yes. Every chapter, lab, quiz and the appendix, with nothing held back and no card or trial involved. It is the beginner rung of the BLE ladder here, and it is free because a first project should be.
Do I need Bluetooth experience?
No. Basic C and having seen a microcontroller is the floor. Advertising, connections, GATT and pairing are all taught from zero, in the order the pad needs them.
Do I need the XIAO board?
No. The course completes on the nRF52840 DK alone (Chapters 1 to 7 plus the appendix). The XIAO appears only in Chapter 8, the optional finale that turns the pad into a standalone battery product.
What comes after Project Zero?
The advanced rung: LE Audio, Engineered, on this same shelf, builds a private LE Audio link and an Auracast broadcast on two nRF5340 Audio DKs. The topics Project Zero deliberately skips (custom profiles in depth, privacy, throughput, OTA, sniffing) are the advanced ladder's syllabus.