Post by thread:[PIC] LED Digit Multiplexing Timer Interrupt Routi

I have a three digit LED display for a thermometer. I had the multiplexing working fine for the three digits when it was in my main code. I simply decremented a variable that was initialized with a value of 3. For each value, I turned on the respective digit, delayed for a while, and went to the next one. I wanted to make changes to the code that would affect the time delay between displays so I thought I should put the digit multiplexing code in a routine that would be called by a TIMER0 rollover-initiated interrupt. I tested the scheme with a called routine that simply toggled an output, and the interrupt stuff all worked well. Once I got that far, I started working on the multiplexing math and logic but have had no success. This is my first time at using interrupts and I suspect that I am doing something wrong that is messing up my code. I show three versions of my routine below. The first worked fine and showed me that I had the interrupt stuff right. The next two show simple attempts at asserting three outputs in succession, however without success. Can someone tell me the errors of my ways here?!?!?!?! Plus, is there a slicker easier way to do this? Thanks. Mark Peterson DISPLAY movwf _w ; Save swapf status,w ; Save movwf _status ; Save bcf intcon,2 ; Clear interrupt bit movfw LOOP ; LOOP to w movwf portb ; Send to port LOOPDEC decfsz LOOP ; Equal to 0? goto $+3 ; No, leave and do it again later. movlw d'3' ; Yes, reinitialize LOOP variable. movwf LOOP ; Yes, reinitialize LOOP variable. swapf _status,w ; Restore. movwf status ; Restore. swapf _w ; Restore. swapf _w,w ; Restore. retfie ; Return. With the code above, bits 0 and 1 on Portb step through 11, 10, 01 with each rollover of TIMER0. With this success, I moved on to transform the LOOP count into individual bit assertions. DISPLAY movwf _w ; Save swapf status,w ; Save movwf _status ; Save bcf intcon,2 ; Clear interrupt bit movfw LOOP ; LOOP to w call DIGIT_T movwf portb LOOPDEC decfsz LOOP ; Equal to 0? goto $+3 ; No, leave and do it again later. movlw d'3' ; Yes, reinitialize LOOP variable. movwf LOOP ; Yes, reinitialize LOOP variable. swapf _status,w ; Restore. movwf status ; Restore. swapf _w ; Restore. swapf _w,w ; Restore. retfie ; Return. ****Tabel located in main code****** DIGIT_T ; 3 digit display table addwf pcl,f ; Jump into lookup table ; _____321' retlw b'11111011' ; Segment 3 retlw b'11111101' ; Segment 2 retlw b'11111110' ; Segment 1 With the code above, portb bits 0, 1, & 2 are on all the time. It's a simple lookup table yet I can't see what I did wrong. DISPLAY movwf _w ; Save swapf status,w ; Save movwf _status ; Save bcf intcon,2 ; Clear interrupt bit bsf portb,0 ; Turn off 100 digit bsf portb,1 ; Turn off 10 digit bsf portb,2 ; Turn off 1 digit movfw LOOP ; LOOP to w sublw d'3' ; 3 - LOOP in w btfss status,2 ; LOOP = 3? goto LOOPDEC ; No, leave. bcf portb,2 ; Yes, turn on 100 digit goto LOOPDEC ; Yes, leave. movfw LOOP ; LOOP to w sublw d'2' ; 2 - LOOP in w btfss status,2 ; LOOP = 2? goto LOOPDEC ; No, leave. bcf portb,1 ; Yes, turn on 10 digit goto LOOPDEC ; Yes, leave. movfw LOOP ; LOOP to w sublw d'1' ; 1 - LOOP in w btfss status,2 ; LOOP = 1? goto LOOPDEC ; No, leave. bcf portb,0 ; Yes, turn on 1 digit goto LOOPDEC ; Yes, leave. LOOPDEC decfsz LOOP ; Equal to 0? goto $+3 ; No, leave and do it again later. movlw d'3' ; Yes, reinitialize LOOP variable. movwf LOOP ; Yes, reinitialize LOOP variable. swapf _status,w ; Restore. movwf status ; Restore. swapf _w ; Restore. swapf _w,w ; Restore. retfie ; Return. With the code above, portb,2 flashes at the rate that TIMER0 rolls over but bits 0 and 1 are on steady. Again, it's straight forawrd stuff that works in regular main code but I can't get to work inside the interrupt-called routine.

Hi. Just a few things... First, what processor ? > DISPLAY > movwf _w ; Save > swapf status,w ; Save > movwf _status ; Save > bcf intcon,2 ; Clear interrupt bit Use the builtin bit-names instead of "2". And move this to the line right before RETFIE. The rest of first code snipped worked, you said... Second code snippet... {Quote hidden}> > DISPLAY > movwf _w ; Save > swapf status,w ; Save > movwf _status ; Save > bcf intcon,2 ; Clear interrupt bit > > movfw LOOP ; LOOP to w > call DIGIT_T > movwf portb > > LOOPDEC > decfsz LOOP ; Equal to 0? > goto $+3 ; No, leave and do it again later. Generaly speaking,m try to avoid the "$" thing. By using lables the code is easier to read. {Quote hidden}> movlw d'3' ; Yes, reinitialize LOOP variable. > movwf LOOP ; Yes, reinitialize LOOP variable. > > swapf _status,w ; Restore. > movwf status ; Restore. > swapf _w ; Restore. > swapf _w,w ; Restore. > retfie ; Return. > > ****Tabel located in main code****** Now, the table isn't realy "located" in any "code". It's just a peice of code someware... > DIGIT_T ; 3 digit display table > addwf pcl,f ; Jump into lookup table > ; _____321' > retlw b'11111011' ; Segment 3 > retlw b'11111101' ; Segment 2 > retlw b'11111110' ; Segment 1 Depending on the processor (> 2 Kwords flash) you *could* have a PCLATH problem here. > > With the code above, portb bits 0, 1, & 2 are on all the time. It's a > simple lookup table yet I can't see what I did wrong. > Third code snippet... {Quote hidden}> > DISPLAY > movwf _w ; Save > swapf status,w ; Save > movwf _status ; Save > bcf intcon,2 ; Clear interrupt bit > > bsf portb,0 ; Turn off 100 digit > bsf portb,1 ; Turn off 10 digit > bsf portb,2 ; Turn off 1 digit > > movfw LOOP ; LOOP to w > sublw d'3' ; 3 - LOOP in w > btfss status,2 ; LOOP = 3? > goto LOOPDEC ; No, leave. > bcf portb,2 ; Yes, turn on 100 digit > goto LOOPDEC ; Yes, leave. This part will *always* jump to LOOPDEC. The code for digit 2 and 1 below will never run, no matter what the value of LOOP is. The first "goto LOOPDEC" should probably jump to the code below. And the same with the first "goto LOOPDEC" below. If LOOP isn't "3", you should not leave, you should test if LOOP is "2", right `? > > movfw LOOP ; LOOP to w > sublw d'2' ; 2 - LOOP in w > btfss status,2 ; LOOP = 2? > goto LOOPDEC ; No, leave. > bcf portb,1 ; Yes, turn on 10 digit > goto LOOPDEC ; Yes, leave. > [snipped rest...]

*** This is my second submission of this question. I never did see it posted on my digest pages so I am assuming it never made it through. Forgive me if some of you did receive it. I have a three digit LED display for a thermometer. I had the multiplexing working fine for the three digits when it was in my main code. I simply decremented a variable that was initialized with a value of 3. For each value, I turned on the respective digit, delayed for a while, and went to the next one. I wanted to make changes to the code that would affect the time delay between displays so I thought I should put the digit multiplexing code in a routine that would be called by a TIMER0 rollover-initiated interrupt. I tested the scheme with a called routine that simply toggled an output, and the interrupt stuff all worked well. Once I got that far, I started working on the multiplexing math and logic but have had no success. This is my first time at using interrupts and I suspect that I am doing something wrong that is messing up my code. I show three versions of my routine below. The first worked fine and showed me that I had the interrupt stuff right. The next two show simple attempts at asserting three outputs in succession, however without success. Can someone tell me the errors of my ways here?!?!?!?! Plus, is there a slicker easier way to do this? Thanks. Mark Peterson DISPLAY movwf _w ; Save swapf status,w ; Save movwf _status ; Save bcf intcon,2 ; Clear interrupt bit movfw LOOP ; LOOP to w movwf portb ; Send to port that selects which of 3 digits to display LOOPDEC decfsz LOOP ; Equal to 0? goto $+3 ; No, leave and do it again later. movlw d'3' ; Yes, reinitialize LOOP variable. movwf LOOP ; Yes, reinitialize LOOP variable. swapf _status,w ; Restore. movwf status ; Restore. swapf _w ; Restore. swapf _w,w ; Restore. retfie ; Return. With the code above, bits 0 and 1 on Portb step through 11, 10, 01 with each rollover of TIMER0. With this success, I moved on to transform the LOOP count into individual bit assertions. DISPLAY ; Use looping variable and lookup table to sequence through bits movwf _w ; Save swapf status,w ; Save movwf _status ; Save bcf intcon,2 ; Clear interrupt bit movfw LOOP ; LOOP to w call DIGIT_T ; movwf portb ; Send to port that selects which of 3 digits to display LOOPDEC decfsz LOOP ; Equal to 0? goto $+3 ; No, leave and do it again later. movlw d'3' ; Yes, reinitialize LOOP variable. movwf LOOP ; Yes, reinitialize LOOP variable. swapf _status,w ; Restore. movwf status ; Restore. swapf _w ; Restore. swapf _w,w ; Restore. retfie ; Return. ****Tabel located in main code****** DIGIT_T ; 3 digit display table addwf pcl,f ; Jump into lookup table ; _____321' retlw b'11111011' ; Segment 3 retlw b'11111101' ; Segment 2 retlw b'11111110' ; Segment 1 With the code above, portb bits 0, 1, & 2 are on all the time. It's a simple lookup table yet I can't see what I did wrong. DISPLAY ; Use looping variable and value comparisons to sequence through bits movwf _w ; Save swapf status,w ; Save movwf _status ; Save bcf intcon,2 ; Clear interrupt bit bsf portb,0 ; Turn off 100 digit bsf portb,1 ; Turn off 10 digit bsf portb,2 ; Turn off 1 digit movfw LOOP ; LOOP to w sublw d'3' ; 3 - LOOP in w btfss status,2 ; LOOP = 3? goto LOOPDEC ; No, leave. bcf portb,2 ; Yes, turn on 100 digit goto LOOPDEC ; Yes, leave. movfw LOOP ; LOOP to w sublw d'2' ; 2 - LOOP in w btfss status,2 ; LOOP = 2? goto LOOPDEC ; No, leave. bcf portb,1 ; Yes, turn on 10 digit goto LOOPDEC ; Yes, leave. movfw LOOP ; LOOP to w sublw d'1' ; 1 - LOOP in w btfss status,2 ; LOOP = 1? goto LOOPDEC ; No, leave. bcf portb,0 ; Yes, turn on 1 digit goto LOOPDEC ; Yes, leave. LOOPDEC decfsz LOOP ; Equal to 0? goto $+3 ; No, leave and do it again later. movlw d'3' ; Yes, reinitialize LOOP variable. movwf LOOP ; Yes, reinitialize LOOP variable. swapf _status,w ; Restore. movwf status ; Restore. swapf _w ; Restore. swapf _w,w ; Restore. retfie ; Return. With the code above, portb,2 flashes at the rate that TIMER0 rolls over but bits 0 and 1 are on steady. Again, it's straight forawrd stuff that works in regular main code but I can't get to work inside the interrupt-called routine.

Thank you to those who pointed out errors in my display routine. I implemented those with success and moved on. Unfortunately, I've run into another problem. For testing and development, I simply assigned fixed values to my display digits. I know the math I did earlier works so I took it out to shorten the program so that readers can focus on the code that is giving me trouble. If I make the assignment inside the TIMER0-interrupt-intiated DISPLAY routine, the program works great and I get a perfect 123 on the display consistently. It also works perfectly if I make the assignment at beginning of the program along with my other variable initializations. However, if I make the assignment in my main program loop, I get a good 123 display only about half of the time. The rest of the time, 1, 2, or all 3 digits will flash the bootup routine FLASH sequence endlessly. I cannot figure where I am doing something on the edge that causes the program's behavior to be inconsistent. You can see the locations where I placed the test assignments in my code below. Any ideas? Thanks. Mark Peterson ;================================================================= ; ; Project: Indicator Device ; File: Indicator_1.asm ; Programmer: Mark Peterson ; Device: Microchip PIC16C773 ; ; Modification History: ; ; Original 10-10-05 MJP ; ; list p=16c77 radix hex ; cpu equates (memory map) porta equ 0x05 ; Analog input, button input. ; RA0 - Oil temperature input ; RA1/4 - Not used portb equ 0x06 ; Indication & control output. ; bit0 - Digit 100 Output ; bit1 - Digit 10 Output ; bit2 - Digit 1 Output ; bit3/7 - Not used portc equ 0x07 ; Indication & control output. ; bit0 - 7-segment LED - a ; bit1 - 7-segment LED - b ; bit2 - 7-segment LED - c ; bit3 - 7-segment LED - d ; bit4 - 7-segment LED - e ; bit5 - 7-segment LED - f ; bit6 - 7-segment LED - g ; bit7 - Not used ; System Variables timer0 equ 0x01 pcl equ 0x02 status equ 0x03 adcon0 equ 0x1f adresh equ 0x1e adresl equ 0x9e intcon equ 0x0b trisa equ 0x85 trisb equ 0x86 trisc equ 0x87 adcono equ 0x1f adcon1 equ 0x9f option_reg equ 0x81 refcon equ 0x9b lvdcon equ 0x9c ; Loop and Temporary Variables COUNT1 equ 0x20 ; Time delay looping variable COUNT2 equ 0x21 ; Time delay looping variable LOOP equ 0x22 ; Display loop vari used in DISPLAY interrupt routine VAR equ 0x23 ; Misc math variable COUNT equ 0x24 ; Misc looping variable _w equ 0x25 ; Interrupt save value _status equ 0x26 ; Interrupt save value ; Program Variables FLAGS equ 0x30 ; Tracking flags. ; bit0 - Temperature out of range ; bit1/7 - Not Used TEMPH_RAW equ 0x31 ; Temperature value - raw high byte TEMPL_RAW equ 0x32 ; Temperature value - raw low byte TEMP_H equ 0x33 ; Temperature value - high byte TEMP_L equ 0x34 ; Temperature value - low byte TEMP equ 0x35 ; Temperature value - scaled single byte DIGIT100 equ 0x36 ; Temperature decimal 100's digit DIGIT10 equ 0x37 ; Temperature decimal 10's digit DIGIT1 equ 0x38 ; Temperature decimal 1's digit ;--------------------------------------------------- org 0x00 goto start org 0x04 goto DISPLAY ; Digit multiplexing display routine start ; SET UP PORTS bsf status,5 ;Switch to bank 1. ; Define data port A directions, 0 output, 1 input movlw b'00011111' movwf trisa ; Define data port B directions, 0 output, 1 input movlw b'00000000' movwf trisb ; Define data port C directions, 0 output, 1 input movlw b'00000000' movwf trisc ; Define porta AI and DI/O bits ; ; 1------- Right justified format ; -011---- Ext Vref+ high and Vss low references ; ----1011 AN9/4=DI, AN03/0=AI movlw b'10111011' movwf adcon1 ; Define OPTION bits ; 0------- Pull ups enabled by values ; -0------ Interrupt on falling edge ; --0----- Use internal clock ; ---0---- Interrupt on L-H transition ; ----0--- Prescaler assigned to timer ; -----111 Prescaler = 256 movlw b'00000111' movwf option_reg bcf status,5 ; Switch back to bank 0. ; Define INTCON bits ; 1------- Enable global interrupts ; -0------ Disable peripheral interrupts ; --0----- Disable TMR0 overflow interrupt ; ---0---- Disable RBO external interrupt ; ----0--- Disable RB port change interrupt ; -----0-- TMR0 overflow flag, 1 yes, 0 no ; ------0- RB0 external interrupt occured, 1 yes, 0 no. ; -------0 RB port bit state change, 1 yes, 0 no. movlw b'10000000' movwf intcon ;;;;;;; INITIALIZE VARIABLES ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; clrf FLAGS ; Clear all flag bits clrf portb ; All outputs off clrf portc ; All outputs off movlw d'3' ; Display routine variable movwf LOOP ; Display routine variable ; Force test values - Works 100% of the time when enabled here ; movlw d'3' ; Write test value to digit. ; movwf DIGIT1 ; Write test value to digit. ; movlw d'2' ; Write test value to digit. ; movwf DIGIT10 ; Write test value to digit. ; movlw d'1' ; Write test value to digit. ; movwf DIGIT100 ; Write test value to digit. call FLASH ; Boot up flash sequence clrf timer0 ; Clear timer0 bsf intcon,5 ; Enable Timer interrupt goto MAIN ; Skip over lookup table BIN2SEG ; 7-segment display table addwf pcl,f ; Jump into lookup table ; _gfedcba' retlw b'11000000' ; Segment for 0 retlw b'11111001' ; Segment for 1 retlw b'10100100' ; Segment for 2 retlw b'10110000' ; Segment for 3 retlw b'10011001' ; Segment for 4 retlw b'10010010' ; Segment for 5 retlw b'10000010' ; Segment for 6 retlw b'11111000' ; Segment for 7 retlw b'10000000' ; Segment for 8 retlw b'10011000' ; Segment for 9 MAIN ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ; Force test values - Upon power up or rest, works fine 50% of the time ; when enabled here and displays a flashing "123". The rest of the time ; it appears the bootup FLASH routine runs endlessly with 1, 2, 3, or no ; digits being displayed. There appears to be no pattern to when it works ; or fails. movlw d'3' ; Write test value to digit. movwf DIGIT1 ; Write test value to digit. movlw d'2' ; Write test value to digit. movwf DIGIT10 ; Write test value to digit. movlw d'1' ; Write test value to digit. movwf DIGIT100 ; Write test value to digit. goto MAIN DISPLAY ; Three digit display/multiplexing routine movwf _w ; Save w swapf status,w ; Save status movwf _status ; Save status bsf portb,2 ; Turn off 100 digit bsf portb,1 ; Turn off 10 digit bsf portb,0 ; Turn off 1 digit ; Force test values - Works 100% of the time when enabled here ; movlw d'3' ; Write test value to digit. ; movwf DIGIT1 ; Write test value to digit. ; movlw d'2' ; Write test value to digit. ; movwf DIGIT10 ; Write test value to digit. ; movlw d'1' ; Write test value to digit. ; movwf DIGIT100 ; Write test value to digit. ; D100 ; Need 100 digit on? movfw LOOP ; LOOP to w sublw d'3' ; 3 - LOOP in w btfss status,2 ; LOOP = 3? goto D10 ; No, check next. bcf portb,2 ; Yes, turn on 100 digit movfw DIGIT100 ; Yes, put digit value into w call BIN2SEG ; Yes, convert value to 7-segment movwf portc ; Yes, send value to digit display goto LOOPDEC ; Yes, leave. D10 ; Need 10 digit on? movfw LOOP ; LOOP to w sublw d'2' ; 2 - LOOP in w btfss status,2 ; LOOP = 2? goto D1 ; No, check next. bcf portb,1 ; Yes, turn on 10 digit movfw DIGIT10 ; Yes, put digit value into w call BIN2SEG ; Yes, convert value to 7-segment movwf portc ; Yes, send value to digit display goto LOOPDEC ; Yes, leave. D1 ; Need 1 digit on. bcf portb,0 ; Turn on 1 digit movfw DIGIT1 ; Yes, put digit value into w call BIN2SEG ; Yes, convert value to 7-segment movwf portc ; Yes, send value to digit display LOOPDEC decfsz LOOP ; Equal to 0? goto $+3 ; No, leave and do it again later. movlw d'3' ; Yes, reinitialize LOOP variable. movwf LOOP ; Yes, reinitialize LOOP variable. bcf intcon,2 ; Clear interrupt bit swapf _status,w ; Restore status. movwf status ; Restore status. swapf _w ; Restore w. swapf _w,w ; Restore w. retfie ; Return. ;;;;;;; SUB - 100 MILLISECOND DELAY - WITH 4M OSC ;;;;;;;;;;;; C D_100MS ; return movlw d'254' movwf COUNT1 movlw d'128' movwf COUNT2 decfsz COUNT2,f goto $-1 decfsz COUNT1,f goto $-5 return ;;;;;;; BOOT UP FLASH SUBROUTINE ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ; ; FLASH ; Figure 8 pattern x3 bcf portb,0 ; Turn 1s digit on bcf portb,1 ; Turn 10s digit on bcf portb,2 ; Turn 100s digit on movlw d'3' ; Do loop 3 times movwf COUNT ; Do loop 3 times FLASHBEGIN movlw b'11111110' ; a movwf portc call D_100MS movlw b'11111101' ; b movwf portc call D_100MS movlw b'10111111' ; g movwf portc call D_100MS movlw b'11101111' ; e movwf portc call D_100MS movlw b'11110111' ; d movwf portc call D_100MS movlw b'11111011' ; c movwf portc call D_100MS movlw b'10111111' ; g movwf portc call D_100MS movlw b'11011111' ; f movwf portc call D_100MS decfsz COUNT goto FLASHBEGIN movlw b'11111111' ; All segments off movwf portc ; All segments off return end ;---------------------------------------------------- ; ; Oscillator XT - 4.0 MHz ; Watchdog Timer Off ; Power Up Timer On ; Brown Out Detect Off ; Brown Out Voltage N/A ; Code Protect Off ; ;====================================================

Hi Mark, one or two things I see no .inc file being used. Which explains why you have to define your own register names. SFR bits also have names, eg GIE and T0IE, and using them would make the code a lot more readable Use #define to make your own bit names, eg #define CHAR100 portb,0 #define CHAR010 portb,1 #define CHAR001 portb,2 Do not use "bsf status,5" to change bank. It is prone to typos and slows debugging banksel can be used in MPLAB banksel trisb ;for example or even a macro bank0 macro bcf status,rp0 bcf status,rp1 bcf status,irp endm bank1 macro bsf status,rp0 bcf status,rp1 bcf status,irp endm bank1 movlw something movwf trisb cblock can be used (but see also the recent thread on RES etc) for a variable list cblock 0x20 COUNT1 ; Time delay looping variable COUNT2 ; Time delay looping variable LOOP ; Display loop var used in DISPLAY interrupt routine etc endc > movlw b'10000000' > movwf intcon GIE has been turned on. If there are any pending interrupts this could cause mayhem. And if you don't know what the interrupt source is, you can't clear it. Clear all interrupt and enable flags, then set the ones you want, before setting GIE Aren't your LEDs active low ? Shouldn't you be setting portb and portc to FF ? > clrf portb ; All outputs off > clrf portc ; All outputs off > D100 ; Need 100 digit on? > movfw LOOP ; LOOP to w > sublw d'3' ; 3 - LOOP in w > btfss status,2 ; LOOP = 3? This is OK, an alternative would be movlw d'3' xorwf LOOP,w ;XORing equal values = 0 skpz > LOOPDEC > decfsz LOOP ; Equal to 0? > goto $+3 ; No, leave and do it again later. Better to goto a label instead of goto $+3 decfsz LOOP goto isr_exit isr_exit bcf intcon,2 ; Clear interrupt bit *** bcf intcon,t0ie *** > swapf _status,w ; Restore status. > movwf status ; Restore status. > swapf _w ; Restore w. > swapf _w,w ; Restore w. > retfie ; Return.