Parameter Service

This module provides functionality to load and update application parameters in a centralized and thread safe way.

The parameters are organized in a namespace tree hierarchy. There are different types of parameters:

• Boolean
• Scalar (float32)
• Integer (int32)
• String
• Vector (constant length array of float32)
• Matrix (constant size 2D array of float32)

An efficient polling API is provided to check for parameter changes.

Configuration Files

Parameters can be loaded from JSON and MessagePack config files. Parameter namespaces are represented by a dictionary of parameters and sub-namespaces. For JSON files comments are allowed using # to start a comment. This makes the config file syntax a subset of YAML.

Example

// create a root-namespace
static parameter_namespace_t root_ns;
parameter_namespace_delcare(&root_ns, NULL, NULL);

// ... somewhere in the control loop initialization code
static parameter_namespace_t pid_ns;
parameter_namespace_delcare(&pid_ns, &root_ns, "pid");
static parameter_t param_kp;
static parameter_t param_ki;
static parameter_t param_kd;
parameter_scalar_declare(&parm_kp, &pid_ns, "kp");
parameter_scalar_declare(&parm_ki, &pid_ns, "ki");
parameter_scalar_declare(&parm_kd, &pid_ns, "kd");

// ... in the control loop:
if (parameter_namespace_contains_changed(&pid_ns)) {
    if (parameter_changed(&param_kp)) {
        pid_set_kp(&pid, parameter_scalar_get(&param_kp));
    }
    if (parameter_changed(&param_ki)) {
        pid_set_ki(&pid, parameter_scalar_get(&param_ki));
    }
    if (parameter_changed(&param_kd)) {
        pid_set_kd(&pid, parameter_scalar_get(&param_kd));
    }
}
ctrl = pid_control(&pid, error);

A config file for this example would look like this: (the syntax is JSON with comments using #, this makes it YAML compatible)

{
    "pid": # pid controller gains
    {
        "kp": 1.4,
        "ki": 0.1,
        "kd": 0
    }
}