Bureaucrats, dave_user, Administrators
8,184
edits
Changes
→Q: How can I enable UART5 – J21?
{{InfoBoxBottom}}
== Introduction ==
This page collects all the Frequently Asked Question regarding Axel Ultra/Lite SOMs and XELK kit.
== General ==
=== Q: Where can I find Axel SOMs information? ===
* has a proper subnet IP address
For detailed information, please refer to [[Booting_Linux_Kernel#Configuration_net_nfs | Configuration net_nfs]]
=== Q: How can I access the git server repositories for updating? ===
'''A''': for accessing '''git.dave.eu''' git server repositories, the VM Netowrk interface should be configured for Internet access
* if the network interface is configured in NAT: the PC host interface should have Internet access and the DNS has to be configured for name resolution. For example, it should ne enough to use the Google DNS, i.e. ''8.8.8.8''
* if the network interface is configured in Bridge: the IP address should have a proper access to Interner and the DNS server has to be properly configured
Here below an wired connection example for an IP address with Bridged configuration via Host network interface:
[[File:VM-IP-fixed.png|300px]]
then simply test the Internet access using the '''ping command''' to Google's web site and then to DAVE's git server:
<pre class="board-terminal">
dvdk@vagrant-ubuntu-trusty-64:~$ ping www.google.it
PING www.google.it (216.58.205.67) 56(84) bytes of data.
64 bytes from mil04s25-in-f67.1e100.net (216.58.205.67): icmp_seq=1 ttl=53 time=7.03 ms
64 bytes from mil04s25-in-f67.1e100.net (216.58.205.67): icmp_seq=2 ttl=53 time=7.74 ms
^C
--- www.google.it ping statistics ---
2 packets transmitted, 2 received, 0% packet loss, time 1003ms
rtt min/avg/max/mdev = 7.036/7.390/7.745/0.364 ms
dvdk@vagrant-ubuntu-trusty-64:~$ ping git.dave.eu
PING pmox001.dave.eu (79.143.179.155) 56(84) bytes of data.
64 bytes from pmox001.dave.eu (79.143.179.155): icmp_seq=1 ttl=53 time=24.1 ms
64 bytes from pmox001.dave.eu (79.143.179.155): icmp_seq=2 ttl=53 time=24.0 ms
^C
--- pmox001.dave.eu ping statistics ---
2 packets transmitted, 2 received, 0% packet loss, time 1001ms
rtt min/avg/max/mdev = 24.034/24.089/24.145/0.164 ms
dvdk@vagrant-ubuntu-trusty-64:~$
</pre>
=== Q: How can I access GPIOs from user space ===
'''A''': Users can access GPIOs using SYSFS entries from user space. This feature is enabled by default in the AXEL Linux kernel configuration. For further details, please refer to:
* https://community.freescalenxp.com/docsthread/DOC-1459379763* https://www.kosagi.com/w/index.php?title=Definitive_GPIO_guide
* https://www.kernel.org/doc/Documentation/gpio/sysfs.txt
'''A''': brightness level can be changed via sysfs entry. To read the current brightness level, enter this command from the Linux shell:
'''Note:''' Xelk-3.0.0 has been released with a new kernel version which no longer requires the .n notation in the path. For this reason, the path to use is : ''/sys/class/backlight/backlight''
<pre class="board-terminal">
=== Q: How to enter RTC mode? ===
By default, iMX6 RTC driver is built into the Linux kernel. Upon power-up, it prints informational messages that look like this.
<preclass="board-terminal">
[ 2.017007] snvs_rtc 20cc034.snvs-rtc-lp: rtc core: registered 20cc034.snvs-rtc-lp as rtc0
[ 2.025312] snvs_rtc 20cc034.snvs-rtc-lp: configured with power off disabled
To initialize it, please use these commands:
<preclass="board-terminal">
root@axel-lite:~# date 053014172016
Mon May 30 14:17:00 UTC 2016
To enter RTC mode, use the <code>shutdown</code> command as shown in the following example:
<preclass="board-terminal">
root@axel-lite:~# shutdown -h now
[ 234.876402] System halted.
</pre>
If a coin call battery is connected to PMIC_LICELL, RTC will be kept alive even if 3V3VIN voltage is removed. Please refer to [[Integration_guide_(Axel)#Real-time_clock_.28RTC.29|these important issues]] related to RTC power handling.
=== Q: How to synchronize date/time? ===
System date and time can be easily kept synchronized using the <code>ntp</code> services available on Internet.
If the ntp package is not present into the rfs, it is possible to install it using the standard <code>smart</code> tool as described [[XELK-AN-003:_Package_Management_with_Yocto#Installing_packages_on_target | here]]
<pre class="board-terminal">
root@imx6qxelk:~# smart install ntp
Loading cache...
Updating cache... ######################################## [100%]
Computing transaction...
Installing packages (2):
ntp-4.2.8p9-r0@cortexa9hf_neon
ntp-tickadj-4.2.8p9-r0@cortexa9hf_neon
346.7kB of package files are needed. 635.1kB will be used.
Confirm changes? (Y/n): y
Fetching packages...
-> http://yocto.dave.eu/.../ntp-tickadj-4.2.8p9-r0.cortexa9hf_neon.rpm
ntp-tickadj-4.2.8p9-r0.cortex.. ######################################## [ 50%]
-> http://yocto.dave.eu/xelk-4.0.0/.../ntp-4.2.8p9-r0.cortexa9hf_neon.rpm
ntp-4.2.8p9-r0.cortexa9hf_neo.. ######################################## [100%]
Committing transaction...
Preparing... ######################################## [ 0%]
1:Installing ntp-tickadj ######################################## [ 50%]
Output from ntp-4.2.8p9-r0@cortexa9hf_neon:
Running useradd commands...
NOTE: ntp: Performing useradd with [ --system --home-dir /var/lib/ntp --no-create-home --shell /bin/false --user-group ntp]
2:Installing ntp ######################################## [100%]
update-alternatives: Linking /usr/sbin/ntpd to /usr/sbin/ntpd.ntp
Created symlink /etc/systemd/system/multi-user.target.wants/ntpd.service → /lib/systemd/system/ntpd.service.
Saving cache...
root@imx6qxelk:~#
</pre>
Then the <code>/etc/ntp.conf</code> file has to be modified according to the ''ntp server pool'' used for time synchronization, for example in Italy:
server 0.it.pool.ntp.org
server 1.it.pool.ntp.org
server 2.it.pool.ntp.org
server 3.it.pool.ntp.org
Must be sure you are properly configured for your ''locatimezone''. For that purposes, you may have to install the proper ''tzdata'' package, for example:
smart install tzdata-europe
and then configure it using <code>timedatectl </code>
<pre>
root@imx6qxelk:~# timedatectl set-timezone Europe/Rome
root@imx6qxelk:~# timedatectl status
Local time: Wed 2020-02-19 15:32:02 CET
Universal time: Wed 2020-02-19 14:32:02 UTC
RTC time: Wed 2020-02-19 14:32:02
Time zone: Europe/Rome (CET, +0100)
Network time on: yes
NTP synchronized: yes
RTC in local TZ: no
root@imx6qxelk:~#
</pre>
=== Q: How can I enable UART5 – J21? ===
UART 5 communication can be enabled by adjusting the led ''rs232_485_422'' level to HIGH.
You can find the configuration's folder here:
<pre class="board-terminal">
ls /sys/class/leds/
mmc0:: mmc1:: rs232_485_422 rs232_on
</pre>
To enable the serial communication, set the led's value to HIGH, as follows:
<pre class="board-terminal">
echo 255 > /sys/class/leds/rs232_485_422/brightness
</pre>
Please rely on the [https://mirror.dave.eu/Manuals/SBC%20Axel/sbcx-ug.pdf SBX User Guide] to set the correct serial operation mode.
