tkt-3500 microcontroller systems microcontroller systems lec 1 ... platform for exercises:...

TKT-3500

Microcontroller

systems

Lec 1 – Introduction to

Microcontrollers, Basics of debugging

Ville Kaseva

Department of Computer Systems

Tampere University of Technology

Fall 2009

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Copyright notice

Course slides originally prepared by

Erno Salminen

Part of the slides

adapted from slide set EE1A2 PIC Course by

Sandra I. Woolley, Univ. Birmingham

based on [B. Colwell, The power of most likely,

Computer, Vol. 35, Iss. 10, Oct. 2002, pp.12 –

14]

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Contents

What and where are microcontrollers

Basic features of microcontrollers

Embedded systems

Commercial microcontrollers, e.g. PIC-family

Platform for exercises: Multisensor node

Key components

Debugging: The power of most likely

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Microcontroller

Merriam-Webster dictionary:

microcontroller [\mī-krō\\-kən-trō-lər\ ]

Function: noun, Date: 1971

a microprocessor that controls some or all of

the functions of an electronic device (as a

home appliance) or system

micro - very small

controller - one that controls or has power or authority to control

control - to exercise restraining or directing influence over

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Microcontroller (2)

Microcontrollers are used in automatically controlled products and devices such as automobile engine control systems,

remote controls, office machines, appliances, power tools, and toys

i.e. in embedded systems

Microcontroller chip includes, for example an integrated microprocessor

memories (RAM, Flash, EEPROM etc.)

input and output peripherals

timers, event counters, PWM generators etc.

clock generator

many include analog-to-digital converters

in-circuit programming and debugging support

A PIC 18F8720

microcontroller in an

80-pin TQFP package.

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Microcontroller (2)

It emphasizes high integration, in contrast to

a microprocessor which only contains a CPU

(and cache)

functional computer system-on-a-chip

Difference between uproc and ukontr is blur

Modest processing capability

Adequate for simple control applications

Usually not meant for heavy number crunching

Low power consumption

Cheap unit price, high volumes

Programmable devices

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Classification of microprocessors

Number of bits 4,8,16,32,64...

Number of instructionsa) RISC (Reduced instruction-set computer)

b) CISC (Complex instruction-set computer) ASIP (Application-specific instruction-set processor)

Memory spacea) von Neumann – same for instr. and data

b) Harvard – separate addr spaces

Data path – where are the operandsa) Stack

b) Accumulator

c) Register-memory

d) Register-register (so called load-store)

Integrated peripherals, pipelining, num of ALUs...

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Where are the processors [Tennenhouse00]

Interactive 2% denotes PCs and

servers

98% of CPUs are elsewhere

Portable devices (cell phones

etc) have spread after 2000

[Tennenhouse, D. 2000. Proactive computing.

Commun. ACM 43, 5 (May. 2000), 43-50]

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What are embedded systems

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Embedded systems (1)

Application specific electronic sub-system used in a larger system such as an appliance, an instrument or a vehicle

Not User-Programmable

System needs to implement only a limited function whose characteristics are known at design time

The design can take advantage of the specification’s characteristics in ways that general-purpose computing systems cannot

Targeting certain performance level instead of maximum

Based on both hardwired and programmable components e.g. CPU, DSP, custom HW

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Fig: [Pinello, TVLSI08]

Hardware/Software co-design required

Resemble distributed systems multiple tasks are running on multiple processing

elements (PE)

interprocess communication and synchronization critical

Are subject to external timing constraints Hard real-time – missed deadlines are fatal

e.g. ABS brakes, safety system of nuclear plant

Soft real-time – missed deadlines cause degraded quality or inconvenience e.g. video frames are dropped

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Reactive Real-Time Systems

Continuous interaction with external

environment

Ideally never terminate

while (1) {

read the sensors

control the actuators

sleep()

}

Where would execution

go after main()?

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Examples of embedded systems

asdcar

digital

camera

mobile phone

harvester

robot

Figures from Wikipedia

network router

elevator

washing

machine

PDA

game console

printer medical

equipment

microwave oven

factory automation

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Commercial microcontrollers, especially

PIC

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Example microcontrollers

Atmel AVR 8- ja 32-bit RISC families

Over 80 models

Texas Instruments (TI) MSP430 – low power

TMS320 – high performance

TMS470 – ARM7-based

Renesas SuperH – High speed / performance

MR32 – 32-bit

H8 – low cost

ST microelectronics

And many others...

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PIC microcontrollers

Designed and sold by Microchip Corporation

http://www.microchip.com

PIC = initially Programmable Interface

Controller

then Programmable Intelligent Computer

Many configurations of 8-, 16- and 32-

microcontrollers

8-bit volume prices ~2$-12$

Minimalist basic ideology

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8-bit PIC Families

8-bit stands for width of data path

PIC10 (and some PIC12 and PIC16)

Baseline architecture, 12-bit program word

16-134 Bytes of SRAM

256- 2K Bytes of flash program memory

4-32 IO-Pins, 2 level deep stack

PIC12 and PIC16

Midrange architecture, 14-bit program word

64-368 Bytes of SRAM

1 -8 kBytes of flash program memory

6-53 IO-pins, 8 level deep stack

Images: www.microchip.com

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PIC18 family

High-tech 8-bit architecture, program word

16-bit

256 bytes – 4kBytes of SRAM

4-128 kBytes of program memory

15-70 GPIO-pins

Plenty of peripherals, for example:

USB, Ethernet, LCD,CAN

75 instuctions (some models have 83)

31 level deep stack

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PIC18LF8722

Used on this course

Symbol L stands for Low Power - Operating

voltage 2-5.5 V,

normally 4.2-5.5 V

F for Flash memory (?)

Accumulator machine

Accumulator= special register for storing results

Makes assembly and high level compiler writing

complicated

W-register= ALU’s working register (WREG)

Many operations can be done only in W-register

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PIC vs. Pentium roughly speaking

PIC

8-bit

1-50 MHz

5 mW

6 €

10-80 pins

Harvard arch.

1-10 MIPS

Few instructions

Accumulator

1 instr/4 cycles

no pipeline or very short

Pentium4

32-bit, 64-bit

2-4 GHz

150 W

150 €

~1000 pins

von Neumann arch.

60 000 MIPS

Zillions of instructions

Register bank, Superscalar/EPIC

Deeply Pipelined

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Platform for exercises –

Multisensor sensor network

node

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TUT Wireless Sensor Network (TUTWSN)

Very large research project in TUT/DCS since 2002

Sensor networks are emerging technology where the network consists of nodes that measure (‖sense‖) the

environment

communicate autonomously and wireleslly

self-organizing topology

may control actuators

Special courses TKT-2300 and TKT-2456

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TUTWSN Nodes

Multisensor node

Includes many sensors

Used in TKT-3500

Other nodes

Pipe Node

Long range pipe node

Badge node

Wrist node

Ethernet gateway

http://www.tkt.cs.tut.fi/research/

daci/ra_tutwsn_prototypes.html

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TUTWSN Multisensor node

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Microcontroller: PIC18LF8722

256 kbyte external SRAM

Sensors and modules

GPS (Global Positioning System)

Radio

Temperature

Humidity

Accelerometer

Compass

Luminance

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Add-on modules (not connected)

PIR (passive infrared, motion detector)

VGA Camera

Microphone

Interface

1 Pushbutton, 1 led

Input/Output

RS-232 serial port

MAX3226E is used to convert voltage levels

SPI (Serial peripheral interface), I2C

4 input/output pins

ADC (analog-to-digital converter)

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Power control

Possible power sources

a) DC power supply

b) 2 AA Batteries

c) Solar panel

All sensors can be turned off by uC

Voltage after regulation: 3 V/2 V and 2,7 V

2.7 V is used for GPS, 3V/2V (software

selectable) for other devices

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PIC18LF8722

8 bit RISC microcontroller with Harvard

architecture

High End 8-bit microcontroller

Accumulator…

Assembly programming complicated

128 kB program memory, 4 kB SRAM, 1kB

EEPROM

Operating voltage: 2.0 – 5.5 V

Max. Power dissipation 1 W

Min. Power dissipation (@1 Mhz): 3 mW

Compare: Normal red led 2V and max 20 mA

Image: www.futurlec.com

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PIC18LF8722

Plenty of peripherals

SPI, i2c, USART

16 channel 10-bit AD-converter

5 timers and capture/compare/PWM module

HW 8-bit multiplier

Watchdog, Brown-out

Max. Frequency: 40 Mhz

Many power management modes

Clock sources on platform:

Low frequency external clock

Internal clock

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C18 compiler and Programming

Microchip’s C-compiler for PIC18

microcontrollers

Not optimal but student version is free

Limitations in student version after 60 days:

No optimiztions

Processor works only in normal mode (77 instructions)

Microchip ICD2 - In-Circuit Debugger

Includes 5V Power supply

Not used with TUTWSN nodes due to lower

voltages -> External voltage source needed

Works fine with MPLAB IDE

Image: www.microchip.com

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GPS: iTrax03-s+GeoHelix–S

Fasttrax iTrax03-s

Includes lots of functionality: only few

extra components needed

Communication: USART with NMEA

(National Marine Electronics Association)

messages


Max power dissipation 500 mW

Sarantel GeoHelix-S

Active GPS antenna

Operating voltage: 2-3.5 V

Typical current 15 mA

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Radio: nRF24L01


Frequency: 2.400 – 2.4835GHz

Communication: SPI

Fully automated packet handling

Current consumption:

Power down 900 nA

Standby 22 uA or 320 ua (Two standby modes)

Transmission < 11.3 mA, Reception < 12.3 mA

Range about 15-30 meters indoors

Antenna dependable

Image: www.nordicsemi.com

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Temperature Sensor Maxim DS620


Communication: i2c

Selectable resolution:

LSB 0.5°C, 0.25°C, 0.125°C or 0.0625°C

Conversion time depends on accuracy

10 bit 25 ms, 13 bit 200 ms

Continuos conversion and one shot modes

Image: www.maxim-ic.com

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Humidity: Sensirion SHT1x

Humidity AND temperature sensor


Communication: ‖almost i2c‖ Not compatible with standard i2c interface

Conversion times: 11 ms (8 bit)

210 ms (14 bit)

Accuracy: Humidity 2 %, temperature 0.3 °K

Current consumption: Sleep 0,3 uA, measuring 550 uA

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Accelerometer: VTI SCA3000

3D accelerometer


Communication: SPI

Modes:

Free fall detection

Motion detection

Normal mode

Current consumption 120 uA in active mode

Image: www.vti.fi

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Compass: Hitachi HM55B


Communication: SPI

Transmission length 4 bits (normal SPI 8 bits)

Current consumption: Sleep 1 uA, Measuring

9 mA

Measuring time 30 ms

Resolution: 11 bits

Measures magnetic field strength

Min. value -180 uT max. 180 uT

Image: www.parallax.com

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Luminance: Agilent APDS-9002

Photosensor: Luminance is relative to current


Connected to uC’s analog-to-digital converter

Resolution equals AD-converter’s resolution

10 bit in PIC18LF8722

Sample rate = ADC’s sample rate

In PIC user selectable, but depends on clock

frequency. About 1 Mhz is theoretical maximum

PIC’s AD-converter operates also in idle

mode

Completion of conversion can cause an interrupt

Image: www.farnell.com

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PIR MS300

PIR = Passive Infra Red

Connected to uC’s ADC, but needs an operating

voltage

Used as motion detector

Operating voltage: 2.6 V – 5.5 V

Current consumption: ~35 uA

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VGA C328

Max. 640x480 pixels, 16 bit

Frames/s depends on image quality

JPEG still picture with best quality 0.75 fps

Camera + compression module + EEPROM

No extra components needed

Connection: RS-232

JPEG picture format


Operation current: 60 mA

Suspend current: 100 uA

Image: www.electronics123.net

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Microphone AOM-6746P-R

Capacitor microphone

Omnidirectional

Picks up sound evenly from all directions

Connection: ADC

PIC18LF8722 has 16 ADC channels, but one converter



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Debugging

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Colwell, Power of most likely

―Unquestioned assumptions are by far the

biggest time-waster for system debuggers‖

The reason why the word ―arrgh!‖ was coined.

When a system malfunctions, the most likely

causes get attention first

Checking simple things first is a good policy,

as anyone who has ever wasted time on a

computer or peripheral only to find it wasn’t

plugged in can testify.

After checking the simple things, attitude

matters

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Colwell (2)

Technicians and engineers generally have

fundamentally different and complementary

attitudes, both valuable in their own contexts.

1. Techs often develop an intuitive sense for how the

system behaves when it is running properly

Several sanity checks before diving into more intellectual

analyses

E.g. is system running hotter than normal or that a

subcomponent was swapped out just prior to the

malfunction?

Technician mindset also seems to encourage a general

willingness to just try things, to see what happens

Techs know that ―kicking the tires‖ of an errant system will

often yield important clues to what’s wrong

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Colwell (3)

2. Design engineers don’t usually kick tires unless

they have precalibrated the exact kicking force and

point of impact—which obviates the whole

approach

DEs often approach a malfunctioning system with the

same mindset they used when designing it in the first

place.

They know where all the difficult corners the design are;

it’s their job know where the product margins slimmest

That very knowledge may lead them to first check the

design rather than the actual machine

Fixing a design flaw is more important than just

getting one machine working

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Debug rules [Colwell]

1. Change one thing at a time

2. Don’t ignore the unexpected

3. Follow the bug trail

4. Reduce complex phenomena to simple absolutes

5. Keep accurate lab notes

6. Debug is an immersion activity

7. Bugs almost never live alone

8. Test your test equipment

9. Know when you’re stuck, and call in the cavalry

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Debug rules (2)

1. Change one thing at a time

Otherwise you won’t know what caused the change in system’s behavior

Even if you’re chasing down a systems issue that requires an hour to set up, the temptation can be very strong to ―try a couple of things‖ per run.

1. Don’t do it.

2. Spend the hour trying to find a way to get the system to the malfunction point more quickly.

However, don’t make irreversible changes to the system during debug

2. Don’t ignore the unexpected

Investigate all suspicious behavior

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Debug rules (2)

3. Follow the bug trail

You need to follow the bug trail wherever it leads,

not just where you wish it would go

4. Reduce complex phenomena to simple

absolutes

Strip the system down to the simplest configuration

that still shows the problem

This reduces the number of possibilities to consider

when generating hypotheses about what could be

wrong and what to try next

Faster compilation, synthesis, simulation, analysis

etc.

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Debug rules (3)

5. Keep accurate lab notes1. What you’re doing

2. why you’re doing it

3. what should be the result

4. the results you get

This way you must focus more deeply in what you are doing

Others can refer to your notebook and leverage your work instead of unknowingly replicating it.

If you forget the details, it becomes a virtual certainty that a related bug will appear several months down the road, and it will be déjà vu—all over again.

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Debug rules (4)

6. Debug is an immersion activity

Allocate several hours

1. to set up a system run

2. to run the experiment,

3. to analyze the result

Don’t allow distractions.

If you are interrupted, you’ll probably have to

start over

This is one reason serious debug often happens

wee hours of the morning.

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Debug rules (5)

7. Bugs almost never live alone

Where you find one bug, there are often others

1. Other problems in the same module Remember that 20% of code modules cause

80% of faults

While you’re in the neighborhood,check for them

2. Similar problems elsewhere Check buffer overflows in all places when you

encounter one

Ensure that the ‖fix‖ does not break anything

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Debug rules (6)

8. Test your test equipment

check instruments against one another

9. Know when you’re stuck, and call in the cavalry

Some people just are good at finding errors When you run across these people in your

career, be nice to them:

1. Give them things

2. Bow down and chant―I’m not worthy‖ when they walk by

3. Bake them chocolate chip cookies

4. Whatever it takes, it’s worth it.

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Further reading

Jakob Engblom, Debugging real-time

multiprocessor systems: Part 1 -Programming

parallel machines and Part 2 - Debugging

Parallel Programs, Embedded.com, March

2006 http://www.embedded.com/columns/technicalinsights/183701679?_requestid=345393

#54/69 Erno Salminen - Nov. 2008

Version control

Use version control (Git, SVN, ...)

Teaches one to take logically consistent steps

in a project

Helps backup process

Easy throw-away code prototyping

Keeps track of your work (how many changes

in a week?)

Keeps track who did what

One can go back to see any previous version

A must for all work

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Conclusions

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At first

Make sure that

simple things work

before even trying

more complex onesHUOM! OBS!

Muy importante!

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Two great truths in design

1.If it's not tested,

it's broken

2.If it's not simple,

it's broken[M. Keating, ISQED, 2006]

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Conclusions

Microprocessors/controllers are used practically everywhere

High volume necessitates cheap price per device

This allows only modest performance

Controllers integrate several peripherals into same chip with processor

In embedded systems, designers target certain performance level, not for max. perf.

System is optimized (made maximally cheap) while still meeting the requirements

Programmability allows faster development and upgrades also after shipping

Connectivity of components is the key in many projects

Exercise platform integrates many sensors. Extremely good for educational purposes

Portability and shorter dev.time favor using high-level languages (C/C++) instead of assembly

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Extra slides

Reminder: microprocessor basics

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Stored program concept

Program’s instructions (control statements) are

stored in memory

In contrast to e.g. ASIC, in which the control is hard-wired

during manufacturing

CPU repeats fetch-execute cycle for every instruction

Originates from Turing machine (1936) that

manipulates data based on the instructions and state

of the machine

The behavior can be programmed

An universal machine – it can simulate the behavior of any

other machine

Theoretical concept that assumes infinite memory capacity

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Memory types

Every microprocessor needs some memory May be internal (on the same chip), external, or

combination

1. Instruction memory Stores the program’s inctructions

Non-volatile – keeps the information when powered off mask-programmed read-only memory (ROM)

(electronically) erasable programmable ROM (EEPROM/EPROM)

flash memory

2. Data memory Stores the program’s variables and status

Most parts volatile – contents lost when powered off static random access memory (SRAM), dynamic RAM

(DRAM)

Some parts may be non-volatile EEPROM, Flash, (in principle also hard-disk)

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Memories (2)

Memory type affects cost, speed, area, and power

consumption notably

E.g. SRAM is expensive, fast, area- and power consuming

technology

The program may be copied from non-volatile mem

to faster RAM during initalization

The same RAM may contain both program and data

sections as well (classical von Neumann architecture)

Whereas Harvard architecture separates program and data

address spaces

‖Memory is guilty until proven innocent‖ –

E.Salminen

= They cause lots of headache in embedded world

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Microprocessor Programming

A program is a set of instructions written in a specific sequence for a processor to accomplish specified tasks

An instruction is defined as a simple task (such as addition) performed by the microprocessor

To the microprocessor, instructions must be supplied in binary, i.e., as machine language

Instruction-set is processor-specific (PIC, x86, MIPS…)

Assembly language is a symbolic language which represents machine-language instructions with short human-readable mnemonics

For example, in PIC assembler a null operation or ‘no operation’is represented by the mnemonic ‘NOP’

One-to-one correspondence between the assembly language mnemonics and the machine code instructions

An assembler is a software tool that converts assembler source programs into machine language object files

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Machine and assembly languages are referred to as low-level languages Generally faster and more

compact than higher-level language programs

Not portable to other processors, tedious to write

High-level languages are machine-independent E.g. C/C++, Java

Program’s source codes are translated by compilers or interpreters into machine language

The translated code is called object code

Easier to debug and port

CPU+mem+etc

compiler

assembler

interpreter

de

sig

n-tim

eru

n-tim

e

.c, .h

.asm

.java

.hex

Microprocessor Programming(2)

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CPU’s instruction-set architecture (ISA)

Defines the supported machine-instructions

Defines size of instruction word and its fields Operation codes (ADD, SUB, JMP...)

Parameters (src0, src0, dst)

Whther params are in registers or in memory

Addressing types (direct, indirect...)

add/sub/

AND/XO

R/OR...

src0 src1 dst

instr type 1

instr type 2

add/sub/

AND/XO

R/OR...

src0

(also dst)

immediate

add reg0, reg5, reg3

i.e. reg3 ← reg0 + reg5

and reg0, 0x500

i.e. reg3 ← reg0 & 0x500

instr type 3jmp address goto Nevada

i.e. PC ← address of label Nevada

...

015 347811

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Micro-architecture

Defines the HW resources that implement ISA arithmetic-logic unit (ALU) performs the actual computation

control logic fetches the instructions, decodes them and passes to ALU

registers store temporary data

(optional) internal memories store instructions and/or data

memory and IO buses provide connection to outisde world

Peripherals perform supplementary tasks

There may be several micro-architectures for the same ISA

digital IO

instr. fetch ext. mem IO

instr. mem

data mem

instr. decode

oscillator

register filepipeline ctrl ALU

timer

power ctrl analog IO

watchdog

CPU

peripherals

micro-

controller

multiplier

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Clock cycle and Instruction cycle

Machine operations are sequenced by clock signal

Provided by external or internal oscillator (RC circuit, INV-

loop, quartz crystal)

Oscillator signal may multiplied/divided by constant (e.g. 10

MHZ * 4 = 40 MHZ)

Execution of machine instruction may take more than

one clock cycle

4 clock cycles/instr. in PIC

40 MHz clock yields approx. 10 MIPS

Some instructions take over 4 cycles, e.g. operations

affecting program counter (PC)

Some CPUs pipeline the execution of instructions

E.g. instr takes 4 cycles but the next finishes after 1 cycle

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Program flow

CPU executes instructions step by step

Instructions are executed consecutively (addresses

0x0, 0x2, 0x4) until

a) Branch occurs – if-then-else, function call, goto

b) Exception occurs – interrupt, div-by-zero

The address of the next instruction is stored into

register program counter (PC)

Interrupts are function calls made from HW

a) Timer overflow (e.g. 1ms passed)

b) Peripheral device (e.g. serial IO transmit completed)

c) External pin (e.g. from button or sensor)

Extremely useful concept

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Program flow (2)

After reset, PC gets the value of reset

vector

Usually rst vec points to some sort of

(ccompiler-generated) initialization

function that will call the user’s main

function

Call graph shows which functions are

called and their order (nesting)

Interrupt service routine (ISR) may be

called ‖anywhere‖

After that execution continues from the

interrupted point

init(){

...

main()}

main(){

...

foo()

...

while(1){}

foo() {

...

bar() ...

return

bar(){

...

return

isr() {

....

return from int}

0x0rst vec

tkt-3500 microcontroller systems microcontroller systems lec 1 ... platform for exercises:...

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