checkByte error on correct byte values

[VaderMester]

I'm using this lib in my Homebridge plugin. I'm getting checkbyte errors. Below byteToPass value is the byte my function is passing to i2c, I write it out in console to see if I'm doing something wrong.

[4/2/2020, 10:27:13 AM] [Pi Thermostat] Initializing Thermostat accessory...
byteToPass: 254
[4/2/2020, 10:27:13 AM] Error: Invalid byte 254
    at checkByte (/home/pi/shared/homebridge-pi-thermostat_Zone1-master/node_modules/i2c-bus/i2c-bus.js:105:11)
    at Bus.writeByte (/home/pi/shared/homebridge-pi-thermostat_Zone1-master/node_modules/i2c-bus/i2c-bus.js:406:5)

As you can see the Byte I'm passing is correct. It first got the error with a value 255, and tried it with 254. No idea what can be the issue. Init of the bus is done like this: this.i2c1 = i2c.openSync(1); //open /dev/i2c-1 Function call:

MCP23017.prototype._send = function (cmd, values) {
    this.i2c1.writeByte(this.address, cmd, values, function (err) {
      if (err) {
        console.error(err);
      }
    });
  };

[fivdi]

Is the value being passed to writeByte an unsigned integer?

In other words, does Number.isInteger(values) return true?

If not, that would explain the problem.

[VaderMester]

Yep, you were right. It is strange, because all of my variables are declared in hex, like

var REGISTER_GPIOA = 0x00,
  REGISTER_GPIOB = 0x01,
  REGISTER_GPIOA_PULLUP = 0x0C,
  REGISTER_GPIOB_PULLUP = 0x0D,
  READ_GPIOA_ADDR = 0x12,
  READ_GPIOB_ADDR = 0x13,
  WRITE_GPIOA_ADDR = 0x14,
  WRITE_GPIOB_ADDR = 0x15;

Putting this into my calling functions brute-force solved the issue :)

. . var reg = (cmd & 0xff); var data = (values & 0xff); i2c1.writeByte(this.address, reg, data, function (err) { . .

[fivdi]

Thank you for providing the feedback and good to hear that it's working now.