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example-linear-sensor-characterization.md

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LinearSensorCharacterization

Purpose

LinearSensorCharacterization is an application example that performs online linear calibration of one ADC reading against a reference value received through generated packets.

It is intended to validate:

  • ADC acquisition on PA0
  • Ethernet runtime loop
  • generated OrderPackets reception
  • generated DataPackets transmission
  • incremental linear regression (slope and offset estimation)

JSON_ADE dependency

This example depends on a different packet schema than ExamplePackets.

It is not compatible with the current TEST packet schema active in this branch.

The required JSON_ADE branch for this example is:

  • linear-sensor-char

It expects a legacy characterization-oriented JSON_ADE branch or board definition that generates the specific packet/order API used by this source.

That means:

  • simply enabling EXAMPLE_LINEAR_SENSOR_CHARACTERIZATION is not enough
  • the active Core/Inc/Code_generation/JSON_ADE contents must match this example
  • the selected BOARD_NAME must generate the legacy characterization symbols

At the moment, ExamplePackets and LinearSensorCharacterization are effectively tied to different JSON_ADE worlds.

Switching the JSON_ADE branch/schema to make this example build can break ExamplePackets, and vice versa.

Current status in this branch

This example is currently not directly buildable with the active BOARD_NAME=TEST packet schema.

Reason:

  • the source expects generated symbols such as OrderPackets::characterize_init
  • the current TEST JSON schema does not generate those symbols
  • building this example with BOARD_NAME=TEST fails at compile time

The failure is expected until a matching board schema is restored or the example is migrated to the new TEST packet definitions.

What it needs to build

This example requires a board JSON definition that generates at least:

  • OrderPackets::characterize_init
  • OrderPackets::characterize_flag
  • DataPackets::characterization_init
  • DataPackets::Value_init
  • DataPackets::packets_socket
  • DataPackets::characterization_packet

In practice, this means you need the legacy characterization schema checked out in JSON_ADE, then a full reconfigure/rebuild so the generated packet headers are replaced.

Typical sequence once that schema is restored:

cmake --preset nucleo-debug-eth -DBUILD_EXAMPLES=ON -DCMAKE_CXX_FLAGS='-DEXAMPLE_LINEAR_SENSOR_CHARACTERIZATION'
cmake --build --preset nucleo-debug-eth

Intended runtime behavior

When backed by a matching packet schema, the example should:

  • read the raw ADC value from PA0
  • receive a reference real_value through a generated order
  • update slope and offset with incremental OLS
  • compute value = slope * sensor_value + offset
  • publish the updated characterization packet over Ethernet

Recommended next step

Pick one of these approaches before using this example again:

  • restore the original board JSON that defined characterize, characterization, and Value
  • or migrate LinearSensorCharacterization.cpp to the new TEST packet names

Validation once restored

After the packet schema matches again, validate it by:

  • sending known reference values
  • checking that slope and offset converge correctly
  • verifying the emitted data packets track the fitted line