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→Q: How can I enable UART5 – J21?
=== 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
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? ===
echo 255 > /sys/class/leds/rs232_485_422/brightness
</pre>
Please rely on the [httphttps://wwwmirror.dave.eu/sitesManuals/default/files/filesSBC%20Axel/sbcx-ug.pdf SBX User Guide] to set the correct serial operation mode.
