Hiển thị nhiệt độ leenled 7 thanh dùng lm35 và atmega8

8/10/2019 Hin th nhit leenled 7 thanh dng lm35 v atmega8

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ti:Thit kthit bo nhit mi trng hin thln LED 7 thanh

Nhm 4i Hc Tin K3 Page 2

Mc Lc

Li Mu ........................................................................................................... 3

Phn 1: Tng quan vVK Atmega 8: ................................................................ 4

1. Tng quan vvi iu khin Atmega 8: .................................................... 4

2. Lp trnh cng vo ra (IO) ........................................................................ 6

3. Sdng timer0 ......................................................................................... 7

4. Truyn thng ni tip - USART ............................................................... 8

5. Two-wire Serial Interface - TWI ............................................................ 106. Serial Peripheral InterfaceSPI ............................................................ 10

7. Ngt ngoi .............................................................................................. 12

Phn 2: Cm Bin LM35 .................................................................................... 14

1.1 Tm hiu cm bin LM35 ......................................................................... 14

1.2 Tm hiu vchuyn i tn hiu tng tsang sADC (Analog-to-digitalconverter) ......................................................................................................... 16

1.2.1 Cc ch tiu k thut ch yu ca ADC.............................................. 17

1.2.2 Cc bc chuyn i AD................................................................... 18

1.2.3 ADC dng sng bc thang.................................................................. 20

1.2.4 ADC lin tip - xp x......................................................................... 23

1.2.5 ADC nhanh .......................................................................................... 23

Phn 3: LED 7 Thanh Anode Chung .................................................................. 26

1. Cu to Led 7 thanh anode chung .......................................................... 26

2. M Led 7 thanh anode chung ................................................................. 26

Phn 4: Sn Phm o Nhit V Hin ThLn LED 7 Thanh ...................... 28

1. M phng................................................................................................ 28

2. S nguyn l ...................................................................................... 28

3. S mch in ......................................................................................... 29

4. Source Code............................................................................................ 29


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Li Mu

Ngy ny, vi nhng ng dng ca khoa hc kthut tin tin, thgiica chng ta v ang ngy mt thay i, vn minh v hin i hn. Sphttrin ca kthut in t to ra hng lot nhng thit bvi cc c im ni

bt nh schnh xc cao, tc nhanh, gn nhl nhng yu tcn thit gpphn cho hot ng ca con ngi t hiu qucao. p dng nhng kin thc hc c trong qu trnh hc mn KThut Vi XL, chng em quyt nhchn ti: Thit kthit bo nhit mi trng hin thln LED 7

thanh.Qua bi tp ln ny, nhm sinh vin chng em xin chn thnh cm n

thy Th.S ng Vn Hiu nhit tnh dy d, gip v hng dn chng emhon thnh bi tp ny.


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Phn 1: Tng quan v VK Atmega 8

1. Tng quan vvi iu khin Atmega 8:- Tc ti a: 16MHz.- Dung lng bnhchng trnh: 8 KB.- BnhEEPROM: 512 Byte.- Dung lng bnhRAM: 1 KB.Bnhchng trnh c khnng ghi 10.000 ln, bnhEEPROM cthghi 100.000 ln. Htrbootloader, c khnng tghi vo bnhchng trnh, cp nht chng trnh cho chip m khng cn mch np.- Timer 8 bit: 2.- Timer 16 bit: 1.

- ADC: 6 knh, 10 bit.- Giao tip: TWI (I2C), UART, SPIin p hot ng:Atmega8L: 2.7V5.5V.Atmega8: 4.5V5.5V.S chn:


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Hthng Clock:Ngun Clock:Chip c thhot ng vi cc ngun Clock tng ng vi vic thit lp ccFUSE tng ng:

Ta chtp trung vo hai ngun clock l sdng thch anh ngoi v sdngmch RC tch hp trong chip (dao ng ni).Sdng thch anh ngoi:

Atmega8 c 4 cch RESET:- Reset khi cp ngun.- Reset ngoi (thng qua chn RESET).- Watchdog RESET.- Reset khi ngun bst p.


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2.

Lp trnh cng vo ra (IO)iu khin vo ra (IO):Atmega8 c 3 cng vo ra: cng B, cng C, cng D.Mi cng c cu hnh, iu khin thng qua 3 thanh ghi: DDRx, PORTx v

PINx. (x: B, C, D).Cc thanh ghi ny c thtruy xut tng bit c thiu khin tng chn (Pin)ca mi cng.- DDRx: quy nh chiu ca chn, DDRx=1: chn c cu hnh lm u ra,ngc li DDRx=0 quy nh chn lm u vo.- PORTx: nu PORTx=1 khi chn c cu hnh lm u vo th skch hotin trtreo dng ti chn tng ng. v hiu ha trtreo ny th PORTx

phi c gn 0 hoc chn c cu hnh lm u ra (DDRx=1).Nu chn c cu hnh lm u ra (DDRx=1):Nu PORTx=1 th chn tng ng sc a ln cao (1 VCC), ngc linu PORTx=0 th chn tng ng sc a xung thp (0GND)- PINx: c dliu tchn VK, c lp vi cu hnh chiu ca chn (ckhiDDRx=0 v DDRx=1) trng thi ca chn c thc c thng qua cc bitca thanh ghi PINx.Ch :

Nu bit th2 (PUD) ca thanh ghi SFIOR c ghi gi tr1 th trtreo sbvhiu ha bt chp cc thit lp thng qua cc thanh ghi PORTx, DDRx nh ni trn.

- Mch vi iu khin c bn:+ Mch sdng thch anh:


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+ Mch sdng dao ng ni:

3.

Sdng timer0Atmega8 c 3 bnh thi/bm (Timer/Counter): Chng c thdng mthi gian, m skin xy ra bn ngoi VK, to ra cc xung iu rngPWMPhn ny ta stm hiu vTimer/Counter 0 (T/C 0). T/C 0 l bm/ nh thi8 bit. Thanh ghi TCNT0 c rng 8 bit. T/C0 c thm xung hthng (xunghthng c thl thch anh ngoi hay dao ng ni m ta ni phntrc), xung hthng sau khi qua bchia tn hoc xung bn ngoi ti chn T0.

Ta c thchn ngun xung m thng qua vic cu hnh cc thanh ghi iukhin TC0 (cc bit CS2..0 ca thanh ghi TCCR0).TCNT0 stng ln 1 mi khi nhn c 1 xung, sau khi TCNT0 t n 0xff(255) nu nhn thm 1 xung na n strv0x00. ng thi lc ny cTOV0(bit th0 ca thanh ghi TIFR) sc gn bng 1. Lu l TCNT0 l thanhghi c thc v ghi v vy ta c thghi gi trvo n bt clc no.Sdng T/C0:- Chn ngun xung clock:Ta cu hnh chn ngun xung clock thng qua vic ghi gi trvo 3 bit CS02..0

ca thanh ghi TCCR0


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4. Truyn thng ni tip - USARTBtruyn thng ni tip trn Atmega8 c thhot ng nhiu chv yta chxt chbt ng b.- Khi to ngun clock cho btruyn thng, khi to tc Baud.khi to tc Baud ta ghi gi trtng ng vi tc Baud vo thanh ghiUBRR.Lin hgia UBRR v tc Baud cho bi cng thc sau:

V dchng ta sdng xung hthng l 3.6864MHz, ta cn dng tc Baudl 9600C 2 trng hp: nu ta chn U2X=0 th UBRR=3.686.400/9600/16-1=23.

Nu ta chn U2X=1 th UBRR=3.686.400/9600/8-1=47.- nh dng khung truyn: ta chxt nh dng khung truyn l 1 bit start, 8 bitdliu, 1 bit stop, khng kim tra chn l.* Cc thanh ghi cu hnh, iu khin bUSART :- Thanh ghi UDR:


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+ truyn dliu i th ta ghi dliu cn truyn vo thanh ghi ny v bUSART sgi dliu cn truyn i.+ Sau khi nhn c dliu th thanh ghi ny scha dliu nhn c.- Thanh ghi USRCA:

Cc bit ta quan tm:+ bit 7 - RXC: cny bng 1 khi c dliu nhn c v sc xa thnh 0khi khng c dliu trong bm (UDR).+ bit 6TXC: cny c bt mi khi truyn xong dliu. Mun xa th taghi gi tr1vo bit ny.+ bit 5UDRE: UDRE c set thnh 1 khi UDR l rng v sn sng chotruyn dliu.- Thanh ghi UCSRB:

Tm thi ta quan tm cc bit sau:- bit 4 - RXEN: cho php nhn, ghi gi tr1 vo bit ny cho php USART nhndliu.- bit 3TXEN: cho php truyn dliu, ghi 1 vo bit ny cho php USARTtruyn dliu.- bit 2UCSZ2: kt hp vi cc bit UCSZ1..0 trong thanh ghi UCSRC quynh sbit dliu trong 1 khung truyn.- Thanh ghi UCSRC:

C cng a chvi thanh ghi UBRRH:- bit 7URSEL: xc nh truy cp UBRRH hay UCSRC, khi URSEL=1: truycp UCSRC, khi URSEL=0: truy cp UBRRH.- bit 6UMSEL: chn chca USART: =0: truyn bt ng b, =1 truyn

ng b. V chng ta chtm hiu truyn bt ng b.


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- bit 3USBS: =1: 2 bit stop; =0: 1 bit stop.- bit UCSZ1..0: kt hp vi UCSZ2 trn quy nh sbit dliu, ta chtmhiu kiu truyn 8 bit dliu UCSZ2=0; UCSZ1=1; UCSZ0=1;

5.

Two-wire Serial Interface - TWI

BTWI ca Atmega 8 c thhot ng nhiu ch.Coi nh bn c nhng kin thc c bn vchun giao tip TWI (I2C) vchng ta stm hiu cch sdng module TWI ca Atmega8 v v dy lgiao tip vi EEPROM 24C512.

Sdng TWI:- Cu hnh cho php TWI hot ng, chn tc xung ti chn SCL, chn chMasterSlaver.- Giao tip vi cc ngoi vi.

+ gi START: ghi 1 vo bit TWSTA ca thanh ghi TWCR.+ gi STOP: ghi 1 vo bit TWSTO ca thanh ghi TWCR.+ gi ACK: ghi 1 vo bit TWEA ca thanh ghi TWCR.+ Dliu cn gi i hoc nhn c sc cha trong thanh ghi TWDR:mun gi 1 byte th ghi byte cn gi vo TWDR, dliu nhn c sccha trn TWDR.

6. Serial Peripheral InterfaceSPI- SPI (Serial Peripheral Bus) l mt chun truyn thng ni tip tc cao dohang Motorola xut. y l kiu truyn thng Master-Slave, trong c 1chip Master iu phi qu trnh tuyn thng v cc chip Slaves c iu khin

bi Master v thtruyn thng chxy ra gia Master v Slave. SPI l mt cchtruyn song cng (full duplex) ngha l ti cng mt thi im qu trnh truynv nhn c thxy ra ng thi. SPI i khi c gi l chun truyn thng 4dy v c 4 ng giao tip trong chun ny l SCK (Serial Clock), MISO(Master Input Slave Output), MOSI (Master Ouput Slave Input) v SS (SlaveSelect).- SPI ca Atmega8 c thhot ng nhiu ch:Ta chtm hiu i din chmaster:

Dliu lun lun truyn theo hng Master ti Slaver thng qua chn MOSI vtSlaver ti Master thng qua chn MISO.Khi ghi mun truyn dliu ta sghi dliu cn truyn vo thanh ghi dliuSPI (SPI Data Register - SPDR).Mi khi gi xong 1 byte th bit SPIF sc thit lp: ta sdng kim traxem khi no th gi xong 1 byte.


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SPI Control RegisterSPCR:

Ta quan tm n cc bit:- Bit 6SPE: SPI Enable: ghi 1 vo bit ny cho php SPI hot ng.- Bit 5DORD: Data Order: khi bit ny bng 1 th khi truyn SPI struyn bitthp nht (LSB) trc, ngc li khi bit bng 0 th SPI struyn bit cao nhttrc (MSB).- Bit 4MSTR: MasterSlaver select: bng 1 chn chMaster, bng 0chn chSlaver.

- Bit 1..0: Chn tc xung SCK:

SPI Status Register:

- Bit 7SPIF: SPI Interrupt Flag: c t bng 1 khi truyn xong 1 byte v taskim tra bit ny xem khi no truyn xong 1 byte.- Bit 0SPI2X: Nhn i tc SCK

sdng SPI ta qua cc bc sau:- Cu hnh bSPI, chmaster.- Cho php bSPI hot ng.- Truyn, nhn dliu.


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7.

Ngt ngoiNgt l 1 tn hiu khn cp c gi n b vi x l, yu cu b vi x l dngcc cng vic hin ti nhy n thc hin nhim v khn cp nhim v nyc gi l trnh phc v ngt. Sau khi thc hin xong nhim v ny th vi x l

tip tc lm cc cng vic tip theo.Khi c 2 tn hiu ngt n cng 1 lc th tn hiu no u tin cao hn s cthc hin. atmega8 c 19 tn hiu ngt t mc u tin cao xung thp nhsau.

Ngt thng c s dng thc hin cc cng vic m khng bit trc thiim nh trong truyn thng, m s kin...Phn ny th chng ta ch nghin cu phn ngt ngoi. cho php cc ngt hot ng th cn set bit I trong thanh ghi SREG ln 1.

chip atmega8 c 2 ngt ngoi c k hiu l INT0 v INT1. Cc thanh ghiiu khin ngt ngoi


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- thanh ghi MCUCR

y l thanh ghi iu khin kiu tc ng ngt theo sn m hay sn dng,hay mc.4 bit cao th khng cn quan tm nhiu 4 bit thp c bit 0 v 1 iu khin int0,

bit 2 3 iu khin int 1.

thanh ghi GICR

thanh ghi ny th ch cn quan tm n 2 bit l INT1 tc l cho php ngt

INT1 hot ng v INT0 cho php ngt INT0 hot ng.thanh ghi c ngt.

thanh ghi ny th ch cn quan tm n 2 bit l INTF1 v INTF0. Khi c 1 skin ngt trn INT1 th bit INTF1 bt 1, khi c 1 s kin ngt trn INT0 thINTF0 bt 1.


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Phn 2: Cm Bin LM35

1.1 Tm hiu cm bin LM35LM35 c bin thin theo nhit : 10mV/1(0C)* chnh xc cao, tnh nng cm

bin nhit rt nhy, nhit 25(0C) n c sai skhng qu1%. Vi tm o t

0(0C) n 128(0C) , tn hiu ng ra tuyn tnh lin tc vi nhng thay i ca tnhiu

ng vo.

* Thng skthut:

- Tiu tn cng sut thp

.- Dng lm vic t400A n 5mA.- Dng ngc 15mA.

- Dng thun 10mA.

- chnh xc: khi lm vic nhit 25(0C) vi dng lm vic 1mA th in p ng

ra t2,94V n3,04V.

c tnh in:

- Theo thng sca nh sn xut LM35, quan hgia in p v ng ra nh

sau:Vout=0.01*T(0K)=2,73+0,01*T(0C).

Vy ng vi tm hot ng t0(0C) n 100(0C) ta c sbin thin in p ng ra

l0(0C) th in p ng ra Vout = 2,73V5(0C) th in p ng ra Vout = 2,78V.

100(0C) th in p ng ra Vout = 3,71V. Tm bin thin in p tng ng vi nhit

t0(0C) n 100(0C) l 1V Lot cc bcm bin LM35 l bcm bin nhit

mch tch hp chnh xc cao m in p u ra ca n tltuyn tnh vi nhit

theo thang Celsius. Chng cng khng yu cu cn chnh ngoi v vn chng c cn chnh. Chng a ra in p 10mV cho mi sthay i 10C.

Nhit (0C) Trkhng ca cm bin (k)

0 29.490

25 10.000

50 3.893

75 1.700

Bng 1.1: Trkhng ca bcm bin nhit theo nhit .


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Di nhit chnh xc u ra

LM35A -55 C to + 150 C + 1.0 C 10 mV/F

LM35 -55 C to + 150 C + 1.5 C 10 mV/F

LM35CA -40 C to + 110 C + 1.0 C 10 mV/F

LM35C -40 C to + 110 C + 1.5 C 10 mV/F

LM35D 0 C to + 100 C + 2.0 C 10 mV/F

Bng 1.2 Hng dn chn cc loi cm bin.

Hnh 1.1 Hnh dng thc t bng LM35

M35 c 3 chn chnh : 2 chn cp ngun v 1 chn out tn hiu Analog

Khi ta cp in p 5V cho LM335 th nhit o c t cm bin s chuyn thnh

in p tng ng ti chn s 2 (Vout). in p ny c t l vi gii nhit m no c. Vi gii ca nhit u ra l 10mV/K. Hot ng trong gii in p t 0

cho n 5V v gii nhit o c t 0 oC n 100oC. V cn ch n nhng

thng s chnh sau :

+ Hot ng chnh xc dng in u vo t 0.4mA n 5mA. Dng in u vo

ngoi

khong ny kt qu o s sai

+ in p cp vo n nh l 5V


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+ Tr khng u ra thp 1 m

+ Gii nhit mi trng l t 0 n 100 C

Nh vy LM335 ncho chng ta tn hiu tng t (Analog) v chng phi x l tn

hiu ny thnh nhit

1.2 Tm hiu vchuyn i tn hiu tng tsang sADC (Analog-to-digitalconverter)

S khi ADCB chuyn i tng t sang s ADC (Analog to Digital Converter) ly

mc in th vo tng t sau mt thi gian s sinh ra m u ra dng s

biu din u vo tng t. Tin trnh bin i A/D thng phc tp v mt

nhiu thi gianhntin trnh chuyn i D/A. Do c nhiu phng phpkhc nhau chuyn i t tng t sang s.

Hnh1.2 S khi ca mt lp ADC n gin.

Hot ng c bn ca lp ADC thuc loi ny nh sau:Xung lnh START khi ng s hot ng ca h thng.

Xung Clock quyt nh b iu khin lin tc chnh sa s nh phn lu trong

thanh ghi.

S nh phn trong thanh ghi c DAC chuyn i thnh mc in th tng

t VAX.

B so snh so snh VAXvi u vo trng t VA. Nu VAX< VAu ra
http://en.wikipedia.org/wiki/Analog-to-digital_converterhttp://en.wikipedia.org/wiki/Analog-to-digital_converterhttp://en.wikipedia.org/wiki/Analog-to-digital_converterhttp://en.wikipedia.org/wiki/Analog-to-digital_converter


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cab so snh ln mc cao. Nu VAX> VAt nht bng mt khong VT(in

th ngng), u dra ca b so snh s xung mc thp v ngng tin trnh bin

i s nh phn thanh ghi.Ti thi im ny VAXxp x VA.gi dtr nh phn

thanh ghi l i lng s tng ng VAXv cng l i lng s tng

ng VA, trong gii hn phn gii v chnh xc ca h thng.

Logic iu khin kch hot tn hiu ECO khi chu k chuyn i kt thc.

Tin trnh ny c th c nhiu thay di i vi mt s loi ADC khc, ch yu

l s khc nhau cch thc b iu khin sa i s nh phn trong thanh ghi.

1.2.1 Cc ch tiu k thut ch yu ca ADC

phn gii

phn gi ca mt ADC biu th bng s bit ca tn hiu s u ra. S lng

bit nhiu sai s lng t cng nh, chnh xc cng cao.

Di ng, in tr u vo.

Mc logic ca tn hiu s u ra v kh nng chu ti (ni vo u vo).

chnh xc tng i

Nu l tng ha th tt c ccim chuyn iphi nm trn mt ngthng. chnh xc tng i l sai ds ca cc im chuyn i thc t so vi

c tuyn chuyn i l tng. Ngoi ra cn yu cu ADC khng b mt bit

trong ton b phm vi cng tc.

Tc chuyn i

Tc chuyn i c xc nh thi gian bi thi gian cn thit hon thnh

mt ln chuyn i A/D. Thi gian ny tnh t khi xut hin tn hiu iu khinchuyn i n khi tn hiu s u ra n nh.

H s nhit

H s nhit l bin thin tng i tn hiu s u ra khi nhit bin i

10C trong phm vi nhit cng tc cho ph p vi iu kin mc tng t u

vo khng i.

T s ph thuc cng sut


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Gi s in p tng t u vo khng i, nu ngun cung cp cho ADC bin

thin m nh hng n tn hiu s u ra cng ln th t s ph thuc ngun

cng ln.

Cng sut tiu hao.

1.2.2 Cc bc chuyn i ADQu trnh chuyn i A/D nhn chung c thc hin qua 4 bc c bn, l:

ly mu; nh mu; lng t ha v m ha. Cc bc lun lun kt hp vi

nhau trong mt qu trnh thng nht.

1.2.2.1 nh l ly mu

i vi tn hiu tng t VIth tn hiu ly mu VSsau qu trnh ly mu c thkhi phc tr li VImt cch trung thc nu iu kin sau y tha mn:

fS 2fImax (10)

Trong fS : tn s ly mu

fImax : l gii hn trn ca gii tn s tng t

Hnh 3biu din cch ly mu tn hiu tng t u vo.Nu biu thc (10)

c tha mn th ta c th dng b t lc thng thp khi phc VIt VS.V mi ln chuyn i in p ly mu thnh tn hiu s tng ng u cn c

mt thi gian nht nh nn phi nh mu trong mt khong thi gian cn thit

sau mi ln ly mu. in p tng t u vo c thc hin chuyn i A/D

trn thc t l gi tr VI i din, gi tr ny l kt qu ca mi ln ly mu.

Hnh 1.3 Ly mu tn hiu tng t u vo


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1.2.2.2 Lng t ha v m ha

Tn hiu s khng nhng ri rc trong thi gian m cn khng lin tc trongbin i gi tr. Mt gi tr bt k ca tn hiu s u phi biu th bng bi s

nguyn ln gi tr n v no , gi tr ny l nh nht c chn. Ngha l nu

dng tn hiu s biu th in p ly mu th phi bt in p ly mu ha thnh

bi s nguyn ln gi tr n v. Qu trnh ny gi llng tha. n v c

chn theo qui nh ny gi l n v lng t, k hiu D. Nh vy gi tr bit 1

ca LSB tn hiu s bng D. Vic dng m nh phn biu th gi tr tn hiu sl m ha. M nh phn c c sau qu trnh trn chnh l tn hiu u ra ca

chuyn i A/D.

1.2.2.3 Mch ly mu v nh muKhi ni trc tip in th tng t vi u vo ca ADC, tin trnh bin i c

th b tc ng ngc nu in th tng t thay i trong tin trnh bin i.

Ta c th ci thin tnh n nh ca tin trnh chuyn i bng cch s dng

mch ly mu v nh mu ghi nh in th tng t khng i trong khi

chuk chuyn i din ra.

Hnh 1.4 S ca mch ly mu v nh mu.

Khi u vo iu khin = 1lc ny chuyn mch ngmch ch ly mu

Khi u vo iu khin = 0lc ny chuyn mch h mch ch gi mu


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Chuyn mch c ng mt thi gian di t Chnp n gi tr dng in

ca tn hiu tng t.V d nu chuyn mch c ng ti thi im t0 th u

ra A1s np nhanh t Ch ln n in th tng t V0.khi chuyn mch m th

t Ch s duy tr in th ny u ra ca A2cung cp mc in th ny cho

ADC. B khuch i m A2 t tr khng cao ti u vo nhm khng x in

th t mt cch ng k trong thi gian chuyn i ca ADC do ADC ch

yu s nhn c in th DC vo, tc l V0.

Trong thc t ngi ta s dng vi mch LF198 l mch S/H tch hp c thi

gian thu nhn d liu tiu biu l 4ms ng vi Ch = 1000pF, v 20ms ng vi

Ch= 0.01mF. Tn hiu my tnh sau s m chuyn mch cho php Chduytr gi tr ca n v cung cp mc in th tng t tng i n nh ti u ra

A2.

Hnh 1.5: S chn ca LF198s

1.2.3 ADC dng sng bc thang

1.2.3.1 S khiPhin bn n gin nht ca lp ADC s dng b m nh phn lm thanh

ghi v cho php xung nhp y b m tng mi mt bc, cho n khi VAX>

VA. y gi l ADC sng dng bc thang, v dng sng ti VAXc tng bc i

ln.Ngi ta cn gi l ADC loi b m.


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Hnh 1.6 : S biu din mt ADC dng sng bc thang.Cc thnh phn ca DAC dng sng bc thang hnh 1.6gm: mt b m, mt

DAC, mt b so snh tng t, mt cng NAND 3 ng vo iu khin. u ra

ca b so snh dng lm tn hiu(End Of Conversionkt thc chuyn i).

1.2.3.2 Hot ng ca b ADC dng sng bc thangGi s VA, tc mc in th cn chuyn i l dng th tin trnh hot ng

din ra nh sau:

Xung Khi ng c a vo Reset b m v 0. Mc cao ca xung

Khi ng cm khng cho xung nhp i qua cng AND vo b m.

Nu u ca DAC ton bit 0 th u ra ca DAC s l VAX= 0V.

V VA>VAXnn u ra b so snh s ln mc cao.

Khi xung Khi ng v thp th cng AND cho php xung nhp i qua cng

ny v vo b m.

Khi gi tr b m tng ln th u ra DAC l VAXs tng mi ln mi bc,

nh minh ha hnh 1.6

Tin trnh c tip tc cho n khi VAXln n bc vt qu VAmt

khong VT. Ti thi im ny ng ra ca b so snh v thp v cm khng

cho xung nhp i vo b m nn b m s ngng m.

Tin trnh chuyn i hon tt khi tn hiu chuyn t trng thi cao xung thp

v ni dung ca b m l biu th dng s ca in p tng t vo VA.


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B m s duy tr gi tr s cho n khi no xung Khi ng k tipvo bt

u tin trnh chuyn i mi.

1.2.3.3 phn gii v chnh xcca ADC dng sng bc thang

Trong ADC dng sng bc thang c nhiu yu t nh hng n sai s ca qu

trnh chuyn i nh: kch c bc thang, tc phn gii ca DAC ci trong

n v nh nht. Nu gim kch c bc thang ta c th hn ch bt sai s nhng

lun c khong cch chnh lch gia i lng thc t v v gi tr gn cho

n.y gi l sai s lng t.

Cng nh trong DAC, chnh xc khng nh hng n phn gii

nhng li ty thuc vo chnh xc ca linh kin trong mch nh: b so snh,in tr chnh xc v chuyn mch dng ca DAC, ngun in quy

chiu,Mc sai s = 0.01% gi tr cc i (y thang) cho bit kt qu ra t

ADC c th sai bit mt khong nh th, do cc linh kin khng l tng.

1.2.3.4 Thi gian chuyn iThi gian chuyn i l khong thi gian gia im cui ca xung khi ng

n thi im kch hot u ra ca. B m bt u m t 0 ln cho n khiVAX vt qu VA, ti thi im xung mc thp kt thc tin trnh

chuyn i. Nh vy gi tr ca thi gian chuyn i tCph thuc vo VA. Thi

gian chuyn i cc i xy ra khi VAnm ngay di bc thang cao nht. Sao

cho VAXphi tin ln bc cui cng kch hot .

Vi b chuyn i N bit, ta c:

tC(max) = (2

N

1) chu k xung nhpADC hnh 1.6s c thi gian chuyn i cc i

tC(max) = (2101)x1ms = 1023ms

i khi thi gian chuyn i trung bnh c quy nh bng thi gian chuyn

i cc i.

Vi b chuyni dng sng bc thang, ta c:

Nhc im ca ADC dng sng bc thang l thi gian chuyn i tng gp i

vi tng bit thm vo b m. Do vy ADC loi ny khng thch hp vi nhng


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ng dng i hi phi lin tc chuyn i mt tn hiu tng t thay i nhanh

thnh tn hiu s. Tuy nhin vi cc ng dng tc chm th bn cht tng

i n gin ca ADC dng sng bc thang l mt u im so vi cc loi ADC

khc.

1.2.4 ADC lin tip - xp xB chuyn i lin tip - xp x ( Successive Approximation Convetr-SAC) l

mt trong nhng loi ADC thng dng nht. SAC c s phc tp hn nhiu

so vi ADC dng sng bc thang. Ngoi ra SAC cn c gi tr tCc nh, khng

ph thuc vo gi tr ca u vo tng t.

Hnh 1.7 l mt cu hnh c bn ca SAC, tng t cu hnh ca ADC dngsng bc thang. Tuy nhin SAC khng s dng b m cung cp u vo cho

DAC m thay vo l thanh ghi. Logic iu khin sa i ni dung lu trn

thanh ghi theo tng bit mt cho n khi d liu thanh ghibin thnh gi tr s

tng ng vi u vo tng t VAtrong phm vi phn gii ca b

chuyn i.

Hnh 1.7 S khi ADC lin tip xp x

1.2.5 ADC nhanh

B chuyn i nhanh (flash converter) l ADC tc cao nht hin nay c mt


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trn th trng, nhng s mch phc tp hn cc loi khc. V d mt ADC

nhanh 6 bit i hi 63 b so snh tng t, cn ADC nhanh 8 bit th con s ny

ln n 255, 10 bit th ln n 1023. Nh vy s lng b so snh qu ln

gii hn kch cca ADC nhanh.

Hnh 1.8 S ca mt ADC nhanh

ADC nhanh hnh 1.8 c phn gii 3 bit.Kch thc bc thang l 1V. B

chia in th thit lp mc quy chiu cho tng bso snh c c 7 mc ng

vi 1V ( trng s ca LSB ), 2V, 3V, 7V (y thang). u vo tng t

VAc ni n u vo cn li ca tng b so snh.

Vi VA< 1V th tt c u ra ca b so snh u ln mc cao.Vi VA> 1V tht mt u ra tr ln s xung mc thp.u ra ca b so snh c a vo b

m ho u tin tch cc mc thp, sinh u ra ng vi u ra c s th t cao

nht mc thpca b so snh. L lun tng t ta s c c bng gi tr nh

Bng 1.3Bng s tht ca ADC nhanh 3 bit hnh1.8


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ADC nhanh hnh 1.8 c phn gii 1V v u vo tng t phi thay i mi

ln 1V mi c th a u ra s ln bc k tip.Mun c phn gii tinh hn

th phi tng tng s mc in th vo (ngha l s dng nhiu in tr chia th

hn) v tng s b so snh. Ni chung ADC nhanh N bit th cn 2N1 b so

snh, 2Nin tr, v logic m ho cn thit.

Thi gian chuyn i

B chuyn i nhanh khng cn thit tn hiu xung nhp v tin trnh ny xy ra

lin tc. Khigi tr u vo thay i th u ra ca b so snh s thay i lm

cho ng ra ca b m ha thay i theo. Nh vy thi gian chuyn i l thi

gian cn thit xut hin mt u ra s mi p li mt thay i VA. Thi

gian chuyn i ch ph thuc vokhong tr do truyn ca b so snh v b

m ha. V vy m ADC nhanh c thi gian chuyn i v cng gn.


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Phn 3: LED 7 Thanh Anode Chung

1.

Cu to Led 7 thanh anode chung

- Led 7 on c cu to bao gm 7 led n xp theo hnh pha trn v c thmmt led n hnh trn nhthhin du chm trn gc di, bn phi ca led 7

thanh.- 8 led n trn led 7 thanh c Anode (cc +) hoc Cathode (cc -) c nichung vi nhau vo mt im v c a chn ra ngoi kt ni vi mchin. 7 cc cn li trn mi led n ca led 7 on v 1 cc trn led n gcdi, bn phi ca led 7 on c a thnh 8 chn ring iu khin choled sng tt theo mun.- Nu led 7 on c Anode (cc +) chung, u chung ny c ni vi +Vcc,cc chn cn li dng iu khin trng thi sng tt ca cc led n, led chsng khi tn hiu t vo cc chn ny mc 0.

- Nu led 7 on c Cathode (cc -) chung, u chung ny c ni xungGround (hay Mass), cc chn cn li dng iu khin trng thi sng tt cacc led n, led chsng khi tn hiu t vo cc chn ny mc 1.

2. M Led 7 thanh anode chung

- i vi dng Led Anode chung, chn COM phi c mc logic 1 v munsng Led no th tng ng cc chn af, dp smc logic 0.

- Bng m cho Led anode chung :


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Phn 4:Sn Phm o Nhit V HinTh Ln LED 7 Thanh

1. M phng

2. S nguyn l


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3.

S mch in

4.

Source Code

#include

#include

#define ADC_VREF_TYPE 0x00

// Read the AD conversion result

unsigned int read_adc(unsigned char adc_input)


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{

ADMUX=adc_input | (ADC_VREF_TYPE & 0xff);

// Delay needed for the stabilization of the ADC input voltage

delay_us(10);

// Start the AD conversion

ADCSRA|=0x40;

// Wait for the AD conversion to complete

while ((ADCSRA & 0x10)==0);ADCSRA|=0x10;

return ADCW;

}

// Declare your global variables here

unsigned char adc_value;float vin;

int a,b,i;

void led (unsigned char x)//ham dua du lieu ra PORT D

{

switch(x)

{

case 0:{PORTD=0x40;break;}//so 0





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}

}void main(void)

{

// Declare your local variables here

// Input/Output Ports initialization

// Port B initialization// Func7=In Func6=In Func5=In Func4=In Func3=In Func2=In Func1=InFunc0=In

// State7=T State6=T State5=T State4=T State3=T State2=T State1=TState0=T

PORTB=0x00;

DDRB=0x00;

// Port C initialization

// Func6=In Func5=Out Func4=Out Func3=Out Func2=Out Func1=OutFunc0=In

// State6=T State5=0 State4=0 State3=0 State2=0 State1=0 State0=T

PORTC=0x00;

DDRC=0x3E;


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// Port D initialization

// Func7=In Func6=Out Func5=Out Func4=Out Func3=Out Func2=OutFunc1=Out Func0=Out

// State7=T State6=0 State5=0 State4=0 State3=0 State2=0 State1=0State0=0

PORTD=0x00;

DDRD=0x7F;

// ADC initialization// ADC Clock frequency: 1000.000 kHz

// ADC Voltage Reference: AREF pin

ADMUX=ADC_VREF_TYPE & 0xff;

ADCSRA=0x83;

while (1)

{

adc_value=read_adc(0); // Doc gia tri adc

vin=((float)adc_value*500)/1023; // vin la gia tri nhiet do thuc te doduoc

a=(int)vin/10; // Lay phan chuc cua nhiet do

b=(int)vin%10; // Lay phan don vi cua nhiet do

while(i


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delay_ms(1); // Thoi gian quet LED la 1ms, thoi giannay nho LED se khong bi nhay

PORTC.1=0;

PORTC.2=1;

led(b);

delay_ms(1);

PORTC.2=0;

PORTC.3=1;

PORTD=0x9c;

delay_ms(1);

PORTC.3=0;

PORTC.4=1;

PORTD=0xc6;

delay_ms(1);

PORTC.4=0;

i=i+1;

}

i=0;

}

}

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Hiển thị nhiệt độ leenled 7 thanh dùng lm35 và atmega8