How to carry out functions in a sequential manner

Is the ack something you receive serially / over RX from the module?

If so, use serial.onData(callback) with callback function receiving the ack and triggering the next command...

For use in application logic, this is of course a bit cumbersome... Therefore, you may use a FIFO with some triggering methods inbetween your app and the display which takes care of feeding the display module with the comands in a timely correct manner/sequence, where as the application just pushes to the FIFO without having to be time aware.

The FIFO is of course a buffer and could over-grow if you have a run-away in your application.

Some code 'in the rough':

var dsp =
{ cmds: [] // fifo
, idling: false
, serial: null
, exec: function(cmd) { // cmd to send to display
    this.cmds.push(cmd);
    if (this.idling) { 
      this.idling = false;
      this._tx();
    }
  }
, _tx: function() {
    this.serial.write(this.cmds.splice(0,1))­;
  }
, _rx: function(data) {
    if (this.cmds.length > 0) { 
      this._tx(); 
    } else { 
      this.idling = true;
    }
  }
, connect: funcrtion(serial) {
    this.serial = serial;
    this._rx.bind(this);
    this.serial.on('data',this._rx);
    this.idling = true;
    this.exec(""); // may be some initializations...
  }
}

Serial1.setup(9600); // setup Serial1
dsp.connect(Serial1);
dsp.exec("....."); // 1st cmd
dsp.exec("....."); // 2nd cmd
dsp.exec("....."); // 3rd cmd

This code has no error handling (over flow, out of synch, etc.) in place. For examples:

• .exec() needs overflow handling (some reasonable limit to the fifo size check)
  - ._rx() needs check ack data received and accdingly acted on
  - some state / timout has to be put in place in case communication gets 'out of sync'
  
  A first enhancement is to leave the command in the fifo (using this.serial.write(this.cmds[0]);) until 'good' ack is received and then removed (this.cmds.splice(0,1);). If 'bad' acc is received (or timout hits), re-send/re-print or drop - with or without error logging - has to be considered.
  
  The .connect() is currently minimal. You may extend it with additional parameter(s) - string (or array of strings) that include some display module initialization that has to be done anyway.
  
  Can you share the code how you got your display initially working?