Porting a module from Arduino

Porting arduino libraries to libmraa as UPM libraries is usually fairly easy. The issues typically come from misunderstanding of how a non real time OS deals with interupts and timers. It also highly depends on the sensor. A concrete example is explained in detail on Making a UPM module for MAX31855

Adding a new module to UPM

1. Choose a name for your module (see Naming a module)
2. Make a new folder in src/modulename
3. Create a CMakeLists.txt file inside src/modulename

CmakeLists.txt

By default you need a header called modulename.h and a C++ file called modulename.cxx. You can have multiple headers and source files. Only public headers need to be added to module_h and all source files need to be in module_src.

set (libname "modulename")
set (libdescription "Module Description")
set (module_src ${libname}.cxx)
set (module_h ${libname}.h)
upm_module_init()

Making your API

The easiest way to do this is to have a look at a similar sensor to yours. Typically create a class for your sensor with a constructor that defines the pins it is on. This constructor will create the mraa_*_context structs that are required to talk to the board's IO. An I2c sensor will create a mraa_i2c_context, keep it as a private member and require a bus number and slave address in it's constructor.

Typically in sensors a simple object->read() function is prefered, depending on your sensor/actuaotr this may or may not be easy or not even make sense. Most UPM apis have a simple set of functions.

Mapping arduino API to libmraa

Your constructor is similar to the setup() function in arduino, you should initialise your IO the way you want it. This means initialising contexts (private members) and setting the correct modes for them.

See the mraa API documentation for exact API.

Building

To build your module just follow Building UPM. By creating a folder and the CMakelists.txt file you have done all that is required to add your sensor to the UPM build system.

Sending your module to us for inclusion in UPM

The last step is when you're happy with your module and it works send us a pull request! We'd love to include your sensor in our repository.

If you don't like github you can also send brend.nosp@m.an.l.nosp@m.e.fol.nosp@m.l@in.nosp@m.tel.c.nosp@m.om a git formatted patch if your sensor. More details are on Contributing a module and on https://help.github.com/articles/creating-a-pull-request