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POC Callback in Objective-C (IOKIT)
 

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  1. POC Callback in Objective-C (IOKIT)
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    <p>I am trying to write some code that interacts with an USB device in Objective C, and I got stuck on setting the callback function for incoming reports. In my case it's an IOKIT function but I think the problem is more general as I (apparently) don't know how to correctly set a C callback function in Objective-C. I've got a Class "USBController" that handles the io functions</p> <p>USBController.m: </p> <pre><code>#include &lt;CoreFoundation/CoreFoundation.h&gt; #include &lt;Carbon/Carbon.h&gt; #include &lt;IOKit/hid/IOHIDLib.h&gt; #import "USBController.h" static void Handle_IOHIDDeviceIOHIDReportCallback( void * inContext, // context from IOHIDDeviceRegisterInputReportCallback IOReturn inResult, // completion result for the input report operation void * inSender, // IOHIDDeviceRef of the device this report is from IOHIDReportType inType, // the report type uint32_t inReportID, // the report ID uint8_t * inReport, // pointer to the report data CFIndex InReportLength) // the actual size of the input report { printf("hello"); //just to see if the function is called } @implementation USBController - (void)ConnectToDevice { ... IOHIDDeviceRegisterInputReportCallback(tIOHIDDeviceRefs[0], report, reportSize, Handle_IOHIDDeviceIOHIDReportCallback,(void*)self); ... } ... @end </code></pre> <p>All the functions are also declared in the header file.</p> <p>I think I did pretty much the same as what I've found <a href="https://stackoverflow.com/questions/316879/handling-callbacks-in-objective-c/" title="here">here</a>, but it doesn't work. The project compiles nicely and everything works up till the moment there is input and the callback function is to be called. Then I get an "EXC_BAD_ACCESS" error. The first three arguments of the function are correct. I'm not so sure about the context.. What did I do wrong?</p>
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