Microcontroller System Design Lecture
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ECE 3700 : Fundamentals of Digital System
Design
Various, School of Computing, University of Utah
These course notes represent a very hands on study of digital
design. They cover the fundamentals of Boolean functions
and their realization in hardware. They also discuss how
to build combinational circuits, arithmetic and logical
functions using combinational circuits, and building sequential
circuits whose behavior depends on state as well as inputs.
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EE 1h : Signals and Systems Theme
Alan Murray, Uni
This course has slides that explain methods for applification
and gain in circuitry.
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Single-chip ICs optimize adaptive front lighting system
design
Electronic control of automotive HID headlight aiming, via
stepper motors, directs beams both to minimize glare for
oncoming traffic and illuminate curving roadways. But the
location of the motor driver chips in the vehicle impacts
system efficiency.
By Bart De Cock, AMI Semiconductor Belgium
High intensity discharge vehicle headlights
are increasingly becoming the technology of choice for vehicle
manufacturers across the globe. In order to make maximum
use of the excellent illumination HID provides, and at the
same time reduce the risk of glare caused by poorly directed
HID beams, adaptive front lighting systems (AFS) are gaining
increased importance.
These systems compensate for changes in
a vehicle's inclination relative to the road surface by
making slight vertical adjustments to the headlamp's light
beam. They also cause the headlamps to swivel in response
to a change in the vehicle's turning direction. The result
is a light beam that dramatically improves the driver's
cornering visibility by providing the optimum and safest
illumination of the road ahead.
Automatic leveling reduced glare
Automatic headlamp leveling systems work to keep light parallel
to the road surface regardless of the vehicle's tilt (see
below). A vehicle may tilt as a result of a standstill event,
such as boarding passengers, loading the trunk, or even
filling the fuel tank. Also while driving, the vehicle tilt
changes during braking or acceleration. In both cases, the
headlamps must be maintained level with the roadway. Automatic
headlamp leveling systems correlate their adjustment angles
based on a variety of sensor data in particular suspension
compression data from the front and rear axles.
Swiveling to improve safety
A vehicle's data network contains real-time sensor data
on steering angle and wheel speed. Based on this information,
AFS equipped headlamps can tailor the light distribution
with the vehicle's turning angle, so that upcoming curves
and turn-offs receive maximum illumination, especially at
the driver's gaze point (see below). Such a significant
increase in light helps reduce driver stress and fatigue
and improves the ability to see obstacles that fixed-beam
headlamps might not illuminate. Various studies on swivel-beam
headlamps have shown up to a 300% increase in the illumination
of the driver's gaze point as the vehicle turns into a corner.
Stepper motor control
The movement of each vehicle headlamp is achieved using
stepper motors one for vertical movements and one for horizontal
(see figure below). The motors are fed with, and react to,
data from numerous sensors around the vehicle. Communication
is carried out via the vehicle's data network system. The
LIN bus is a practical choice for headlamp control, while
the CAN bus collects and distributes the sensor data throughout
the vehicle. Stepper motors are ideal for headlamp adjustment
applications because the motors are low cost, very rugged,
and provide a high torque in relation to their size.
Motor driver methods
There are two approaches that can be adopted
in relation to the positioning of the driver IC chips that
control the stepper motors. The first is known as direct
drive. In this approach, the driver chips are mounted on
the main microcontroller PCB (see top image in figure below).
This board is remote from the headlamp unit and associated
stepper motors, perhaps located in a central electronics
control unit (ECU) attached to the vehicle bulkhead (firewall)
or in "friendly" environment in the vehicle passenger
compartment. The main disadvantages of this approach are
the excessive wiring that is required and the high level
of EMC radiation.
The second approach is mechatronic, in
this scenario the driver chip is mounted together with the
motor (at bottom in figure above). Mechatronic solutions
for AFS have become more feasible and easier to execute
since the introduction of highly integrated single chip
offerings (for example, AMIS-30621 and AMIS-30623 stepper
motor controller ICs from AMI Semiconductor) that are able
to be mounted directly on the motor. This method is beneficial
because interfacing between the central microcontroller
and the mechatronic module can run over a low EMC bus. There
are also significant pluses to a mechatronic approach relating
to the modularity and ease of maintenance of the headlamp
assembly.
Partitioning hardware and software
Stepper motor driver applications require the design of
both hardware and software. This can become quite complex,
especially where multiple axes need to be controlled simultaneously
as in adaptive headlighting. Until the emergence of integrated
stepper motor controller ICs, the established approaches
had been to invest in a microcontroller and develop dedicated
software, or use translator chips (see figure below, left
and center).
View a full-size image
The main problems with a software-based solution are the
high cost of development and the inherent difficulty in
proving correct operation of multiple axes under all conditions.
So called translator ICs that interface
between the microcontroller and the driver chips add some
additional hardware to the overall solution but result in
more manageable complexity and extent of the software required
(see figure above, right). The disadvantage of using translator
chips is that the PCB design becomes more complex and loses
any modularity.
Single-chip approaches
Integrated stepper motor controller ICs cut through the
complexities of other approaches to multiple axes AFS and
provide a straightforward solution that supports the modular
and mechatronic design that vehicle manufacturers desire.
AMI Semiconductor offers four mixed-signal
devices that integrate bus connection, positioning, and
control electronics with motor driver in a single 7 x 7-mm
package footprint. The small size and high degree of functionality
of these devices allows modular design of motion control
software and robust motor operation even when mounted directly
to the stepper motors.
View a full-size image
Two derivatives mentioned previously (AMIS-30621 and AMIS-30623),
feature a LIN interface. Compared to systems with remotely
placed drivers, this approach saves wiring cost and has
better EMC performance key for the difficult environments
encountered in automotive applications. Two other variants
(AMIS-30622 and AMIS-30624), have an I2C serial interface
and are able to act as a peripheral device positioned next
to the microcontroller on a single PCB.
Sensorless stall detection
Most automatic headlamp systems perform an initial position
calibration when the lights are switched on. This routine
basically drives the headlamp for a given time, to the lowest
point physically possible. A problem with this procedure
is that it introduces noise and increases wear due to the
stepper motor hitting the end-stop. Another solution can
be achieved by using the sensorless stall-detection feature
of the AMIS-30623 and AMIS-30624. These parts offer silent
operation, low wear, yet accurate position-calibrations
and allow semi-closed loop operation when approaching the
mechanical end-stops without the need for an external sensor.
Conclusion
Using single-chip stepper motor controller ICs can greatly
simplify AFS design and provide outstanding technical performance
in what are typically difficult operating conditions. The
integrated design promotes better overall reliability and
means that the external circuitry required is limited to
just a few capacitors. Time to market, design, and overall
system cost are also impacted positively.
Mechatronic and modular solutions, both
well supported by integrated single-chip stepper motor controller
ICs, are highly sought after by vehicle manufacturers in
a world where rapidly increasing vehicle electronic content
threatens to make the electronics system architecture over-complex
and expensive. Ads by Google Microcontroller Kit Microcontroller
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Our doubts are traitors, and make us lose the good we oft
might win by fearing to attempt
- Shakespeare
11/1/2002 | View
Significant Embedded Systems News
Embedded System Product News
Dec 10, 2007 Texas Instruments New MSP430 Family Offers
Even Lower Power and 120KBytes Flash
Nov 5, 2007 New Microchip PIC32 32-bit Microcontrollers
Run 72MHz with 512KB Flash
Sep 19, 2007 New High Performance PIC18 K Family from Microchip
Sep 18, 2007 Ramtron Introduces 8051 Microcontroller with
64 KBytes Flash and 2 KBytes Nonvolatile F-RAM
Development Tools News
Apr 4, 2007 Embedded BIOS by General Software Provides Rapid
x86 Development
Jan 22, 2007 New USB Development Kit from STMicroelectronics
Supports STR7 (ARM7) and STR9 (ARM9) Development with Free
Software
Apr 4, 2006 Embedded Internet & Embedded RTOS Support
for Coldfire from CMX
Oct 28, 2005 ARM Purchases Keil Software
Industry News
Sep 17, 2007 IAR Systems appoints Andreas Lifvendahl Sales
and Marketing Director
Feb 12, 2007 Darin Billerbeck of Intel Hired as ZiLOG's
New CEO
Sep 29, 2006 Jazz Semiconductor Aquired by Acquicor in an
Unusual Transaction
Sep 25, 2006 Freescale Semiconductor Bought Out by Blackstone
for $17.6Billion *UPDATED 18-Nov-06*
Embedded Networking
Nov 23, 2006 New ColdFire Embedded Ethernet Kit from NetBurner
Oct 1, 2006 NetBurner Introduces 147MHz ColdFire Module
with Complex Timer Module
Sep 26, 2006 New ZigBee Application Kit from Rabbit Semiconductor
Sep 22, 2006 Ethernet to CAN Server from NetBurner is Fully
Customizable
Embedded IP
Jun 16, 2003 MIPS Introduces New 550MHz Embedded Microarchitecture
Nov 4, 2002 MIPS Technologies Introduces New Secure Licensable
Processor Core
Bits and Bytes (short news)
Sep 17, 2007 ThreadX Supports Renesas SH-2A Microcontrollers
Sep 12, 2007 General Software Offers BIOS for AMD Opteron
Jun 18, 2007 Ellen Hancock Resigns as President of Jazz
Semiconductor
Aug 21, 2006 In Circuit Debugging Supported with Microchip
PICkit 2 Debug Express
