How to read directly from Serial1? (baby steps into CASIC)

here's my variation of your code. Attempted to print out the checksum in Hex as it makes it
easier to manually check. I'm concerned about the negative checksum - this should not happen.

//cs1=0,cs2=0,cs3=0,cs4=0,

var h1=0,h2=0, l1=0,l2=0,
    protocolType="Unknown",
    casicPos=-1, payloadPos=0,
    inCasicMessage=false, casicIsCompleted=false;

var cs1 = new Uint32Array(1);
var cs2 = new Uint32Array(1);
var cs3 = new Uint32Array(1);
var cs4 = new Uint32Array(1);

cs1[0] = 0;
cs2[0] = 0;
cs3[0] = 0;
cs4[0] = 0;

var casicMsg={};

function parseCASIC(data){
  for(var i=0;i<data.length;i++){
    c=data.charCodeAt(i);
    //print("i:",i,"c:",c, "casicPos:",casicPos,"payloadPos:",payloadPos);
    if(c==0xBA && casicPos<0){
      h1=c;
      protocolType="CASIC";
      inCasicMessage=true;
      casicIsCompleted=false;
      casicPos=0; payloadPos=0;
      h2=0; l1=0; l2=0; cs1[0]=0;cs2[0]=0;cs3[0]=0;cs4[0]=0;
      casicMsg={};
    }
    else if(!inCasicMessage) return;
    // header byte 2
    else if(c==0xCE && casicPos==0){
      h2=c;
      casicPos++;
      casicMsg.hdr = (h1<<8) + h2;
      casicMsg.hdr = '0x' + (casicMsg.hdr).toString(16).toUpperCase();
    }
    // length byte1
    else if(inCasicMessage && casicPos==1){
      l1=c;
      casicPos++;
    }
    // length byte2
    else if(inCasicMessage && casicPos==2){
      l2=c;
      casicPos++;
      casicMsg.len = (l2<<8) + l1;
      //casicMsg.len = '0x' + casicMsg.len.toString(16).toUpperCase();
    }
    // class 
    else if(inCasicMessage && casicPos==3){
      casicMsg.class = c;
      casicPos++;
    }
    // msg id
    else if(inCasicMessage && casicPos==4){
      casicMsg.msgId = c;
      casicMsg.payload=[];
      payloadPos=0;
      casicPos++;
    }
    // accumulate payload
    else if(inCasicMessage && casicPos>4 && payloadPos<casicMsg.len){
      casicMsg.payload.push(c);
      payloadPos++;
      casicPos++;
    }
    // checksum bytes cs1, cs2, cs3, cs4
    else if(inCasicMessage && casicPos==casicMsg.len+5){
      cs1[0] = c;
      casicPos++;
    }
    else if(inCasicMessage && casicPos==casicMsg.len+6){
      cs2[0] = c;
      casicPos++;
    }
    else if(inCasicMessage && casicPos==casicMsg.len+7){
      cs3[0] = c;
      casicPos++;
    }
    else if(inCasicMessage && casicPos==casicMsg.len+8){
      cs4[0] = c;
      casicMsg.checkSum = ((cs1[0]<<24)+(cs2[0]<<16)+(cs3[0]<<8)+cs4[0]);
      casicMsg.checkSum16 = '0x' + casicMsg.checkSum.toString(16).toUpperCase();
      inCasicMessage = false;
      casicIsCompleted = true;
      casicPos = -1;
      protocolType="Unknown";
      print(casicMsg);
    }
  }//for
}

function setup() {
  print("setup()");
  D29.write(0);
  Serial2.removeAllListeners();
  Serial2.setup(9600,{rx:D30,tx:D31});
  Serial2.on('data', function(data){parseCASIC(data);});
}

function pon() {
  print("power on");
  setup();
  D29.write(1);
}


function pof() {
  print("power off");
  D29.write(0);
}

function prt() {
  Serial2.write([0xBA,0xCE, 0x00,0x00, 0x06,0x00, 0x00,0x00,0x06,0x00]);
}

Here's the output

>prt();
=undefined
{
  "hdr": "0xBACE",
  "len": 8, "class": 6, "msgId": 0,
  "payload": [ 1, 7, 192, 8, 0, 194, 1, 0 ],
  "checkSum": 164218632,
  "checkSum16": "0x9C9C708"
 }
{
  "hdr": "0xBACE",
  "len": 8, "class": 6, "msgId": 0,
  "payload": [ 0, 119, 192, 8, 128, 37, 0, 0 ],
  "checkSum": -2002991608,
  "checkSum16": "0x-776339F8"
 }
{
  "hdr": "0xBACE",
  "len": 4, "class": 5, "msgId": 1,
  "payload": [ 6, 0, 0, 0 ],
  "checkSum": 167773441,
  "checkSum16": "0xA000501"
 }
>pof();
power off
=undefined