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Advertisement Feature
T
he demand for more sophisticated features
is common to most of today’s markets,
including home appliances, personal
medical devices and industrial terminals.
Fortunately for designers of user interfaces,
decreasing prices mean colour TFT-LCDs are a
viable solution to help users access extensive
functions quickly and intuitively. As usual,
however, designers need to short cut the
learning curve when integrating colour displays,
as well as establishing the lowest cost
techniques for implementation.
Demand for colour
Examples of emerging products using next
generation display technology include home
appliances such as refrigerators. There are moves
to integrate an eye level TFT-LCD supporting
features to record shopping lists, play MP3 music
or even to playback video messages such as
cooking tips. The notion of the multifunction
remote control is also gaining traction as home
owners seek to consolidate the numerous
remotes into one unit that can be stored tidily
and located easily when needed.
Ease of use is of paramount importance and
the latest multifunction designs are
implementing colour displays as large as 15cm
and featuring touchscreen capabilities. Colour
graphics help to make functions such as mode
selection and soft key assignment easy to
understand and can help users navigate the
functions of multiple devices quickly and easily.
In other sectors, such as medical care,
portable monitoring devices are increasingly
used to help patients self administer treatments
at home and to record their vital signs, including
blood pressure, heart rate and respiration, for
direct data download by the supervising doctor
or consultant. The use of colour in man machine
interface (MMI) design is an effective way to
understand and use the equipment correctly.
Low power consumption is also a prime concern
in such applications.
In professional markets, such as industrial
machines, data logging terminals or security
equipment, colour coded controls provide an
effective solution to demands for safety and to
simplify the setup and monitoring of complex
processes. In security applications, a colour
control unit can help staff to identify and classify
potential threats and to coordinate effective
defences.
Dreaming
in colour
Roland Gehrmann describes a fast, low risk solution
for feature rich user interfaces in advanced professional
and domestic equipment designs.
Impact on controllers
To support these forthcoming capabilities,
controlling devices will need to add support for
functions such as Mpeg4 decoding for video
playback. Industry standard external interfaces,
such as USB, and removable media, such as
Secure Digital or CompactFlash cards, will also be
required. These will allow external devices to
plug in and share media such as MP3 tracks and
digital camera images or to apply software
upgrades or feature updates. Touchscreen
functionality will also be a core feature, not only
to eliminate the need for external hardware such
as a keypad, but also to support value added
features such as handwriting recognition. This
will be particularly important where notepad
functions are required, such as in kitchen
appliances.
Suitable microcontrollers will also face
increased demands for high processing power
and larger memory capacity. But display driving
duties have typically been the preserve of 8bit
devices, usually featuring monochrome LCD
drivers and with limited memory and processing
power. But while there are new demands for
more performance and connectivity, the
pressures on cost and time to market – as well as
power consumption for handheld devices – are as
intense as ever. Hence identifying a suitable MCU
for forthcoming colour display products,
incorporating all of the necessary features and
peripherals is a difficult task.
Integrating a discrete processor and a
separate colour display interface IC and
incorporating additional features such as a
touchscreen as required, is complex and time
consuming. This approach will also result in a
larger than ideal footprint, as well as an
increased part count. This, in turn, leads to
additional inventory, manufacturing and
warranty replacement costs throughout the
lifetime of the device.
An integrated solution is more desirable, but
engineers must typically choose a device
originally designed for a specific application in a
high volume market. Finding the closest match is
not the best route to an optimal solution:
support for a colour display or CompactFlash or
Secure Digital media card interfaces, for
example, may come at the expense of an
overpowered processor, such as those aimed at
the PDA market. On the other hand, an ideally
“Although not an immediately obvious choice for home appliance or
medical applications, (these MCUs) possess a suitable combination of core
processing power, colour display support and external interfaces.”
22
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SPONSORED TUTORIAL
Microcontrollers
Figure 1: TMP92CZ26XBG/TMP92CF29FG
10MHz
PLL
PLL
32kHz
WDT
WDT
136I/O
boot ROM
8 bit timer
(8 channels)
timer/counter output
timer/counter input
input/output
key input
16 bit timer
(2 channels)
key port
melody alarm
900/HI core
80MHz
(uDMA)
touchscreen
timer/counter output
timer/counter input
touchscreen
interrupt
LCD data
colour LCD
controller
sound data
I2S interface
(2 channels)
analogue input
external trigger
10 bit ADC
(6 channels)
SIO/UART
MMU/SDRAM
controller
MLC NAND
Flash
interface
MAC
DMA
priced device may only support a proportion of
the consumer oriented features required.
Looking further afield
There is a class of MCUs originally developed to
support pocket electronic dictionaries, which are
popular in Asian markets but which have not
penetrated Europe or the US. Although not an
immediately obvious choice for home appliance
or medical applications, they possess a suitable
combination of core processing power, colour
display support and external interfaces.
Frugal power management, through the use
of multiple low power modes and advanced
techniques to minimise leakage, is also valuable
for designers of handheld products such as
multifunction remotes, industrial data logging
terminals and portable medical monitors.
The Toshiba TMP92CZ26 series of MCUs
provides an example of the types of processors
that have been successful in pocket
e-dictionaries.
Built around a 32bit 80MHz CISC core, the
device runs at 80MHz internally to achieve 40MIPS
computing performance with power consumption
of only 80mW. This is the best processing
performance and lowest power consumption of
any MCU in this product category.
CS/wait
(4 channels)
TXD/RXD/SCK/SI/SO
CS/wait
USB
USB (48MHz)
SPI
CLK/DO/DI
For single twisted nematic displays, the device
supports monochrome, 4, 16 and 64 grey levels,
as well as 256 or 4096 colours. For TFT LCDs, the
device supports up to 16million colours. Screen
resolutions ranging from 320 x 240 QVGA to 640
x 480 VGA are supported and there is also a full
speed USB controller and an SPI interface,
enabling engineers to quickly implement
interfaces for flash memory cards.
There is also a built in interface to external
NAND flash program/data memory. In addition,
the processor architecture features a memory
management unit (MMU). The MMU not only
allows an operating system to maintain stability
while managing multiple programs, but also
enables the application to operate with reduced
physical memory to save cost and reduce power
consumption.
As well as support for 24bit/pixel colour
resolution for true colour display, further
features important to designers targeting
emerging applications include picture and data
rotation capabilities. These will allow pictures
from a digital camera, for example, to be
manipulated and presented in the most suitable
orientation. This would allow owners of
advanced appliances to view digital photographs
on the embedded display or to upload scanned
images, such as cooking instructions or a
calendar.
Support for video images requires a higher
level of processing performance in the core of
the chosen MCU, for example to execute Mpeg4
decoding.
To accelerate DSP operations, suitable
devices implement dedicated hardware, such as
the TMP92CZ26’s 32 x 32 + 64 Multiply
Accumulate (MAC) module. This can perform
calculations on three operands within one cycle
– equivalent to 12.5ns at 80MHz.
To implement successfully the advanced
connectivity features being proposed for
tomorrow’s domestic appliances, medical
instruments and industrial controllers, designers
also need access to versatile libraries of software
functions, including networking stacks, USB
firmware, memory card drivers and graphics
software support.
Support for these types of IP can be difficult
to find for the low cost MCUs traditionally used
in display driving duties. But there is a wide
variety of IP available for the e-dictionary class
of MCU, not only providing support for popular
interface standards, but also including functions
such as handwriting recognition, text to speech,
MP3 playback and Jpeg decode/animation.
Evaluation boards and development support
also benefit from the existing infrastructure that
services developers targeting the Asian edictionary markets.
First to market
Historically, designers of niche and low volume
embedded systems have had to choose a best fit
MCU for their application. As vendors’ product
ranges have matured, this approach has proved
adequate to satisfy the majority of requirements.
But many vendors have not reacted quickly to
the advent of low cost colour displays and are
currently unable to meet all of the requirements
of developers who are now eager to explore the
opportunities for powerful new MMI techniques.
Looking further afield for a solution can yield
a crucial head start in the race to reach the
emerging markets. ■
Author profile:
Roland Gehrmann is manager of MCU and
Audio/Video IC Microcomputer, Automotive and
Consumer IC Marketing for Toshiba Electronics
Europe.
For more information, go to www.toshiba-components.com
www.newelectronics.co.uk 8 January 2008
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