I've been wrestling with sending data to a USB HID device. I was
originally using HID Utilities, but spent today re-writing
everything to use pure IOKit calls. I've confirmed that my callback
and transaction code works by capturing keyboard button presses and
turning the Caps Lock key on.
When communicating with my USB device (a Motorola MX240a), I can't
get any response out of the thing. It has two 8-bit outputs (which
I will refer to as L and R). The sequence I have to send to the
device is 0xAD, 0xEF, 0x8D, and 5 nulls. This should elicit a
response from the device, but it remains silent.
Specifically, I'm not sure when to commit my transaction. Can I
change the value of an element multiple times in one transaction,
or is the last one the only change that is kept? Should I do
L: AD R: EF *commit*
L: 8D R: 00 *commit*
L: 00 R: 00 *commit*
L: 00 R: 00 *commit*
Or
L: AD R: EF
L: 8D R: 00
L: 00 R: 00
L: 00 R: 00 *commit*
Or is it more likely that I should stream all of the data through
one output and ignore the other? I've tried pretty much every
combination I can think of.
There is some Linux code online that uses libusb to communicate
with the device (see write_packet function), but I can't figure out
how to translate it into IOKit calls.
http://mx240ad.cvs.sourceforge.net/mx240ad/mx240ad/mx240ad/imopen.c?
revision=1.7&view=markup
Sorry for the rambling, but I haven't had any luck for a few days
now... If anyone has any suggestions, I'd be extremely grateful to
hear them.
Regards,
Ryan Govostes
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