I'm writing to a centronics cable and blinking some LEDs via a simple "bufferized" circuit.
I'm able to write out the bits via C code referencing the device location on /dev/usb/lp0 on an Ubuntu machine.
However, I'd like to be able to do this on OSX Mavericks. I don't see the same type of device file as I do in Linux.
i.e. is there an OSX analog to /dev/usb/lp0 on Linux?
Thanks much.
Under the concept of "everything's a file" lp0 is just a special file that allows raw access to a device, in this case a 'special character file' for the first parallel device. The same would exist on OSX if a driver was present that matched the device, or something like /dev/parport0. OSX has a pretty limited collection of parallel drivers though. You could try to fudge it - create a 'character' device file pointing it to some generic parallel driver with mknod.
e.g. mknod lp0 c x y where x an y are the major and minor numbers for the device type. Typically you find these numbers in the documentation/devices.txt file on linux, not sure where this info is on OSX though.
I've seen devices handle this using generic printer drivers, such as a "gadget printer":
https://www.kernel.org/doc/Documentation/usb/gadget_printer.txt
(my initial assumption)
In this case the device will actually show up on the system as a printer. You can find a list of printers and their location using CUPS utilities like lpstat:
https://developer.apple.com/library/mac/documentation/Darwin/Reference/ManPages/man1/lpstat.1.html#//apple_ref/doc/man/1/lpstat
There's also the environment variables LPDEST and PRINTER which should list the default print location:
echo $LDPEST
Related
Is there a way with pyusb to unbind a USB device?
I know using the following bash the USB is unbound.
DEVICE=$(grep 064f /sys/bus/usb/devices/*/idVendor | tr '/' ' ' | awk '{ print $5 }')
/bin/bash -c "echo $DEVICE >/sys/bus/usb/drivers/usb/unbind"
But for various reasons I like to move away from bash and switch to Python, and ideally avoid maintaining my custom, complicated logic. So using a existing library makes sense to me.
Selected answer in stackoverflow.com#q54863367 suggests detach_kernel_driver to work for this purpose, but I don't see that happening on my environment; It does unmount the volume in the designated USB device (confirmed by watching the disk space on the USB disappears in lsblk's output) but I still see that OS detects the USB device.
$ ipython
In [7]: import usb
...: dev = usb.core.find(idVendor=0x064f, idProduct=0x03f3)
In [8]: dev.detach_kernel_driver(0)
$ watch lsusb
:
Bus 002 Device 043: ID 064f:03f3 WIBU-Systems AG CmStick/M (article no. 1011)
Environment
Linux (At the time of writing, Ubuntu 16.04 (I know EoLed) or 18.04. But environment shouldn't be a limiting factor. Open for available solutions regardless the version.
UPDATE: My usecase requires mimicing removal of USB device. We've been happy with the operation typically called as un/bind, and also happy with the bash solution to realize un/bind.
A quick search of the PyUSB code makes it seem like there is no feature for binding or unbinding. So PyUSB is not the answer.
However, you don't need to use Bash to unbind a device. Python has a standard library that lets you get directory listings, read files, and write to files, so you can just use Python's standard library instead of Bash.
Thought I'd close OP but coudln't choose an appripriate reason so answer by myself instead.
As I concluded myself with a help from the maintainer in pyusb#399 I found I was misunderstood. Using detach_kernel_driver as suggested in stackoverflow.com#q54863367 worked for my purpose as well.
Linux newbie question.
Just wondering how Linux determines which device class a device is? Specifically, when I plug a barcode scanner in how does it know it is an ttyACM device? I have a scanner that works with my Linux OS but the new model isn't recognized so I'm wondering if I can alter a file somewhere in the system that tells it to recognize the scanner as ttyACM0 and use the existing drivers.
USB devices (I assume your scanner is USB) are identified by vendorId and productId (two 16bit integers), each driver fill an array with the list of supported vendor/prods id (creating a relation vendor:prod->driver), I guess at compile time all the id in the array are merged together in a list which then is used for a lookup search when a device is plugged in.
Usually you can see vendor and product id of the attached device with dmesg command right after the device is plugged in (or with lsusb).
For ttyACM see acm_ids[] in drivers/usb/class/cdc-acm.c
Careful playing around with device drivers, even being ttyACM a terminal interface only if the interface tty->hardware is implemented poorly some command may break the hardware.
Perhaps this question should be in Unix & Linux stackexchange
I have been working for a few days trying to get the UART1 port to work on a bbb. I flashed the prebuilt kernel from the elinux wiki (http://www.elinux.org/BeagleBoardUbuntu#Flasher), and the UART1 appears in the /dev folder (as /dev/ttyO1, with a capital "o" not a zero), but when I write to it, nothing comes out of the pins. I can use UART0 (on a separate little serial header, but not the one I need) without any trouble.
I see a lot of tutorials for enabling UART1 that deal with a folder called /sys/devices/bone_capemgr.* but I don't have one. I think it is because I have a newer kernel, and nearly all of those tutorials are exclusively for older kernels (<=3.8).
I read that the current 3.13 images from Robert C Nelson don't have a cape-manager (https://groups.google.com/forum/m/#!topic/beagleboard/ND3_w7_dn8Q), and you can use the "really simple cape manager" (https://github.com/RobertCNelson/rscm), but the build.sh script doesn't work on my 3.14 kernel. I tried to change a path in the script to fix it and now that bbb won't boot.
I also tried the beaglebone-universal-io script (
https://github.com/cdsteinkuehler/beaglebone-universal-io) but when I query the relevant pin:
sudo ./config-pin -q P8_26
I get the error:
P8_26 pinmux file not found!
Please verify your device tree file
Am I missing something really simple here?
I'm developing app with qt4 (c++) for Linux platform. When I'm using QTextDocument::drawContext method(), sometimes (not always) printer is printing some junks and wasting a lot of paper. I think it can be related with printer driver. This is Oki MicroLine 3390 eco printer. This printer is emulating EPSON LQ driver.
I have tested few epson drivers but that did not help at all. I cannot fix this issue so I have started looking for some alternative solution - write directly to device.
I'm looking for info:
How to write raw data (formatted text) to usb dot matrix printer?
is any one know how to fix printing issue?
any write command will do print on device /dev/usb/lp0
test it # cat [file] > /dev/usb/lp0
Try to send reset sequence before printing process:
[ write_2_printer("\x1b\x40");]
I need to write a Red Hat Linux command line tool that launches a window and captures its appearance to disk as a JPEG.
Typically the target machines don't have graphics cards, but we can install any software components (e.g., X).
Question or two:
What libraries or tools might you suggest for this?
If I were to use something like GTK+ to create this tool, would lacking a video card hamper its execution?
I saw scrot, but it doesn't appear to support capturing a specific window without user interaction.
It sounds like you'll need to use the "virtual framebuffer" driver for the X.org server, combined with the xwd, NetPBM, and cjpeg utilities.
I'm not sure about the particular configuration you'll need for the X server, but you will likely have to make sure the server you're using has the virtual framebuffer driver built into to. The virtual framebuffer driver is a display driver just like one you'd use to connect to an NVidia or ATI video card, except it's "output" is a chunk of memory that contains the pixels, not an LCD screen.
xwd is one of the standard X tools, that can create a X Window Dump. xwd can be told on the command line which window to dump. It outputs a funky "xwd" formatted stream to standard out.
The NetPBM utilities are a collection of command line tools that convert one image format to another. It includes one that converts xwdtoppm. PPM is a very basic, non-compressed format that is the intermediate format understood by most of the NetPBM tools.
cjpeg is part of the standard JPEG tools collection, and is probably installed if you also have NetPBM. cjpeg can take a stream of PPM bytes and emit a stream of JPEG bytes.
Through the magic of Unix scripting and pipes, you can string these utilities together to fire up the app with the window, call xwd, xwdtoppm, and cjpeg to dump the image to a file.
You might try running vncserver to create a virtual X window display - no graphics card needed. Be sure to set your DISPLAY variable to the display number that gets printed when vncserver starts. Next, start your app on the created display (in hte background) and use xwd with data formatters or a gimp command to capture the screen image to jpeg.
By the way, check the similar answers for Command line program to create website screenshots (on Linux).