- Controller wired with Pulsar device
- A Bluetooth Low Energy capable device (phone, tablet, PC, or Dreamcast with BLE receiver like iBlueControlMod)
The same firmware runs on three boards. They behave identically as a gamepad — everything in Button Mapping, Profiles, and the VMU Display applies to all of them — but they differ in what they can show you and how you update them. Where a section below is board-specific, it says so.
| Pulsar v1 | XIAO (DIY) | DK (bench) | |
|---|---|---|---|
| What it is | The designed carrier board, with a XIAO nRF52840 module mounted on it | A XIAO nRF52840 wired up by hand on perfboard or a breadboard | Nordic nRF52840-DK dev kit |
| Status light | 5-LED bar: LED 0 status, LEDs 1–4 battery | The XIAO's onboard RGB (one LED) | Discrete kit LEDs |
| Battery gauge | IP5306 fuel gauge, four levels | Voltage estimate from the battery ADC | None — no battery |
| Rumble | Motor output (CN3), no motor fitted as shipped | No | No |
| Charging | Onboard, USB-C | Onboard, via the XIAO's USB-C | Not applicable |
| Firmware update | Wireless (OTA) | USB drag-and-drop (UF2) | Debug probe |
| Sleep | Deep sleep (System Off) | Deep sleep (System Off) | Halts instead of sleeping |
Pulsar v1 and the DIY build share the same XIAO module, so they run the same silicon — the carrier adds power management, the LED bar, and the motor output around it.
- Power on the adapter. The status light blinks briefly, then shows searching while it looks for the controller — red on Pulsar v1 and XIAO, LED4 on the DK.
- Once the controller is detected, the status light turns green (LED3 on the DK).
Pulsar v1 waits for your host before it powers the controller. The adapter only switches on the controller's 5 V supply once a Bluetooth host is connected, so that a plugged-in adapter sitting idle charges its battery instead of running the controller. Until you pair, the controller is unpowered and a docked VMU is blank — that is normal. The moment your host connects, the VMU chirps as it powers up and the status light goes green. So on this board, expect to pair first and see the controller come alive after, which is the reverse of steps 1 and 2 above.
- The adapter automatically enters pairing mode on first boot (since no device is bonded yet). It will be discoverable for 60 seconds.
- On your host device, open Bluetooth settings and look for "Xbox Wireless Controller".
- Select it to pair. The LED will turn solid to indicate a connection.
That's it! The adapter remembers your device and will reconnect automatically in the future.
After the first pairing, the adapter reconnects automatically:
- Power on the adapter.
- Turn on Bluetooth on your host device.
- The adapter will find and connect to your previously paired device within a few seconds.
No need to re-pair each time.
| Dreamcast | Xbox Equivalent |
|---|---|
| A | A |
| B | B |
| X | X |
| Y | Y |
| Start | Menu |
| D-pad Up | D-pad Up |
| D-pad Down | D-pad Down |
| D-pad Left | D-pad Left |
| D-pad Right | D-pad Right |
| Left Trigger | Left Trigger |
| Right Trigger | Right Trigger |
| Analog Stick | Left Stick |
The Dreamcast controller has one analog stick, which maps to the left stick. The right stick is not available.
The Dreamcast pad has no Guide button, so it's a chord: pull Left Trigger + Right Trigger and hold Start together (about a third of a second). This sends the Guide (Xbox) button — e.g. it opens the Steam overlay / Big Picture, or the Xbox Game Bar.
- It's deliberately a hold so it won't fire by accident during play, and it's kept off the face buttons so it never collides with the Dreamcast/GDEMU
A+B+X+Y+Startreset combo. While held, the triggers and Start are suppressed so the host sees only Guide. - The chord works on both profiles. On Xbox it's the real native Guide button (the Steam overlay opens automatically). On Dreamcast it comes through as a plain Button 11 — bind that to "Guide" in Steam Input (or your host's controller settings) if you want the overlay shortcut there.
| Action | Result |
|---|---|
| Short press | Wake / request reconnect |
| Hold 2s | Pairing mode (60s) — clears the current bond |
| Hold 3.5s + controller Start | Firmware update mode (OTA) — Pulsar v1 only |
| Tap, tap, then hold 3.5s | Same update mode, no controller needed — Pulsar v1 only |
| Tap once, then hold 3.5s | Browser configuration mode — remap buttons |
| Hold 7s | Sleep — shows BYE, releases into deep sleep (the DK halts instead) |
| Triple-press | Switch profile (Xbox ⇄ Dreamcast) and reboot |
The three tap-then-hold gestures are told apart by the number of taps before the hold: one tap is configuration, two is controller-free update, three short presses (no hold at all) is the profile toggle. Begin the hold within about two seconds of the first tap, or it counts as an ordinary hold.
The sync LED blinks faster once you pass 2s, so you can see the next step coming before you reach it. Release at that point to pair; keep holding to sleep.
Firmware update has two routes. The usual one needs both hands: hold the sync button past 3.5s while the Dreamcast controller's Start button is held. Three fast flashes confirm it. It is refused below 50% battery unless you are charging — the display shows CHRG if so. Holding past 3.5s with Start down does not clear your pairing.
The second route needs no controller at all: tap the sync button twice, then hold it past 3.5s. Begin the hold within about two seconds of the first tap, or it counts as an ordinary hold. Two taps rather than three keeps it distinct from the profile toggle, which is three short presses. This exists so an adapter with nothing plugged in — or with a controller that has stopped responding — can still be updated.
This gesture is for Pulsar v1, which updates wirelessly. On a XIAO or DK build the gesture does nothing useful — those boards are reflashed over USB or a probe instead. See Updating the firmware.
After holding 2s and pairing fresh, the old host still has us in its Bluetooth list. Forget the adapter there before it'll let you pair again — same as any single-bond controller (Xbox, etc.).
Two identities, switchable with a triple-press. Use Xbox by default — it now works essentially everywhere tested: macOS (browser + Steam), Windows (+ Steam), Linux (xpadneo), BlueRetro, and BLE receivers.
The Dreamcast profile is not a Dreamcast-controller emulation — it's just a plain, generic BLE HID gamepad; the only "Dreamcast" thing about it is the Bluetooth name. Pick it if you'd rather not present as an Xbox controller (e.g. to avoid Xbox button prompts in games) or for a host that prefers a neutral HID gamepad.
| Profile | Best for | Bluetooth name |
|---|---|---|
| Xbox (default) | macOS (browser + Steam), Windows (+ Steam), Linux (xpadneo), BlueRetro, iBlueControlMod / BLE receivers — anything that recognizes an Xbox controller | Xbox Wireless Controller |
| Dreamcast | A plain, generic BLE HID gamepad (neutral identity — only the Bluetooth name is Dreamcast-branded) — Android, simple HID consumers, or hosts where you'd rather not present as Xbox | Dreamcast Wireless Controller |
After switching, forget the adapter on your host and pair again so it picks up the new HID layout. The profile is saved to flash.
Firmware 243 or later. You can change what every Dreamcast control sends. The saved map lives on the adapter, applies to both profiles, and follows the controller to every host you pair with — there is nothing to install on the host and nothing to re-do when you switch computers.
Tap sync once, then press it again and hold through 3.5 seconds, until the adapter
resets. It disconnects from your host and advertises as Pulsar Configure for 60
seconds.
This is a separate, unbonded identity: while it is in configuration mode the adapter is not a gamepad, has no bond, and will not appear as a controller. Anything that ends the session — finishing, disconnecting, letting the 60 seconds lapse, or losing power — resets it straight back to normal operation with your existing pairing intact.
Open the configure page in Chrome or Edge on a computer, or Chrome on Android (it uses
Web Bluetooth, which Safari and Firefox do not implement), connect to Pulsar Configure,
and you get a live view of the controller: press a button and you see it register. Changes
preview live on the adapter before you commit them, so you can try a layout and feel it
working. Nothing is written to flash until you choose to save.
Only the durable map survives. A preview is exactly that — if the session ends while you are previewing, the adapter reverts to the last map you saved. Save before you walk away.
Remapping is board-independent — it is the same firmware, and a XIAO or DK build enters configuration mode with the same gesture and is configured the same way.
The adapter draws on the VMU LCD while connected — a profile splash on every connect, then a rotating pulsar with battery indicator. Mode transitions get their own splash.
 Xbox profile (boot) |
 Dreamcast profile (boot) |
 In-session |
 Pairing mode |
 Sleeping |
The profile splash holds for ~30 seconds after connect, then transitions to the rotating pulsar with battery indicator.
Battery note: the VMU advances the pulsar animation about 4 times per second (every ~260 ms), plus extra writes on splash transitions. This costs roughly 5–10% of battery life vs. running with no LCD activity. Worth it for the visual feedback, but worth knowing.
The adapter monitors the LiPo battery and reports the level over Bluetooth (visible in your host device's Bluetooth settings or supported games), and draws it on the VMU.
A single-cell LiPo runs from about 4.2 V charged down to about 3.3 V empty. The firmware's own curve treats ≥ 4.10 V as 100% and ≤ 3.30 V as 0%, the measured cutoff — so the reported level reaches empty a little above the cell's absolute floor, deliberately.
How the level is measured depends on the board:
| Board | How it reads | What you see |
|---|---|---|
| Pulsar v1 | IP5306 fuel gauge over I²C | Four levels (25 / 50 / 75 / 100%). LEDs 1–4 of the bar light in magenta, one per level — a deliberately different colour from the status LED so the two meanings can't be confused. |
| XIAO | Battery ADC against a LiPo discharge curve | A continuous percentage. The single onboard RGB has no room for a gauge, so it shows status only — read the level on the VMU or your host. |
| DK | No battery, no gauge | Nothing. The board reports no battery at all rather than a fake reading. |
Because the Pulsar v1 gauge moves in 25% steps, its indicator jumps between four states rather than sliding down gradually. That's the gauge, not a fault.
The USB-C port faces out through the slot opening on the controller's underside — the adapter charges in place, and a VMU in the second slot is unaffected.
While a charger is attached, the VMU's battery icon shows a lightning bolt inside the outline instead of the level bars. It is not an extra level — it replaces the reading, and the level returns the moment charging stops.
This is deliberate. A charging pack's terminal voltage is pulled up by the charger, so the level read while charging is optimistic — a battery reading "full" that empties as soon as you unplug. Showing the bolt says the reading is not meaningful right now rather than quietly showing a wrong one.
When the battery is genuinely critical the icon empties completely, which is the cue to plug in.
Charge the battery over USB-C — on Pulsar v1 that's the carrier's own port, on a DIY build it's the XIAO's. A USB power brick or phone charger is recommended. Note: Some laptops (especially MacBooks) have smart USB ports that may reduce or cut power when the adapter is in deep sleep, since the USB peripheral is off and the laptop doesn't detect a device. If you notice the battery not charging from a laptop, either use a standard USB charger or keep the adapter awake while plugged in.
No board rumbles at this revision. Pulsar v1's carrier has a motor output (CN3) and the firmware drives it, but no motor is fitted to units as shipped — CN3 is left empty. Rumble commands from the host arrive and are ignored, which is harmless.
The XIAO and DK builds have no motor output at all. On every board the Xbox profile still advertises rumble support, because the report is part of the identity the host expects, not a per-board capability.
The adapter enters deep sleep to save battery in these situations:
- Manual sleep -- hold the sync button for 7 seconds.
- No Bluetooth connection for 60 seconds after power-on (advertising timeout).
- Controller not found for 60 seconds after Bluetooth connects (detection timeout).
- Controller disconnected for 60 seconds while BLE is connected (re-detect timeout).
- No controller input for 10 minutes while connected (inactivity timeout).
When asleep, the nRF52840 itself draws microamps, but the board around it draws more — the LED rail and the power path stay powered, and the figure has not been characterized on Pulsar v1 yet. Treat deep sleep as low power, not as zero: expect a unit left for weeks to need charging. The battery charges normally from USB while asleep.
To wake up: Press the sync button. The adapter performs a full restart and will reconnect to your paired device.
The DK has no battery and no power management, so it halts on the sleep gesture instead of entering deep sleep — the goodbye splash still runs, which is what makes the flow testable on the bench.
Updating from v0.3.0 or earlier: you will need to pair again.
This release moves where the adapter stores its Bluetooth pairing, so the old bond is not carried across. After updating, the adapter will not reconnect to your host on its own. Forget the adapter in your host's Bluetooth settings, hold sync for 2 seconds, and pair fresh. This is a one-time step — future updates keep your pairing.
How you update depends on the board:
Pulsar v1 — wireless. Hold sync past 3.5s with the controller's Start held; three fast
flashes confirm it and the adapter reboots into update mode advertising as PulsarDFU. It is
refused below 50% battery unless you're charging, showing CHRG on the VMU — charge first
and retry. The update is signed, so the adapter only accepts official firmware.
There is no reset-button route into update mode on Pulsar v1, and no USB drive. Double-tapping reset does nothing, holding a button while powering on does nothing, and no
XIAO-BOOTvolume will appear. Both button entry and pin-reset entry are deliberately switched off in this board's bootloader — the sync + Start gesture is the only way in.Two consequences worth knowing before you need them:
- You do not need the controller attached. The sync + Start gesture checks that Start is held, but the tap-tap-hold chord — two taps, then hold past 3.5s — reaches update mode on its own. Older firmware had only the first route, so an adapter with nothing plugged in could not be updated by hand at all.
- A failed or interrupted update is not a brick. If the firmware is missing or incomplete, the adapter enters update mode on its own at power-on and waits to be re-flashed. Plug it in, reload the update page, and try again.
The update page talks to the adapter over Bluetooth from the browser, and not every browser allows that. If the page never shows a device chooser, this is almost always why.
| Browser | Works? |
|---|---|
| Chrome / Edge / Opera on Windows or macOS | Yes, out of the box |
| Brave | Yes, but you must turn it on first — see below |
| Chrome on Linux | Needs chrome://flags/#enable-experimental-web-platform-features enabled, plus BlueZ 5.41 or newer |
| Firefox | No — not supported on any platform |
| Safari, including iPhone and iPad | No — not supported, and not planned |
Brave ships with Web Bluetooth switched off deliberately, as a privacy choice. To enable
it: open brave://flags, search for Web Bluetooth API, set it to Enabled, and relaunch
the browser. Without that step the page loads normally and simply never finds your adapter,
with no error to explain why — which is exactly what makes it worth checking first.
On an iPhone or iPad there is no way to make Safari work, because Apple does not implement the API. Update from a computer, or use a third-party Web Bluetooth browser such as Bluefy.
XIAO — USB drag-and-drop. Double-tap the reset button; the board mounts as a USB drive
called XIAO-BOOT. Copy the .uf2 file onto it and it reboots into the new firmware.
The web updater will not find a XIAO build — use the USB route. This is not a fault in your browser or your board. A DIY XIAO runs the stock Adafruit bootloader, which speaks an older update protocol whose Bluetooth service Chrome blocks permanently, by name, as a matter of policy. No browser will ever reach it. Pulsar v1 carries a different bootloader specifically so the web route works there.
DK — debug probe. Flash over the onboard debugger with your usual tool.
Release builds are required on every board. Debug builds miss the Maple Bus timing window and the controller will not be read reliably.
Every board shows the same states; what lights up differs.
Pulsar v1 — five-LED bar. LED 0 carries status; LEDs 1–4 are the battery gauge and stay lit through status changes, so losing the controller doesn't blank your battery reading. The colours are deliberately dim to avoid glare through the shell window.
| LED 0 | Meaning |
|---|---|
| Dim red | Searching for controller |
| Dim green | Controller found / connected |
| All dark | Sleeping, or idle and waiting for a host to connect |
The status LED lighting the shell from the VMU slot (green = connected). The magenta gauge LEDs sit behind the same window.
XIAO — onboard RGB (one LED). No battery gauge; the level is on the VMU and your host.
DK — discrete kit LEDs. LED4 searching, LED3 connected, LED2 flickers on Maple TX activity. LED1 is the sync LED.
| State | XIAO (RGB) | DK | Meaning |
|---|---|---|---|
| Starting up | Green blink ×3 | — | Boot |
| Searching | Solid red | LED4 on | Looking for the controller |
| Connected | Solid green | LED3 on | Controller found |
| Pairing mode | Fast blue blink | Sync LED blinking | Discoverable for 60s |
| Sync held | Blink | Sync LED blink | Button held, action pending |
| Past sync point | Faster blink | Faster blink | Approaching sleep |
| Profile switched | 5 quick flashes | 5 quick flashes | Confirmed, about to reboot |
| Off | Off | Off | Sleeping or idle |
The sync LED behaviour (blink while held, faster past the 2s point, five flashes on profile switch) is the same on all three boards — on Pulsar v1 and XIAO it's the blue channel of the status light, on the DK it's LED1.
Controller and VMU are dead until I connect a host (Pulsar v1)
- Expected. The adapter only powers the controller once a Bluetooth host is connected, so an idle adapter charges instead of running the controller. Connect your host: the VMU chirps as it powers up and the status light goes green. If it stays dark after connecting, work through the entry below.
Controller not detected (status stays on searching — red, or LED4 on the DK)
- Check that the controller cable is securely connected to the adapter.
- Make sure the controller is receiving 5V power.
- Try unplugging and re-plugging the controller.
Double-tapping reset does nothing / no USB drive appears (Pulsar v1)
- Expected. This board has no reset-button route into update mode and no
XIAO-BOOTvolume — button and pin-reset entry are both disabled in its bootloader. Use the sync + Start gesture instead. See Updating the firmware.
The update page never shows a device chooser (Pulsar v1)
- Check the browser first. Brave has Web Bluetooth off by default — enable Web Bluetooth API in
brave://flagsand relaunch. Firefox and Safari don't support it at all, including on iPhone and iPad. Chrome on Linux needschrome://flags/#enable-experimental-web-platform-features. Chrome, Edge, and Opera on Windows or macOS work as-is. See Updating the firmware. - If the browser is fine, make sure the adapter is actually in update mode — it advertises as
PulsarDFU, not under its usual name.
The web updater never finds my adapter (XIAO build)
- Expected, and not fixable from your side. A DIY XIAO runs the Adafruit bootloader, whose update service Chrome blocks by policy. Update it over USB with the
.uf2file instead.
I can't get into update mode — no controller attached (Pulsar v1)
- Use the controller-free chord instead: tap sync twice, then hold it past 3.5s, starting the hold within about two seconds of the first tap. If the firmware itself is broken or missing, the adapter enters update mode on its own at power-on without any gesture.
It won't reconnect after a firmware update
- Expected when coming from v0.3.0 or earlier — the pairing does not survive that update. Forget the adapter on your host, hold sync for 2 seconds, and pair fresh. See Updating the firmware.
Battery indicator jumps in big steps (Pulsar v1)
- Normal. The IP5306 gauge reports four levels, so the bar moves 100 → 75 → 50 → 25 rather than sliding down continuously.
Rumble does nothing
- Expected on every board at this revision. Pulsar v1 has a motor output but ships with no motor fitted; XIAO and DK have no motor output at all. Rumble commands are accepted and ignored. See Rumble.
Can't find "Xbox Wireless Controller" in Bluetooth
- The adapter may not be in pairing mode. Hold the sync button for 2 seconds to enter pairing mode.
- Make sure you're within Bluetooth range (about 10 meters / 30 feet).
- On some devices, you may need to "forget" the old pairing first, then hold sync for 2 seconds to re-pair.
Previously paired device can't reconnect after syncing to a new device
- Go to Bluetooth settings on the old device and select "Forget This Device" for the adapter.
- Then hold the sync button for 2 seconds on the adapter to enter pairing mode and pair fresh.
Connected but no input
- Some hosts need a moment after connecting to discover services. Wait a few seconds after the connection is established.
- Try pressing buttons on the Dreamcast controller to verify it's responding.
Adapter keeps going to sleep
- Press the sync button to wake it up.
- The adapter sleeps after 60 seconds without a Bluetooth connection, 60 seconds if Bluetooth connects but no controller is detected, or after 10 minutes of no controller input. Keep interacting with the controller to prevent the inactivity timeout.
Inputs feel wrong or mapped incorrectly
- Try the other profile: triple-press sync to switch between Xbox and Dreamcast. After switching, forget the adapter on your host and pair fresh — most hosts cache the HID layout per-bond.
- Some hosts remap buttons in their own settings (Steam Input, accessibility shortcuts). Check there too.
Flycast's mapping screen shows the stick "Up"/"Left" rows blank
- Use the Xbox profile for SDL-based emulators (Flycast, RetroArch); the Dreamcast stick maps to the left analog stick.
- After "Reset to default," Flycast may label only the Down/Right rows ("Left Stick Y+/X+") and leave Up/Left blank. That's cosmetic — it binds the full axis to both directions, so the stick works fully in-game. No need to reset again or hand-map the blank rows.