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Jogger Developer Documentation

Writing a Custom Joystick Module

There are a few devices which could be used for jogging, but don’t fall into the analog potentiometer category, and can’t be used with the base joystick module. Some examples include:

• Encoder / MPG devices, where speed of the knob controls speed of jogging
• Joystick with digital output
• Paddle switch / buttons to jog at a fixed speed when pressed

In these cases, you will need to write a module which:

1. Manages reading your device and converting the reading into a number from -1 to 1 (or 0 to 1 if desired)
2. Responds to a public data request from the jogger with the reading

For an example on how #1 is done for analog devices, see the source code for JoystickAxis.cpp. The following examples will explain how to accomplish #2.

Including Necessary Headers

You will need to include the following in your module:

#include "JoystickPublicAccess.h"
#include "PublicDataRequest.h"
#define joystick_checksum     CHECKSUM("joystick")

This allows your code to conform to the data format the jogger will be expecting.

Responding to Public Data Requests

Your module will need to respond to a public data request from the Jogger. To do so, you must first register your module with the Kernel so it knows to call your module when a public data request is made:

void YourModule::on_module_loaded()
{
    this->register_for_event(ON_GET_PUBLIC_DATA);
}

Then, you will need to write a function which handles the data request:

void YourModule::on_get_public_data(void *argument)
{
    //cast the argument to a PublicDataRequest pointer
    PublicDataRequest *pdr = static_cast<PublicDataRequest *>(argument);
    
    //check if the request is for a joystick module, return if not
    if (!pdr->starts_with(joystick_checksum)) return;
    
    //check if the request is for this particular joystick module, return if not
    if (!pdr->second_element_is(this->name_checksum)) return;
    
    //caller has provided the location to write the state to
    struct PAD_joystick* pad = static_cast<struct PAD_joystick *>(pdr->get_data_ptr());
    pad->name_checksum = this->name_checksum;
    pad->raw = //fill in your raw device reading if appropriate
    pad->position = //fill in your scaled device reading scaled to +/- 1
    pdr->set_taken();
}

You will need to fill in a few areas of the above example for your own module. The module “name_checksum” will need to be determined at startup, see “JoystickAxisPool.cpp” for an example of how to create many different named modules.

Adding Axes

The jogger module was written to support up to 6 concurrent jog axes. By default, the module enables 3, which means if you setup a 3D joystick, you can have three axes jogging at the same time. An example jogger config is shown below:

jogger.data_source_alpha           joystickX
jogger.data_source_beta            joystickY
jogger.data_source_gamma           joystickZ
jogger.jog_axes                    XYZ

The example assumes you have properly set up three joystick modules with names “joystickX”, “joystickY” and “joystickZ”.

Then, to set the jog axes, simply run M777 followed by three letters of the axes you want the joystick to control.

For up to 6 axes (maybe you have two 2D joysticks running at the same time, or a 4D joystick?), you will need to recompile the smoothie source code changing the default jog axes in Jogger.h:

#define NUM_JOG_AXES 3

Changing the value to your desired number of axes and recompiling will give you new firmware which enables the extra axes. The jogger data source names for each axis are:

Axis 1	Axis 2	Axis 3	Axis 4	Axis 5	Axis 6
data_source_alpha	data_source_beta	data_source_gamma	data_source_delta	data_source_epsilon	data_source_zeta

Note that M777 and jogger.jog_axes will then accept up to 6 letters.

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