I am developing a USB composite device. The composite device have 8 switches and one LED.
When I plugged the Composite device to PC,I could find five devices (each with same device ID but different instance IDs) in the HID section of Device Manager.
Why OS is showing multiple instances instead of One. Can anyone help me understand the concept?
As I recall 'composite device' is just a name in windows to mark that you have multiple devices on your USB line. There isn't a composite device class in the USB protocol. When you connect your USB device to your PC it communicates with all the devices contained in it and reports individually all their address and types. If you are missing some devices in your device manager it could be a driver issue or the device itself is broken. I don't know for sure but maybe there is a limit lower then it could be in theory in the windows hid host driver for the number of supported devices on a single line.
Related
If I connect a USB device to the host and then upgraded the USB device with a new firmware with changes in the Descriptor of the device. The host will use the old descriptor.
I know that I can force the device to re-enumerate itself by deleting Windows initialized driver for the device etc. or I can bump the ProductId in the descriptor and the device will re-enumerate.
Windows cash the information about the device etc. and thereby windows never ask the device to provide the information again on reconnecting about interfaces, configuration, endpoints, HID descriptor etc.
idProduct - changing this will re-enumerate the device because windows will think its a different device.
iSerialNumber - changing this will re-enumerate because windows need to differentiate between two same idProducts (two of same products connected)
bcdDevice - should do the trick of re-enumeration but it's not working as specified in USB specification.
My question is how can I force Re-enumeration of the USB device without deleting drivers etc. or changing idProduct or iSerialNumber?
Any help will be appreciated...
When I connect several USB audio devices using the default drivers I usually end up with some kind of friendly device description like "nn- USB Audio codec" or something else, so I have currently no unique property which refers to a specific hardware the e.g. manufacturer ID. I would like to ensure that in case of re-enumerating or replugging the hardware to a different port that my software will automatically identify the changed windows audio device which maps to this hardware. I there a possibility to gather further windows audio device information which can be used to determine the physical hardware ?
Maybe a little clarification is needed:
I have two or more USB audio devices, not necessarily same product or manufacturer. The audio connections have different purposes, so I want to ensure that I my software uses constantly the same physical audio devices for different tasks. This sometimes fails when a re-enumeration occurs ( sometimes without changing the physical USB port connections, it's a windows thing...)
Ideally I would distinguish them by an individual serial number, which usually is only available with storage devices. But what I can retrieve is the "physical" USB topology when I'm looking at the device with a tool such as USBDeview from Nir Sofer. There I have a property like "Hub 3, Port1". If I could map this to a sound device I get from audio audio api like "nn- USB Audio codec" as seen in the sound control panel I would be perfectly happy.
Edit2:
May be this[1] post helps here, but I still have to figure out how to get a USB Port <-> Windwos Sounddevice mapping.
[1]: Can the physical USB port be identified programatically for a device in Windows? "
This is the closest I could fine but it enumerates all usb devices. In my case I am handling WM_DEVICECHANGE event where I handle arriving usb device and want to gather extended information from this device when its plugged in other than the simple USB strings that contains the vid and pid.
I can't find any resource on it, is that possible?
I am using windows 7 and qt 5.5
I am working on a project that involves the auto-detection of USB and firewire devices being plugged and unplugged from an OS X system. For a given device, the system needs to recognise a device when it is plugged in (no matter which port) and load a device-specific bundle to deal with it.
The key to making this work is obviously the unique identification of each device. I know that USB devices are identified by a combination of the vendor ID and product ID fields, but this does not provide a unique ID, only the "kind" of device. If I have two devices the same and I plug both of them in to the computer, I would like some way to distinguish them. Is there a general and reliable way to do this, perhaps using other fields in the USB descriptor?
A related question, how does this work for USB serial ports? Suppose I plug in two USB serial ports of the same make/model. OS X should give them unique inodes in the /dev tree. However, suppose it calls them /dev/usbserial1 and /dev/usbserial2. If I then unplug the ports and plug in only one one of them, will that port be given the same name as it previously had, or will it just get /dev/usbserial1 (since it is the only) port plugged in?
Same question for firewire devices, although I think firewire devices are supposed to have a 64-bit GUID. In this case I am looking for someone to verify that using the GUID for firewire device identification would be reliable. In other words, if I plugged in two separate cameras of the same make and model, would I expect them to have different GUIDs?
I know I could test some of these with the appropriate hardware, but I don't have multiple bits of hardware at this time, so I am hoping someone may know at least some of the answers to the above questions.
With luck, your USB devices should have unique serial numbers, in addition to the VID/PID combination. If you're enumerating IOUSBDevice objects, look at the USB Serial Number property.
On Windows, Microsoft remembers device-specific settings by:
the device's serial number (the iSerialNumber field in the USB device descriptor), if available
or otherwise, by the "path" to the device: its bus (i.e. what hub it's plugged into etc.) + USB VID and PID
Without serial numbers, USB devices are virtually indistinguishable. You could tell apart different USB disk drives, but for devices which have no non-volatile memory of any kind (and many USB devices fall into this category), they are just indistinguishable, so you just have to make the best effort to do what the user expects.
I need to create a application that will allow a Windows PC (XP/Vista) to emulate a thumbdrive. That is, when the PC is plugged into either another Windows system, or in this case, a piece of hardware that allows for USB thumbdrives to be plugged in, a folder on the computer looks like a giant thumbdrive. Any thoughts on where a guy would start to investigate this?
Update (more specific description):
I need to connect my PC to one of the newer multifuction devices that support scanning to a USB thumbdrive that is inserted into the front of the device. These units do not support WIA or TWAIN via the rear USB connector that you'd typically use for connectivity to a PC.
Most USB controllers in regular pc's dont have the possibility to function as an USB slave. So I'd start with investigating what kind of hardware you're going to use.
Another way to go: there are USB Link cables to link up 2 pc's over USB, maybe that's usable for you?
You cannot do this in an application. At the lowest level, the USB ports on your computer are controlled by an Host Controller Interface. This chip will manage up to 127 slave USB devices. You would need to seriously reprogram this chip before it implements the slave side of the USB protocol. Of course, at that point any USB hub in your PC will break down - those 8 USB ports you probably have are usually implemented by 2 smart USB hubs connecting to both USB1 and USB2 host controllers. Next, your USB keyboard and mouse will stop working.
Take an MCU with two Slave USBs. Write a simple frimware which makes one USB act as a Special Device Class and wait until PC on this USB provides mandatory data (including Device Class, of course) for the other USB. Write a PC program which connects to the Special Device (your MCU), uploads Mass Storage Device Class and redirects I/O to a dedicated partition. The other USB on the MCU will become an emulated Mass Storage Device.
Some of those code can be taken from Linux.