# serial.write

## Function

Write data to the opened serial port. Supports String, byte arrays and Bytes.

## Syntax

```bt
device.open(config).write(data)
```

## Parameters

| Parameters | Type | Required | Default value | Description |
| ------ | ------ | ------ | ------ | ------ |
| data | String/Array/Bytes | Yes | None | String is written as UTF-8; Array elements must be 0 to 255; Bytes writes raw bytes directly. |

## Return value

| Type | Description |
| ------ | ------ |
| Int | Returns the number of bytes written. |

## Example

```bt
port = device.open({type: 'serial', port: 'COM3'})
result = port.write(bytes('010300000002c40b', 'hex'))

// Output: 8
print result
```

## Notes

- An error will be reported when illegal bytes appear in the array.
- No string conversion is done when writing Bytes.