Your First Test

A complete walkthrough of testing a device with Lager

This guide walks you through a complete test workflow — from verifying connectivity to running an automated Python script. By the end, you’ll have used the CLI interactively and written your first Lager test script.

This tutorial assumes you have completed the Getting Started guide: the CLI is installed, your box is added, and your instruments are configured with nets.

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Part 1: CLI Walkthrough

Let’s step through a typical test flow using individual CLI commands. This is useful for ad-hoc testing, debugging, and getting familiar with your setup.

Step 1: Verify your box is online

lager hello --box my-lager-box

Expected output:

my-lager-box says hello!

Step 2: Check connected instruments

lager instruments --box my-lager-box

This shows all instruments the box can see. Confirm your power supply, debug probe, and any other instruments appear.

Step 3: View your configured nets

lager nets --box my-lager-box

This shows the named nets you’ll use in subsequent commands. Note the net names — you’ll need them below.

Step 4: Set defaults to reduce typing

lager defaults add --box my-lager-box
lager defaults add --supply-net POWER
lager defaults add --debug-net DEBUG_NET

With defaults set, you can omit --box and net names from subsequent commands.

Step 5: Flash firmware

lager debug flash --hex firmware.hex

Expected output:

Flashing firmware.hex to target...
Flash complete. 32768 bytes written.

Step 6: Power on your device

# Set voltage with protection thresholds
lager supply voltage 3.3 --ovp 3.6 --ocp 0.5 --yes

# Enable the output
lager supply enable --yes

Step 7: Take a measurement

lager adc SENSOR_1

Expected output:

ADC 'SENSOR_1': 2.450000 V

Step 8: Power down

lager supply disable --yes

Always disable power supplies when you’re done testing.

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Part 2: Your First Python Script

Now let’s convert the manual CLI steps into a repeatable Python script. The key advantage of a script is that it always cleans up after itself (disabling power) even if an error occurs.

Create a file called my_first_test.py:

from lager import Net, NetType

def main():
    # Get our nets
    psu = Net.get('POWER', type=NetType.PowerSupply)
    debug = Net.get('DEBUG_NET', type=NetType.Debug)
    sensor = Net.get('SENSOR_1', type=NetType.ADC)

    try:
        # Flash firmware
        print("Flashing firmware...")
        debug.connect()
        debug.flash(['firmware.hex'])
        debug.reset()
        print("Flash complete.")

        # Power on the DUT
        print("Enabling power supply at 3.3V...")
        psu.set_voltage(3.3)
        psu.set_current(0.5)
        psu.enable()
        print("Power enabled.")

        # Take a measurement
        voltage = sensor.input()
        print(f"Sensor reading: {voltage:.4f} V")

        # Check the result
        if 2.0 <= voltage <= 3.0:
            print("PASS: Sensor voltage within expected range.")
        else:
            print(f"FAIL: Sensor voltage {voltage:.4f}V outside range [2.0, 3.0]")

    finally:
        # Always clean up, even if an error occurs
        print("Disabling power supply...")
        psu.disable()
        print("Done.")

if __name__ == '__main__':
    main()

The try/finally block ensures the power supply is always disabled, even if the script encounters an error. This is important for protecting your hardware.

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Part 3: Running It

Execute the script on your Lager Box:

lager python my_first_test.py --box my-lager-box

Expected output:

Flashing firmware...
Flash complete.
Enabling power supply at 3.3V...
Power enabled.
Sensor reading: 2.4500 V
PASS: Sensor voltage within expected range.
Disabling power supply...
Done.

If you need to send additional files along with your script (firmware binaries, config files), use --add-file:

lager python my_first_test.py --box my-lager-box --add-file firmware.hex

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What’s Next

You’ve completed your first test with Lager. Here are some directions to explore:

• CLI Reference — Full documentation for every CLI command
• Python API — Complete Python SDK reference
• Troubleshooting — Solutions when things go wrong
• Glossary — Definitions for technical terms used in the docs

For a more comprehensive automation example combining robot arm control, USB hub power cycling, debug probe flashing, and ADC measurement, see the demo script.