Calibration

This page explains how to integrate the calibration results generated by the dashboard into the Embedded project and what happens internally once the new calibration sources are added to the firmware.

Overview

The dashboard generates a set of C++ source files that contain updated polynomial coefficients, steering offset values, spline data points, and speed/steer correction tables. These files replace the previous calibration implementation inside the Embedded_Platform project.

During firmware build, the embedded code automatically incorporates the new calibration parameters and uses them at runtime for:

  • Translating steering commands into corrected wheel angles

  • Adjusting motor speed using the updated polynomial mapping

  • Applying the zero-offset correction obtained during calibration

  • Improving trajectory accuracy using the newly generated splines

No manual editing of the source code is required — only copying the generated source folder into the correct location.

Internal behavior

The generated archive contains a source folder with two files:

  • speedingmotor.cpp

  • steeringmotor.cpp

These files already exist in the Embedded_Platform project. When you copy the new versions over the existing ones, the firmware behavior is updated as follows.

Calibration flags and limits

Both files define a common calibration configuration:

#define calibrated      0
#define calib_sup_limit 500
#define calib_inf_limit -500

In the default Embedded_Platform sources:

  • calibrated is set to 0 (calibration disabled)

  • calib_sup_limit and calib_inf_limit use generic default bounds

In the generated files:

  • calibrated is set to 1 to enable the calibrated behavior

  • calib_sup_limit and calib_inf_limit are updated with the limits computed during the calibration process

These limits are used to clamp the output of the control logic to safe ranges.

Polynomial-based control

Both speedingmotor.cpp and steeringmotor.cpp implement a computePWMPolynomial method. In the default sources this function only contains a placeholder:

int CSpeedingMotor::computePWMPolynomial(int speed)
{
    int64_t y = zero_default;
    // POLYNOMIAL CODE START

    // POLYNOMIAL CODE END
    return (int)y;
}

The generated files fill in this method with the polynomial expression obtained during calibration. The polynomial maps the requested speed or steering angle to a PWM value, using the calibration data captured on the track.

Runtime selection: calibrated vs. legacy behavior

The motor classes expose high-level setters such as setSpeed (for the speed motor) and setAngle (for the steering motor). Their structure is similar to:

void CSteeringMotor::setAngle(int f_angle)
{
    pwm_value = zero_default;

    if (calibrated == 1)
    {
        pwm_value = computePWMPolynomial(f_angle);
    }
    else
    {
        pwm_value = interpolate(f_angle,steeringValueP, steeringValueN, pwmValuesP, pwmValuesN, 3);
    }

    m_pwm_pin.pulsewidth_us(pwm_value);
}

  • When calibrated == 0 (default firmware), the code uses the legacy interpolation tables (interpolate(...) and pre-defined lookup arrays).

  • When calibrated == 1 (after copying the generated files), the firmware switches to the polynomial model by calling computePWMPolynomial(...).

As a result, once the new speedingmotor.cpp and steeringmotor.cpp are copied and the firmware is rebuilt and flashed, all speed and steering commands are translated using the newly calibrated polynomial models and updated limits, rather than the generic factory interpolation curves.

Steps

Step 1. Extract the archive

  1. Locate the downloaded file (e.g. calibration-source-2025-10-17T10-15-35.zip).

  2. Extract the archive to a temporary location.

  3. After extraction, you should see a folder named source.

Step 2. Copy the calibration source folder

  1. Open the extracted contents.

  2. Copy the source folder.

  3. Paste it into the Embedded_Platform directory of your Embedded project (example: <project-root>/Embedded_Platform).

  4. If asked to overwrite existing files, choose Replace.

After this step, the firmware project will contain the latest calibration sources. These files will automatically be compiled and linked during the next build.

Copying calibration source files into the Embedded_Platform project

Step 3. Build and flash

Flash the firmware to the vehicle by following the instructions in the Build & Flash Guide.

Once flashing is complete, the vehicle will run using the newly generated calibration model (steering, speed, and offset corrections).