> ## 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.

# GPO

> Set GPIO output level

Set the digital output level of GPIO pins, with an optional hold mode that keeps the output asserted until interrupted.

## Syntax

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

## Arguments

| Argument  | Description                                                                            |
| --------- | -------------------------------------------------------------------------------------- |
| `NETNAME` | GPIO net name (optional if default is set). If omitted, lists all available GPIO nets. |
| `LEVEL`   | Output level (see below)                                                               |

## Level Values

The following values are accepted (case-insensitive):

| Value             | Result               |
| ----------------- | -------------------- |
| `high`, `on`, `1` | Set pin high         |
| `low`, `off`, `0` | Set pin low          |
| `toggle`          | Invert current state |

## Options

| Option      | Description                                          |
| ----------- | ---------------------------------------------------- |
| `--box BOX` | Lagerbox name or IP address                          |
| `--hold`    | Hold output state (keeps process alive until Ctrl+C) |

***

## Usage

```bash theme={null}
# Set pin high
lager gpo LED1 high --box my-lager-box

# Set pin low
lager gpo LED1 low

# Toggle pin state
lager gpo LED1 toggle

# Using numeric values
lager gpo LED1 1
lager gpo LED1 0

# List available GPIO nets (omit net name and level)
lager gpo --box my-lager-box
```

### Hold Mode

The `--hold` flag keeps the process alive after setting the output level. The pin state is maintained until you press Ctrl+C. This is useful when you need to assert a signal for manual testing or when the pin state would otherwise be reset between CLI invocations.

```bash theme={null}
# Hold reset line low until manually released
lager gpo RESET_N low --hold --box my-lager-box
# Press Ctrl+C to release

# Hold enable pin high during manual testing
lager gpo EN high --hold
# Press Ctrl+C when done
```

***

## Supported Hardware

| Device      | Pins                                | Voltage     |
| ----------- | ----------------------------------- | ----------- |
| LabJack T7  | FIO0-FIO7                           | 3.3V logic  |
| MCC USB-202 | DIO0-DIO7 (0-7)                     | 3.3V/5V TTL |
| Aardvark    | 0-5 (SCL, SDA, MISO, SCK, MOSI, SS) | 3.3V        |
| FT232H      | 0-15 (AD0-AD7, AC0-AC7)             | 3.3V        |

<Note>
  Aardvark and FT232H GPIO support is currently disabled and may be re-enabled in a future release. LabJack T7 and MCC USB-202 are the active GPIO backends.
</Note>

### Aardvark Pin Mapping

The Aardvark I2C/SPI adapter exposes 6 GPIO pins on its 10-pin header. Pins can be specified by number or signal name:

| Pin | Name | Header Pin |
| --- | ---- | ---------- |
| 0   | SCL  | 1          |
| 1   | SDA  | 3          |
| 2   | MISO | 5          |
| 3   | SCK  | 7          |
| 4   | MOSI | 8          |
| 5   | SS   | 9          |

### FT232H Pin Mapping

The FT232H provides 16 GPIO pins across two ports:

| Pins | Names   | Description         |
| ---- | ------- | ------------------- |
| 0-7  | AD0-AD7 | Port A data pins    |
| 8-15 | AC0-AC7 | Port A control pins |

***

## Examples

```bash theme={null}
# Control an LED
lager gpo LED1 on --box lab-gw
sleep 1
lager gpo LED1 off --box lab-gw

# Toggle reset line
lager gpo RESET_N low
sleep 0.1
lager gpo RESET_N high

# Blink pattern
for i in {1..5}; do
    lager gpo LED1 toggle
    sleep 0.5
done

# Hold a signal during manual testing
lager gpo BOOT0 high --hold --box lab-gw
# Ctrl+C to release, then flash firmware

# Assert chip select for manual SPI debugging
lager gpo CS_N low --hold --box lab-gw
```

***

## Related Commands

* [`lager gpi`](/source/reference/cli/gpi) - Read GPIO input state

***

## Notes

* GPO is for setting output pins only
* Use `lager gpi` to read input pins
* Default net can be set with `lager defaults add --gpio-net`
* Pin must be configured as output in net configuration
* Toggle reads current state and inverts it
* USB-202 channels can be specified as `0`-`7` or `DIO0`-`DIO7`
* `--hold` keeps the process running; press Ctrl+C to release the pin and exit
* Without `--hold`, the output level is set and the command exits immediately; the pin retains its state until the next command