# device serial communication

## Function

After opening the serial port through `device.open({type: 'serial', ...})`, you can call `read()`, `read_bytes()`, `read_text()`, `write(data)`, `flush()` and `close()`.

## Syntax

```bt
port = device.open({
    type: 'serial',
    port: 'COM3',
    baud_rate: 9600,
    data_bits: 8,
    stop_bits: 1,
    parity: 'none',
    timeout: 1000
})

port.write(bytes('010300000002c40b', 'hex'))
data = port.read_bytes()
port.flush()
port.close()
```

## Parameters

| Field | Type | Required | Default value | Description |
|------|------|------|------|------|
| type | String | No | serial | Device type, currently only serial is supported. |
| port | String | Yes | None | Serial port name. |
| baud_rate | Int | No | 9600 | Baud rate. |
| data_bits | Int | No | 8 | Data bits. |
| stop_bits | Int | No | 1 | Stop bits. |
| parity | String | No | none | Parity digit. |
| timeout | Int | No | 1000 | Read and write timeout in milliseconds. |

## Return value

| Type | Description |
|------|------|
| Device | Returns the serial port device handle. |

## Example

```bt
port = device.open({type: 'serial', port: 'COM3'})
result = type(port)

// Output: Device
print result
```

## Notes

-Configuration fields use snake_case uniformly.
- read() returns a legal UTF-8 string; non-UTF-8 data returns a byte array.
- read_bytes() always returns Bytes, suitable for binary protocols such as Modbus RTU.
- read_text() strictly converts strings according to UTF-8, and returns null if UTF-8 is illegal.
- write(data) can write a string, byte array, or Bytes.