vent.js

const TS = require('./ts.js')
const SerialPort = require('serialport')
const ByteLength = require('@serialport/parser-byte-length')
const port = new SerialPort('/dev/ttyAMA0', {
    baudRate: 60096
})

port.on('open', () => {
    console.log('open')
})

port.on('error', (err) => {
    console.log(err)
})

const parser = port.pipe(new ByteLength({length: 1}))

// ok, packets are like:
/*
start (uint8) | length (uint8) | packet type (uint8) | data (len - 1) | crc (uint8) |
start byte is always 0xFA
*/

let packet = new Uint8Array(255)
let pi = 0
let pl = 0 
let ip = false // in packet 

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
    }
})

let onPacket = (pck) => {
    // now this looks like 
    // [0] length 
    // [1] packet type 
    // [...] data bytes 
    // [n] crc byte 
    //console.log("packet", pck)
    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 ? 
            console.log(data)
            break;
        default:
            //not plotting others currently 
            break;
    }
}