I have been playing with creating sounds using mathematical wave functions in C. The next step in my project is getting user input from a MIDI keyboard controller in order to modulate the waves to different pitches.
My first notion was that this would be relatively simple and that Linux, being Linux, would allow me to read the raw data stream from my device like I would any other file.
However, research overwhelmingly advises that I write a device driver for the MIDI controller. The general idea is that even though the device file may be present, the kernel will not know what system calls to execute when my application calls functions like read() and write().
Despite these warnings, I did an experiment. I plugged in the MIDI controller and cat’ed the “/dev/midi1” device file. A steady stream of null characters appeared, and when I pressed a key on the MIDI controller several bytes appeared corresponding to the expected Message Chunks that a MIDI device should output. MIDI Protocol Info
So my questions are:
Why does the cat’ed stream behave this way?
Does this mean that there is a plug and play device driver already installed on my system?
Should I still go ahead and write a device driver, or can I get away with reading it like a file?
Thank you in advanced for sharing your wisdom in these areas.
Because that is presumably the raw MIDI data that is being received by the controller. The null bytes are probably some sort of sync tick.
Yes.
I’m not sure what you’re reading or how you’re coming to this conclusion, but it’s wrong. 🙂 You’ve already got a perfectly good driver installed for your MIDI controller — go ahead and use it!