So how do they format the velocity data? Position is limited by whatever the pulses per revolution are but velocity can be pretty unbounded. Is it 7 bit? How is it scaled?
Does each manufacturer have their own scale and the sensitivity setting on the host is used to normalize that value in software? I assume some practical bound on velocity is used like say a user can only spin a jog wheel once a second max so anything greater than 1 rps is a 63, and -1 rps is -63. So that gives you greater than 6 degree/s accuracy, which would likely not be accurate enough for some people, so it's gotta cap at something smaller like 0.5 rps or less to be sensitive enough. Is it a delta velocity that gets transmitted? I could see that and then saving 0x7F as a means of re-zero-ing the velocity. That would increase encoder resolution without increasing the data rate, assuming the update frequency was fast enough to begin with. If they do send 14-bit data and the latency is not an issue, then I guess this point is less important. If you send data on the order of less than every 10 ms, then you can send somthing meanigful. I don't think you even necessarily need position data for a motorized jog wheel unless you want to do output control over the wheel. Thanks Mark, -Nick ----- Original Message ---- From: Mark Glines <[email protected]> To: Nick Conway <[email protected]> Cc: [email protected] Sent: Wednesday, March 11, 2009 3:27:23 PM Subject: Re: [Mixxx-devel] Midi Encoder data details Nick Conway wrote: > I'm interested in building my own encoder/jog wheel interface and I want it > to be compatible with Mixxx, but I need to know some formatting of how jogs > wheels generally respond. > > Do they transmit position or velocity data? It's velocity data. The only time I could see position data being useful is when the controller actually spins on its own, which doesn't seem like a common thing for usb controllers (and would have to vary depending on the tempo slider anyway). (The numark total control doesn't, and neither does the griffin powermate. They both send velocity data.) Mark ------------------------------------------------------------------------------ Apps built with the Adobe(R) Flex(R) framework and Flex Builder(TM) are powering Web 2.0 with engaging, cross-platform capabilities. Quickly and easily build your RIAs with Flex Builder, the Eclipse(TM)based development software that enables intelligent coding and step-through debugging. Download the free 60 day trial. http://p.sf.net/sfu/www-adobe-com _______________________________________________ Mixxx-devel mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/mixxx-devel
