Some bits are not being send via serial

[Rafael-Dagostim]

SerialPort Version

9.2.7

Node Version

16.3.0

Electron Version

No response

Platform

Windows

Architecture

x64

Hardware or chipset of serialport

FTDI

What steps will reproduce the bug?

I'm testing the modbus protocol manually using the serial port, I'm writing on multiple coils (FC15 on modbus protocol), that's the test code I'm using:

//CRC generator for modbus
function crc16(buffer) {
  var crc = 0xFFFF;
  var odd;

  for (var i = 0; i < buffer.length; i++) {
    crc = crc ^ buffer[i];

    for (var j = 0; j < 8; j++) {
      odd = crc & 0x0001;
      crc = crc >> 1;
      if (odd) {
        crc = crc ^ 0xA001;
      }
    }
  }

  return crc;
}

const SerialPort = require('serialport')
const port = new SerialPort('COM3', {
  baudRate: 38400,
  dataBits: 8,
  stopBits: 1,
  parity: 'none'
})

var data = [10, 15, 0, 0, 0, 11, 2, 255, 7] // The data to send via modbus

var buffer = new Buffer.alloc(11);
for (let i = 0; i < data.length; i++){
  buffer[i] = data[i];
}

buffer.writeUInt16LE(crc16(buffer.slice(0, -2)), 9); // Create and insert the CRC into the buffer

port.write(buffer); // Send the buffer to FTDI

What happens?

All the time I write that on controller using the FTDI, there are some bits that do not appear on the data. Apparently those bits that disappear are always from the end of a byte (like this 255 on the 8th position of Buffer, always miss the last bit when I read)

What should have happened?

On the read of those datas I've send, It should came a value of 255 (11111111) instead of 254 (11111110). To check the modbus coil data I'm using the program CAS Modbus Scanner. On the code test I'ven send, the coil starting on 0 to 9 (10 first bit address) should be with value 1, but note on print the 8th address of first byte is 0.

Additional information

I've opened an issue on the modbus library I'm using, thinking the problem was there, but after creating manually the modbus structure and sending via pure serialPort I noted this problem happens to.

Edit: I forgot to say the data being read are only the last two values of Buffer before the CRC (in this case there are 255 and 7), all the rest of Buffer are infomation needed for the protocol (slave id, command id, etc tec...)