LeRobot RC

Serve LeRobot supported SO-ARM 101 servo driver board over WebSocket server with nice looking GUI integrated on M5Stack Cardputer mini screen. Supported board & device:

• M5Stack Cardputer
• M5StickC Plus2

Server

The WebSocket server will start listening on port 81 by default. Servo commands can be issued through WebSocket messages over ws://<device-ip>:81.

API

The server accepts both the legacy flat JSON payload and a typed message. Typed messages are recommended for new clients.

Event index:

• servo:move - Command a servo to move to an absolute or relative position.
• servo:move:ack - Acknowledges a servo:move command with applied values.
• telemetry:servos - Periodic full-state telemetry for all servos.
• servos:torque:enable - Enable torque for all servos.
• servos:torque:disable - Disable torque for all servos.
• servos:torque:enable:ack - Ack for enabling torque on all servos.
• servos:torque:disable:ack - Ack for disabling torque on all servos.
• servo:torque:enable - Enable torque for one servo.
• servo:torque:disable - Disable torque for one servo.
• servo:torque:enable:ack - Ack for enabling torque on one servo.
• servo:torque:disable:ack - Ack for disabling torque on one servo.
• servo:read - Read a servo register by address/length.
• servo:read:ack - Ack for reading a servo register.
• servo:write - Write a servo register by address/length.
• servo:write:ack - Ack for writing a servo register.
• servo:eprom:unlock - Unlock EEPROM for a servo.
• servo:eprom:unlock:ack - Ack for EEPROM unlock.
• servo:eprom:lock - Lock EEPROM for a servo.
• servo:eprom:lock:ack - Ack for EEPROM lock.
• error - Error response for typed messages.

servo:move (typed)

Send a command to move a servo. clamp is optional and limits the allowed range for this command only.

{
  "type": "servo:move",
  "data": {
    "id": 1,
    "pos": 1000,
    "delta": 0,
    "speed": 1500,
    "clamp": { "min": 0, "max": 4095 }
  }
}

Ack:

{
  "type": "servo:move:ack",
  "data": {
    "id": 1,
    "pos": 1000,
    "speed": 1500,
    "requested": 1200,
    "clamped": true,
    "clamp": { "min": 0, "max": 1000 }
  }
}

Notes:

• pos or delta can be used; if pos is omitted, delta is applied to the current servo position.
• requested, clamped, and clamp appear only when clamping is used and the requested value differs from the applied value.

telemetry:servos (stream)

Emitted periodically with full servo telemetry.

Note

You can implement force feedback on the client by using load and/or current as a proxy for resistance. For example, compare the latest load or current to a threshold and slow down or stop user motion when it rises, or scale the input by (1 - load/load_max) to soften motion under higher load.

{
  "type": "telemetry:servos",
  "data": {
    "ts": 123456,
    "joints": [
      {
        "id": 1,
        "pos": 960,
        "speed": 0,
        "load": 12,
        "current": 45,
        "move": 0,
        "voltage": 74,
        "temp": 32
      }
    ]
  }
}

Torque control (typed)

Enable or disable torque for all servos:

{
  "type": "servos:torque:enable"
}

{
  "type": "servos:torque:disable"
}

Ack:

{
  "type": "servos:torque:enable:ack",
  "data": {
    "ids": [1, 2, 3, 4, 5, 6],
    "enabled": true,
    "ok": true
  }
}

Enable or disable torque for a specific servo:

{
  "type": "servo:torque:disable",
  "data": { "id": 1 }
}

Ack:

{
  "type": "servo:torque:disable:ack",
  "data": {
    "id": 1,
    "enabled": false,
    "ok": true
  }
}

Servo registers (typed)

Read a register (1 or 2 bytes):

{
  "type": "servo:read",
  "data": { "id": 1, "addr": 31, "len": 2 }
}

Ack:

{
  "type": "servo:read:ack",
  "data": { "id": 1, "addr": 31, "len": 2, "value": 123 }
}

Write a register (1 or 2 bytes):

{
  "type": "servo:write",
  "data": { "id": 1, "addr": 31, "len": 2, "value": 123 }
}

Ack:

{
  "type": "servo:write:ack",
  "data": { "id": 1, "addr": 31, "len": 2, "value": 123, "ok": true }
}

Unlock/lock EEPROM for register writes:

{ "type": "servo:eprom:unlock", "data": { "id": 1 } }

{ "type": "servo:eprom:lock", "data": { "id": 1 } }

Ack:

{
  "type": "servo:eprom:unlock:ack",
  "data": { "id": 1, "locked": false, "ok": true }
}

Mock server (Rust)

The Rust mock server listens on port 81 and accepts the same WebSocket payloads.

cargo run --bin mock-server

Use ws://localhost:81 for local testing.