在应用程序级别从USB设备以Xcode获取序列号

Question

我刚开始进行硬件编程，一直在尝试从USB设备获取序列号。我正在应用程序级别而不是内核级别实现所有功能。

我已经有一个字典可以匹配USB设备，因此我知道我有正确的设备。我不确定的是要返回的数据，如何解释它以及我是否正确处理了该问题。

因此，这里有一些我一直在尝试使用的代码，用于从设备获取序列号。

IOReturn retSerialIndex;
UInt8 snsi;
retSerialIndex = (*usbDevice)->USBGetSerialNumberStringIndex(usbDevice, &snsi);
if (retSerialIndex != kIOReturnSuccess)
{
    printf("Could not get serial number string index (error: %x)\n", retSerialIndex);
}
printf("Serial string index is %x\n", retSerialIndex);
IOReturn retSerial;
IOUSBConfigurationDescriptorPtr *desc;
if (retSerialIndex)
{
    retSerial = (*usbDevice)->GetConfigurationDescriptorPtr(usbDevice,
                                                            retSerialIndex,
                                                            desc);
    if (retSerial != kIOReturnSuccess)
    {
        printf("Could not get serial number using string index (error: %x)\n", retSerial);
    }
}
printf("Serial number is %x\n", retSerial);
char serialString;
serialString = getUSBStringDescriptor(usbDevice, retSerial);
printf("Serial string is %c\n", serialString);

这是我的getUSBStringDescriptor实现：

char MyClass::getUSBStringDescriptor( IOUSBDeviceInterface300** usbDevice, int idx )
{
   assert( usbDevice );
   UInt32 buffer[32];
   IOUSBDevRequest request;
   request.bmRequestType = USBmakebmRequestType(
                                             kUSBIn,
                                             kUSBStandard,
                                             kUSBDevice );
   request.bRequest = kUSBRqGetDescriptor;
   request.wValue = (3 << 8) | idx;
   request.wIndex = 0x0904; // english
   request.wLength = sizeof( buffer );
   request.pData = buffer;
   kern_return_t err = (*usbDevice)->DeviceRequest( usbDevice, &request );
   if ( err != 0 )
   {
       // the request failed.
       return NULL;
   }
   static char charstring[33];
   int count = ( request.wLenDone - 1 ) / 2;
   int i;
   for ( i = 0; i < count; i++ )
        charstring[i] = buffer[i+1];
    charstring[i] = '\0';
    return charstring[33 - 1];
}

任何帮助将不胜感激。谢谢！

Answer 1

所以我想通了。我在错误的位置获取了错误的信息，而没有足够注意存储值的位置。这是修改后的代码，用于返回所选设备的序列号。

//My call to get serial number
NSString * serialString;
serialString = getUSBStringDescriptor(usbDevice);
printf("Serial string is %s\n", [serialString UTF8String]);

//My function that gets the serial number for me
NSString * MyUSBClass::getUSBStringDescriptor( IOUSBDeviceInterface300** usbDevice)
{
    UInt8 snsi;
    UInt8 buffer[256];
    IOUSBDevRequest request;
    IOReturn err;
    err = (*usbDevice)->USBGetSerialNumberStringIndex(usbDevice, &snsi);
    if (err != kIOReturnSuccess)
    {
        printf("Could not get serial number string index (error: %x)\n", err);
        return 0;
    }
    request.bmRequestType = USBmakebmRequestType(
                                             kUSBIn,
                                             kUSBStandard,
                                             kUSBDevice );
    request.bRequest = kUSBRqGetDescriptor;
    request.wValue = (kUSBStringDesc << 8) | snsi;
    request.wIndex = 0x409; // english
    request.wLength = sizeof( buffer );
    request.pData = &buffer[0];
    bzero(&buffer[0], sizeof(buffer));
    err = (*usbDevice)->DeviceRequest( usbDevice, &request );
    if ( err != kIOReturnSuccess )
    {
        printf("Could not get serial number string using index\n");
        // the request failed.
        return 0;
    }
    int strLength;
    CFStringRef serialNumberString;
    strLength = buffer[0] -2;
    serialNumberString = CFStringCreateWithBytes(kCFAllocatorDefault, &buffer[2], strLength, kCFStringEncodingUTF16LE, FALSE);
    CFShow(serialNumberString);
    NSString *stringBuffer = (__bridge NSString *)serialNumberString;
    return stringBuffer;
}

我希望这可以节省很多时间！我希望在尝试解决这个问题时得到这个答案。