> ## Documentation Index
> Fetch the complete documentation index at: https://docs.lagerdata.com/llms.txt
> Use this file to discover all available pages before exploring further.

# UART

> Connect to UART serial ports

Connect to UART serial ports on Lagerboxes for serial communication with devices.

## Syntax

```bash theme={null}
lager uart [NETNAME] [OPTIONS]
```

## Arguments

| Argument  | Description                                |
| --------- | ------------------------------------------ |
| `NETNAME` | UART net name (optional if default is set) |

## Options

| Option                       | Description                             |
| ---------------------------- | --------------------------------------- |
| `--box BOX`                  | Lagerbox name or IP address             |
| `--baudrate RATE`            | Baudrate (e.g., 9600, 115200)           |
| `--bytesize SIZE`            | Data bits (5, 6, 7, 8)                  |
| `--parity MODE`              | Parity: none, even, odd, mark, space    |
| `--stopbits BITS`            | Stop bits (1, 1.5, 2)                   |
| `--xonxoff` / `--no-xonxoff` | Software flow control                   |
| `--rtscts` / `--no-rtscts`   | Hardware flow control (RTS/CTS)         |
| `--dsrdtr` / `--no-dsrdtr`   | Hardware flow control (DSR/DTR)         |
| `-i` / `--interactive`       | Enable input mode for typing            |
| `--opost` / `--no-opost`     | Convert \n to \r\n on output            |
| `--line-ending MODE`         | Line ending: lf, crlf, cr (default: lf) |

***

## Usage

### Read-Only Mode (Default)

```bash theme={null}
# Monitor serial output
lager uart SERIAL1 --box my-lager-box

# With specific baudrate
lager uart SERIAL1 --baudrate 115200
```

### Interactive Mode

```bash theme={null}
# Type commands and see responses
lager uart SERIAL1 --interactive

# With specific settings
lager uart SERIAL1 -i --baudrate 9600 --parity none
```

### Get Serial Port Info

```bash theme={null}
# Show device path for a UART net
lager uart SERIAL1 serial-port
```

***

## Serial Configuration

### Baudrate

Common baudrates:

* 9600 (default for many devices)
* 19200
* 38400
* 57600
* 115200 (common for embedded development)
* 230400
* 460800
* 921600

### Data Format

| Setting  | Options                      | Default |
| -------- | ---------------------------- | ------- |
| Bytesize | 5, 6, 7, 8                   | 8       |
| Parity   | none, even, odd, mark, space | none    |
| Stopbits | 1, 1.5, 2                    | 1       |

### Flow Control

| Type     | Options     | Description         |
| -------- | ----------- | ------------------- |
| Software | `--xonxoff` | XON/XOFF characters |
| Hardware | `--rtscts`  | RTS/CTS pins        |
| Hardware | `--dsrdtr`  | DSR/DTR pins        |

Flow control types cannot be combined.

***

## Line Endings

| Mode   | Sequence | Use Case       |
| ------ | -------- | -------------- |
| `lf`   | \n       | Unix/Linux     |
| `crlf` | \r\n     | Windows        |
| `cr`   | \r       | Legacy systems |

Use `--opost` to automatically convert line endings on output.

***

## Supported USB Serial Adapters

The following USB-to-serial adapters are automatically detected and supported:

| Adapter               | VID:PID   | Description                 |
| --------------------- | --------- | --------------------------- |
| Prolific USB-Serial   | 067b:23a3 | Common USB-Serial adapter   |
| Silicon Labs CP210x   | 10c4:ea60 | Popular embedded dev boards |
| FTDI FT232R           | 0403:6001 | Single-channel USB-Serial   |
| FTDI FT4232H          | 0403:6011 | Quad-channel USB-Serial     |
| ESP32 USB JTAG/Serial | 303a:1001 | Built-in ESP32-S3/C3 USB    |

These adapters are automatically recognized by `lager instruments` and can be configured as UART nets.

***

## Device Path Support

UART nets can reference devices two ways:

**USB Serial Number** (preferred):

```
Net configured with USB serial number
Automatically resolves to correct /dev/ttyUSBx
```

**Direct Device Path** (fallback):

```bash theme={null}
# When adapter has no serial number
lager uart /dev/ttyUSB0 --baudrate 115200
```

***

## Examples

```bash theme={null}
# Basic serial monitor
lager uart DEBUG_UART --box lab-gw

# Interactive shell with common embedded settings
lager uart CONSOLE -i --baudrate 115200

# Legacy device with specific format
lager uart LEGACY --baudrate 9600 --bytesize 7 --parity even --stopbits 2

# With software flow control
lager uart MODEM --xonxoff

# Windows-style line endings
lager uart TERMINAL --line-ending crlf --opost
```

***

## WebSocket Connection

The UART command uses WebSocket for communication:

* Provides real-time bidirectional data
* Supports both read-only and interactive modes
* Automatically reconnects on connection loss

***

## Troubleshooting

### Device Not Found

```bash theme={null}
# List available instruments to find UART devices
lager instruments --box my-lager-box

# Check if USB serial adapter is connected
ssh lagerdata@my-lager-box 'ls -la /dev/ttyUSB*'
```

### Permission Denied

```bash theme={null}
# Ensure udev rules are installed
lager update --box my-lager-box --yes
```

### No Output

* Check baudrate matches device
* Verify TX/RX connections
* Try interactive mode to test input
* Check flow control settings

***

## Notes

* Interactive mode requires a TTY terminal
* USB serial numbers are truncated for display
* Default net can be set with `lager defaults add --uart-net`
* Connection retry logic handles temporary disconnections

## See Also

* [Python UART API](/source/reference/python/uart) -- Access UART nets from Python scripts
* [Python Serial API](/source/reference/python/serial) -- Native pyserial support for advanced serial use cases