ant-plus/src/cadence-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 CadenceSensorState {
	constructor(deviceID: number) {
		this.DeviceID = deviceID;
	}

	DeviceID: number;
	CadenceEventTime: number;
	CumulativeCadenceRevolutionCount: number;
	CalculatedCadence: 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 CadenceScanState extends CadenceSensorState {
	Rssi: number;
	Threshold: number;
}

export class CadenceSensor extends AntPlusSensor {
	static deviceType = 0x7A;

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

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

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

	private state: CadenceSensorState;

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

export class CadenceScanner extends AntPlusScanner {
	protected deviceType() {
		return CadenceSensor.deviceType;
	}

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

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

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

	protected createStateIfNew(deviceId) {
		if (!this.states[deviceId]) {
			this.states[deviceId] = new CadenceScanState(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: CadenceSensor | CadenceScanner, state: CadenceSensorState | CadenceScanState, 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 oldCadenceTime = state.CadenceEventTime;
	const oldCadenceCount = state.CumulativeCadenceRevolutionCount;

	let cadenceTime = data.readUInt16LE(Messages.BUFFER_INDEX_MSG_DATA + 4);
	let cadenceCount = data.readUInt16LE(Messages.BUFFER_INDEX_MSG_DATA + 6);

	if (cadenceTime !== oldCadenceTime) {
		state.CadenceEventTime = cadenceTime;
		state.CumulativeCadenceRevolutionCount = cadenceCount;

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

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

		const cadence = ((60 * (cadenceCount - oldCadenceCount) * 1024) / (cadenceTime - oldCadenceTime));
		if (!isNaN(cadence)) {
			state.CalculatedCadence = cadence;
			sensor.emit('cadenceData', state);
		}
	}
}