If I want to be able to send Raw HID packets to openFrameworks is it just a matter of doing a #include to add the C library and putting the library in the proper oF folder? I’m not clear on how to be able to incorporate this into my code. If openFrameworks already has a library that can handle Raw HID on a Linux PC let me know because I was only able to find OSX related code.
Host (PC or Mac) Side Functions
int rawhid_open(int max, int vid, int pid, int usage_page, int usage);
Open up to "max" devices that match vid, pid, usage_page and usage. Return is the number of devices actually opened.
If its built in system functionality there should be native system handlers which is what I assume they are referring to with the host functions. Is there a reason you need it to do rawhid vs firmata or some other communication protocol?
To get that in firmata you would have to alter the standard firmata to make the latency that low. Firmata comes packaged with arduino it utilizes a midi style communication protocol between arduinos and a client. A client is part of the core of openframeworks and there are examples how to use it.
I can see why using a raw hid might be applicable. try adding the header and appropriate c file to your project and then import it into ofApp.h which should allow you to connect once you call the appropriate functions. so in the setup call
these defines seem arbitrary and i just got them from the example but include them in ofApp.h
you may want to thread this because if you want that kind of latency you will have to call rawhid_recv faster than update and draw is called in openframeworks unless you disable vertical syncing and another problem would be filling the buffer faster than it can be read or cleared which then you are losing accuracy anyways.
What keywords should I be searching for in openFrameworks to learn how to create a thread and make the reading part independent from update() and draw(). My understanding is that audioOut() is independent from update() and draw() so maybe I could come up with a function that takes care of reading the values from the USB buffers.
BTW: I’ve always wondered what happens in an OS when a variable is being written to while your program is trying to get its value. Is that something that is handled by the Linux OS?
I would recommend against using audio out as your separate thread though it does get polled much more often. It will be better to make your own thread and then you can have it do more robust functions and signal events like a change in value etc…
Your question about variable read writes is why mutexes exist so that such a case does not happen
I’ve got my work cut out for me… I have to learn how to call C from C++ but that seems straight forward. Learning how to use hidapi is going to be the hard part. Finally learning some Linux fundamentals won’t hurt either.
BTW I visited your site… You’re doing some amazing research.