Project description:
For my final design project I decided to design and build a digital dot matrix message device. I’ve seen devices similar to this before and I wanted to find out if I could build one myself. The display consists of 7 LEDs in a vertical row. By moving them fast enough back and forth over each other, I can display a message which appears to be generated by a 7*n matrix of LEDs and not a single column of LEDs.
Link: http://instruct1.cit.cornell.edu/courses/e...nslow/index.htm
For my final design project I decided to design and build a digital dot matrix message device. I’ve seen devices similar to this before and I wanted to find out if I could build one myself. The display consists of 7 LEDs in a vertical row. By moving them fast enough back and forth over each other, I can display a message which appears to be generated by a 7*n matrix of LEDs and not a single column of LEDs.
Link: http://instruct1.cit.cornell.edu/courses/e...nslow/index.htm
| CODE |
;***** Simple time-based scheduler ******** ;LED display code for spinning disc ; ;******************************** ;You will need to CHANGE this path ;,nolist .include "c:\users\jkw10\8515def.inc" .list ;******************************** ;define registers .def save =r1 .def Letter =r3;Letter Value .def clock0 =r4;time between hit and display .def complow =r5;compare values for position .def comphigh =r6 .def spacelow =r9;used to computer the spacing .def spacehigh =r10;between flashes on wand .def temp =r16;temporary register .def LED =r17;the actual LED value to display .def reload =r18;holds timer reload value .def Cin =r19;Input from PortC .def checksensor =r20;check sensor flag .def letterpos =r21;Which of the 7 letter portion outputs .def state =r22;state of state machine .def spacecounter =r23;counter for value of spacing .def Letnum =r24;Which of the 14 letters are we now displaying .def perlow =r28;Holds ticks for wheel period low .def perhigh =r29;Holds ticks for wheel period high .equ messagelength=16 ;************************************************************************ ; Initialization .cseg .org $0000 rjmp RESET;reset entry vector reti reti reti reti reti reti rjmp TIMER reti reti reti reti reti ;************************************************************************* ;The following include file contains the db table containing ;all the rastorization information for the LED display segments ; ;The table after that contains references to sections of the ;rastorization table ;15 references the 15th line in the rastorization table ;which references the segment information for the letter E .include "c:\users\jkw10\rastor2.inc" Message: .db 63,63,63,63,63,63,63,15,15,4,7,6,63,63,63,63 ;.db 19,63,22,51,58,41,63,14,45,50,51,65,55,63;I Love Dino's ;************************************************************************* RESET: ldi Temp, LOW(RAMEND) ;setup stack pointer out SPL, Temp ldi Temp, HIGH(RAMEND) out SPH, Temp ;set up the PORTs ser Temp ;set PORTB to be out DDRB,Temp;all outputs ldi Temp, 0xff;turn off LEDs out PortB, Temp clr Temp ;set PORTC to be out DDRC,Temp;all inputs ;set up timer 0 for 10 uSec ticks ldi Temp,exp2(TOIE0);enable timer interrupt out TIMSK, Temp ldi Temp, 3 ;prescale timer by 64 out TCCR0, Temp ldi Reload,256-1;preload timer since out TCNT0, Reload;1 x (64x.125) microSec = 8 uSec. ;initialize variables ldi LED, 0xff;initialize all variables ldi letnum,0 ldi state,0 ldi temp,0 mov Letnum,temp ;Start the clock ticking sei ;enable all interrupts ;************************************************************** SPIN: cpi checksensor,0;this ensures that the phototransistor brne done ;makes a revolution before another hit in Cin,PinC;check phototransistor sbrc Cin, 0 rjmp done rcall SensorHit;call subroutine if a hit done: rjmp SPIN ;now all work is done by intr routine GetLetter: ldi temp,messagelength cp letnum,temp breq lettermax ldi temp,0 ldi ZL, low(message*2);table pointer in FLASH ldi ZH, high(message*2);so convert from word to byte addr add ZL, Letnum ;double precision add for specific letter adc ZH, temp inc letnum lpm rjmp getletter2 lettermax: ldi temp,63 mov r0,temp getletter2: ldi temp,0 mov letter,r0 ldi ZL, low(rastor*2) ldi ZH, high(rastor*2) lsl letter ;rastorization.db is 8*65 add Zl,letter;so letter is between 0 and 65 adc ZH,temp ;but we need to point to proper byte addres so add Zl,letter;the following lines add letter*8 to the pointer adc ZH,temp ;I shift once and add 4 times to maintain letter add Zl,letter;as only 1 byte adc ZH,temp ;2 shifts might result in overflow add Zl,letter;overflow=bad adc ZH,temp ;bad=no worky ret SensorHit: ldi letnum,0;reset all variables ldi state,0 ldi checksensor,1 mov complow,perlow mov comphigh,perhigh ldi LED,0xff;turn all LEDs off out PortB,LED lsr comphigh;computer cycle/2 ror complow ;for when to begin display mov spacelow,perlow;use for letter spacing mov spacehigh,perhigh ldi perlow,0 ldi perhigh,0 ret ;************************************************************** ;timer 0 ISR (timer-zero overflow) ;Enters every 8 uSec TIMER: in save, SREG out TCNT0, Reload; keeps clock ticking at 9 usec push temp adiw perlow, 1;increment period counter cpi state,0 breq state0 cpi state,1 breq state1 cpi state,2 breq state2 state0: cp perlow,complow;compare to period/2 to begin display brne t0end cp perhigh,comphigh brne t0end ldi checksensor,0 ldi state,1 rjmp t0end state1: rcall Getletter;Call get letter ldi state,2 ldi letterpos,7 state2: cpi spacecounter,0;Spacing for letter display breq state2_2 dec spacecounter rjmp t0end state2_2: mov spacecounter,spacehigh lpm out PortB,r0;Output the next letter segment adiw ZL,1 ;increment memory pointer cpi letterpos,0 breq letterdone;If letter is done, reset letterpos and state dec letterpos rjmp t0end letterdone: ldi state,1 ldi letterpos,7 t0end: pop temp out SREG, save reti ;back to backgound tasks ;************************************************************** |