Jake Read
LTV 1200 Display

Repository

let packet = new Uint8Array(255)
let pi = 0	// packet indice (where inside of, during parse)
let pl = 0 	// packet length (expected len)
let ip = false // in packet (delineation state)

parser.on('data', (data) => {
    // read if
    if(ip){
        if(pi == 0){
            // length byte
            pl = data[0]
        }
        // store all bytes, increment ptr
        packet[pi] = data[0]
        pi ++
        if(pi > pl + 1){
            onPacket(packet)    // pass, then ptr swap to new... shouldn't leak back
            packet = new Uint8Array(255)
            pi = 0
            pl = 0
            ip = false
        }
    }
    // start byte / 0xFA
    if(data[0] == 250 && !ip){
        ip = true
        pi = 0
    }
})
// switch on the packet type:
switch(pck[1]){
    case 1:
        //realtime data
        //[2] uint8 insp state (table of 18 states)
        //[3,4] int16 prox pres (-5 to 120)
        //[5,6] int16 xdcr flow (-200 to 200)
        //[7,8] int16 volume (1ml res) (0 to 3000)
        let data = {
            inspState: TS.read('uint8', pck, 2),
            proxPres: TS.read('int16', pck, 3),
            xdcrFlow: TS.read('int16', pck, 5),
            volume: TS.read('int16', pck, 7)
        }
        // seems like this works, I guess timestamp these things now and keep them around locally...
        // then run a server, client should req. the local store ?
        store.push([indice, data.inspState, data.proxPres, data.xdcrFlow, data.volume])
        indice ++
        // occasionally lop off 1000 entries, so as not to explode local memory
        if(store.length > 3000){
            console.log("rollover")
            store = store.slice(-2000)
        }
        //console.log(data)
        break;
    default:
        //not plotting others currently
        break;
}
TS.read = (type, buffer, start) => {
    switch(type){
        case 'uint8':
            return buffer[start]
        case 'uint16':
            return (buffer[start] & 255 | buffer[start + 1] << 8)
        case 'int16':
            return new Int16Array(buffer.slice(start, start + 2).buffer)[0]
        case 'uint32':
            return (buffer[start] | buffer[start + 1] << 8 | buffer[start + 2] << 16 | buffer[start + 3] << 3)
        default:
            console.log("bad type to read")
            break;
    }
}