duagon MC50M, User Manual, Page: 36 / 85

Getting Started
20MC50M00 E5

2020-10-20 36
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To trigger the watchdog, toggle the value of the GPIO:
Linux Kernels from 4.8
Newer Linux kernels provide more comfortable access through dedicated GPIO tools.
Example:
gpio-hammer tool
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Go to kernel source directory /tools/gpio .
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Build and install gpio-hammer :
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To trigger the watchdog, toggle GPIO no. 8 on gpiochip0 :
2.6.5 Managing RTC Time Adjustments
During the boot process the CPU firmware gets the time from the system RTC (ERTC) and
sets the CRTC (Chipset Real-Time Clock) accordingly. In the next step, the operating
system (OS) gets the time from the CRTC and sets the system time accordingly. Now the
OS system time is updated independently of the CRTC via periodic clock interrupts. Thus,
over time (i.e. as the system runs), the system time may become out of sync with the
CRTC/ERTC time.
If the system time is adjusted (e.g., by the user), the ERTC time will not be automatically
adjusted by the time management, because the OS is not aware of the additional ERTC.
The ERTC time will not be updated and is out of date. During the next system boot, the
OS would use the outdated time.
duagon provides a dedicated ERTC driver to manage system time adjustments.
2.6.6 Configuring the Serial Interfaces
The ASIX AX99100 UART controller on MC50M needs a special software driver to make
the interfaces usable under Linux.
# echo 0 > /sys/class/gpio/gpio442/value
# echo 1 > /sys/class/gpio/gpio442/value
# make && make install
# gpio-hammer -n gpiochip0 -o 8
See the duagon website for application note Using the System RTC (ERTC) on
MEN CPUs under Linux .
 If you use the Yocto BSP, you do not need to install the software driver; a
tested version is already included and pre-configured in the Yocto BSP.

In a modular DIN-rail system, the ASIX driver handles all of the serial
interfaces of the system. You have to install the driver once on the MC
module (CPU) and can configure all of your serial interfaces on system
level, including those on ME modules.
Note:There can be a maximum of three ME3 modules in one system.
However, the Yocto BSP only supports one ME3 module.