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Flashing Firmware Before Testing

Every setup needs to put the device into a known state prior to testing. Usually this means flashing firmware to your device under test. To do this, we will use HIL Extras to send the file to the gateway and then use a PyTest fixture to actually flash the firmware as a setup step to all testing.

Adding the Firmware as an Extra

To start, modify your .embedops/hil/config.yml file to include your firmware as an extra:

hil_extras:
    - path/to/firmware.hex
      external_module: false

If your project uses multiple HEX files, simply add another extra.

Setting Up a Flash Fixture

Next, create a file <hil_root>/conftest.py with the following contents (if you already have a conftest.py, add these lines):

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# Run flash fixture once, prior to the testing session
@pytest.fixture(autouse=True, scope="session")
def flash_fixture(hil_extras_get_path):

    jlink_interface = JLinkInterface(HIL_TARGET_DEVICE)
    flash_commands = [
        'r', 
        f'loadfile {hil_extras_get_path("path/to/firmware.hex")}', 
        'exit'
    ]

    assert jlink_interface.run_commands(flash_commands)
    assert jlink_interface.reset_and_go()

This is a basic fixture that uses a J-Link to perform the flashing. We use the hil_extras_get_path fixture to get the actual path to the firmware file, and then the JLinkInterface from the HIL SDK to perform the flashing. You only need to populate HIL_TARGET_DEVICE with your target device name. The list of supported devices can be found on Segger's website. This string must be for a specific device and not a family (e.g., nRF52840_xxAA).

Because of the decorator @pytest.fixture(autouse=True, scope="session"), the fixture will run automatically at the session level, which means it will run only once, because there is only a single session event per test run.