ant-plus/src/speed-sensors.ts

A node module for ANT+

/*
 * ANT+ profile: https://www.thisisant.com/developer/ant-plus/device-profiles/#523_tab
 * Spec sheet: https://www.thisisant.com/resources/bicycle-speed-and-cadence/
 */

import { AntPlusSensor, AntPlusScanner, Messages } from './ant';

class SpeedSensorState {
	constructor(deviceID: number) {
		this.DeviceID = deviceID;
	}

	DeviceID: number;
	SpeedEventTime: number;
	CumulativeSpeedRevolutionCount: number;
	CalculatedDistance: number;
	CalculatedSpeed: number;

	OperatingTime?: number;
	ManId?: number;
	SerialNumber?: number;
	HwVersion?: number;
	SwVersion?: number;
	ModelNum?: number;
	BatteryVoltage?: number;
	BatteryStatus?: 'New' | 'Good' | 'Ok' | 'Low' | 'Critical' | 'Invalid';
	Motion?: boolean;
}

class SpeedScanState extends SpeedSensorState {
	Rssi: number;
	Threshold: number;
}

export class SpeedSensor extends AntPlusSensor {

	static deviceType = 0x7B;

	wheelCircumference: number = 2.199; // default 70cm wheel

	public setWheelCircumference(wheelCircumference: number) {
		this.wheelCircumference = wheelCircumference;
	}

	public attach(channel, deviceID): void {
		super.attach(channel, 'receive', deviceID, SpeedSensor.deviceType, 0, 255, 8086);
		this.state = new SpeedSensorState(deviceID);
	}

	private state: SpeedSensorState;

	protected updateState(deviceId, data) {
		this.state.DeviceID = deviceId;
		updateState(this, this.state, data);
	}
}

export class SpeedScanner extends AntPlusScanner {
	protected deviceType() {
		return SpeedSensor.deviceType;
	}

	wheelCircumference: number = 2.199; // default 70cm wheel

	public setWheelCircumference(wheelCircumference: number) {
		this.wheelCircumference = wheelCircumference;
	}

	private states: { [id: number]: SpeedScanState } = {};

	protected createStateIfNew(deviceId) {
		if (!this.states[deviceId]) {
			this.states[deviceId] = new SpeedScanState(deviceId);
		}
	}

	protected updateRssiAndThreshold(deviceId, rssi, threshold) {
		this.states[deviceId].Rssi = rssi;
		this.states[deviceId].Threshold = threshold;
	}

	protected updateState(deviceId, data) {
		updateState(this, this.states[deviceId], data);
	}
}

const TOGGLE_MASK = 0x80;

function updateState(sensor: SpeedSensor | SpeedScanner, state: SpeedSensorState | SpeedScanState, data: Buffer) {
	const pageNum = data.readUInt8(Messages.BUFFER_INDEX_MSG_DATA);
	switch (pageNum & ~TOGGLE_MASK) { //check the new pages and remove the toggle bit
		case 1:
			//decode the cumulative operating time
			state.OperatingTime = data.readUInt8(Messages.BUFFER_INDEX_MSG_DATA + 1);
			state.OperatingTime |= data.readUInt8(Messages.BUFFER_INDEX_MSG_DATA + 2) << 8;
			state.OperatingTime |= data.readUInt8(Messages.BUFFER_INDEX_MSG_DATA + 3) << 16;
			state.OperatingTime *= 2;
			break;
		case 2:
			//decode the Manufacturer ID
			state.ManId = data.readUInt8(Messages.BUFFER_INDEX_MSG_DATA + 1);
			//decode the 4 byte serial number
			state.SerialNumber = state.DeviceID;
			state.SerialNumber |= data.readUInt16LE(Messages.BUFFER_INDEX_MSG_DATA + 2) << 16;
			state.SerialNumber >>>= 0;
			break;
		case 3:
			//decode HW version, SW version, and model number
			state.HwVersion = data.readUInt8(Messages.BUFFER_INDEX_MSG_DATA + 1);
			state.SwVersion = data.readUInt8(Messages.BUFFER_INDEX_MSG_DATA + 2);
			state.ModelNum = data.readUInt8(Messages.BUFFER_INDEX_MSG_DATA + 3);
			break;
		case 4: {
			const batteryFrac = data.readUInt8(Messages.BUFFER_INDEX_MSG_DATA + 2);
			const batteryStatus = data.readUInt8(Messages.BUFFER_INDEX_MSG_DATA + 3);
			state.BatteryVoltage = (batteryStatus & 0x0F) + (batteryFrac / 256);
			const batteryFlags = (batteryStatus & 0x70) >>> 4;
			switch (batteryFlags) {
				case 1:
					state.BatteryStatus = 'New';
					break;
				case 2:
					state.BatteryStatus = 'Good';
					break;
				case 3:
					state.BatteryStatus = 'Ok';
					break;
				case 4:
					state.BatteryStatus = 'Low';
					break;
				case 5:
					state.BatteryStatus = 'Critical';
					break;
				default:
					state.BatteryVoltage = undefined;
					state.BatteryStatus = 'Invalid';
					break;
			}
			break;
		}
		case 5:
			state.Motion = (data.readUInt8(Messages.BUFFER_INDEX_MSG_DATA + 1) & 0x01) === 0x01;
			break;
		default:
			break;
	}

	//get old state for calculating cumulative values
	const oldSpeedTime = state.SpeedEventTime;
	const oldSpeedCount = state.CumulativeSpeedRevolutionCount;

	let speedEventTime = data.readUInt16LE(Messages.BUFFER_INDEX_MSG_DATA + 4);
	let speedRevolutionCount = data.readUInt16LE(Messages.BUFFER_INDEX_MSG_DATA + 6);

	if (speedEventTime !== oldSpeedTime) {
		state.SpeedEventTime = speedEventTime;
		state.CumulativeSpeedRevolutionCount = speedRevolutionCount;

		if (oldSpeedTime > speedEventTime) { //Hit rollover value
			speedEventTime += (1024 * 64);
		}

		if (oldSpeedCount > speedRevolutionCount) { //Hit rollover value
			speedRevolutionCount += (1024 * 64);
		}

		const distance = sensor.wheelCircumference * (speedRevolutionCount - oldSpeedCount);
		state.CalculatedDistance = distance;

		//speed in m/sec
		const speed = (distance * 1024) / (speedEventTime - oldSpeedTime);
		if (!isNaN(speed)) {
			state.CalculatedSpeed = speed;
			sensor.emit('speedData', state);
		}
	}
}