This is the second article about this board.
The first part is here.
The code here is not actually a message board. It only demonstrates the principle of image rendering.
It may be usable for test purposes.
The image is hardcoded into the program memory. It is loaded from the program memory into the RAM and is transferred to the display in several cycles.
This scheme is good to check if the basic hardware is working – the PIC is started, shift registers are controlled correctly and so on.
Schematic diagram:
In the real device I used the cheapest transistors I could find.
In the real device I did not use resistors R11-R26 and especially R7-R10.
R11-R26 may make sense, because I really saw some flickering in unconnected rows that could be caused by unstable transistor’s condition when its base is connected only to high-impedance latch output. So, these resistors close column’s transistors by default..
But R7-R10 is demand of Proteus. It can’t calculate this scheme if you do not give him these resistors or if their value will be over 21k.
Actually, 21k is unstable too.
ASM
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list p=pic16f84a
include p16f84a.inc
__config _hs_osc & _wdt_off & _pwrte_on & _cp_off
errorlevel -302 ;Eliminate bank warning
;**************** Label Definition ********************
cnt500u equ 0c ;500usec counter Address
cnt1m equ 0d ;1msec counter Address
cnt100m equ 0e ;100msec counter Address
cnt500m equ 0f ;500msec counter Address
cnt1s equ 10 ;1sec counter Address
count equ 11 ; number of bits that has been sent to the shift register
str equ 12 ;
count2 equ 13 ; number of column shifts to display all message
pzsn equ 14 ; here value is stored for initializing indirect addressing
count3 equ 15 ; number of one frame renders before column shift
;**************** Program Start ***********************
org 0 ;Reset Vector
goto init
org 4 ;Interrupt Vector
goto init
;**************** Initial Process *********************
org 5
init bsf status,rp0 ;Change to Bank1
clrf trisa ;Set PORTA to Output mode
clrf trisb ;Set PORTB to Output mode
bcf status,rp0 ;Change to Bank0
movlw h'00' ;
movwf portb ;
;*********** disposing the image of the first string in RAM ***************
;*********** here 53 colums of data + 7 empty (buffer) columns
;000000000000000000000000000000000000000000000000000000000000
;011111011111001110011111011101000100111000010000000000000000
;000100010000010001000100001001000101000100010000000000000000
;000100010000010000000100001001100101000000010000000000000000
;000100011110001110000100001001010101001100010000000000000000
;000100010000000001000100001001001101000100010000000000000000
;000100010000010001000100001001000101000100000000000000000000
;000100011111001110000100011101000100111100010000000000000000
fst
movlw 0x16 ; starting address
movwf fsr ; using indirect addressing
movlw b'00000000'
movwf indf ;
incf fsr ; 0x17
movlw b'00000010'
movwf indf ;
incf fsr
movlw b'00000010'
movwf indf ;
incf fsr
movlw b'11111110'
movwf indf ;
incf fsr
movlw b'00000010'
movwf indf ;
incf fsr
movlw b'00000010'
movwf indf ;
incf fsr
movlw b'00000000'
movwf indf ;
incf fsr
movlw b'11111110'
movwf indf ;
incf fsr
movlw b'10010010'
movwf indf ;
incf fsr
movlw b'10010010'
movwf indf ;
incf fsr
movlw b'10010010'
movwf indf ;
incf fsr
movlw b'10000010'
movwf indf ;
incf fsr
movlw b'00000000'
movwf indf ;
incf fsr
movlw b'01001100'
movwf indf ;
incf fsr
movlw b'10010010'
movwf indf ;
incf fsr
movlw b'10010010'
movwf indf ;
incf fsr
movlw b'10010010'
movwf indf ;
incf fsr
movlw b'01100100'
movwf indf ;
incf fsr
movlw b'00000000'
movwf indf ;
incf fsr
movlw b'00000010'
movwf indf ;
incf fsr
movlw b'00000010'
movwf indf ;
incf fsr
movlw b'11111110'
movwf indf ;
incf fsr
movlw b'00000010'
movwf indf ;
incf fsr
movlw b'00000010'
movwf indf ;
incf fsr
movlw b'00000000'
movwf indf ;
incf fsr
movlw b'10000010'
movwf indf ;
incf fsr
movlw b'11111110'
movwf indf ;
incf fsr
movlw b'10000010'
movwf indf ;
incf fsr
movlw b'00000000'
movwf indf ;
incf fsr
movlw b'11111110'
movwf indf ;
incf fsr
movlw b'00001000'
movwf indf ;
incf fsr
movlw b'00010000'
movwf indf ;
incf fsr
movlw b'00100000'
movwf indf ;
incf fsr
movlw b'11111110'
movwf indf ;
incf fsr
movlw b'00000000'
movwf indf ;
incf fsr
movlw b'01111100'
movwf indf ;
incf fsr
movlw b'10000010'
movwf indf ;
incf fsr
movlw b'10000010'
movwf indf ;
incf fsr
movlw b'10000010'
movwf indf ;
incf fsr
movlw b'11110100'
movwf indf ;
incf fsr
movlw b'00000000'
movwf indf ;
incf fsr
movlw b'00000000'
movwf indf ;
incf fsr
movlw b'00000000'
movwf indf ;
incf fsr
movlw b'10111110'
movwf indf ;
incf fsr
movlw b'00000000'
movwf indf ;
incf fsr
movlw b'00000000'
movwf indf ;
incf fsr
movlw b'00000000'
movwf indf ;
incf fsr
movlw b'00000000'
movwf indf ;
incf fsr
movlw b'00000000'
movwf indf ;
incf fsr
movlw b'00000000'
movwf indf ;
incf fsr
movlw b'00000000'
movwf indf ;
incf fsr
movlw b'00000000'
movwf indf ;
incf fsr
movlw b'00000000'
movwf indf ;
;--------------- buffer ------------------------------------
incf fsr
movlw b'00000000'
movwf indf ;
incf fsr
movlw b'00000000'
movwf indf ;
incf fsr
movlw b'00000000'
movwf indf ;
incf fsr
movlw b'00000000'
movwf indf ;
incf fsr
movlw b'00000000'
movwf indf ;
incf fsr
movlw b'00000000'
movwf indf ;
incf fsr
movlw b'00000000'
movwf indf ;
; -------------- main program start --------------
; here we selecting initial address in RAM (pointer)
; where image of the string is stored (60 bytes)
; and sending to the screen 16 bytes that can be visible for 8x16 matrix
; then we increasing pointer by one and repeat this procedure
;
; after 50 shifts all data will go through the screen.
clrf count
movlw b'00001110' ; '14' is placed to count2
movwf count2
clrf count3
movlw 0x16 ; initial RAM address for string image
movwf pzsn ; value for indirect addressing
movf pzsn,0
movwf fsr
movlw b'00000000' ; select the 0-th row of the LED matrix
movwf porta
; collecting and sending data for row 0
egh0 btfsc indf,0 ; sending bit 0 to shift register
call dsend1 ;
btfss indf,0 ;
call dsend0 ;
incf fsr,1 ; next byte to render
incf count,1 ; count number of bytes that been sended to register
btfss count,4 ; all 16 bytes has been sent?
goto egh0 ; no, send the 0-th bit of the next byte from FSR
movf pzsn,0 ; reset indirect addressing to the beginning for the next row
movwf fsr ;
clrf count ; reset column (bytes) count for the next row
call oport ; show collected row on the screen
movlw b'00000001' ; switch matrix to the 1-st row
movwf porta ;
; collecting and sending data for row 1
egh1 btfsc indf,1 ; sending bit 1 to shift register
call dsend1 ;
btfss indf,1 ;
call dsend0 ;
incf fsr,1 ; next byte to render
incf count,1 ; count number of bytes that been sended to register
btfss count,4 ; all 16 bytes has been sent?
goto egh1 ; no, send the 1-st bit of the next byte from FSR
movf pzsn,0 ; reset indirect addressing to the beginning for the next row
movwf fsr ;
clrf count ; reset column (bytes) count for the next row
call oport ; show collected row on the screen
movlw b'00000010' ; switch matrix to the 2-nd row
movwf porta ;
; collecting and sending data for row 2
egh2 btfsc indf,2
call dsend1
btfss indf,2
call dsend0
incf fsr,1
incf count,1
btfss count,4
goto egh2
movf pzsn,0
movwf fsr
clrf count
call oport
movlw b'00000011'
movwf porta
; collecting and sending data for row 3
egh3 btfsc indf,3
call dsend1
btfss indf,3
call dsend0
incf fsr,1
incf count,1
btfss count,4
goto egh3
movf pzsn,0
movwf fsr
clrf count
call oport
movlw b'00000100'
movwf porta
; collecting and sending data for row 4
egh4 btfsc indf,4
call dsend1
btfss indf,4
call dsend0
incf fsr,1
incf count,1
btfss count,4
goto egh4
movf pzsn,0
movwf fsr
clrf count
call oport
movlw b'00000101'
movwf porta
; collecting and sending data for row 5
egh5 btfsc indf,5
call dsend1
btfss indf,5
call dsend0
incf fsr,1
incf count,1
btfss count,4
goto egh5
movf pzsn,0
movwf fsr
clrf count
call oport
movlw b'00000110'
movwf porta
; collecting and sending data for row 6
egh6 btfsc indf,6
call dsend1
btfss indf,6
call dsend0
incf fsr,1
incf count,1
btfss count,4
goto egh6
movf pzsn,0
movwf fsr
clrf count
call oport
movlw b'00000111'
movwf porta
; collecting and sending data for row 7
egh7 btfsc indf,7
call dsend1
btfss indf,7
call dsend0
incf fsr,1
incf count,1
btfss count,4
goto egh7
movf pzsn,0
movwf fsr
clrf count
call oport
movlw b'00000000'
movwf porta
incf count3
btfss count3,6 ; each frame should be displayed 64 times before shift
goto egh0
clrf count3
; here the string is shifting to one column
btfss count2,6 ; check if count2 over 64. it means 64-14=50 column shifts
incf pzsn,1 ; if less the 50 shifts, change initial fsr value (shift by one column)
btfsc count2,6 ; if less then 50 shifts - do not go to the next word
goto stop ; if 50 shifts has been done go to end
incf count2 ; increase column shifts count
goto egh0 ; render row 0
stop goto $
; I think this should control Output Enable pin of 4094 shift-register
oport movlw b'00000001'
movwf portb
call t1m
movlw b'00000000'
movwf portb
return
; sends one bit to the 4094 shift register
; portb 6 is DATA
; portb 7 is CLOCK
dsend1 movlw b'00000000'
movwf portb
nop
movlw b'01000000'
movwf portb
nop
movlw b'11000000'
movwf portb
nop
movlw b'01000000'
movwf portb
return
dsend0 movlw b'00000000'
movwf portb
nop
movlw b'00000000'
movwf portb
nop
movlw b'10000000'
movwf portb
nop
movlw b'00000000'
movwf portb
return
; These timers had been written by somebody else
;********************************************************
; Timer Subroutine for 10MHz clock
;********************************************************
;************* 1msec Timer Subroutine *****************
t1m movlw d'2' ;(1) Set loop cnt1
movwf cnt1m ;(1) Save loop cnt1
tm1lp1 movlw d'190' ;(1)*2 Set loop cnt2 was 249
movwf cnt500u ;(1)*2 Save loop cnt2
tm1lp2 nop ;(1)*249*2 Time adjust
nop ;(1)*249*2 Time adjust
decfsz cnt500u,f ;(1)*249*2 cnt500u-1=0 ?
goto tm1lp2 ;(2)*248*2 No, continue
decfsz cnt1m,f ;(1)*2 cnt1m-1=0 ?
goto tm1lp1 ;(2) No. Continue
return ;(2) Yes. Cnt end
;Total 2501*0.4usec=1msec
;************* 100msec Timer Subroutine ***************
t100m movlw d'100' ;Set loop counter
movwf cnt100m ;Save loop counter
tm2lp call t1m ;1msec subroutine
decfsz cnt100m,f ;cnt100m - 1 = 0 ?
goto tm2lp ;No. Continue
return ;Yes. Count end
;************* 500msec Timer Subroutine ***************
t500m movlw d'5' ;Set loop counter
movwf cnt500m ;Save loop counter
tm3lp call t100m ;100msec subroutine
decfsz cnt500m,f ;cnt500m - 1 = 0 ?
goto tm3lp ;No. Continue
return ;Yes. Count end
;************** 1sec Timer Subroutine *****************
t1s movlw d'2' ;Set loop counter
movwf cnt1s ;Save loop counter
tm4lp call t500m ;500msec subroutine
decfsz cnt1s,f ;cnt1s - 1 = 0 ?
goto tm4lp ;No. Continue
return ;Yes. Count end
end |
Downloads:
ASM file for PIC16F84.
HEX file for flashing into PIC16F84.
Project file for Proteus 8.4