1

University Brunei Darussalam

PH 2234

MICROPROCESSOR SYSTEM

PROGRESS REPORT 2

MUHAMMAD FAIZ BIN AWG HAJI SULAIMAN

08B2009

Year : 2nd year

Semester: 3rd semester

B. Electrical & Electronics Engineering

Comments:- Marks:-

2

Table of Contents 1) POTENTIOMETER .................................................................................................................................. 4

1.1 TEST WITH DMM ........................................................................................................................... 4

1.2 Using DMM to find the measured resistor value. ......................................................................... 5

1.3 MODEL OF POTENTIOMETER (Ratiometric device) ...................................................................... 5

2) Threshold of Potentiometer ................................................................................................................. 7

3) RC TIME ............................................................................................................................................... 10

3.1 Classic method for transducing analogue to digital .................................................................... 10

3.2 INSIDE OF BS2 ............................................................................................................................. 15

3.3 UNDERSTANDING THE RC TIME INSTRUCTION ........................................................................... 16

3.4 Difference between Analog and Digital in charging and discharging a capacitor. ..................... 17

Capacitor charging equation ............................................................................................................... 19

Discharge circuit .................................................................................................................................. 19

Program 3.1 ......................................................................................................................................... 22

Program 3.2 ......................................................................................................................................... 23

Program 3.3 ......................................................................................................................................... 24

Program 3.4 ......................................................................................................................................... 25

4) POLLED INTERUPT ............................................................................................................................... 26

4.2 PRINCIPLE OF THE MICROPROCESSOR OF THE SERVO ............................................................... 28

5) SX28 microcontroller (used in BS2SX microcontroller) ..................................................... 29

Program 5.1 ........................................................................................................................................ 29

Explanation of the program 5.1 .......................................................................................................... 30

Program 5.2 ......................................................................................................................................... 30

Explanation of the program 5.2 .......................................................................................................... 31

Program 5.3 ......................................................................................................................................... 31

Further about SX-28 ............................................................................................................................ 32

Overview of i/o ports of SX-28 ............................................................................................................ 33

INSIDE SX28 ......................................................................................................................................... 33

More on the SX28 program ................................................................................................................ 34

Program 5.4 ......................................................................................................................................... 34

More explanation on program 5.4 ...................................................................................................... 34

Program 5.5 ......................................................................................................................................... 35

3

Program 5.6 ......................................................................................................................................... 35

Program 5.7 ......................................................................................................................................... 36

Program 5.8 ......................................................................................................................................... 37

CIRCUIT FOR SWITCHING LED ON AND OFF ........................................................................................ 38

Program 5.9 ......................................................................................................................................... 38

Further explanation on the program 5.9 ............................................................................................ 39

SX INTRUCTION SET “rl” ...................................................................................................................... 39

6) 8-BIT ANALOGUE-TO-DIGITAL CONVERTER (ADC) with serial output ............................................ 40

Program 6.1 ............................................................................................................................................. 41

Further on ADC ....................................................................................................................................... 42

How the ADC no. is implemented in the debug .................................................................................. 43

Application of ADC .............................................................................................................................. 45

4

1) POTENTIOMETER

3

1

2

Red (“regulated” 5 V)

yellow

Black (0 V)

Vdd

Vss

POTENTIOMETER

1.1 TEST WITH DMM Point 1 and 3 = Maximum value of the resistor

Point 1 and 2 & point 2 and 3 = can be changed (variable)

Given blue potentiometer:

3 (NC)

1 (Vss)

2 (Vdd)

There are 6 half turns (3 complete turns)

Maximum resistor value: 10kΩ

5

1.2 Using DMM to find the measured resistor value.

Connect Vdd to point 2 (5V) and 1 to Vss (0V)

Anticlockwise 0V

Clockwise 5V

1.3 MODEL OF POTENTIOMETER (Ratiometric device)

5V

Wiper

0V

R2

R1VOut

( ) (

) assmume RTOTAL and V are constant.

Point Measured Resistor value Turning Max/Min

1&3 10.6kΩ Both Maximum

1&2 1.8Ω / 0.02kΩ CCW Minimum

1&2 10.04kΩ CW Maximum

2&3 1.8Ω / 0.02kΩ CW Maximum

2&3 10.04kΩ CCW Maximum

Ratiometric part

6

ALTERNATIVELY:

(

)

For the given 3 turn potentiometer (1080 ⁰)

(

)

For example,

For example,

Finally:

(

)

NOTE: tranducer is a component that can change angle to voltage (trans=across; ducer=to lead)

Fixed constant in

this case

Thus equation means we have a transducer

as known as sensor

R1

7

2) Threshold of Potentiometer Practical 1:

DIR0=0

DIR0=1

out0=1

out0=0

+5V

0V

IN0

Out0

DIR0

Vss 0V

Vdd +5V

V

Program2.1: results: V thresholdp0=1.417 V

Ω

3

2

1 black

( )

DIR=0 Again: DEBUG BIN IN0 PAUSE 500 GOTO again

8

Demonstrate the use RC time instruction to measure resistance of potentiometer connected as a

variable resistor.

2

1

0.1μF

220kΩ

10kΩ

variable resistor

Vdd (+5V)

Vss (0V)

Vdd (+5V)

Vss (0V)

p0

in0

out0

dir0

Inside

microprocessor

Outside

microprocessor

3

12

NC

Program2.2:

chargetime VAR Word DIR0=1 OUT0=1 PAUSE 1 again: RCTIME 0,1,chargetime DIR0=1 PAUSE 1 DEBUG DEC chargetime, CR GOTO again

9

Further explanation of program2.2:

+5V

0V

++++++

++++++0.1μF

220 Ω

+5V+5V

Below pbasic language

means discharge the

0.1μF capacitor through 220Ω resistor:-

DIR0=1

OUT=0

PAUSE 1

Remainder: KE=1/2 mv2 Elight=1/2 LI2

Ecapacitor=1/2 CV2

P.S: Discharging capacitor has two meaning:-

1) Voltage across plates = 0 volts 2) (Be aware): Voltage of the plates can be 0V,1000V,-1000V,any volts

10

3) RC TIME

3.1 Classic method for transducing analogue to digital

Below is the simplified basic circuit

C

R

+

-

5 V

+5V

0V

V0=5v

t=0

Zero internal

resistance

i.e. perfect

power supply

When switch is

closed, the capacitor

C discharges

1) Before time, t=0s, we have this circuit:-

R

+

-

5 V

V0=5v

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2) So after time, t=0, we have the following circuit:-

iR

+

-

5 V

iC

3) Differentiate wrt time on both sides:-

( )

Assume C is constant

Rearranging,

4) Sum of voltages in circuit = zero

Recall:-

Q=CV

Where D=dt;

Q is the no of coulombs and;

Solution is:-

I(A)

t(s)

5/R

0

12

Differentiating w.r.t. time constant,

Multiply through by C

Set RC=τ (time constant in seconds)

(1)

(2)

(3)

Substitute equation 2 and 3 into 1

When A=0,

Therefore,

5) So far,

(4)

Solve for B using boundary conditions (b.c.)

To get the bc, we need to know about capacitors

a) Capacitors act like a short circuit or low resistance to fast change of current or voltage.

b) Capacitors act like an open circuits or high resistance to slow change of current or voltage.

Capacitive reactance is

(Unit Ω)

For more, the properties of inductor are opposite to the capacitor.

a) Inductors act like an open circuit or high resistance to fast changes of current or voltage.

b) Inductors act like a short circuit or low resistance to slow change of current or voltage.

Inductive reactance is (Unit Ω)

13

Hence at time i=0

When substitute into equation 4

At time, t= , Thus b.c. 1 is of no used. Then try time t=0, therefore there will be fast-changes of current or voltage

The capacitor is short circuit, ,

R

It=0

+

-

5V

Substitute b.c.2 into 4

So

Finally as capacitor charged,

Voltage across capacitor, Vc given by

( )

Where

b.c. 1

b.c. 2

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Now add the BS2 microcomputer circuit looks like following figure:-

+

-

5V

in0

(Classic method for transducing analogue to digital)

More detail inside the Basic Stamp for RC time instruction

1

V

t

5V

1.4

in0

tcross

0

in0

V threshold =1.4 V

5e-t/RC

At time of RC time is program as

e.g. RCTIME 0,1,chargetime

Pin 0

Measure time from start & instruction from 1 to 0 transmitters of in0

Put measured time

into this variable

2μs

15

Solve for R because given t=tcross, C is given

Take natural loop of both sides

Hence where k is a constant.

3.2 INSIDE OF BS2 500kHz internal clock used for RCTIME, PULSOUT and PULSIN

&In0

Time t=0

1

0

“ Start RC

time”

instructions

2μs

Clock goes through to 16bit counter only

when in0=1 AND “start RCTIME” =1

16 bit counter counts every positive going

edge that it receives

16 bit counter already clever to zero before

RC time instruction implemented

1000 dec

Therefore tcross=0.002s

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3.3 UNDERSTANDING THE RC TIME INSTRUCTION

+5V

0V

220Ω

10kΩ

VariableVR

BS2

2

1

Program used:

Chargetime VAR word OUT0=1 DIR0=1 PAUSE 1 Again: RCTIME 0,1,chargetime ‘measure chargetime which is debug dec chargetime,CR ‘time for VR to fall from 5V to V threshold (1.45V) DIR0=1 PAUSE 1 goto again

Gives 1ms to discharge C

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3.4 Difference between Analog and Digital in charging and discharging a

capacitor.

Shorting link

(For discharge)

+5V

0V

RVR

C5V

5V

i=5/R e-t/τ

ANALOG BS2 (DIGITAL)

+5V

0V

5V

0V

id

P0Dir0=0

Out0=1

in0

Shorting link is connected to discharge the capacitor

Shorting link is disconnected to charge the capacitor

To charge or discharge the capacitor the bs2 automatically

charge or discharge the capacitor depends on the

programmer setting.

1

0 t

Small R

large R

+5V

0V t

V

Small R

Large R

C in top R in botom

VR

C in bottom R in top

id

t

Vc

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Simplify discharge circuit

5V

0V

220Ω

Simplify further discharge circuit

+5V

0V

R

220Ω

+5v

VR |t=0

Simplify still further

+5V

0V

R

220Ω

VR |t=0

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Capacitor charging equation

Discharge circuit

Discharge equation

220ΩC

+5V

0V

Fully

charge

voltage

Discharge equation:-

Where

Where t=nτ

Not constant

5/220 Fully charge when current falls to

0.1% of starting current

Starting current I

t

20

Where n=number of time constants

So discharge for 7 time constants, i.e. allow to “fully” discharge

Discharge equation:-

220ΩC V220

VR

i

V

5V

0

t 22μ

s

( )

( )

Actual approximation is:

21

Next we used the potentiometer to light up the eight LED with different style of lighting it up:-

Debug of the rctime of potentiometer: 1642

Total LED =8

Therefore, 1 LED = 80

Waveform, VR, charging charge RC time instruction and during discharge procedure

V

t

VR=1.45 V

5 V

0

Discharge of C

Charge

RCtime charged time

Vthreshold

( )

2cm=500μs 2.6cm=650μs

Graph scale

Basic stamp

The value that came

out in the Basic

stamp debug

“rctime”

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Program 3.1

This program is bar chart of lighting up the LEDs. Here we used 4 LEDs only.

' $STAMP BS2 chargetime VAR Word OUT0=1 DIR0=1 PAUSE 1 DIRD=%1111 '$f or 15 again: RCTIME 0,1,chargetime 'measure chargetime which is DEBUG DEC chargetime,CR 'timefor VR tofall from 5V to threshold 1.45V DIR0=1'allow 1ms to PAUSE 1'discharge C IF chargetime < 76 THEN one IF chargetime < 226 THEN two IF chargetime < 376 THEN three four: OUTD=%1111'all led's on GOTO again one: OUTD=%0001 GOTO again two: OUTD=%0011 GOTO again three: OUTD=%0111 GOTO again

#1

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Program 3.2

Similar to program 3.1 but using different technique of writing the IF command (see #1 and #2)

' $STAMP BS2 chargetime VAR Word OUT0=1 DIR0=1 PAUSE 1 DIRD=%1111 '$f or 15 again: RCTIME 0,1,chargetime 'measure chargetime which is DEBUG DEC chargetime,CR 'timefor VR tofall from 5V to threshold 1.45V DIR0=1'allow 1ms to PAUSE 1'discharge C IF chargetime > 525 THEN four IF chargetime > 375 THEN three IF chargetime > 225 THEN two IF chargetime > 75 THEN one

off: OUTD=%0000 GOTO again four: OUTD=%1111'all led's on GOTO again

one:OUTD=%0001 GOTO again

two: OUTD=%0011 GOTO again

three:OUTD=%0111 GOTO again

#2

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Program 3.3

Here we used 8 LEDs

' $STAMP BS2 CT VAR Word DIR0=1 OUT0=1 PAUSE 1 DIRH=%11111111 again: RCTIME 0,1,CT DEBUG DEC CT,CR DIR0=1 PAUSE 1 IF CT < 2 THEN off IF CT < 76 THEN one IF CT < 151 THEN two IF CT < 226 THEN three IF CT < 300 THEN four IF CT < 375 THEN five IF CT < 450 THEN six IF CT < 525 THEN seven IF CT < 601 THEN eight limit: OUTH=%01010101 GOTO again eight: OUTH=%11111111 GOTO again off: OUTH=%00000000 GOTO again one: OUTH=%00000001 GOTO again two: OUTH=%00000011 GOTO again three: OUTH=%00000111 GOTO again four: OUTH=%00001111 GOTO again five: OUTH=%00011111 GOTO again six: OUTH=%00111111 GOTO again seven: OUTH=%01111111 GOTO again

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Program 3.4

Now we used the potentiometer as Dimmer for the LED

Here are the waveforms that help to understands how the potentiometer can be used as dimmer.

Space=period-mark

Dimmer

10ms 10ms

20ms

15ms 5

15ms 5

50% brightness

75% brightness

15% brightness

space mark

( )

Duty ratio

' $STAMP BS2 CT VAR Word ontime VAR Word DIR0=1 OUT0=1 PAUSE 1 again: RCTIME 0,1,CT DEBUG DEC CT,CR DIR0=1 ontime = CT*100/660*100 PULSOUT 15, ontime PULSOUT 7, 10000-ontime GOTO again

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4) POLLED INTERUPT In this experiment we used two basic stamp – BS#1 and BS#2

+5V

Vss 0V

BS #2 BS #1

220Ω

P1P11P0

P15

Vss

Servo

220Ω

Following are the program for BS#1 (Transmitter) and BS#2 (receiver)

1mm

This is the waveform where a “spike” send every 20ms approximately from BS#1 to BS#2

' $STAMP BS2 'TX polled interupt program (BS#1) again: PULSOUT 1,1 ‘take about 2μs PAUSE 19 ‘pause for 19000μs GOTO again ‘repeat the again instruction

Just want a spike interrupt

so as not to waste time

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By chance 180⁰ out of phase to BS#1 clock will lead to a missed count in the programme.

The count positive edge of BS#2 clock is after receipt of positive going edge of pulse.

In each basic stamp, there have different tolerance for example BS#1 – 501kHz and BS#2 – 499kHZ.

' $STAMP BS2 'RX polled interupt program (BS#2) chargetime VAR Word polledinterrupt VAR Nib theta VAR Word OUT0=1 DIR0=1 again: PULSIN 11, 1, polledinterrupt 'DEBUG DEC polledinterrupt, CR ' to check rcv 1 RCTIME 0,1,chargetime DIR0=1 'DEBUG DEC chargetime, CR ' to check the RC time chargetime=chargetime MIN 1 MAX 651 theta =(chargetime-1)*10/13 +500 'x*500/650 +500 'x=(chargetime-1) 'using y=mx+c 'DEBUG DEC theta,CR ' to get correct no. range PULSOUT 15, theta GOTO again

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

Pulse of 15 X2μs = 30μs

Free running clock

BS#1

BS#2

Not counted

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4.2 PRINCIPLE OF THE MICROPROCESSOR OF THE SERVO 1) Servo angle controlled by pulse width,t

2) Angel is not controlled by period

+45⁰

-45⁰

0.5 1.0 1.5 2.0

Pulsewidth, t(ms)

theta

periodtime

Approximately

20ms

(10ms25ms)

t

29

5) SX28 microcontroller (used in BS2SX microcontroller)

SX28 microcontroller is used in BS2SX microcontroller where BS2 use PIC microcontroller

Assembler Language programming short word mnemonic/programming

Assembly is usually used 3 or 4 letter instruction

Also cover machine code programming all numbers for instructions & data….no letters, no english

No symbols e.g. + - X / don’t exist, gosub, pulsout

Rctime, don’t exist

Following are the example of a simple program:-

Program 5.1

Device sx28L,oschs3 Device Turbo, StackX, optionX IRC_cal IRC_4MHz Freq 50_000_000 Reset 0 loop mov w,#%00000000 ; load specified binary number intoworking register,w mov rc,w ; load contents of w into register C jmp loop

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Explanation of the program 5.1

Mov w,#%00000000

Mov Rc,w; load contents of w into register C Jmp loop

Program 5.2

470Ω

rc7

0V

Immediate instruction

binary

;load specified binary number

intoworking register,w

Device sx28L,oschs3 Device Turbo, StackX, optionX IRC_cal IRC_4MHz Freq 50_000_000 Reset 0 mov w,#%00000000 ; load specified binary number intoworking register,w mov rc,w ; load contents of w into register C mov w,#%01111111 mov !rc,w loop mov w,#%10000000 mov rc,w mov w,#%00000000 mov rc,w jmp loop

The circuit for the programs below

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Explanation of the program 5.2

To make the led at C7 to blink…..

loop mov w,#%10000000 ; load specified binary number intoworking register,w

mov rc,w ; load contents of w into register C

mov w,#%01111111

mov !rc,w

Program 5.3

Following show that the SX-28 take last few bit used in state using the whole 8bit as shown in the

program 5.2 above. Also the instruction of “djnz” is used here for delay (like pause instruction in BS2)

P7P0 BS2

outL=%00000000

Outc7 to out.0=%00000000

Zero volts from rc.7, rc.6…..rc.0

Set directions of rc

Exclamation mark means direction

No colon

must be

at the left

corner

No exclamation mark

mean output voltages

Device sx28L,oschs3 Device Turbo, StackX, optionX IRC_cal IRC_4MHz Freq 50_000_000 Reset 0 mov w,#%0000 mov ra,w mov w,#%1110 mov !ra,w loop mov w,#%0000 mov ra,w call delay1 mov w,#%0001 mov ra,w call delay1 jmp loop

32

The time taken in the delay is:

255X255X255X80E-9=1.3 sec (speed)

Further about SX-28

The usual

Odd ball

The i/o direction of SX28 and BS2 (there are opposite)

i/o direction for SX28

1=input

0=output

i/o direction for BS2

1=output

0=input

The time taken for for each SX-28 instruction

50 000 000 Hz per sec 20 nano sec

1ms 1000μs 1 000 000 ns

delay1 mov $0A,#$FF ‘255 skip2 mov $0B,#$FF ‘255 skip1 mov $0C,#$FF ‘255 skip0 djnz $0C,skip0 djnz $0B,skip1 ‘decriment of not zero djnz $0A,skip2 ret

33

Overview of i/o ports of SX-28

INSIDE SX28

RC0 port is used for example.

5V Vdd

0V Vss

rc.0bit

rc.0=1

rc.0=0

RC0

dir! switch

!rc.0=1

!rc.0=0

SX28 i/O ports

Ra.0 Ra.1 Ra.2 Ra.3

Rb.0 Rb.1 Rb.2 Rb.3

Rc.7 Rc.6 Rc.5 Rc.4 Rc.3 Rc.2 Rc.1 Rc.0

Rb.7 Rb.6 Rb.5 Rb.4

Register a

Register b

Register c

Register b

34

More on the SX28 program

Frequency of SX28 is 50 MHz

1/50 μs = 0.020μs = 20ns

Program 5.4

More explanation on program 5.4

Jmp 0.3 ms in BStamp

Jmp 20ns in SX28

Gosub in BS call in SX28

Return in BS ret in SX28

Djnz takes four clock pulse to implement djnz time = 4 X 20ns = 80 ns

1000,000,000ns = 1 sec

12.5 million djnz’s

delay mov $0C,#$ff

0A,0B,$ 0C

are each 8.bit

registers

loop setb rc.7 ;setb=setbit=,ale equal to"1" ;only effect one bit call delay clrb rc.7 ;clrb=clearbit=make equal to "0" ;only affects rc.7 call delay jmp loop delay mov $0C,#$ff ;ff in dec is 255 ;load register C with 255 skip2 mov $0B,#$ff ;load register C with 255 skip1 mov $0A,#$ff ;load register C with 255 skip0 djnz $0A,skip0 ;decrement by 1 registerA and if result is not equal to zero then jump to skip0 djnz $0B,skip1 ;decrement by 1 registerB and if result is not equal to zero then jump to skip1 djnz $0C,skip2 ;decrement by 1 registerC and if result is not equal to zero then jump to skip2

35

Program 5.5

To ensure the hardware (LED) is working

Program 5.6

Use 2 as the delay for output A, B and C.

mov !rc,#%01111111 main setb rc.7 clrb rc.7 jmp main

Device sx28L,oschs3 Device Turbo, StackX, optionX IRC_cal IRC_4MHz Freq 50_000_000 Reset 0 mov !rc,#%01111111 main setb rc.7 call delay clrb rc.7 call delay jmp main delay mov $0C,#2 skip3 mov $0B,#2 skip2 mov $0A,#2 skip1 djnz $0A,skip1 djnz $0B,skip2 djnz $0C,skip3 ret

36

Program 5.7

In order to get one second delay

Set the outputs to 255,255 and 192

Since 255 X 255 X 255 X 80ns =1.33s

Device sx28L,oschs3 Device Turbo, StackX, optionX IRC_cal IRC_4MHz Freq 50_000_000 Reset 0 mov !rc,#%01111111 main setb rc.7 call delay clrb rc.7 call delay jmp main delay mov $0C,#255 skip3 mov $0B,#255 skip2 mov $0A,#192 skip1 djnz $0A,skip1 djnz $0B,skip2 djnz $0C,skip3 ret

37

Program 5.8

The following circuit is used for the program. The program will control the opening of the switches

digitally.

Vdd(+5V)

10k

270

Vss (0V)

470

0V

rc3

rc7

Not-pressed/

unpressed

pressed

Not-pressed/

unpressed

pressed

The four type of switches

Device sx28L,oschs3 Device Turbo, StackX, optionX IRC_cal IRC_4MHz Freq 50_000_000 Reset 0 mov !rc, #%01111111 main mov $0D,rc rl $0D rl $0D rl $0D rl $0D rl $0D jnc onlight clrb rc.7 jmp main onlight setb rc.7 jmp main

38

CIRCUIT FOR SWITCHING LED ON AND OFF

The Figure below is the complete circuit of the switching LED On and off.

SX28

Vdd +5V

Vss 0V

10kΩ

RC3

Vss 0V

When V=+5V OFF light

V=0V ON light

This the program used where “rl” is used here

Program 5.9

Device sx28L,oschs3 Device Turbo, StackX, optionX IRC_cal IRC_4MHz Freq 50_000_000 Reset 0 mov !rc,#%01111111 mov rc,#00000000 loop ;mov $0D, #0 ;move literally value of 0 inyo register D clc ; clear the C flag to zero mov $0D,rc rl $0D rl $0D rl $0D rl $0D rl $0D jc offlight onlight setb rc.7 jmp loop offlight clrb rc.7 jmp loop

39

Further explanation on the program 5.9

SX INTRUCTION SET “rl”

For “rl” which means rotate left as shown in the diagram below.

It rotate left (rl), $0D register sequence as follows:

Start $ØD

0

0 0 0 0 1 0 0 0

rl $ØD

0

0 0 0 1 0 0 0 0

rl $ØD

0

0 0 1 0 0 0 0 0

rl $ØD

0

0 1 0 0 0 0 0 0

rl $ØD

0

1 0 0 0 0 0 0 0

rl $ØD

1

0 0 0 0 0 0 0 0

rl

Bit7

Bit6

Bit5

Bit4 Bit3

Bit2

Bit1

Carry bit

rc.3 Carry bit

40

6) 8-BIT ANALOGUE-TO-DIGITAL CONVERTER (ADC) with serial output Using ADC 0831 chip

BS2

“Brain”

P9

P10

P11CLK

DO

Vcc (+5V)

VrefGND

Vin(-)

Vin(+)

CSADC

0831

Vss (0V) Vdd (+5V)

Variable voltage

between 0 to 5V

Program 6.1 is used for this

Measuring -temp. -acceleration -velocity -pressure

-microprocessor -microcontroller -microcomputer (only no. here)

sensors brain actuators

ADC DAC

OVERVIEW OF THE USE OF ADC

(muscles)

Converter to change physical

quantities into number

Converter to change number

into physical quantities

Digital to analogue converter

Specifically variable voltage

variable quantity

41

Program 6.1

' $STAMP BS2 dvolts VAR Byte DIR11=1 DIR10=0 DIR9=1 HIGH 9 LOW 11 loop: LOW 9 HIGH 11 LOW 11 HIGH 11 LOW 11 HIGH 11 dvolts.BIT7=IN10 LOW 11 HIGH 11 dvolts.BIT6=IN10 LOW 11 HIGH 11 dvolts.BIT5=IN10 LOW 11 HIGH 11 dvolts.BIT4=IN10 LOW 11 HIGH 11 dvolts.BIT3=IN10 LOW 11 HIGH 11 dvolts.BIT2=IN10 LOW 11 HIGH 11 dvolts.BIT1=IN10 LOW 11 HIGH 11 dvolts.BIT0=IN10 LOW 11 HIGH 9 DEBUG DEC dvolts,CR GOTO loop

42

Further on ADC We used three power supplies to conduct this experiment. Following are the circuit used:

BS2

“Brain”

P9

P10

P11CLK

DO

Vcc (+5V)

VrefGND

Vin(-)

Vin(+)

CSADC

0831

Vss (0V)

Power supply 1

Power supply 2Power supply 3

We still used program 6.1 to do this experiment.

Following data are observed on the debug screen of “dvolts”

Vin (-) [power supply 2]

0 V 1 V 1 V

Vref [power supply 3]

5 V 4 V 3 V

Vin + (V) ADC.no. ADC.no. ADC.no.

0 0 0 0

1 51 0 0

2 103 62 83

3 154 126 167

4 205 190 252

5 255 253 255

43

Below is the graph of the data above:-

This graph show that the higher the different of Vin(+), the gradient is less steeper. On the other hand

the lower the different of Vin(-), the gradient is steeper. The gradient means the resolution of the ADC

no. Therefore the lower the potential difference, the higher the resolution.

How the ADC no. is implemented in the debug

For Vin(-)=0V and Vref=5V, following are extra data collected.

0

50

100

150

200

250

300

1 2 3 4 5 6

Vin(-)=0, Vref=5V

Vin(-)=1V, Vref=5V

Vin(-)=1, Vref=3V AD

C N

O.

Vin +(V)

Vin + (V) ADC.no.

0 mV 0

10 mV 1/0

20 mV 1

30 mV 1

40 mV 2

50 mV 2/3

Vin + (V) ADC.no.

15 mV 0

25 mV 1

35 mV 1

45 mV 2

44

These data are used to find the smallest increment of Vin in terms of ADC number.

The graph of ADC no. against Vin (mv) is plot from the data above.

3

2

1

0

10 20 30 40 50

ADC

no.

Vin (mV)

From the graph above show that:-

This can be proved by calculation:-

Therefore

( ) ( )

When calculating the ADC no., always used the round down value of integer.

( )

( )

45

Application of ADC

It can be used for temperature sensor

Where

To convert degree ( ) to Fahrenheit ( )

( ) ( ( )

)

To convert Fahrenheit ( )to degree ( )

( ) ( ( ) )

Therefore using the formula above, following data can be determined:-

0

1

2

3

4

5

0 100 200 300 400 500

vo

ltag

e O

/P (

V)

temperature ( ⁰F)

46

Thus below is the graph for temperature in degree against temperature in Fahrenheit.

Therefore, in order to fully utilize the range of the ADC for greater accuracy to make a temperature

sensor especially for usage in Brunei.

Let say is the temperature of Brunei throughout the year ( )

This means the Vin(-) should be 0.7 and Vref=0.3

0

20

40

60

80

100

0 15 30 45 60 75 90 105 120 135 150 165 180 195 210

temperature ( ⁰F)

tem

per

atu

re (

⁰C

)

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

0 20 40 60 80 100 120 140 160 180 200 220 240 260

temperature ( ⁰C)

vo

ltag

e O

/P (

V)

Vin (-) 0.7

Vref 0.3

Vin + (V) ADC.no.

0.3 0

0.4 34

0.5 71

0.6 109

0.7 143

0.8 180

0.9 218

1 255

2 255

3 255

4 255

5 255