Developers Guide

Developer Guide

layout: default title: Contributing to Smoothieware —

Contributing

Contributing

The Smoothieware project is always looking for help.

Whatever your skills are, there are things you can do to improve the project with other volunteers.

Help and working together is what has made this project so advanced and precious over the years, and is very welcome.

We appreciate all contributions, whether it's code, documentation, bug reports, or helping other users in the community!

Getting Started

Here is a list of the useful resources you want to read if you want to contribute to the project:

Ways to Contribute

Code Contributions

If you can code, there are always features to implement and bugs to fix.

Check the Todo list for current priorities.

Documentation

Help improve this documentation by fixing errors, adding examples, or writing new guides.

See Editing the Wiki for instructions.

Community Support

Answer questions on IRC, the forum, or mailing lists.

Helping other users is a valuable contribution!

Testing

Test new features on different hardware configurations and report your findings.

Beta testing helps catch issues before releases.

Contact

If you want to contribute but aren’t sure how, please contact us.

We’ll help you find something that matches your skills and interests!

This page contains information you need to know when coding for Smoothie.

It covers the configuration system, coding standards, and how to submit contributions to the project.

How to submit a pull request to the Smoothieware Github project

See the Github page for detailed instructions on submitting pull requests.

Config system and checksums

When to read configuration

When coding a Smoothie module, you probably want the user to be able to configure it.

In Smoothie, configuration is stored in a configuration file, which is read at startup time (when your module is being loaded).

If you want your config values to be read only upon module loading, read your config values from the on_module_loaded callback of your module: example.

Checksums

Consider a setting that looks like this in our config file:

maximum_death_star_hourly_power_consumption    100000000000

In our code, if we want to read it, we’ll do something like this:

void MyModule::on_config_loaded(void* argument){
	// Config does not actually work like that, this is just a hypothetical example to explain, Don't do it like this.
	this->maximum_power = this->kernel->config->value("maximum_death_star_hourly_power_consumption")->as_number();
}

To save flash storage space, we use Checksums: we don’t store the actual string, but a checksum of that string.

We can compare the checksums of the configuration lines in the config file and still know if they correspond to our string.

An online tool to compute checksums when needed can be found here.

The actual code for the checksum calculation is in src/libs/utils.cpp:

uint16_t get_checksum(string to_check){
   // From: http://en.wikipedia.org/wiki/Fletcher%27s_checksum
   uint16_t sum1 = 0;
   uint16_t sum2 = 0;
   for( int index = 0; index < to_check.length(); ++index ){
      sum1 = (sum1 + to_check[index]) % 255;
      sum2 = (sum2 + sum1) % 255;
   }
   return (sum2 << 8) | sum1;
}

Now our code will look like this:

#define maximum_death_star_hourly_power_consumption_checksum CHECKSUM("maximum_death_star_hourly_power_consumption") 

void MyModule::on_config_loaded(void* argument){
	// Config works more like this
	this->maximum_power = this->kernel->config->value(maximum_death_star_hourly_power_consumption_checksum)->as_number();
}

Config value types

There are different types of config values you can retrieve from the config file.

They are all strings, but there are convenience methods that allow you to convert them into other types.

ConfigValue object

This is not very useful. It’s what you get when you do:

	this->kernel->config->value(whatever_checksum);

You get an object of type ConfigValue.

It stores the string (if the config option was found in the file) and has all kinds of convenience methods.

String

If your value is a string, you can access it using the as_string() method:

	this->whatever_option = this->kernel->config->value(whatever_checksum)->as_string();

Note: if you provided a default string, and the option is not found in the config file, that default will be returned. See below.

Number

Converts your string to a double:

	double trouble = this->kernel->config->value(whatever_checksum)->as_number();

Note: if you provided a default number, and the option is not found in the config file, that default will be returned. See below.

Boolean

This is convenient for stuff like:

void Laser::on_module_loaded() {
    if( !this->kernel->config->value( laser_module_enable_checksum )->by_default(false)->as_bool() ){ return; }

This prevents the module from being loaded if the laser_module_enable config option is not present (defaults to false) or set to false explicitly.

“true” and “1” are valid true values, anything else is false.

Pin

Pin objects represent a pin configuration.

They store the port number, the pin number, whether the pin is inverted, and other stuff. See: Pin.h.

They are generated from the result of as_string() (making default values as strings possible).

	this->step_pin = this->kernel->config->value(extruder_step_pin_checksum)->by_default("1.22")->as_pin()->as_output();

Defaults

You can set a default value in case that option is not specified in the config file using the by_default() method, which can take either a string or a double.

Doubles are used as defaults only by the as_number() and as_bool() methods.

	this->acceleration = this->kernel->config->value(acceleration_checksum)->by_default(1)->as_number();
	this->step_pin = this->kernel->config->value(extruder_step_pin_checksum)->by_default("1.22")->as_pin()->as_output();

If you want Smoothie to die if no config value is set in the config file, you can also use ->required(), but that’s mean.