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.
Related
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
I have developed a kernel driver for a USB device. Such a device has some pins that can provide functionality both as CDC ACM serial port or as input buttons. So to implement that I had to use two different USB configuration descriptors.
The driver works as expected, but I have to hardcode the chosen setup before compiling and loading the firmware to the micro-controller. I am searching a mechanism to change that device configuration from userspace.
I read about a SET_CONFIGURATION message on USB documentation, but coudn't find any Linux tool to send such kind of standard USB messages from userspace to the USB bus.
Does some of you (with more experience on this topic) know some userspace Linux tool to send a SET_CONFIGURATION message to a device connected to the USB bus?
Thanks in advance! :)
The function libusb_set_configuration() in LibUSB could do that in theory, but there is no need.
One can simply put both HID (for the button) and CDC (serial port) into one configuration using an "Interface association descriptor" (IAD).
This github repo resolves my issue:
https://github.com/avtolstoy/usbtool
No need for any special tools. You can simply do it via sysfs:
Find your device cd /sys/bus/usb/devices/X-Y/ where X is the bus number and Y is the device number.
Edit bConfigurationValue e.g., using sudoedit
Set the file contents to the desired configuration number and save it
That’s it!
I'm researching ways to communicate with a USB device in Linux and would prefer to not write a Linux Kernel driver. I understand that libusb exists and is a user-land library that would work, but our embedded device doesn't support usbfs ( and would be really a pain to change kernels to add the support ).
So my question is basically this: Is it possible / advisable to communicate with a USB device by directly reading and writing to the /dev/USB or the udev file corresponding to the USB device thus bypassing the need for a custom Linux Driver and usbfs?
I'm hoping it's possible to communicate using the USB devices protocol just by reading / writing protocol packets directly through file-type read/write commands once the /dev/USB or udev device file is open.
Thoughts and suggestions please.
FOLLOW UP:
Since the USB device I needed to talk to is a USB HID class device, I was able to use libudev and the standard Linux USB HID RAW driver by reading / writing directly to /dev/hidraw0 ( or the appropriate /dev/hidraw device ). It wasn't necessary to write a custom driver for a simple USB HID device.
Jim, I don't think you can escape the need to write a driver and just manage to read the USB file in /dev. Because who defines as to what should happen when you do a read() on the USB device file? And who defines what action should be initiated when you invoke sysioctl()? Your driver! In other words, the device files are themselves incapable of anything until they are supported by the underlying drivers. In fact, you can treat the device files to be an abstraction of the underlying driver! So, no driver, no use of device file :(
I suggest you go through the following articles about how to write a driver and also understand the USB internals-
http://www.linux-usb.org/USB-guide/c15.html
http://www.linuxjournal.com/article/4786 ( Slightly outdated )
I have a Linux virtual machine running on VMWare Fusion (on Mac OS X) that I intend to use as a development environment for an embedded system. Would it be possible for my Linux VM to talk to my embedded system's serial port using a USB-to-serial adapter? Any recommendations for what sort of adapter I should get?
There are two ways to do it:
Your host-OS supports your USB<->serial converter (very likely). If so you can just allow your VM to talk to the serial port. If so the VM will see a standard serial port and everything will be fine.
Your guest-os in the VM supports the USB<->serial converter, AND your host-OS allows raw USB forwarding.
All in all the chances are good that it works..
Btw: there are good and bad USB<->Serial converters. If you find out that the serial connection seems to work (everything detects/works as expected for a couple of seconds), but you can't get a reliable connection for a longer time, then it's very possible that the usb<->serial dongle sucks....
You get what you pay for... When buying these things I'd check comp.arch.embedded and ask which usb dongles are known to just work, and which not. (My recommendation is to stick with products from Assmann. You can order them at digikey).
I've found USB serial adaptors to be a bit hit & miss with embedded work. One thing to be aware of is that the buffering tends to work differently from "real" serial ports, and latency of characters through the system can be quite variable. Some embedded development systems (think bootloaders, cheap JTAG probes etc) can be quite sensitive to this and will give timeouts and so on.
Note this doesn't only apply to USB serial adaptors, I've had similar problems with high end multi-port serial cards, but usually with those you can tweak the FIFO / IRQ settings to get something working.
I have experienced that a USB to serial adapter with a FTDI chipset and drivers is more reliable and compatible with more devices than the Prolific chipset
Depends upon the VM software, but VMWare Fusion does support USB devices. The question becomes, does your IDE support talking to a USB device instead of an old-fashioned serial port? With Linux, probably yes.
I had no problems whit serial adapters from ATEN.
USB serial adapter is USB standard device (just like mass storage) that mean that any USB compliant adapter should work.
pl2303: I have found this device to be very reliable and are often in the generic and cheap USB to RS232 adapters. I've seen expensive adapters fail and my generic adapter from geeks.com work great.
I just picked up a USB 1.1 - RS232 adapter (Digitus DA-70119) from WeirdStuff for 10 bucks. I plugged it into my Mac mini and VMWare Fusion showed me this.
Once I clicked on the USB icon, my Ubuntu 9.10 VM had no trouble seeing it
$ lsusb
Bus 002 Device 004: ID 067b:2303 Prolific Technology, Inc. PL2303 Serial Port
$ dmesg
usb 2-1: new full speed USB device using uhci_hcd and address 4
usb 2-1: configuration #1 chosen from 1 choice
pl2303 2-1:1.0: pl2303 converter detected
usb 2-1: pl2303 converter now attached to ttyUSB0
I can now use /dev/ttyUSB0 in my Linux VM to talk to my target system.
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).