Databases
StackOverflow2013
Postsdbo
POReading and writing to USB (HID) interrupt endpoints on Mac
 

Note that there are some explanatory texts on larger screens.

plurals
  1. POReading and writing to USB (HID) interrupt endpoints on Mac
    primarykey
    data
    text
    <p>I am attempting to communicate with a rather specific USB device and developing both Windows and Mac code to do so. </p> <p>The device is a USB device with a HID interface (class 3) with two endpoints, an interrupt input and an interrupt output. The nature of the device is such that data is sent out from the device on the input endpoint only when data is requested from the host: the host sends it data which the device responds to on its input interrupt endpoint. Getting data to the device (a write) is much more simple...</p> <p>The code for Windows is rather straight-forward: I get a handle to the device and then call either ReadFile or WriteFile. Apparently much of the underlying asynchronous behavior is abstracted out. It appears to work fine.</p> <p>On Mac, however, it is a bit stickier. I have tried a number of things, none which have been fully successful, but here are the two things which seemed most promising...</p> <p>1.) Attempt to get access to the device (as USB) via IOUSBInterfaceInterface, iterate through the endpoints to determine the input and output endpoints, and (hopefully) use ReadPipe and WritePipe to communicate. Unfortunately I am unable to open the interface once I have it, with the return value (kIOReturnExclusiveAccess) noting that something already has the device open exclusively. I have tried using IOUSBinterfaceInterface183, so that I could call USBInterfaceOpenSeize, but that results in the same return error value.</p> <p>--- update 7/30/2010 ---<br> Apparently, the Apple IOUSBHIDDriver matches early to the device and this is what likely is preventing opening the IOUSBInterfaceInterface. From some digging about it seems that the common way to prevent the IOUSBHIDDriver from matching is to write a code-less kext (kernel extension) with a higher probe score. This would match early, preventing the IOUSBHIDDriver from opening the device, and should, in theory, permit me to open the interface and to write and read to endpoints directly. This is OK, but I would much prefer not having to install something additional on the user machine. If anyone knows of a solid alternative I would be thankful for the information.</p> <p>2.) Open the device as an IOHIDDeviceInterface122 (or later). To read, I set up an async port, event source and callback method to be called when data is ready - when data is sent from the device on the input interrupt endpoint. However, to write the data — that the device needs — to initialize a response I can't find a way. I'm stumped. setReport typically writes to the control endpoint, plus I need a write that does not expect any direct response, no blocking.</p> <p>I have looked around online and have tried many things, but none of them is giving me success. Any advice? I can not use much of the Apple HIDManager code since much of that is 10.5+ and my application must work on 10.4 as well.</p>
    singulars
    1. PO
      singulars
      1. PTAnswer
    1. This table or related slice is empty.
    1. PTQuestion
    1. USDemi
    1. USDemi
    plurals
    1. This table or related slice is empty.
    1. PL
      singulars
      1. LTLinked
    2. PL
      singulars
      1. LTLinked
    1. This table or related slice is empty.
    1. PO
      singulars
      1. PTAnswer
    2. PO
      singulars
      1. PTAnswer
    3. PO
      singulars
      1. PTAnswer
    1. VO
      singulars
      1. POReading and writing to USB (HID) interrupt endpoints on Mac
      1. This table or related slice is empty.
      1. VTUpMod
    2. VO
      singulars
      1. POReading and writing to USB (HID) interrupt endpoints on Mac
      1. USdar
      1. VTFavorite
    3. VO
      singulars
      1. POReading and writing to USB (HID) interrupt endpoints on Mac
      1. This table or related slice is empty.
      1. VTUpMod
    1. This table or related slice is empty.
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload