STM32 Journal - Digikey

STM32 Journal
down, developers must minimize
the expense for both of these
processes as well as eliminate
any unnecessary design delays.
In the past, UIs for embedded
systems were designed
specifically for the hardware on
which they were going to be
run. With increasing pressure to
shorten product design cycles, IP
Java Application
Java Class/API
Wrapper C Java
API C
Driver C
External
Port
Figure 1 Abstracting the hardware through a
Hardware Abstraction Layer (HAL)
frees the GUI framework from
handling specific low-level details,
leading to faster code development
and greater reusability.
reuse has become an important
consideration in UI design.
Ideally, developers need to be
able to carry a UI across different
products using MCUs that may
be from different families as well.
To achieve this, GUI application
code is abstracted above
the hardware. A Hardware
Abstraction Layer (HAL) handles
specific low-level details such
as how graphical data is stored
in memory and transferred to
the display (see Figure 1). By
interacting with the HAL using
APIs, the GUI application code
becomes a framework that can
be ported across an MCU family
with minimal rewriting required.
Creating an extensible GUI
framework is an involved
process. The HAL enables
developers to build the
framework using a language
other than assembly, leading to
faster code development and
greater reusability. Designing the
framework using C, however,
can still require substantial
development resources.
Ideally, rather than design
a framework from scratch,
developers can use off-the-shelf
software to minimize development
investment. With the right tools,
the GUI design cycle can be
shortened from months to weeks.
GWStudio from GeeseWare,
for example, is a Java Framework
with a wide array of preexisting
GUI libraries providing a complete
human-machine interface (HMI)
development environment. Its Java
engine based on IS2T MicroEJ ®
technology is specifically optimized
for embedded applications that
have limited memory, constrained
peripherals, restricted network
connectivity, and low power
consumption requirements.
Java brings many advantages to
GUI-based design compared to
working in C. Java was designed
to facilitate GUI creation with an
emphasis on reuse. In addition, its
flexibility ensures a simple revision
process that enables developers
to quickly implement changes
to existing designs. With the
availability of Java for embedded
applications, developers can
leverage the benefits of Java in
many applications:
〉〉 Improved code portability
and reuse
〉〉 Accelerated development up
to 3-5 times faster than
working in C
〉〉 Equivalent performance to
C-based designs; i.e., less
than 1 ms responsiveness for
machine-to-machine (M2M)
processes (i.e., Ethernet) or
touchscreen latency
〉〉 Greater functionality in a
smaller footprint
〉〉 Higher reliability and
robustness by eliminating
manual management of
memory and exceptions
〉〉 Operating system
independence
〉〉 Large development community
Note that even though the GUI is
written in Java, the main application
can be based on C. This enables
developers to introduce a GUI to an
existing design without having to
rewrite the application.
Even with the framework in
place, however, only half the job
is done. Now the look and feel of
the GUI needs to be designed.
Intuitive Look and Feel
Developing an effective GUI can
be one of the most challenging
aspects of system design. GUI
design involves much more
than simply arranging icons on
a screen. To be intuitive, a user
interface has to anticipate how a
variety of different types of people
are going to use the device.
However, it can be very difficult
to know how an end-customer
is going to use a device from
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