[libhid-discuss] python works but not C

[Will Woods]

I was using 0.2.15 versions of libhid and python bindings that come from
ubuntu 8.02 (Hardy). I downloaded the latest version 0.2.16 and it works
fine...

Will


>
> I am successfully talking to my device via the python bindings, but my C
> version fails with error 21 "could not claim interface 0: Device or
> resource busy" after successfully opening the device. The two pieces of
> code look the same to me, but I must be missing something?
>
> Any advice would be much appreciated...
>
>
> Python code:
>
> import sys
> from struct import unpack
> from hid import *
>
>
> ret = hid_init()
> if ret != HID_RET_SUCCESS:
>     sys.stderr.write("hid_init failed with return code %d.n" % ret)
>
> hid = hid_new_HIDInterface()
> if hid == 0:
>     sys.stderr.write("hid_new_HIDInterface failed.")
>
> matcher = HIDInterfaceMatcher()
> matcher.vendor_id = 0x0488
> matcher.product_id = 0x0020
>
> ret = hid_force_open(hid, 0, matcher, 3)
> if ret != HID_RET_SUCCESS:
>     sys.stderr.write("hid_force_open failed with return code %d.n" % ret)
>
> while True:
>     ret, bytes = hid_interrupt_read(hid, 0x81, 8, 100)
>     if ret == 0:
>         a = unpack('Q',bytes)[0]
>         print a
>
>
>
>
>
>
> and the C version:
>
>
> #include <stdio.h>
> #include <hid.h>
>
> #define VENDOR_ID 0x0488
> #define PRODUCT_ID 0x0020
>
>
> int main(int argc, char *argv[])
> {
>     unsigned char bytes[8];
>
>     HIDInterface* hid;
>     int iface_num = 0;
>     hid_return ret;
>
>     HIDInterfaceMatcher matcher = { VENDOR_ID, PRODUCT_ID, NULL, NULL, 0
> };
>
>     // see include/debug.h for possible values
>     hid_set_debug(HID_DEBUG_ALL);
>     hid_set_debug_stream(stderr);
>     // passed directly to libusb
>     hid_set_usb_debug(0);
>
>     ret = hid_init();
>     if (ret != HID_RET_SUCCESS) {
>         fprintf(stderr, "hid_init failed with return code %d\n", ret);
>         return 1;
>     }
>
>     hid = hid_new_HIDInterface();
>     if (hid == 0) {
>         fprintf(stderr, "hid_new_HIDInterface() failed, out of
> memory?\n");
>         return 1;
>     }
>
>     ret = hid_force_open(hid, iface_num, &matcher, 3);
>     if (ret != HID_RET_SUCCESS) {
>         fprintf(stderr, "hid_force_open failed with return code %d\n",
> ret);
>         return 1;
>     }
>
>     while( 1)
>     {
>         ret = hid_interrupt_read( hid, 0x81, bytes, 8, 100);
>
>         printf( "ret=%d\n", ret);
>         if( ret == HID_RET_SUCCESS )
>         {
>             // do something
>         }
>
>     }
>
>     ret = hid_close(hid);
>     if (ret != HID_RET_SUCCESS) {
>         fprintf(stderr, "hid_close failed with return code %d\n", ret);
>         return 1;
>     }
>
>     hid_delete_HIDInterface(&hid);
>
>     ret = hid_cleanup();
>     if (ret != HID_RET_SUCCESS) {
>         fprintf(stderr, "hid_cleanup failed with return code %d\n", ret);
>         return 1;
>     }
>
>     return 0;
> }
>
>
>
>
>
>
>
> _______________________________________________
> libhid-discuss mailing list
> libhid-discuss at lists.alioth.debian.org
> http://lists.alioth.debian.org/mailman/listinfo/libhid-discuss
> http://libhid.alioth.debian.org/
>