> ## 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.

# Interacting With Nets

> Control your instruments through the Lager Client using CLI or Lager Python

Nets act as named interfaces to your instruments. Once your Nets are configured, you can begin controlling those instruments using the Lager Client — via the CLI or Python SDK.

The examples below demonstrate how to issue commands to common instrument types such as power supplies, battery simulators, debuggers, and communication buses.

***

## Setting Defaults

Before diving into examples, you can set default values for `--box` and common nets to avoid repeating them on every command:

```bash theme={null}
# Set a default box so you don't need --box on every command
lager defaults add --box my-lager-box

# Set default nets for common instrument types
lager defaults add --supply-net POWER
lager defaults add --debug-net DEBUG_NET
lager defaults add --i2c-net I2C_0
```

With defaults set, you can run commands more concisely (e.g., `lager supply voltage 3.3` instead of `lager supply POWER voltage 3.3 --box my-lager-box`). See the [defaults reference](/source/reference/cli/defaults) for all options.

***

## CLI Examples

### Supply Nets

Power supply Nets can be controlled using the `lager supply` command.

Set voltage and protection thresholds (note: this does **not** enable output):

```bash theme={null}
lager supply POWER voltage 5 --ovp 5.1 --ocp 0.5 --box my-lager-box
```

<Note>
  **OVP** (Over-Voltage Protection) and **OCP** (Over-Current Protection) are safety thresholds. If the output voltage or current exceeds these limits, the supply automatically shuts off to protect your device. You can clear a tripped fault with `lager supply POWER clear-ovp` or `clear-ocp`.
</Note>

Enable the output:

```bash theme={null}
lager supply POWER enable --box my-lager-box
```

Disable the output:

```bash theme={null}
lager supply POWER disable --box my-lager-box
```

***

### Battery Nets

Some programmable power supplies support battery simulation. These can be controlled using the `lager battery` command.

Set the simulated battery's state of charge (SOC):

```bash theme={null}
lager battery BATT soc 50 --box my-lager-box
```

<Note>
  **SOC** (State of Charge) represents the battery's charge level as a percentage (0-100%). Setting SOC to 50 simulates a half-charged battery, which is useful for testing how your device behaves at different battery levels.
</Note>

Set max charge and discharge current:

```bash theme={null}
lager battery BATT current-limit 1.0 --box my-lager-box
```

***

### Debug Nets

Debugger nets (e.g. J-Link) can be used to flash firmware, erase memory, and inspect devices.

Flash a hex file to your device:

```bash theme={null}
lager debug DEBUG_NET flash --hex firmware.hex --box my-lager-box
```

Where `DEBUG_NET` is the name of your debug net. You can also use a default debug net if configured.

***

### I2C and SPI Nets

For communicating with peripheral devices over I2C or SPI buses:

```bash theme={null}
# Scan the I2C bus for connected devices
lager i2c I2C_0 scan --box my-lager-box

# Read 2 bytes from register 0x00 on device at address 0x76
lager i2c I2C_0 transfer 2 --address 0x76 --data 0x00 --box my-lager-box

# Read a SPI device ID (send 0x9F command, read 3 response bytes)
lager spi SPI_0 transfer --data 0x9f 4 --box my-lager-box
```

***

## Programmatic Control with Python

For more complex automation or integration into test frameworks, you can use the Lager Python SDK to perform the same operations programmatically.

The following example shows how to write a Python script using the Net API:

1. **Create a Python script.** Save the following code to a file named `flash.py`:

   ```python theme={null}
   from lager import Net, NetType

   # Get a debug net by name
   dbg = Net.get('DEBUG_NET', type=NetType.Debug)

   # Reset and flash the firmware
   dbg.reset(halt=True)
   dbg.flash('path/to/firmware.hex')

   print("Firmware flashing complete.")
   ```

2. **Execute the script with Lager.** Use the `lager python` command to run the script in the Lager Box environment, ensuring it has access to the connected hardware.

   ```bash theme={null}
   lager python flash.py --box my-lager-box
   ```

> For detailed Python API documentation, see the [Python Reference](/source/reference/python/overview) section.

For a more comprehensive example combining power supply control, firmware flashing, ADC measurement, and safe cleanup, see the [demo script](https://github.com/lagerdata/lager/blob/main/docs/examples/demo_script.py).

***

## Next Steps

You've completed the Getting Started guide. Here's where to go from here:

* **[Your First Test](/source/getting-started/first-test)** -- Walk through a complete end-to-end test workflow
* **[CLI Reference](/source/reference/cli/overview)** -- Full documentation for all CLI commands
* **[Python API](/source/reference/python/overview)** -- Automate tests with the Python SDK
* **[Defaults Reference](/source/reference/cli/defaults)** -- Reduce typing by setting default box and net values
* **[Troubleshooting](/source/getting-started/troubleshooting)** -- Solutions for common issues