boost-movehub/src/messages/PortOutput.js

Connects with your Lego Boost Movehub vie Bluetooth Low Energy (BLE).

const DeviceMessage = require("./DeviceMessage");
const { encodeFlags, toHexString } = require("../helpers");

/**
 * Downstream message to make peripherals do something.
 *
 * As defined in https://lego.github.io/lego-ble-wireless-protocol-docs/index.html#port-output-command
 */
class PortOutput extends DeviceMessage {
  get isWriteDirectModeData() {
    return this.data[5] === PortOutput.SUB_CMD_WRITE_DIRECT_MODE_DATA;
  }

  get subCommand() {
    return this.data[6];
  }

  toString() {
    const encoding = this.isWriteDirectencodingData
      ? "WriteModeDirectData"
      : "WriteMode";
    const cmd = toHexString(this.subCommand);
    return `PortOutput(encoding=${encoding}, subCommand=${cmd})`;
  }
}

/**
 * Instantiates a proper PortOutput to send to Hub encoded with writeDirectModeData
 *
 * @param {number} portId
 * @param {number[] | number} startupCompletionFlags Bitlist containing flags as defined in Startup and Completion Information or array of flags to set (Available flags: `PortOutput.SC_FLAGS`)
 * @param {number} subCommand
 * @param {number[]} payload Bytes of data to send
 * @returns {PortOutput}
 */
PortOutput.buildWriteDirectModeData = function buildWriteDirectModeData(
  portId,
  startupCompletionFlags,
  subCommand,
  payload
) {
  const length = 7 + payload.length;

  return new PortOutput(
    Buffer.from([
      length,
      0x00,
      PortOutput.TYPE,
      portId,
      encodeFlags(startupCompletionFlags),
      PortOutput.SUB_CMD_WRITE_DIRECT_MODE_DATA,
      subCommand,
      ...payload
    ])
  );
};

/**
 * Instantiates a proper PortOutput to send to Hub
 *
 * @param {number} portId
 * @param {number[] | number} startupCompletionFlags Bitlist containing flags as defined in Startup and Completion Information or array of flags to set (Available flags: `PortOutput.SC_FLAGS`)
 * @param {number} subCommand
 * @param {number[]} payload Bytes of data to send
 * @returns {PortOutput}
 */
PortOutput.build = function build(
  portId,
  startupCompletionFlags,
  subCommand,
  payload
) {
  const length = 6 + payload.length;

  return new PortOutput(
    Buffer.from([
      length,
      0x00,
      PortOutput.TYPE,
      portId,
      encodeFlags(startupCompletionFlags),
      subCommand,
      ...payload
    ])
  );
};

PortOutput.TYPE = 0x81;

PortOutput.SUB_CMD_WRITE_DIRECT = 0x50;
PortOutput.SUB_CMD_WRITE_DIRECT_MODE_DATA = 0x51;

// https://lego.github.io/lego-ble-wireless-protocol-docs/index.html#startup-and-completion-information
PortOutput.SC_FLAGS = {
  NONE: 0b00000000,
  EXECUTE_IMMEDIATE: 0b00010000,
  COMMAND_FEEDBACK: 0b00000001
};

module.exports = PortOutput;