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” executableWe might get each task to run by its selfThen add each task as a “thread” inside a

multi-threaded 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

Each Lab. 4 task has its own threadfunction which replaces the sleep

While task “pends” (wait till ready), it automatically gets switched out of the processor

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VDK History shows tasks switched out when they have to wait

Concept of task priority

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 onBlackfin® 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 timeyou try using it

However, that’s what you do inan industrial environment

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All the non-hardwarestuff from Lab. 1, 2 and3 stays the same

VDK

All the hardwarestuff from Lab. 1, 2 and3 – “better?”

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Powerful – once we know how to use it

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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