I have a NUC in Ubuntu. I would like to write a program in c for serial port send and receive message.
The device is /dev/ttyUSB0.
It is success to use Linux command echo "message" > /dev/ttyUSB0 and use minicom to get the result.
But the device is open fail when using c program, fd always return -1
int fd;
fd = open ("/dev/ttyUSB0", O_RDWR);
Then I try to use raspbian pi in debian, and run the same program. It can open the device.
Is there any setting is missing in Ubuntu platform in NUC? Thanks you very match.
Update:
I print out the error message: open() failed with error [Permission denied],
then I try to use sudo to run the exe file, then I can get the usb device
this is current file detial
-rwxrwxr-x 1 u u 9048 Aug 22 19:15 uart
-rw-rw-r-- 1 u u 1424 Aug 22 19:15 uart.c
Beside I use chown change the permission of file, is there any other method?
sudo usermod -a -G dialout <User>
/dev/ttyxy is owned by the user root and the group dialout , so I added myself to the dialout group. At least worked for me.
If your situation allow you to use sudo, then why any alternative !
Related
when i try to login on packet tracer after putting my mail the program closes and this shows on my terminal.
:~$ sudo packettracer
Starting Packet Tracer 7.2.2
/usr/local/bin/packettracer: línea 8: 3352 Excepción de coma flotante (`core' generado) ./PacketTracer7 "$#" > /dev/null 2>&1
:~$
the error in spanish says something like : line 8: 3352 Floating point exception ( 'core' generated)
I had to install a packet tracer on a newly installed ubuntu 18.04.3 I followed this guide, with the exception that instead of .tar.gz I had to download the PacketTracer-7.2.2-ubuntu-setup.run, it has to be the version 7.2.2. I had it installed and working until recently that I had to format my computer.
Also if I close the login window I can see that the UI it's loaded but since I didn't log in it closes.
additional information:
:~$cat /var/log/syslog
[...]
Jan 27 19:32:00 skynet kernel: [ 5160.136825] traps: PacketTracer7[4124] trap divide error ip:7f2540ec7ef4 sp:7fff1119dc80 error:0 in libQt5XcbQpa.so.5[7f2540e0b000+111000]
as for now I could bypass my problem by installing a virtual machine with a windows 10 and running packet tracer there, I hope this is just a temporary solution.
I am trying to receive a trap generated by a cisco router on my VM- Ubuntu 14.04. I can do a snmwalk so I guess snmp is working fine but I am not able to receive the traps generated by router on my VM.
a#ubuntu:~$ sudo /etc/init.d/snmpd restart
* Restarting network management services:
a#ubuntu:~$ sudo /etc/init.d/snmpd status
* snmpd is running
* snmptrapd is running
Here is what I have inside files-
/etc/default/snmpd-
export MIBS=
SNMPDRUN=yes
SNMPDOPTS='-Lsd -Lf /dev/null -u snmp -I -smux -p /var/run/snmpd.pid -c /etc/snmp/snmpd.conf'
TRAPDRUN=yes
# snmptrapd options (use syslog).
TRAPDOPTS='-n -On -t -Lsd -p /var/run/snmptrapd.pid'
/etc/snmp/-
snmpd.conf-
rocommunity public
snmptrapd.conf-
disableAuthorization yes
snmp.conf-
mibs:
The command I am running for viewing the traps on VM-
a#ubuntu:/etc/snmp$ sudo snmptrapd -f -Lo -c snmptrapd.conf
couldn't open udp:162 -- errno 98 ("Address already in use")
I am confused since the port is being used by snmptrap itself-
a#ubuntu:~$ cat /etc/services|grep 162
snmp-trap 162/tcp snmptrap # Traps for SNMP
snmp-trap 162/udp snmptrap
a#ubuntu:~$ sudo netstat -lnp| grep 162
udp 0 0 0.0.0.0:162 0.0.0.0:* 6216/snmptrapd
a#ubuntu:~$ ps -ef | grep snmptrapd
root 6216 2076 0 10:43 ? 00:00:00 /usr/sbin/snmptrapd -Lsd -p /var/run/snmptrapd.pid
a 6493 2667 0 11:47 pts/8 00:00:00 grep --color=auto snmptrapd
Generating a trap from windows using SnmpTrapGen.exe leads to the same error.
Is there any way of solving this issue? I have googled a lot and stuck on this for days, any help will be very much appreciated.
Thanks a lot in advance!!
Port 162 can listen only with an application. If you get this error , you have an app already running which listens port 162 , those can be snmptrapd service or your own application for snmp traps. You should close one of the applications.
For some reason i am not able to attach to my very own processes?! Works fine if i try strace as root.
$ ./list8 &
[1] 3141
$ child4 starts...
$ strace -p 3141
attach: ptrace(PTRACE_ATTACH, ...): Operation not permitted
Could not attach to process. If your uid matches the uid of the target
process, check the setting of /proc/sys/kernel/yama/ptrace_scope, or try
again as the root user. For more details, see /etc/sysctl.d/10-ptrace.conf
$ cat /proc/sys/kernel/yama/ptrace_scope
1
Running on lubuntu 13.10
Linux goal 3.8.0-19-generic #29-Ubuntu SMP Wed Apr 17 18:19:42 UTC 2013 i686 i686 i686 GNU/Linux
So then how does gdb attach to user's own processes without having to muck around with kernel settings (ptrace_scope)??
Looks like you answered your own question -- you have ptrace_scope set to 1, so you can only trace direct children. To allow tracing any process belonging to the same user, set it to 0. This is also required to use the gdb attach command.
READ the /etc/sysctl.d/10-ptrace.conf file as your error message suggested...
If strace fails as root, try checking whether... gdb or strace is not running in the background (that was my case).
Command: ps aux | grep "gdb\|strace"
If this fails as root, I had a problem stracing enlightenment (e17) and the reason was that you can't strace a process already being straced or run under gdb, which some programs will do so that they can get their own debugging info.
How can I control Parallel Port outputs/inputs with Batch files or other Executable File ?
Like i say, i want to high pin number 3,4 and 7.
Please Any One Give me any idea.
Thanks in advance.
Microsoft locked down I/O ports after windows 9x due to security issues but you can get usermode access to them using a special kernel mode driver found here. After you run that program, you can use debug to toggle pins. Debug uses Hex values so, to switch on 3,4 and 7 you'd do
debug
-o 378 02
G
-o 378 04
G
-o 378 20
G
You can wrap that into a batch file or just run it from a CMD prompt.
I'm trying to use a somewhat old DAQ, and had to jump through a few hoops to get an old (circa 2004) device driver for it to compile (DTI-DT340 Linux-DAQ-PCI).
I've gotten to the point where it compiles, I can load the kernel module, it finds the card, and I can create the character devices using mknod.
But I can't seem to open these devices and keep getting errno 19 (ENODEV) 'No such device' when I try to
open("/dev/dt340/0",O_RDWR);
but mknod had no complaints about making it, and it's there:
# ls -l /dev/dt340/
total 0
crw-rw-r-- 1 root staff 250, 0 2009-04-23 11:02 0
crw-rw-r-- 1 root staff 250, 1 2009-04-23 11:02 1
crw-rw-r-- 1 root staff 250, 2 2009-04-23 11:02 2
crw-rw-r-- 1 root staff 250, 3 2009-04-23 11:02 3
Is there something I'm neglecting to do? What might be a reason open fails?
Here's the script I use to load the driver and make the devices.
#!/bin/bash
module="dt340"
device="dt340"
mode="664"
# invoke modprobe with all arguments we were passed
#/sbin/modprobe -t misc -lroot -f -s $module.o $* || exit 1
insmod $module.ko
# remove stale nodes
rm -f /dev/${device}/[0-3]
major=`awk "\\$2==\"$module\" {print \\$1}" /proc/devices`
mkdir -p /dev/${device}
mknod /dev/${device}/0 c $major 0
mknod /dev/${device}/1 c $major 1
mknod /dev/${device}/2 c $major 2
mknod /dev/${device}/3 c $major 3
# give appropriate group/permissions, and change the group
# not all distributions have staff; some have "users" instead
group="staff"
grep '^staff:' /etc/group > /dev/null || group="users"
chgrp $group /dev/${device}/[0-3]
chmod $mode /dev/${device}/[0-3]
Some additional info:
#grep dt340 /proc/devices
250 dt340
# lsmod | grep dt340
dt340 21516 0
# tail /var/log/messages
Apr 23 11:59:26 ve kernel: [ 412.862139] dt340 0000:03:01.0: PCI INT A -> GSI 22 (level, low) -> IRQ 22
Apr 23 11:59:26 ve kernel: [ 412.862362] dt340: In function dt340_init_one:
Apr 23 11:59:26 ve kernel: [ 412.862363] Device DT340 Rev 0x0 detected at address 0xfebf0000
#lspci | grep 340
03:01.0 Multimedia controller: Data Translation DT340
ANSWER: A printk confirmed that the -ENODEV was thrown from inside open(). Following an oldstyle
while ((pdev = pci_find_device(PCI_VENDOR_ID_DTI, PCI_ANY_ID, pdev)))
(which is deprecated), if(!pdev) ends up true, and returns the -ENODEV.
I'm inching closer - I guess I have to work through and update the pci code to use more modern mechanisms...
If the device shows up in /proc/devices, and you're sure you've got the number right in mknod, then the driver itself is refusing the open. The driver can return any error code from open() - including "no such device", which it might if it discovered a problem initialising the hardware.
I'd guess it is a problem in the driver, check the open function.
It shows up in /proc/devices, so all the generic device stuff seems to be ok.
mknod doesn't care if there is an device corresponding to the given major/minor numbers. Are you sure insmod is installing your module? What does lsmod tell you?
I'm unfamiliar with having to add the ".ko" extension. Is that something specific to your device driver?
Check through lspci and make sure hardware is properly initialized. If your system supports hotplug, pci_find_device won't work. The problem with this is a refcnt. The best way to deal and learn is to dissect the API. BOL !!