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{{AppliesToAxel}}
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== Introduction ==
This page collects all the Frequently Asked Question regarding Axel Ultra/Lite SOMsand XELK kit.
== General ==
=== Q: Where can I found find Axel SOMs information? ===
'''A''': please refer to the following table:
| [[:Category:AxelLite|Axel Lite category page]] || This page lists all the wiki pages regarding the Axel Lite CPU module
|-
| [[Axel_Ultra_SOM :Category:AxelUltra| Axel Ultra SOMcategory page]] || This page reports Axel Ultra SOM specification and basic information
|-
| [[Axel_Lite_SOM :Category:AxelLite| Axel Lite SOMcategory page]] || This page reports Axel Lite SOM specification and basic information
|-
| [[Hardware_Manual_(AxelUltra) | Axel Ultra Hardware Manual]] || This page points to the Axel Ultra Hardware Manual
* 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 ===
</pre>
Please note that <u>OPP can be changed only using the '''<code>userspace''' </code> governor</u>. If governors like ondemand is used, OPP change happens automatically based on the system load. Please also note that the imx6q-cpufreq driver (http://lxr.free-electrons.com/source/drivers/cpufreq/imx6q-cpufreq.c?v=3.10) works on a per-SOC policy (and not on a per-core one), so the cpufreq governor changes the clock speed for all the ARM cores simultaneously. To change the governor (<code>userspace</code> in the example):<pre class="board-terminal">echo userspace > /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor</pre>
=== Q: How can I read the CPU temperature? ===
'''A''': CPU temperature is reported by the Anatop Thermal driver. To read the he temperature, enter this command from the Linux shell:
<pre class="board-terminal">
CPU temperature is shown without decimal point, but the latest three digits are decimal.
=== Q: How can I adjust LCD brightness? ===
'''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">
root@axel-lite:~# cat /sys/class/backlight/backlight.30/brightness
75
</pre>
To set a new brightness level, enter this command from the Linux shell (100 is an example):
<pre class="board-terminal">
root@axel-lite:~# echo 100 > /sys/class/backlight/backlight.30/brightness
</pre>
Max value accepted for brightness can be read entering the following commands:
<pre class="board-terminal">
root@axel-lite:~# cat /sys/class/backlight/backlight.30/max_brightness
100
</pre>
'''N.B.''' The brightness index is related to the kernel and dtb compiled version. I.e. in the example index .30 maybe different on your system.
The right index can be found entering the following command from Linux shell:
<pre class="board-terminal">
root@xelk-l:~# ls -la /sys/class/backlight/
drwxr-xr-x 2 root root 0 Jun 13 11:50 .
drwxr-xr-x 50 root root 0 Jan 1 1970 ..
lrwxrwxrwx 1 root root 0 Jun 13 11:50 backlight.30 -> ../../devices/soc0/backlight.30/backlight/backlight.30
</pre>
=== Q: How can I modify the splash screen in U-Boot? ===
'''A''': The splash screen in U-Boot is supported starting from version 2013.04-xelk-2.2.0. For detailed information, please refer to [[Customizing the splash screen (Axel)]].
=== 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.
<pre class="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
[ 3.290548] snvs_rtc 20cc034.snvs-rtc-lp: setting system clock to 1970-01-01 00:00:01 UTC (1)
</pre>
To initialize it, please use these commands:
<pre class="board-terminal">
root@axel-lite:~# date 053014172016
Mon May 30 14:17:00 UTC 2016
root@axel-lite:~# hwclock -w
root@axel-lite:~# hwclock
Mon May 30 14:17:07 2016 0.000000 seconds
</pre>
To enter RTC mode, use the <code>shutdown</code> command as shown in the following example:
<pre class="board-terminal">
root@axel-lite:~# shutdown -h now
Broadcast message from root@axel-lite (ttymxc2) (Mon May 30 14:17:37 2016):
The system is going down for system halt NOW!
INIT: Switching to runlevel: 0
INIT: Sending processes the TERM signal
root@axel-lite:~# Stopping XServer
Stopping Dropbear SSH server: stopped /usr/sbin/dropbear (pid 686)
dropbear.
* Stopping Avahi mDNS/DNS-SD Daemon: avahi-daemon
** (oprofile-server:732): WARNING **: Avahi error: Daemon connection failed
...done.
Stopping advanced power management daemon: no /usr/sbin/apmd found; none killed
apmd.
Stopping system message bus: dbus.
stopping statd: done
stopping mountd: done
stopping nfsd: done
Stopping OProfileUI server
Stopping syslogd/klogd: stopped syslogd (pid 712)
stopped klogd (pid 714)
done
Stopping Connection Manager
Stopping Telephony daemon
ALSA: Storing mixer settings...
not deconfiguring network interfaces: network file systems still mounted.
Stopping Linux NFC daemon
Sending all processes the TERM signal...
rpcbind: rpcbind terminating on signal. Restart with "rpcbind -w"
Error VT_WAITACTIVE failed
: Interrupted system call
Sending all processes the KILL signal...
Unmounting remote filesystems...
Stopping rpcbind daemon...
not running.
Deactivating swap...
Unmounting local filesystems...
[ 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 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 [http://www.dave.eu/sites/default/files/files/sbcx-ug.pdf SBX User Guide] to set the correct serial operation mode.
