performanceassemblymicrocontrollerpicmicrochip
How can I improve my LED display code so that it reacts in real-time
This is a carry on question from my previous one and I was wondering how I can go about improving my code, which currently has an extreme delay in outputting the numbers to the display and also not showing the expected outputs under all situations, i.e., some segments are not lit up.
Please see the images below!
Correct but delayed output 1
Correct but delayed output 2
Correct but delayed output 3
Incorrect and delayed output
From an inexperienced point of view, I imagine that it's a timing issue. But, how I go about solving it isn't quite clear to me at the moment. Therefore, any insights or proposed numbers that I can use will be very much appreciated.
The working code with the ADC code block is below:
LIST p=16f1829 ;list directive to define processor
#INCLUDE <p16f1829.inc> ;processor specific variable definitions
__CONFIG _CONFIG1, (_FOSC_INTOSC & _WDTE_OFF & _PWRTE_OFF & _MCLRE_OFF & _CP_OFF & _CPD_OFF & _BOREN_ON & _CLKOUTEN_OFF & _IESO_OFF & _FCMEN_OFF);
__CONFIG _CONFIG2, (_WRT_OFF & _PLLEN_OFF & _STVREN_OFF & _LVP_OFF);
;-------------------------------------------------------------------------
; UDATA_SHR declares a section of shared (all across the banks) uninitialised data
INT_VAR UDATA_SHR ; INT_VAR is the section name in ACCESS RAM
TempC RES 1 ;
L0 RES 1 ;
w_temp RES 1 ; variable used for context saving
pclath_temp RES 1 ; variable used for context saving
status_temp RES 1 ; variable used for context saving
;-------------------------------------------------------------------------
LEDtrisA EQU TRISA
LEDtrisC EQU TRISC
LEDlatA EQU LATA
LEDlatC EQU LATC
;-------------------------------------------------------------------------
RESET_VECTOR CODE 0x0000
GOTO START ; When using debug header, ICD2 may not stop
; on instruction 0 during reset.
;-------------------------------------------------------------------------
INT_VECTOR CODE 0x0004 ; Interrupt vector location
ISR ; Relocatable Interrupt Service Routine
; Context saving for ISR
MOVWF w_temp ; save off current W register contents
MOVF STATUS, w ; move status register into W register
MOVWF status_temp ; save off contents of STATUS register
MOVF PCLATH, w ; Saves value in register PCLATH
MOVWF pclath_temp
;-------------------------------------------------------------------------
; If the interrupt came from the timer, execute the TMR0 interrupt
; service routine.
BANKSEL TMR0
MOVLW .96
MOVWF TMR0
BTFSC INTCON, TMR0IF
CALL Service_TMR0
BRA UpdateDisplay ; Refresh the display
UpdateDisplay
BANKSEL LATA ; Selects memory bank containing LATA register
MOVF LEDlatA, w ; display status -> w register
ANDLW 0x0f ; Separate the lower half byte
MOVWF TempC ; Save display status in TempC
BSF TempC, 4 ; Beginning status of LSD display
RRF TempC, F ; Set the status of the next display
BTFSS STATUS, C ; C = 1?
BCF TempC, 3 ; If not, turn off the LSD display
BTFSC TempC, 0
BRA UpdateMsd ; If it is turned on, display the MSD
; digit of the number
UpdateLsd
BCF TempC, 3
BSF TempC, 1
BTFSS STATUS, Z ; If it is, skip
MOVF L0, w ; Third LSD digit -> w
ANDLW 0x0f ; /
BRA DisplayOut ; Show it on the display
UpdateMsd
SWAPF L0, w ; MSD figure - >
ANDLW 0x0f ; /
BTFSC STATUS, Z ; MSD = 0?
MOVLW 0x0a ; If it is, skip
DisplayOut
CALL LedTable ; Take the mask for a digit
MOVWF LEDlatC ; Set the mask on port B
MOVF TempC, W ; Turn on displays
MOVWF LEDlatA
BRA ISR_END
;-------------------------------------------------------------------------
ISR_END
; Restore contents before returning from interrupt
MOVF pclath_temp,w ; PCLATH is given its original content
MOVWF PCLATH
MOVF status_temp,w ; STATUS is given its original content
MOVWF STATUS
SWAPF w_temp,f ; W is given its original content
SWAPF w_temp,w
BSF INTCON,GIE ; Global interrupt enabled
RETFIE ; Return from interrupt routine
;-------------------------------------------------------------------------
; LOOKUP TABLE
;-------------------------------------------------------------------------
LUT_VECTOR CODE 0x0030 ; Lookup Table location
LUT ; Lookup table is at the top of third page,
; but can be placed at some other place, it
; is important to have it all on one page
LedTable
ADDWF PCL, F
RETLW B'00111111' ; mask for digit 0
RETLW B'00000110' ; mask for digit 1
RETLW B'01011011' ; mask for digit 2
RETLW B'01001111' ; mask for digit 3
RETLW B'01100110' ; mask for digit 4
RETLW B'01101101' ; mask for digit 5
RETLW B'01111101' ; mask for digit 6
RETLW B'00000111' ; mask for digit 7
RETLW B'01111111' ; mask for digit 8
RETLW B'01101111' ; mask for digit 9
RETLW B'01110111'
RETLW B'01111100'
RETLW B'00111001'
RETLW B'01011110'
RETLW B'01111101'
RETLW B'01110001'
RETLW B'00000000' ; no digit ......
;-------------------------------------------------------------------------
MAIN_PROG CODE
START
;-------------------------------------------------------------------------
ERRORLEVEL -302 ; Disable warning accessing register not in bank 0
BANKSEL OSCTUNE ; Configure OPTION_REG and TMR0
MOVLW 0x00 ; Set oscillator to factory calibrated frequency
MOVWF OSCTUNE ;
BANKSEL STATUS
ERRORLEVEL +302 ; Enable warning accessing register not in bank 0
CLEAR_RAM ; code sequence initialises all GPR's to 0x00
MOVLW 0x70 ; initialise pointer
MOVWF FSR0 ; to RAM
CLRF FSR0H
NEXT
CLRF INDF0 ; Clear INDF0 register
INCF FSR0L, F ; Inc pointer
BTFSS FSR0L, 7 ; All done?
GOTO NEXT ; No, clear NEXT
CONTINUE ; Yes, CONTINUE
NOP
;-------------------------------------------------------------------------
; MAIN BODY OF PROGRAM
;-------------------------------------------------------------------------
; Setup main init
BANKSEL OSCCON ; Selects memory bank containing OSCCON register
MOVLW b'01011000' ; Set CPU clock speed of 500KHz -> correlates to (1/(500K/4)) for each instruction
MOVWF OSCCON ; OSCCON <- 0x38
; Configure the ADC/Potentimator
; Already in bank1
MOVLW b'00001101' ; Select RA4 as source of ADC and enable the module (careful, this is actually AN3)
MOVWF ADCON0
MOVLW b'00010000' ; Left justified - Fosc/8 speed - vref is Vdd
MOVWF ADCON1
BANKSEL ANSELA ; Selects memory bank containing ANSELA register
; Setup pins as digital I/O
MOVLW 0x10 ; Selects memory bank containing ANSELA register
ANDWF ANSELA ; All pins are digital
CLRF ANSELC
; Configure the input & output pins
BANKSEL TRISA ; Selects memory bank containing TRISA register
MOVLW b'11111100' ; RA0 and RA1 are configured as outputs and
; used for 7-segment display multiplexing
; RA2 is input push-button for initialization
MOVWF TRISA
CLRF LEDtrisC ; Port C is output
BANKSEL LATA ; Selects memory bank containing LATA register
CLRF LEDlatA ; Set all outputs to "0"
CLRF LEDlatC ;
BSF LEDlatA, 1 ; Turn on MSD display
; Setup Timer0 as the delay
BANKSEL OPTION_REG
MOVLW b'10000100' ; TMR0 is incremented each 32us (Fclk=8MHz)
MOVWF OPTION_REG ; ps = 32
BANKSEL TMR0 ; Selects memory bank containing TMR0 register
BSF INTCON, GIE ; Global interrupt enabled
BSF INTCON, TMR0IE ; Timer TMR0 interrupt enabled
MAINLOOP
BRA MAINLOOP ; Continue forever
A2D:
; Start the ADC
NOP ; Requried ADC delay of 8uS => (1/(Fosc/4)) = (1/(500KHz/4)) = 8uS
BANKSEL ADCON0 ; Selects memory bank containing ADCON0 register
BSF ADCON0, GO ; Start the ADC
BTFSC ADCON0, GO ; This bit will be cleared when the conversion is complete
GOTO $-1 ; Keep checking the above line until GO bit is clear
; Grab Results and write to the LEDs
SWAPF ADRESH, w ; Get the top 4 MSbs (remember that the ADC result is LEFT justified!)
MOVWF L0
RETURN
; TIMER 0 Interrupt routine clears the TMR0 interrupt flag.
Service_TMR0:
BANKSEL INTCON
BCF INTCON, TMR0IF ; MUST ALWAYS clear this in software or else stuck in the ISR forever
BTFSC LATA, 1 ; Check if ADC value already determined
CALL A2D ; Get the ADC result
RETURN
;-------------------------------------------------------------------------
; END OF PROGRAM
;-------------------------------------------------------------------------
END ; End of program
Solution
Here are some issues that some may be bad practices.
1- Here you call the ADC routine in the Timer0 ISR.
Service_TMR0:
BANKSEL INTCON
BCF INTCON, TMR0IF ; MUST ALWAYS clear this in software or else stuck in the ISR forever
BTFSC LATA, 1 ; Check if ADC value already determined
CALL A2D ; Get the ADC result
RETURN
Then the Timer0 isr calls ADC and the program loops in there at least 20us approximately which can lead to miss another pending interrupts or pending input events.
A2D:
; Start the ADC
NOP ; Requried ADC delay of 8uS => (1/(Fosc/4)) = (1/(500KHz/4)) = 8uS
BANKSEL ADCON0 ; Selects memory bank containing ADCON0 register
BSF ADCON0, GO ; Start the ADC
BTFSC ADCON0, GO ; This bit will be cleared when the conversion is complete
GOTO $-1 ; Keep checking the above line until GO bit is clear
; Grab Results and write to the LEDs
SWAPF ADRESH, w ; Get the top 4 MSbs (remember that the ADC result is LEFT justified!)
MOVWF L0
RETURN
As far as I see you do everything in the timer isr which is a bad programming practice. You update the display as well. Updating the display doesn't take much time so it can be ignored in the isr. But some routines wihch take much time should not be processed within the isr. Therefore you better process the routines which can take more time or can poll a flag within your main loop.
2- In this section you multiplex the digits. You multiplex them using RRF instruction as if there are 4 digits, but you have only 2 digits in your application.
UpdateDisplay
BANKSEL LATA ; Selects memory bank containing LATA register
MOVF LEDlatA, w ; display status -> w register
ANDLW 0x0f ; Separate the lower half byte
MOVWF TempC ; Save display status in TempC
BSF TempC, 4 ; Beginning status of LSD display
RRF TempC, F ; Set the status of the next display
BTFSS STATUS, C ; C = 1?
BCF TempC, 3 ; If not, turn off the LSD display
BTFSC TempC, 0
I don't know which pins are used for multiplexing the digits, but you must set the correct bit in Temp register in order to multiplex them correctly. For example if your digit1 and digit0 connected to A1 and A0 respectively, You must set the second bit Tempc,2 in order to multiplex them correctly. Then when the set bit reaches to carry then you must set it again and so forth.