# ps4-lego-bridge PS4 controller -> two LEGO Technic hubs, using two ESP32 boards. Driving a Johnny 5 (Short Circuit) MOC — seven motors across two hubs. ## Why two boards The obvious sketch — Bluepad32 for the gamepad, Legoino for the hubs, one ESP32 — does not work, and it is not a library-version problem. * **Bluepad32** needs Bluetooth Classic (BR/EDR), because a DualShock 4 is a BR/EDR device. It gets that from **BTstack**, and it ships as a whole replacement ESP32 board package rather than a normal library. * **Legoino** talks to the hubs over BLE using **NimBLE-Arduino**. BTstack and NimBLE are both Bluetooth *host* stacks. There is one radio and one VHCI interface on the chip, and whichever stack registers second wins. You cannot run both in one firmware image. So: board A runs Bluepad32 and nothing else. Board B runs Legoino and nothing else. Three jumper wires between them. (The single-board version, which speaks the LEGO protocol directly against BTstack, lives in `ps4-lego-onebrain`. It works, but it is a lot more code and a lot more ways to be wrong.) ## Hardware * 2x ESP32 dev boards. Both must be the **original ESP32** (WROOM/WROVER). S3, C3, C6 and H2 have no Bluetooth Classic, so a PS4 pad will not pair. * 3 jumper wires, or 4 if you daisy-chain power. ``` Board A (Bluepad32) Board B (Legoino) GPIO17 TX -------------> GPIO16 RX GPIO16 RX <------------- GPIO17 TX GND -------------- GND <- do not skip this one 5V -------------- 5V <- only in the model setup, see below ``` TX goes to RX, not TX to TX. If nothing arrives, that swap is the first thing to check. Without a common ground the UART has no shared voltage reference and you get garbage or silence, so that wire is not optional even when both boards have their own USB. ## Power Two arrangements, and the choice matters more than it looks. **Bench setup — separate USB, no 5V wire.** Both boards on their own USB cables. You get both serial monitors and can reflash either board without unplugging anything. Use this for everything up to step 5. **Model setup — one supply, 5V jumper.** USB into board A, then a fourth wire from **A's 5V pin to B's 5V pin** (labelled VIN on some boards). Ground is already joined by the wire you have. Use 5V to 5V, never 3.3V to 3.3V. Each board's onboard AMS1117 regulator makes its own 3.3V, and tying the outputs together back-feeds one regulator from the other. **Never have both USB cables plugged in while the 5V wire is connected.** That ties two host supplies together through your jumper. Some devkits have a Schottky diode on VBUS that prevents it, plenty do not, and you cannot tell by looking. Pull the 5V jumper before plugging in a USB cable to reflash. **Current budget.** An ESP32 idles around 80-120mA and peaks at a few hundred mA on Bluetooth transmit. Two of them off one USB 2.0 port sits right at the 500mA that port promises. It usually works, but a marginal supply shows up as random reboots that look exactly like a software fault. A 1A+ charger or power bank removes the doubt. **Diode drops.** Many boards put a diode between VBUS and the 5V pin, so board A's 5V pin sits nearer 4.7V. Through board B's own diode you are at maybe 4.4V into a regulator wanting roughly 1.1V of headroom. It works, but the margin is thin. If you are running off a power bank anyway, prefer separate leads to each board's 5V pin over chaining B off A — same wire count, no stacked drops. ## Test the power-loss case deliberately The 400ms failsafe in `receiver.ino` only fires if the receiver is *running*. If board B loses power mid-command — and on a shared supply that now happens whenever board A does — the failsafe cannot fire, and whether the motors stop is left to the hub's own behaviour on BLE disconnect. Find that out on purpose rather than by accident. Set a track running slowly, pull power from board B, and watch what the motor does. If it keeps running you want a physical switch on the hubs within arm's reach before driving this anywhere interesting. Worth doing the same test by pulling the UART wire instead — that path *does* hit the failsafe, and confirming it works takes ten seconds. ## Step by step **1. Board A — the gamepad board.** Preferences -> Additional board manager URLs, add: ``` https://raw.githubusercontent.com/ricardoquesada/esp32-arduino-lib-builder/master/bluepad32_files/package_esp32_bluepad32_index.json ``` Boards Manager -> install **esp32_bluepad32**. Tools -> Board -> pick ESP32 Dev Module from under **esp32_bluepad32**, not the plain `esp32` group. Getting that wrong is what produces `fatal error: Bluepad32.h: No such file or directory`. Flash `transmitter/transmitter.ino`. Nothing else needs installing — Bluepad32 lives inside the board package. Do not install Legoino or NimBLE on this board. **2. Pair the pad, before wiring anything.** Open Serial Monitor at 115200. Hold SHARE + PS on the controller until the light bar flashes. You want `Controller connected in slot 0`. Once it pairs reliably, comment out `BP32.forgetBluetoothKeys()` in `setup()` — it is in there to clear stale pairings, and leaving it means re-pairing on every boot. Set `DEBUG_FRAMES` to 1 temporarily and confirm frames stream past as you move the sticks. If they do, board A is finished. **3. Board B — the hub board.** Boards Manager -> the standard **esp32** package by Espressif. Library Manager -> **NimBLE-Arduino**, pinned to **1.4.x** (Legoino has not moved to the 2.x API, and 2.x gives a wall of compile errors), then **Legoino**. Flash `tools/hub_scanner/hub_scanner.ino` first. Press each hub's green button and note the addresses it reports, then paste them into `receiver.ino` as `HUB0_ADDR` and `HUB1_ADDR`. **4. Verify the port map before you trust it.** Flash `receiver/receiver.ino` with `DEBUG_MOTORS` set to 1. Every motor command logs which hub and port it lands on. Move one control at a time and check the log matches what physically moves. This is worth doing properly — a swapped hub address or a motor in the wrong port looks exactly like a software bug and will waste an afternoon. Set `DEBUG_MOTORS` back to 0 once it checks out. **5. Wire the boards together** per the diagram above, power both, and drive it. Onboard LED on board A is solid when the pad is connected. On board B it is solid when both hubs are connected. ## Controls Tank drive — every input drives exactly one motor. | Input | Function | | --- | --- | | Left stick Y | Left track (hub 0 port B) | | Right stick Y | Right track (hub 0 port A) | | D-pad up / down | Head tilt (hub 1 port A) | | D-pad left / right | Head turn (hub 1 port B) | | R2 / L2 | Body lift up / down, proportional (hub 0 port D) | | Square / Circle | Left arm up / down (hub 1 port C) | | Triangle / Cross | Right arm up / down (hub 1 port D) | | L1 held | Precision, 40% track speed | | R1 held | Full, 100% track speed | | L1 + R1 | All stop | Default track scale is 75%. Stick X axes are unused. **Everything except the tracks runs into a mechanical end stop**, and there is no position feedback, so holding a direction at a stop stalls the motor. That is what `HEAD_MAX`, `LIFT_MAX` and `ARM_MAX` are for. Lower them if an axis feels forceful, and do not hold a direction once an axis has stopped moving. ## Link protocol ASCII, newline terminated, 115200 8N1: ``` G,,,,,,,,*\n ``` * axes are Bluepad32 raw values, -512..511 * `buttons` is the 16-bit mask, `dpad` the 8-bit mask, both decimal * `l2`/`r2` are the analog triggers, 0..1023 * `XX` is a two-digit hex XOR checksum of everything before the `*` Plain text means you can watch the link with any USB-serial adapter when something misbehaves. The receiver drops any frame that fails the checksum, and stops all motors if nothing valid arrives for 400ms. ## Things that bite * **Nothing arrives at board B.** TX/RX swapped, or no common ground. Both are silent failures. * **Random reboots under load.** Supply, not software. See the current budget above. * **One hub connects, the other does not.** Legoino shares a single NimBLE scanner. `receiver.ino` connects them strictly one at a time for this reason — do not "optimise" that into two parallel `init()` calls. * **Motors stutter or a hub drops out.** Commands are outrunning the hub. Raise `MOTOR_MIN_GAP_MS` (per port) or `HUB_MIN_GAP_MS` (per hub). Hub 1 carries four motors, which is why the per-hub limit exists at all. * **Wrong motor command.** Technic/Control+ motors want `setTachoMotorSpeed`; train and simple PU motors want `setBasicMotorSpeed`. Toggle `USE_TACHO_MOTORS`. * **Button masks.** The values in `receiver.ino` are Bluepad32's standard layout. If a face button does the wrong thing, set `DEBUG_BUTTONS` in the transmitter, press each one, and correct the constants. * **More than 3 hubs later on.** Edit `CONFIG_BT_NIMBLE_MAX_CONNECTIONS` in `NimBLE-Arduino/src/nimconfig.h`, then restart the IDE to force a rebuild. --- Created by: Jess Rogerson (yelling commands at Claude.AI)