mangavalk
3d879ad803
Comments in Config.h and the README referred to LEGACY/, which is folded into the generation folders. Also 'from the repo root' -> 'from the 2026-current folder'. Comment and documentation changes only; approved by the owner.
151 lines
7.6 KiB
Markdown
151 lines
7.6 KiB
Markdown
# Hexapod robot firmware (Teensy 3.6)
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This is the **robot-side** firmware. It is fully functional on its own
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(driven by the serial test harness below) and receives commands from the
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remote (`../remote/`) over nRF24L01. The packet format lives in
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`../shared/HexapodProtocol/HexapodProtocol.h` — the single definition both
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sketches compile against.
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## Building
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From the `2026-current` folder (PlatformIO): `pio run -e robot`, flash with
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`pio run -e robot -t upload`, monitor with `pio device monitor -e robot`.
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RF24 is pulled in automatically via `lib_deps`. Servos are driven by the
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Teensy's hardware PWM directly, so no servo library is needed.
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Arduino IDE also works if you copy `shared/HexapodProtocol/` into your
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sketchbook `libraries/` folder and install **RF24** by TMRh20.
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## Before you trust this on the floor
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The leg geometry in `Config.h` is taken from the Unity model
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(`Hexapod_Simulation_Unity`, 1 unit = 10 mm). Everything else there is
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still a placeholder. Check all of it against the real robot:
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- `LEG_MOUNT_ANGLE_DEG` / `LEG_MOUNT_X_MM` / `LEG_MOUNT_Y_MM` — where each
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coxa pivot actually sits on your chassis, and which way it points
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- `COXA_LEN_MM` / `FEMUR_LEN_MM` / `TIBIA_LEN_MM` — your link lengths
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- `COXA_MIN_DEG..TIBIA_MAX_DEG` — your servos' real safe range of motion
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- `STANCE_RADIUS_MM` / `STANCE_HEIGHT_MM` — how far out/down you want the
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resting foot position
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- `LEG_CLEARANCE_MM`: how close neighbouring legs may get. Walking speed
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and body pose are scaled down to keep it, so set it to about one leg's
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width.
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- `SERVOS`: one entry per servo with pin, pulse at 0°, signed µs per
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degree (sign = direction) and pulse limits. It's prefilled from the old
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robot sketch (`../../2019-teensy-nrf24/Hexapod_Teensy/config.h`): pins, ranges, trims, and
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directions from the old Unity servo mapping. Check every joint's
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direction on the bench.
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- **Before powering up:** re-mount the rear-left and front-left coxa servo
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horns 90° so those legs point straight out at servo center. The old code
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needed ±90° offsets there, which left the servos at the end of their
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travel.
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- `RADIO_CE_PIN` / `RADIO_CSN_PIN` / `RADIO_SCK_PIN`: 39 / 15 / 14, as in
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the old sketch. Address, channel, data rate, PA level and payload size
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are in `shared/HexapodProtocol` so they can't drift from the remote.
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## Bench-check checklist (do this before the first stand-up)
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These are sign conventions that depend on which way your hardware is
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physically mounted, and the code has a best-guess default that may be wrong
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for your build:
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1. **IK knee direction** (`Kinematics.cpp`). The femur elevation sign bug
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(the foot was solved *above* the hip) is fixed and verified in the
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simulation: the stance pose comes out femur −1.2°, tibia −98.3°. Still
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command one leg to a few known foot positions on the bench and check the
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knee bends the way the sim shows.
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2. **BodyPose roll/pitch sign** (`BodyPose.cpp`). Fixed in the simulation:
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the pose was applied as the forward rotation, which inverted roll, pitch
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and yaw. On the bench, command a small roll/pitch and verify the body
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leans the way the protocol says (+roll = right side down, +pitch = nose
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down).
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3. **RobotIMU register map** (`RobotIMU.cpp`) — written for an MPU6050-style
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chip (I2C addr `0x68`). If your gyro is a different part, its register
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addresses and scale factors will differ; swap them in.
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4. **Sit-pose assumption** — the built-in sit pose in `robot.ino` assumes all
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six feet stay grounded and simply lowers the body (a 0.4x height blend).
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If your chassis is meant to rest its belly on the ground instead, this
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needs a different, sequenced approach (fold legs up rather than just
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lowering).
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5. **Gait travel direction** (`GaitEngine.cpp`). Fixed: stance now sweeps
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each foot opposite to the commanded motion. The smoke test checks that
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`+vx` moves the body forward and `+yaw_rate` turns it left (CCW). On
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the bench, confirm `w` walks forward and `z` turns left.
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6. **Per-servo calibration** (`Config.h` `SERVOS`). Arm the robot,
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stand it on a box, and move one joint at a time (or watch the sim next
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to it): each servo must turn the way the sim shows. To flip a direction,
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flip that entry's `dir`. Also check that a femur moves the commanded
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angle: its old range gives only ≈6.7 µs/° against ≈10.4 for coxa and
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tibia.
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## Testing in the simulation
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This exact code also compiles for the PC and runs in the Unity model. See
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`../sim/README.md`. `sim/build/sim_smoke.exe` is a quick headless check
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after every change.
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## Testing without a remote yet
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`robot.ino` has `#define TEST_SERIAL_INPUT` enabled by default. With that on,
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open the Arduino Serial Monitor (115200 baud, no line ending needed — single
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keystrokes) and use:
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| Key | Action |
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|-----|--------|
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| `a` | toggle armed |
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| `s` | toggle sit / stand |
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| `w` / `x` | walk forward / backward (`vx` ±) |
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| `q` / `e` | strafe left / right (`vy` ±) |
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| `z` / `c` | turn left / right (`yaw_rate` ±) |
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| `g` | toggle gait: tripod ↔ wave |
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| `m` | toggle walk mode: direct (A) ↔ heading-hold (B) |
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| space | zero all velocity (stop walking, stay in current state) |
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Each keystroke injects a `CmdPacket` through `Comms::injectPacket()` — the
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exact same path a real remote's received radio packets go through, so the
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rest of the pipeline (mapper → state machine → gait → pose → IK → servos)
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runs identically to how it will with real hardware. Once you have a real
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remote transmitting, just remove the `#define TEST_SERIAL_INPUT` line (or
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leave it — injected packets simply won't happen if you don't type).
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Arm (`a`), then stand (`s`), before trying to walk — the state machine
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enforces `DISARMED → SIT → STAND → WALKING` in order and will otherwise
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ignore walk commands.
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## Link with the remote
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- `CmdPacket` and the `FLAG_*` bits in `shared/HexapodProtocol` are the
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exact wire format. Both radios set a static payload size of
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`sizeof(CmdPacket)`, so a robot and remote built from different protocol
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versions won't receive each other at all (and the robot fails safe).
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- Failsafe: if no packet arrives for `LINK_TIMEOUT_SEC`, `Comms::linkOk()`
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goes false and the main loop falls back to a zeroed `CmdPacket`, which
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disarms the robot.
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- The right stick's roll/pitch/yaw (or X/Y/Z) always apply. The remote's
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handset tilt arrives in its own `remote_roll` / `remote_pitch` fields and
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is added on top only while `FLAG_REMOTE_GYRO` is set, capped at
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`MAX_TILT_DEG` total (`InputMapper`). `FLAG_ROBOT_GYRO` independently
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enables the robot's own IMU stabilization.
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- `FLAG_RSTICK_XLATE` switches the right stick between rotation-axes and
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translation-axes interpretation, and `FLAG_MODE_B` switches between the
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two walk modes, all inside the existing `InputMapper`.
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## File layout
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```
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robot/
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├── robot.ino - main sketch: setup/loop, state wiring, serial test harness
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├── Config.h - all placeholder constants (edit this first)
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├── SmoothedValue.h - generic rate-limited setpoint smoother
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├── Kinematics.h/.cpp - per-leg 3-DOF analytical IK
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├── GaitEngine.h/.cpp - tripod/wave gait, per-leg phase, dynamic gait swap
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├── BodyPose.h/.cpp - 6-axis body pose composition (feedforward + IMU correction)
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├── RobotIMU.h/.cpp - gyro/accel read + complementary filter
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├── StateMachine.h/.cpp - DISARMED/SIT/STAND/WALKING with smoothed sit-stand blend
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├── InputMapper.h/.cpp - CmdPacket -> twist/pose/mode decoding
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├── Limits.h/.cpp - workspace clamp, joint rate limit, stance polygon check
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├── Comms.h/.cpp - nRF24L01 receive (packet definition is in shared/HexapodProtocol)
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└── ServoDriver.h/.cpp - servo attach/relax/write
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```
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