I'm new to the embedded Linux world. I'm using Nvidia Jetson Nano as my embedded SOC.
Now I need my application to do some specific thing, for example, show an icon, as long as a USB disk is plugged into the embedded board. How can I know if such a USB disk is plugged in?
I need to know the approach for knowing the as long as a USB disk is plugged in
You can check all USB devices that are plugged in with the commands :
$ lsusb
Or with the command :
$ ls /dev/ttyUSB
You could then check if one of the listed devices (/dev/ttyUSB0 for example) is in the list and do your action.
What programming language are you using for your application ? There must be libraries that can help you check easily if a USB is connected/disconnected
Related
I want to use alsa on a Beaglebone Black to send audio through usb audio out and receive it on my computer.
I have seen that there are some gadgets in a legacy folder in the kernel, and seen some tutorials on how to set up mass storage and network gadgets, but I am confused about what the state of audio gadgets is and what to compile and configure for this.
Can you explain the various components and configurations that need to go into place to make this happen, covering which kernel modules, drivers, kinds of scripts, and configurations that might be needed to do this?
You need to enable USB gadget subsystem in your Linux kernel for Beaglebone Black. Assuming of course that you have USB device controller and USB device connector on your Beaglebone. Here there are more information:
https://www.lynxbee.com/usb-audio-gadget-driver/
USB devices contains so called USB descriptors which tells USB host (PC) as a what device type it works. Audio gadget is one of the type of that descriptor that tells that this device (in this case BeagleBone) should be working as a audio device.
I am learning to program a USB device (iBall 3.5g USB Dongle) using libusb.h header library.
Until now I am able to identify my device using the Vendor ID and also open the device for operation.
As a next step I would like to know the available commands (or the controls) for example : command to scan the surroundings for available GSM networks.
Obviously I will have to talk to the devices' firmware to extract the necessary information.
I tried to search for the technical datasheet for the 3g dongle, but couldn't find any.
The dongle is powered by a Qualcomm chip
Do you know any of the methods in which I can get the control commands for a usb device ?
Thanks in advance.
There is no simple procedure for figuring out what commands a USB device has. You need to use a combination of looking at the descriptors reported by the device, seeing if the device supports any particular USB device class, reading the USB specification, and maybe doing some reverse engineering using a protocol analyzer.
A good first step would be for you to use lsusb -v to print human-readable descriptions of the device's USB descriptors.
I have a USB HID device that can work in two different modes. The selection of modes is based on the sequence of USB enumeration/initialization packets sent to it.
I am using a Raspberry Pi 3 running Raspbian, however I also see the same issue if I compile my code for my desktop Ubuntu distro.
The issue I have is that linux is recognizing the USB device as a HID device and then sending the sequence of commands that it deems necessary to start the device, and this works correctly and starts the device in "Mode 1".
However I need to start the device in "Mode 2" and to do this I need to send a slightly different set of enumeration/initialization commands.
I am new to linux but very experienced with LibUSB and LibUSBDotNet under windows and can get the behavior I desire under windows.
Windows has similar behaviour to linux in that it will enumerate, recognise the device as a USB HID device and then initialise it as it deems fit resulting in the device going into "Mode 1". To prevent windows doing this I can create a LibUSB filter driver for the device, which then replaces the default driver, so windows will now do the initial enumeration, realise that the VID and PID of the device are managed by the LibUSB filter driver (rather than the windows HID driver) and then stop enumeration/initialization - this allows my code to take over and complete the initialization into "Mode 2".
How can I stop Linux from fully enumerating/initializing this device (as I do with windows). Perhaps I need to do something with udev rules or something, but I would have no idea what as I am new to linux.
Any help greatly appreciated
you have right, you have to play with the udev rules.
First of all you have to identify your device. Find the idProduct and the idVendor of your device. You can use:
lsusb
Then in the rules.d folder (/etc/udev/rules.d) create a new file with the name:
10-my-usb.rules
In this file add this line
SUBSYSTEM=="usb",ATTRS{idVendor}=="XXXX", ATTRS{idProduct}=="XXXX", MODE="666", GROUP+="plugdev"
Replace the XXXX with the value you get before
Then restart your udev rules:
sudo udevadm trigger
Then unplug and replug normally you can use it
My goal is to create a virtual USB char device (not block device) for Linux 2.6.32 and above (I use debian squeeze) that would be recognize by the system.
I would like that this device be listed with lsusb as a normal USB device, and that every application could use libusb in order to open the device, and send control message, and make bulk write/read. But behind this virtual device, it's behavior would be set by my application. I want to set it's product ID, it's vendor ID, answer to USB status, and bulk read.
I've read some posts about how to use USB/IP in order to create a virtual USB device, and that's exactly what I want to do
Installation and emulation of virtual USB Device
http://breaking-the-system.blogspot.fr/2014/08/emulating-usb-devices-in-python-with-no.html
But unfortunately, when I tried with 2.6.32 kernel and above, I didn't succeed making it work. So I looked at how to create a kernel module that would create the virtual device :
http://pete.akeo.ie/2011/08/writing-linux-device-driver-for-kernels.html
This one looks great also, but the sample provided doest not indicate how to make it an USB device.
I've seen some post talking about it with windows but none that could help me with Linux.
I would like to avoid buying some USB programmable cards when it can be done with software.
Have anyone any leads on how to make the first methods works under newer kernel, or convert the sample code of the second method for making an USB device ?
I have fixed the code of http://breaking-the-system.blogspot.fr/2014/08/emulating-usb-devices-in-python-with-no.html (first method using USB/IP) to work with linux 4.3.
In the original code are missing USB requests like set configuration and get status. Without the implementation of all USB requests used for the OS driver the code will not work.
The fixed code can be downloaded in https://github.com/lcgamboa/USB-Emulation .
I guess raw-gadget kernel module is the thing that you want?
you can check the dummy_hcd and tests directory inside the repo, it will guide you how to create a virtual USB device
I am wondering, do you need a specific device driver to read a usb device in Linux, or should it just be able to be read. If I connect my cell phone or iPod touch to my linux box, it is not found is /proc/partitions and thus is not a mountable device by fdisks standards, though gnomes nautilus does in fact mount the iPod but not the windows mobile touch pro cell phone.
So I am interested, If I just wanted to read a device(iPod touch) in linux, how can I do so. How can I get a hold of a descriptor of a set usb device so I can read it.
Thanks all.
You can access raw USB endpoints under /dev/usbdev. There is user-space libusb that makes it easier.
Unfortunately there is no simple concept of "just read it" for USB devices (I am assuming that you are not referring to reading and writing the data on the USB bus that make up the USB protocol). In short, you always need a device driver for accessing a USB device and it is up to the driver to implement "the abstraction" of the device used by the system (disk, serial device, etc).