Temperature and Pressure Control using the AT90S8535
by Louis Mo Stephen Yu
Overview:
This project involves the implementation of control and monitor for dual processes. The variables monitored are pressure and temperature. The input control is a 16 button keypad and the output is monitored in a 16 character LCD The device can be widely deployed as a cheap solution to room and automobile climate control automation.
Functionality:
1. Display Pressure or Temperature
Pressure will be displayed when button A is pressed.
Temperature will be displayed when button B is pressed.
Temperature is displayed in intervals of five Celsius from –20° C to 20° C and 30° C to 80° C.
Displays the closest to 20° C, 23° C, 25° C, 28° C when in the range between
20° C and 30° C.
Pressure will be displayed in lb/inch2 from 0 to 30 PSI in intervals of one PSI.
2. Temperature can be controlled to any of the displayable threshold with approximately +/- 2° C control range.
When Button D is pressed, user will be prompted to enter the temperature range desired.
There are 24 temperature ranges available as shown in table 1. These ranges are selected by punching the range number in the keyboard.
Temperature control has a three stage differential sensing scheme. When temperature is within approximately 2° C within desired temperature range, then a lower intensity fan is deployed. When temperature is approximately between 2° C to 4° C within the desired range, a higher intensity fan is deployed. When the temperature discrepancy from the desired temp is more than 4° C then the highest fan intensity is selected.
3. When Pressure is selected as LCD output, temperature is monitored every 20 read cycles or approximately 70035 m secs.
4. Pressure change alarm LED is flashed when the increase in pressure is past 5 PSI within five read cycles or approximately 35 m secs.
Implementation:
Hardware: 1 AT90S8535, 1 STK200, 1 RCM2034R LCD,
1 16 button keypad, Lucas NovaSensor NPC 410 pressure sensor,
1 NTC GE 76 thermistor
Circuit Specification:
Clock rate 4Mhz AREF 4.096 Volts
The following graph depicts the linearization relationship for the GE 76 thermistor:
Temperature^2 VS Resistance
Voltage step per PSI increase for the Lucas Novasensor:4.1667mv per PSI
DC offset from output of NPC-410 7mv
Link: http://instruct1.cit.cornell.edu/courses/e...inalwriteup.htm
by Louis Mo Stephen Yu
Overview:
This project involves the implementation of control and monitor for dual processes. The variables monitored are pressure and temperature. The input control is a 16 button keypad and the output is monitored in a 16 character LCD The device can be widely deployed as a cheap solution to room and automobile climate control automation.
Functionality:
1. Display Pressure or Temperature
Pressure will be displayed when button A is pressed.
Temperature will be displayed when button B is pressed.
Temperature is displayed in intervals of five Celsius from –20° C to 20° C and 30° C to 80° C.
Displays the closest to 20° C, 23° C, 25° C, 28° C when in the range between
20° C and 30° C.
Pressure will be displayed in lb/inch2 from 0 to 30 PSI in intervals of one PSI.
2. Temperature can be controlled to any of the displayable threshold with approximately +/- 2° C control range.
When Button D is pressed, user will be prompted to enter the temperature range desired.
There are 24 temperature ranges available as shown in table 1. These ranges are selected by punching the range number in the keyboard.
Temperature control has a three stage differential sensing scheme. When temperature is within approximately 2° C within desired temperature range, then a lower intensity fan is deployed. When temperature is approximately between 2° C to 4° C within the desired range, a higher intensity fan is deployed. When the temperature discrepancy from the desired temp is more than 4° C then the highest fan intensity is selected.
3. When Pressure is selected as LCD output, temperature is monitored every 20 read cycles or approximately 70035 m secs.
4. Pressure change alarm LED is flashed when the increase in pressure is past 5 PSI within five read cycles or approximately 35 m secs.
Implementation:
Hardware: 1 AT90S8535, 1 STK200, 1 RCM2034R LCD,
1 16 button keypad, Lucas NovaSensor NPC 410 pressure sensor,
1 NTC GE 76 thermistor
Circuit Specification:
Clock rate 4Mhz AREF 4.096 Volts
The following graph depicts the linearization relationship for the GE 76 thermistor:
Temperature^2 VS Resistance
Voltage step per PSI increase for the Lucas Novasensor:4.1667mv per PSI
DC offset from output of NPC-410 7mv
Link: http://instruct1.cit.cornell.edu/courses/e...inalwriteup.htm
| CODE |
;***** AtoD Test with interrupt driven timing ******** ;Timer 1 match function is used to take 1 sample/sec ; and display the top 8 bits on the LEDs. ;THIS HAS AREF AS 2.048 VOLTS ;You will need to CHANGE this path .include "c:\academic\476\8535def.inc" .device AT90S8535; specifies to the assembler which chip we are using .def save =r1;SREG temp reg .def temp =r16;temporary register .def maintenance =r17 .def Analo =r18;;A to D result .def butnum =r19 .def wreg =r20 .def longtime=r21 .def timeout =r22 ;.def charcnt =r23 .def objective=r23 ;.def auto =r24 .def one =r25 .def ten =r26 .def hundred =r24 .equ lcdrs =PD6 ;LCD rs pin connected to PD6 .equ lcdrw =PD5 ;LCD r/w pin connected to PD5 .equ lcde =PD4 ;LCD enable pin connected to PD4 ; Timer/Counter prescaler values .equ TSTOP =0 ;Stop Timer/Counter .equ TCK1 =1 ;Timer/Counter runs from CK .equ TCK8 =2 ;Timer/Counter runs from CK / 8 .equ TCK64 =3 ;Timer/Counter runs from CK / 64 .equ TCK256 =4 ;Timer/Counter runs from CK / 256 .equ TCK1024 =5 ;Timer/Counter runs from CK / 1024 .equ TEXF =6 ;Timer/Counter runs from external falling edge .equ TEXR =7 ;Timer/Counter runs from external rising edge .equ azero=0x30 .dseg tempthreshold: .byte 1 ; one bytes to store the threhold valu ;initialize to 01000111 for 25 celcius ;***** Initialization .cseg .org $0000 rjmp RESET;reset entry vector reti reti reti reti reti rjmp t1match reti reti rjmp t0int reti reti reti reti reti reti reti ;this table is rearranged so numbers will take up the first ten spaces in butnum ;A is 11, B is 12, C is 13, D is 14, * is 15, # is 16 ;keytbl: .db 0b11101110, 0b11101101, 0b11101011, 0b11100111 ; .db 0b11011110, 0b11011101, 0b11011011, 0b11010111 ; .db 0b10111110, 0b10111101, 0b10111011, 0b10110111 ; .db 0b01111110, 0b01111101, 0b01111011, 0b01110111 keytbl: .db 0b01111101, 0b11101110, 0b11101101, 0b11101011 .db 0b11011110, 0b11011101, 0b11011011, 0b10111110 .db 0b10111101, 0b10111011, 0b11100111, 0b11010111 .db 0b10110111, 0b01110111, 0b01111110, 0b01111011 temptable: .db 0b01111010, 0b01110010, 0b01100111, 0b01011011 .db 0b01001101, 0b01000111, 0b01000000, 0b00110100 .db 0b00101001, 0b00100000, 0b00011001, 0b00010011 RESET: ldi temp, LOW(RAMEND);setup stack pointer out SPL, temp ldi temp, HIGH(RAMEND) out SPH, temp ;************************************************initialize LCD************ loop: ldi wreg,TSTOP;Timer 0 off (just in case) out TCCR0,wreg;Stop timer clr temp out TCCR1B,temp;stop timer1 as well ldi wreg,0x05;Enable Timer 0 interrupt out TIMSK, wreg sei ;Enable interrupts ;power down the LCD ;ldi wreg, 0b11000000;LCD power connection ;out DDRA, wreg;power it down after reset ; power the LCD with PORTB 7 ;ser temp ;out DDRB, temp ;cbi PORTB, 7 ;ldi wreg, 0x00 ;out PORTA,wreg ldi longtime,100; then Wait 1.5 second with LCD power off ldi timeout,0;Delay 15 mS offwait: rcall delay dec longtime brne offwait ;now power up LCD ;ldi wreg, 0xff ;out PORTA, wreg ;SBI PORTB, 7 ldi longtime,100;Wait 1.5 second for LCD power up ldi timeout,0;Delay 15 mS puwait: rcall delay dec longtime brne puwait rcall lcdinit ;Initialize LCD module rcall lcdclr ;Clear LCD screen ;clr charcnt ;zero the character countv ;not neccessary since we don't plan to write more than 8 characters ;********************************finish initializing LCD************** ;********************************set up sampling specs**************** ;set up Timer 1 to interrupt on compare A match ;and set the compare time to 62500 ticks ldi temp,0b00010000;enable t1 matchA interrupt out TIMSK, temp ldi temp, 0xf4;set the match A register to out OCR1AH, temp;62500 since 62500*16microsec=sec ldi temp, 0x24;62500 = 0xf424 out OCR1AL, temp ldi temp,0b00001010;prescale timer by 8 (one tick=1.6E-5 /8 sec) out TCCR1B, temp;and clear-on-matchA ;*********************************finish set up sampling************** ;set PORTB to output port ser temp out DDRB, temp ;initiate maintenance sequence clr maintenance ;remember to initiate butnum ;actually turns out that butnum should be initiated to 0 ??? ;ldi butnum, 11 ; initial value set to button B for temperature ldi butnum, 0 ; initiate temperature threshold level at 25 celcius ldi ZL, LOW(tempthreshold);ptr to ram ldi ZH, HIGH(tempthreshold) ldi temp, 0b01000111 st Z,temp ;reads keypad preswait: rjmp keypad ;decide which operation by comparing value of butnum afterkey: cpi butnum, 11 ; display pressue loop breq pressure cpi butnum, 12; display temperature loop breq temperature cpi butnum, 14;threshchange breq thresh cpi butnum, 17 ;program initiated pressure callback breq pressure cpi butnum, 18 breq temperature ; if not a valid operation rcall keypad rjmp preswait pressure: ;set up analog converter to read channel zero ldi temp, 0 rjmp setadmux temperature: ;set up analog converter to read channel 4 ldi temp, 0x04 rjmp setadmux thresh: ldi temp, 0x55 out PORTB, temp ldi temp, 0x0f;set lower four lines to output out DDRC, temp ldi temp, 0xf0;and turn on the pullups on the inputs out PORTC, temp nop ;Need some time for the pullups to nop ;charge the port pins nop nop in temp, PINC;read the high nibble mov wreg, temp;and store it (with zeros in the low nibble) ldi temp, 0xf0;set upper four lines to outputs out DDRC, temp ldi temp, 0x0f;and turn on pullups on the inputs out PORTC, temp nop ;As before wait for the pin to charge nop nop nop in temp, PINC;read the low nibble or wreg, temp;combine to make key code ;At the point the raw key code should have exactly one zero each in ;the lower and upper nibbles. Any other number of zeros indicates ;either no-button pressed or multiple-button pressed. ;Now search the table for a match to the raw key code ;and exit with a button number ldi ZL, low(keytbl*2);table pointer in FLASH ldi ZH, high(keytbl*2);so convert from word to byte addr ldi one, 0 tbllp2: lpm ;get the table entry cp wreg, r0 ;match? breq foundit2 inc one ;if not, have we exhaused the cpi one, 0x0a;table breq thresh adiw ZL, 1 ;if not, get the next table entry rjmp tbllp2 foundit2: subi one, -1;add one for comparison rjmp changethreshold setadmux: out ADMUX, temp ;value of admux preloaded into temp sei ;enable all interrupts ;start timer1 ldi temp,0b00001010;prescale timer by 8 (one tick=1.6E-5sec/8) out TCCR1B, temp;and clear-on-matchA swait: in temp, ADCSR;wait for A to D start andi temp, 0b01000000;by checking if ADSC bit is set breq swait ;this bit is set by t1match interrupt await: in temp, ADCSR;wait for A to D done andi temp, 0b01000000;by checking ADSC bit brne await ;this bit is cleared by the AtoD hardware in AnaLo, ADCL;read the voltage in hundred, ADCH; using this to save register in temp, ADMUX andi temp, 0x07 cpi temp, 0 breq pressureproc cpi temp, 4 breq tempprocessing rjmp preswait pressureproc: ldi temp,0b00001000;stop the clock out TCCR1B, temp;and clear-on-matchA ; for pressure, each tick is equal to one PSI so simply display ;tare offset of 7mv first though clr ten clr one ldi hundred, 0x20 ;this is a null characters for the LCD ;out portb, AnaLo subi AnaLo, 7 ;offset ;only display if value is positive cpi AnaLo, 0 brge checkforten ldi AnaLo, 0 ;else assume zero since gauge is only 0-30 PSI ; only display when called upon checkforten: cpi butnum, 11 breq checkfortenII rjmp preswait checkfortenII: inc ten subi AnaLo, 10 brmi donetens rjmp checkforten donetens: subi ten, 1 subi AnaLo, -10 mov one, AnaLo ldi temp, azero add one, temp add ten, temp rcall displaylcd rjmp preswait changethreshold: ldi ZL, low(temptable*2) ldi ZH, high(temptable*2) adiw ZL,1 lookfor: dec one breq getval adiw ZL, 1 rjmp lookfor getval: lpm mov ten, r0 out portb, ten ldi ZL, LOW(tempthreshold);ptr to ram ldi ZH, HIGH(tempthreshold) st Z,ten ldi butnum, 11 rjmp afterkey tempprocessing: ldi temp,0b00001000;stop the clock out TCCR1B, temp;and clear-on-matchA ;just want 8 bit accuracy, refer to excel sheet ror hundred ; ror AnaLo ror hundred ; ror AnaLo mov wreg, AnaLo ; since this temperature call can be made by program instead of user we first see ; how the temperature processing is triggered. if temperature control is called ; bysetting butnum into 17 then that is a program hidden call. cpi butnum, 17 brne pretemptbllp rjmp tcontrol;if not called by program but by user then follow usual routine ; to determine what to display on LCD ; begin tracin range of temperature from -20 to 80 pretemptbllp: ldi ZL, low(temptable*2);table pointer in FLASH ldi ZH, high(temptable*2);so convert from word to byte addr ldi objective, 1;initialize the objective value to one (temp-range =-20) temptbllp: lpm ;get the table entry cp wreg, r0 ;match? ;now eliminate range by comparing and if greater than, then we know temprange. brge foundtemp ;this returns upper bound since this is a cooling system, it should maximum worst case ;according to binning inc objective;if not, have we exhaused the cpi objective, 0x0d;table (limited to N+1 since initial is 1) breq outofrange adiw ZL, 1 ;if not, get the next table entry rjmp temptbllp outofrange: rjmp preswait foundtemp: ldi ten, 0x30 ldi one, 0x30 ; most one digit will be zero except for 25 ldi hundred, 0x2b;load with a positive sign for +- temperature cpi objective, 5 breq range20 cpi objective, 6 breq range25 cpi objective, 7 breq range30 cpi objective, 8 breq range40 cpi objective, 9 breq range50 cpi objective, 10 breq range60 cpi objective, 11 breq range70 cpi objective, 4 ;put more typical number first breq range10 cpi objective, 1 breq rangen20 cpi objective, 2 breq rangen10 cpi objective, 3 breq check ; this case we have as initial value cpi objective, 12 breq range80 range20: ldi ten, 0x32 rjmp check range25: ldi one, 0x35 ldi ten, 0x32 rjmp check range30: ldi ten, 0x33 rjmp check range40: ldi ten, 0x34 rjmp check range50: ldi ten, 0x35 rjmp check range60: ldi ten, 0x36 rjmp check range70: ldi ten, 0x37 rjmp check range80: ldi ten, 0x38 rjmp check range10: ldi ten, 0x31 rjmp check rangen10: ldi hundred, 0x2d ;include a negative sign ldi ten, 0x31 rjmp check rangen20: ldi hundred, 0x2d ldi ten, 0x32 check: ; checks to see if temperature has passed a user set threshold level ; store in RAM ; but first display value on LCD rcall displaylcd ;load the threshold value from RAM tcontrol: ldi ZL, LOW(tempthreshold) ldi ZH, HIGH(tempthreshold) ld r0, Z mov temp, r0 ;this control is only for cooling of device but has two degrees of cooling at +4 or +8 ;which is about between 3 degrees and 10 degrees depending on which temperature range you are in ;but since this is a cooling system about 3 degree leniency will be observed for higher temp range ; >20 degrees subi temp, 2 mov one, temp subi temp, 6 mov ten, temp cp AnaLo, one brge controldone ;if not over temperature turn cooling device off ;relay is controlled by portb0 and b1 cp AnaLo, ten brge midfan highfan: cbi PORTB, 0 sbi PORTB, 1 clr temp out portb, temp ldi temp, 0b11110000 out portb, temp rjmp preswait midfan: cbi PORTB, 1 ;make sure the other relay is not on sbi PORTB, 0 clr temp out portb, temp ldi temp, 0b11011100 out portb,temp rjmp preswait controldone: clr temp out portb, temp ldi temp, 0b00011100; out portb,temp cbi PORTB, 0 cbi PORTB, 1 rjmp preswait ;*************************************displaylcd******************************* displaylcd: ldi wreg,0x80 ;Set address to first char (set to 0) rcall lcdcmd ldi wreg,TSTOP;Timer 0 off out TCCR0,wreg;Stop timer mov wreg, hundred rcall lcdput nop ldi wreg,TSTOP;Timer 0 off out TCCR0,wreg;Stop timer mov wreg, ten rcall lcdput nop ldi wreg,TSTOP;Timer 0 off out TCCR0,wreg;Stop timer mov wreg, one rcall lcdput ;don't need to keep track of char number because under 8 nop cpi butnum, 17 breq doneshow cpi butnum, 18 breq doneshow cpi butnum, 11 breq showpsi cpi butnum, 12 breq showC showpsi: ldi ZH, high(message1*2) ldi ZL, low(message1*2) rjmp showloop showC: ldi ZH, high(message2*2) ldi ZL, low(message2*2) rjmp showloop ;in case there are newer functions showloop: lpm tst R0 breq doneshow mov wreg, R0 rcall lcdput adiw ZL,1 rjmp showloop doneshow: ret ;*************************************reads keypad******************************************* keypad: ;increment the maintenance counter to see if hidden control should be performed ; however program only does hidden controls.ie, if the item is the currently selected ;(diplayed) item then no need to perform hidden callback. inc maintenance cpi maintenance, 40 ; if it is 200 then we perform temperature hidden call breq hiddentemp cpi maintenance,20; if it is 20 then we perform pressure hidden call breq hiddenpressure rjmp comingback hiddenpressure: push butnum ;push the current butnum so we kwnow where to go back to after ldi butnum, 17;hidden call rjmp afterkey ; by pushing here we have to ensure no other pushing will be done ;prior to the next pop. hiddentemp: ldi maintenance, 0x00 ;need to set to zero to ensure next hidden control will be called push butnum ldi butnum, 18 rjmp afterkey comingback: ; coming back checks if we came back from a hidden control call ;butnum values of 17 and 18 are computer triggered for hidden control purposes cpi butnum, 17 breq reading cpi butnum, 18 breq reading ;if it is neither 17 nor 18 for the last operation then we can push butnum value in push butnum reading: ldi temp, 0x0f;set lower four lines to output out DDRC, temp ldi temp, 0xf0;and turn on the pullups on the inputs out PORTC, temp nop ;Need some time for the pullups to nop ;charge the port pins nop nop in temp, PINC;read the high nibble mov wreg, temp;and store it (with zeros in the low nibble) ldi temp, 0xf0;set upper four lines to outputs out DDRC, temp ldi temp, 0x0f;and turn on pullups on the inputs out PORTC, temp nop ;As before wait for the pin to charge nop nop nop in temp, PINC;read the low nibble or wreg, temp;combine to make key code ;At the point the raw key code should have exactly one zero each in ;the lower and upper nibbles. Any other number of zeros indicates ;either no-button pressed or multiple-button pressed. ;Now search the table for a match to the raw key code ;and exit with a button number ldi ZL, low(keytbl*2);table pointer in FLASH ldi ZH, high(keytbl*2);so convert from word to byte addr ldi butnum, 0 tbllp: lpm ;get the table entry cp wreg, r0 ;match? breq foundit inc butnum ;if not, have we exhaused the cpi butnum, 0x10;table breq same adiw ZL, 1 ;if not, get the next table entry rjmp tbllp foundit: pop temp ;just to complement the push pop so stack doesn't overflow subi butnum, -1;add one for display rjmp afterkey same: ;obtain previous value of butnum from stack pop butnum rjmp afterkey ================================================ ; Clear entire LCD and delay for a bit lcdclr: ldi wreg,1 ;Clear LCD command rcall lcdcmd ldi timeout,256;Delay 15 mS for clear command rcall delay ret ================================================ ; Initialize LCD module lcdinit: ;cbi PORTB,0 ;Turn on LED 0 ldi wreg,0 ;Setup port pins out PORTD,wreg;Pull all pins low ldi wreg,0xff;All pins are outputs out DDRD,wreg ldi timeout,256;Wait at least 15 mS at power up rcall delay ; LCD specs call for 3 repetitions as follows ldi wreg,3 ;Function set out PORTD,wreg;to 8-bit mode nop ;nop is data setup time sbi PORTD,lcde;Toggle enable line cbi PORTD,lcde ldi timeout,256;Wait at least 15 mS rcall delay ldi wreg,3 ;Function set out PORTD,wreg nop sbi PORTD,lcde;Toggle enable line cbi PORTD,lcde ldi timeout,256;Wait at least 15 ms rcall delay ldi wreg,3 ;Function set out PORTD,wreg nop sbi PORTD,lcde;Toggle enable line cbi PORTD,lcde ldi timeout,256;Wait at least 15 ms rcall delay ldi wreg,2 ;Function set, 4 line interface out PORTD,wreg nop ; rcall strobe ;Toggle enable line sbi PORTD,lcde;Toggle enable line cbi PORTD,lcde ldi wreg,0b11110000;Make 4 data lines inputs out DDRD,wreg ; Finally, ; At this point, the normal 4 wire command routine can be used ldi wreg,0b00100000;Function set, 4 wire, 1 line, 5x7 font rcall lcdcmd ldi wreg,0b00001100;Display on, no cursor, no blink rcall lcdcmd ldi wreg,0b00000110;Address increment, no scrolling rcall lcdcmd ;sbi PORTB,0 ;Turn off LED 0 ret ============================================ ; Wait for LCD to go unbusy lcdwait: ;cbi PORTB,1 ;Turn on LED 1 ldi wreg,0xF0;Make 4 data lines inputs out DDRD,wreg sbi PORTD,lcdrw;Set r/w pin to read cbi PORTD,lcdrs;Set register select to command waitloop: sbi PORTD,lcde;Toggle enable line cbi PORTD,lcde ;in auto,PIND;Read busy flag in temp,PIND;Read busy flag ;Read, and ignore lower nibble sbi PORTD,lcde;Toggle enable line cbi PORTD,lcde ;sbrc auto,3;Loop until done sbrc temp,3;Loop until done rjmp waitloop ;sbi PORTB,1 ;Turn off LED 1 ret ============================================= ; Send command in wreg to LCD lcdcmd: push wreg ;Save character rcall lcdwait ;Wait for LCD to be ready ldi wreg,0xFF;Make all port D pins outputs out DDRD,wreg pop wreg ;Get character back push wreg ;Save another copy swap wreg ;Get upper nibble andi wreg,0x0F;Strip off upper bits out PORTD,wreg;Put on port nop ;wait for data setup time sbi PORTD,lcde;Toggle enable line cbi PORTD,lcde pop wreg ;Recall character andi wreg,0x0F;Strip off upper bits out PORTD,wreg;Put on port nop sbi PORTD,lcde;Toggle enable line cbi PORTD,lcde ldi wreg,0xF0;Make 4 data lines inputs out DDRD,wreg ret ============================================= ; Send character data in wreg to LCD lcdput: push wreg ;Save character rcall lcdwait ;Wait for LCD to be ready ldi wreg,0xFF;Make all port D pins outputs out DDRD,wreg pop wreg ;Get character back push wreg ;Save another copy swap wreg ;Get upper nibble andi wreg,0x0F;Strip off upper bits out PORTD,wreg;Put on port sbi PORTD,lcdrs;Register select set for data nop sbi PORTD,lcde;Toggle enable line cbi PORTD,lcde pop wreg ;Recall character andi wreg,0x0F;Strip off upper bits out PORTD,wreg;Put on port sbi PORTD,lcdrs;Register select set for data nop sbi PORTD,lcde;Toggle enable line cbi PORTD,lcde ;cbi PORTD,lcdrs;-- ldi wreg,0xF0;Make 4 data lines inputs out DDRD,wreg ret delay: in wreg,SREG;Save status register push wreg out TCNT0,timeout clt ;Clear T ldi wreg,TCK256;Timer 0 prescaler, CK / 256 out TCCR0,wreg;Run timer dwait: brtc dwait ;Wait for timer 0 interrupt to set T pop wreg ;Restore status register out SREG,wreg ret ============================================= ;***** Timer 0 overflow interrupt handler t0int: set ;Set T flag ;ldi wreg,0xFF;Turn off all LEDs ;out PORTB,wreg ldi wreg,TSTOP;Timer 0 off out TCCR0,wreg;Stop timer reti ;Done, return ;**** timer 1 compare A match 1/sec t1match:in save, SREG ldi temp, 0b11000101;start A to D conversion out ADCSR, temp out SREG, save reti message2: .db " C ", 0x00 message1: .db " PSI", 0x00 |