webHID syntax for USB-Relay-2

Question

I bought one of the really inexpensive USB relay boards from china with two relays. I am trying to switch the relays on and off from Chrome Javascript using webHID.

Found this sample code https://blink1.thingm.com/ and modified it for this relay hardware. I made good progess I found the data strings that would turn both relays On and Off
see code below. This code works for the all on and all off cases.

But I am stuck without away to control each Relay separately. I am pretty sure 0xFD and 0xFF are part of the data set needed and assume I need to give the relay number as well. I have tried a lot of different combinations with no luck.

Anyone have an idea?

    document.getElementById('start-button').addEventListener('click', handleConnectClick);

    async function handleConnectClick() {
        let device = await openDevice();
        let allOn = [0xFE, 0, 0, 0, 0, 0, 0, 0];
        await setRelay(device, allOn);
        alert(allOn);
        let allOff = [0xFC, 0, 0, 0, 0, 0, 0, 0];
        await setRelay(device, allOff);
        alert(allOff);
    }

    async function openDevice() {
        const vendorId = 5824; // 16C0
        const productId = 1503; // 05DF
        const device_list = await navigator.hid.getDevices();
        console.log(device_list)
        let device = device_list.find(d => d.vendorId === vendorId && d.productId === productId);
        if (!device) {
            // this returns an array now
            let devices = await navigator.hid.requestDevice({
                filters: [{vendorId, productId}],
            });
            console.log("devices:", devices);
            device = devices[0];
            if (!device)
                return null;
        }

        if (!device.opened) {
            await device.open();
        }
        console.log("device opened:", device);
        return device;
    }

    async function setRelay(device, [a, b, c, d, e, f, g, h]) {
        if (!device)
            return;
        const reportId = 0;
        const data = Uint8Array.from([a, b, c, d, e, f, g, h]);
        try {
            await device.sendFeatureReport(reportId, data);
        } catch (error) {
            console.error('set_Relay: failed:', error);
    }
    }

Answer 1

Well I fiugred it out when I found this post Can webusb connect a website to a Kmtronic Usb one relay device in a ChromeOs chromebox?. The USB data doesn't need all eight elements. It only works for single relay when it has 3 elements.

let oneOn = [0xFF, 0x01, 0x01];
let oneOff= [0xFD, 0x01, 0x01];
let twoOn = [0xFF, 0x02, 0x02];
let twoOff= [0xFD, 0x02, 0x02];

Kinda strange the all eight elements version worked for the all Relay USB sentence.