Try to increase this value until the corresponding interface fails due to the signal quality of the
clock signal. Decrease the serial resistor again in order to have a suitable margin.
Instead of using the clock output signals, some of the interfaces also allow using a different
asynchronous clock reference. For example, if the audio codec needs to be located far away from
the Apalis computer module, it might be a better solution to use an oscillator instead of the
reference clock output of the module. This oscillator can be placed close to the audio codec. Check
whether the audio codec has any restrictions in using an asynchronous clock source.
2.24.3 Unused Clock Output Signal Termination
Unused clock output signals can be left unconnected. The output should be disabled for reducing
power consumption and EMI problems.
2.25 GPIO
The Apalis form factor features 8 dedicated general purpose input output pins (GPIO). Beside these
8 GPIOs, several pins can be used as GPIO if their primary function is not in use. The Table 2 in
Section 2.1.1 shows an overview of the interfaces. Some interfaces are stated as “GPIO Capable”
This means, all Apalis modules shall provide GPIO functionality on these pins as secondary
function. The interfaces that are listed as optional GPIO capable may be compatible on some
modules.
For carrier board designs that provide the highest compatibility with all Apalis modules, it is
recommended to use the 8 dedicated GPIO signals first. If additional GPIO signals are required
still, unused signal pins of the interfaces that are stated as “GPIO Capable” should be used.
2.25.1 GPIO Signals
The following table contains only the dedicated GPIO pins of the Apalis modules. Consult the
relevant datasheet of the modules for information on the other MXM3 pins that can be used as
GPIO interface.
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