Question

I am having big trouble to communicate through USB, from a Mac to an external HID device. The hardware has been proven fine when running under the Windows XP platform, but I can t find a GOOD exemple of programming the HID with Cocoa / objective-C. Several exemples are available in the Apple center, but they are either poorly documented, or too much complex ( in term of software with mixed objective-C and C, making the file difficult to understand), or not up to date. Well, I must say that I am more an hardware electronic engineer than a software specialist ! So far, I can enumerate the USB port, identify my device using the HID Apple s tools ( I read PID and VID ), but I miserably fail to send a report and/or to read a report back from the external device. I would certainelly appreciate if one of you has used the new Apple s HID API and can share some know how. On the other hand, is there any "USB spy" tool operating with the Apple s OSX ? Thank you so much for your help

Michael

Answer 1

So yes, you re going to have to dive down and write C, not Objective-C, to do your thing.

Luckily, there s an additional Apple resource to make the USB/HID Manager MUCH easier.

See the HID Utilities Sample/Library from Apple

Answer 2

You are not going to find an Objective-c interface for the HID. At least, not anything more than a wrapper. Because of dynamic binding and delayed messaging, Objective-c is poorly suited to programming time dependent task like device drivers or for communicating with same. You re going to have to work in C.

The Apple resources: Accessing Hardware From Applications,the HID Class Device Interface Guide are going to be your best resources. This tech note offers a good overview as well.

The Apple System profiler will scan you USB chain to see what devices are visible to the hardware itself.

Edit01:

Can t believe I forgot about /Developer/Applications/Utilities/IORegistryExplorer. It gives you a detailed breakdown of the entire hardware tree.

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