Multi-threaded projects
Services and Drivers
Alternate ways of doing
Labs 1, 2, 3 and 4.
ENCM415 – “Ideal” final project
Plans for a “complete” Lab. 4
Run the audio input and output (Lab. 0)
Reading the light sensor (Lab. 2)
Reading the thermal sensor (Lab. 3)
Displaying values in the Flash LED (Lab. 1)
Displaying values on the external LCD screen over
the SPI interface (Lab. 4)
Using interrupts (Labs. 2, 3 and 4)
Control that robot car (Lab. 17) and plane (Lab.
22000)
Do-able with knowledge we already have
Spend 40 hours to complete – is there a simpler way
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A simpler way
Some teams prefer to use development
approaches essentially equivalent to what we
have done in Labs 1, 2 and 3
Becomes easier with practice, but does not
come easy.
Other teams are using “prepared” code from the
manufacturer.
Threads
Services and Drivers
Reliability issues “forcing” manufacturers to ensure
“prepared code” works well
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Doing Lab. 4 project in industry
We might not develop a final “.dxe” executable
We might get each task to run by its self
Then add each task as a “thread” inside a multithreaded operating system.
The processor (using core timer interrupts)
would automatically switch between tasks as
each data became available
Easier to integrate new Lab. with the previous
labs

Straight forward to do with Analog Devices VDK –
Visual DSP Kernel, uCLinux, uC-OS etc etc
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Initialization Thread
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Main Thread – example
While task “pends” (wait till ready),
it automatically gets switched out of the processor
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Each Lab. 4 task has its own thread
function which replaces the sleep
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VDK History shows tasks switched
out when they have to wait
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Concept of task priority
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Would VDK make 415 easier
NO, using VDK would make 415 harder as you
have another interface to learn
How do you debug a function (LED display) when the
function works with one thread and not with
another?
Answer – with great difficulty
But learning VDK would make the ENCM491
(real time) and ENCM515 (DSP architectures)
easier to learn as you could cut 6 weeks out of
each class because of the extra 6 weeks needed
in ENCM415 (a saving of 6 weeks).
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Would threads make industry easier?
 PROBABLY NOT, using threads the first time makes the
project harder, you have another interface to learn
 However “PROVIDED” the real-time operating system is
“inexpensive” and “reliable” you have a common
interface that many developers on your team can all
use. Product is shorter time and lower cost
 However, many developers don’t want to use
“commercial” OS as “too slow”, “too difficult to
customize” for the product. They would rather use the
techniques you have used in ENCM415.
 Also, using threads only changes about 20% of the code
you have to develop. Basically all you have is better
“while loops” and “easier semaphores” and”messaging”
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System Services
Much of this presentation is based on Analog
Devices on-line Blackfin training by David
Lannigan at
my.analog.com/onlinetraining/Static/BOLDList.html
There are audio and video presentations on
Blackfin® Device Drivers (May 2006)
Blackfin System Services (Jan. 2006)
Introduction to VDK (Sept. 2006)
It is recommended that users have some understanding of the Blackfin
architecture, basic knowledge of software terminology and
experience in embedded systems. Meaning have taken ENCM415
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Would system services help in ENCM415?
For Labs. 1, 2 and 3 – No
You have to know the sort of thing that is
supposed to happen with the hardware in
some very simple cases (Flash memory,
GPIO, LEDs)
How do you start an interrupt?
How do you build an interrupt service
routine?
How can you build a fast ISR in assembly
code?
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Would system services help in Lab. 4?
System services provide you all the
functions that you developed in Labs. 1, 2
and 3 for GPIO etc
If the services are simple to learn how to
use for GPIO control, then perhaps we
can quickly get it to work for the SPI
interface.
Analog Devices has just recently updated
their “services” software, so using services
has potential
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Proposed Lab. 4 – Demo-based
 Demonstrate in class using services to do Labs. 1 and 2
 50% -- Connect LCD screen to logic lab and switches.
Place commands in an array. Manually (using switches)
send commands to LCD screen to show “Happy 415
Christmas”
 30% -- Demonstrate Lab. 4 Temperature and Light
sensor using – You will need to add a modified
“CalculateTemperature( )” from Lab. 3 and the PF9
service
 20% -- Add a “SPI SERVICE” to transfer the commands
from the Blackfin to the LCD
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All true, the third time
you try using it
However, that’s what you do in
an industrial environment
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All the non-hardware
stuff from Lab. 1, 2 and
3 stays the same
VDK
All the hardware
stuff from Lab. 1, 2 and
3 – “better?”
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Powerful – once we know how to use it
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Lots of new syntax to learn
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Something related to Lab. 2
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Some of these functions are recognizable
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Interrupt handler hidden
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But there is much to learn
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Service for fast memory transfer
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Sounds like Lab. 2
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Many functions recognizable
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Perhaps try for Lab. 4
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