4 bit 7 segment display with two 74HC595

[richard]

Could you point to an example of that?

me too
I have never had to do that and can find no mention of that short coming anywhere


anyways here is my take on the 7 seg display
if you have a chip with mssp why waste time and code space when the hardware can do it for you

I cheated a bit and did it in asm for speed and size gains
no nasty pauses , all gone
my displays are common anode so the data is inverted see comments

'****************************************************************
'*  Name    : 4 bit 7 segment display                           *
'*  Author  : RICHARD                                           *
'*  Notice  :                                                   *
'*          :                                                   *
'*  Date    : 18. 2. 2018                                       *
'*  Version : 1.0                                               *
'*  Notes   :                                                   *
'*  MCU     : PIC 16F1825 @32MHZ                                *
'****************************************************************
#CONFIG
             __config        _CONFIG1,    _FOSC_INTOSC & _CP_OFF & _WDTE_ON  &  _PWRTE_ON  &  _MCLRE_ON  & _CLKOUTEN_OFF
              __config      _CONFIG2, _PLLEN_OFF & _LVP_OFF
#ENDCONFIG

 goto overasm
 asm
timer1  = TMR1L 
 
seg_val       
    addwf   PCL, F                  
    retlw  0xc0;0B11000000     0  
    retlw  0xf9;0B11111001     1     
    retlw  0xa4;0B10100100     2
    retlw  0xb0;0B10110000     3
    retlw  0x99;0B10011001     4
    retlw  0x92;0B10010010     5                     
    retlw  0x82;0B10000010     6
    retlw  0xf8;0B11111000     7
    retlw  0x80;0B10000000     8  
    retlw  0x90;0B10010000     9
 endasm

 overasm:
DEFINE OSC 32            ; Use internal clock 
ANSELC=0
SSP1CON1=$22  
SSP1STAT=$40
OSCCON=$f0

INCLUDE "DT_INTS-14.bas" ; Base Interrupt System

TRISC = %11101010
LPIN var portc.4         ; Latch
DPIN var portc.2         ; Data  SDO
CPIN var portc.0         ; Clock SCK
segment var byte
value var word
d_index var byte
buff var byte[5]
tmp var byte             
d_pointer      var byte  
timer1 var word ext
timer1_reload con    1543      ;8mS
ASM
INT_LIST macro ; IntSource, Label, Type, ResetFlag?
    INT_Handler TMR1_INT, _DISP, ASM, yes
  endm
  INT_CREATE ; Creates the interrupt processor
ENDASM
@ INT_ENABLE TMR1_INT ; enable Timer 1 interrupts
T1CON = $1
d_index=0
;---[simple counter 0 - to 9999]------------------------------------------------ 
Main:
for value = 0 to 9999
arraywrite buff ,[dec4 value]
pause 100
next value
value = 0
GOTO Main
;---[TMR1 - interrupt handler]--------------------------------------------------
DISP:
asm
    MOVE?CT 0, T1CON, TMR1ON ; 1 stop timer
    MOVLW LOW(_timer1_reload) ; 1 Add TimerReload to the 
    ADDWF TMR1L,F ; 1 value in Timer1
    BTFSC STATUS,C ; 1/2
    INCF TMR1H,F ; 1
    MOVLW HIGH(_timer1_reload) ; 1
    ADDWF TMR1H,F ; 1
    MOVE?CT 1, T1CON, TMR1ON ; 1 start timer
    MOVE?CB  high _buff, FSR0H         ;load highbyte 
    MOVE?CB  low  _buff, FSR0L         ;load low byte
    MOVE?BA  _d_index  
    ADDWF  FSR0L,F
    MOVLW 0X30
    SUBWF INDF0,W
    L?CALL seg_val
    MOVE?AB _segment
    MOVE?BB  _d_index ,_tmp
    BANKSEL   _tmp
    MOVLW 1
    ADDWF  _tmp,F
    BANKSEL   _d_pointer
    CLRF _d_pointer
    BSF STATUS ,C
N_BIT 
    BANKSEL   _d_pointer
    RLF    _d_pointer,F
    BCF STATUS ,C
    BANKSEL   _tmp
    DECFSZ  _tmp,F
    GOTO N_BIT 
    MOVLW 1
    BANKSEL  _d_index
    ADDWF  _d_index,F
    MOVLW 3 
    ANDWF  _d_index,F
    BANKSEL  LATC
    BCF LATC ,4
    BANKSEL PIR1
    BCF     PIR1,3 
    BANKSEL  _segment
    COMF    _segment,W  ;COMMENT USED TO INVERT DATA FOR COMMON ANODE DISPLAY
    BANKSEL SSP1BUF
    movwf   SSP1BUF
    BANKSEL PIR1
    BTFSs   PIR1,3
    GOTO    $-1
    BANKSEL  _d_pointer
    COMF    _d_pointer,W ; ;COMMENT USED FOR COMMON ANODE DISPLAY
    BANKSEL PIR1
    BCF     PIR1,3 
    BANKSEL SSP1BUF
    movwf   SSP1BUF
    BANKSEL PIR1
    BTFSs   PIR1,3
    GOTO    $-1
    BANKSEL  LATC
    BSF LATC ,4
    BANKSEL 0
    INT_RETURN
endasm

[mpgmike]

OK, looked through a K50 and 16F1619 Data Sheet for that note or catch phrase indicating a full write to TxCON is recommended after writing to the TMRxH/L registers and cannot find it. It might be for an older processor, or maybe I read it on a forum somewhere and now it's that propagating myth. Sorry.

[louislouis]

anyways here is my take on the 7 seg display
if you have a chip with mssp why waste time and code space when the hardware can do it for you

I cheated a bit and did it in asm for speed and size gains
no nasty pauses , all gone
my displays are common anode so the data is inverted see comments

Hello Richard, thanks for response. Your code is probably for 4 digit 7 segment display where the segments is driven via 74HC595 shift register, and the common anodes via transistors directly from MCU or for multiplexing a bare display whitout driver right?

Look at mi first post, my display is driven by two 74HC595 shift register, one for segments, and the second for digits (like common anodes/cathodes).

To send data I used:

 
SHIFTOUT DPIN, CPIN, MSBFIRST,[ones,%0001]  ;(segment pattern, digit position)

Now I tring to find more elegant way to extract ones, tens, hundreds and thousands like my previous solution:

 
setdisp:
segment = value//10
gosub look
ones=segment            ; extract ones

segment =  value/10 
segment = segment//10
gosub look
tens=segment            ; extract tens

segment =   value/100
segment = segment//10
gosub look
hundreds=segment        ; extract hundreds

segment = value/1000
gosub look
thousands=segment       ; extract thousands

Can you help me with it?

[richard]

Your code is probably for 4 digit 7 segment display where the segments is driven via 74HC595 shift register, and the common anodes via transistors directly from MCU or for multiplexing a bare display whitout driver right

wrong , my code is for your circuit but using a different pic chip . I don't have a 12f1840 on hand but I cannot see any reason for it not to work on that chip . if you use the right pins.
your code is for common anode mine common cathode the commented lines can be changed to suit


COMF _segment,W for common Anode becomes MOVF _segment,W
COMF _d_pointer,W for common Anode becomes MOVF _d_pointer,W
ie the current is reversed in the display

[richard]

here is a 12f1822 version
with full hex [upper and lower case] space and - sign also
note comments for common anode/cathode

'****************************************************************
'*  Name    : 4 bit 7 segment display                           *
'*  Author  : RICHARD                                           *
'*  Notice  :                                                   *
'*          :                                                   *
'*  Date    : 18. 2. 2018                                       *
'*  Version : 1.0                                               *
'*  Notes   :                                                   *
'*  MCU     : PIC 12F1822 @32MHZ                                *
'****************************************************************
#CONFIG
  __config _CONFIG1, _FOSC_INTOSC & _WDTE_OFF & _PWRTE_ON & _MCLRE_OFF & _CP_OFF & _CPD_OFF & _BOREN_ON & _CLKOUTEN_OFF & _IESO_ON & _FCMEN_ON
  __config _CONFIG2, _WRT_OFF & _PLLEN_ON & _STVREN_ON & _BORV_19 & _LVP_OFF
#ENDCONFIG

 goto overasm
ASM
timer1  = TMR1L    
seg_val 
    CHK?RP  _TM_TMP
    MOVWF   _TM_TMP
    SUBLW   0x21
    btfsc   STATUS, C
    retlw   0   ;" "
    MOVF    _TM_TMP,W
    SUBLW   0x2f
    btfsc   STATUS, C
    retlw   64   ;"-"
    MOVF    _TM_TMP,W
    MOVLW   0X40
    SUBWF   _TM_TMP,W
    btfsC   STATUS, C
    GOTO    TM_ALPHA
    MOVF    _TM_TMP,W
    ANDLW   0X0F
    GOTO    TM_LU
TM_ALPHA 
    ANDLW   0xdf    ;ucase
    SUBLW   6
    btfsS   STATUS, C
    retlw   0       ;ERROR
    MOVLW   0X37
    SUBWF   _TM_TMP,W
    ANDLW   0xdf    ;ucase
TM_LU     
    BRW                                         
    retlw 	0X3F    ;0   
    retlw 	6            	
    retlw 	0X5B   
    retlw 	0X4F 
    retlw 	0X66
    retlw 	0X6D                        
    retlw 	0X7D  
    retlw 	7   
    retlw 	0X7F          
    retlw 	0X67    ;9
    retlw 	0X77    ;A
    retlw 	0X7C    ;b
    retlw 	0X39    ;C
    retlw 	0X5E    ;d
    retlw 	0X79    ;E
    retlw 	0X71    ;F 
endasm 



 overasm:

DEFINE OSC 32            ; Use internal clock 
ANSELA=0
SSP1CON1=$22  
SSP1STAT=$40
OSCCON=$70

INCLUDE "DT_INTS-14.bas" ; Base Interrupt System
"
TRISA = %11111000
@LPORT=LATA 
LPIN CON 2     ;var LATC.4         ; Latch
DPIN var porta.0         ; Data  SDO
CPIN var porta.1         ; Clock SCK

segment var byte
value var word
d_index var byte
buff var byte[5]
tmp var byte 
TM_TMP    var byte         
d_pointer      var byte  
timer1 var word ext
timer1_reload con    1543  ;8mS
                       
ASM
INT_LIST macro ; IntSource, Label, Type, ResetFlag?
    INT_Handler TMR1_INT, _DISP, ASM, yes
  endm
  INT_CREATE ; Creates the interrupt processor
ENDASM

@ INT_ENABLE TMR1_INT ; enable Timer 1 interrupts
T1CON = $1
d_index=0
;---[simple counter 0 - to ffff]------------------------------------------------ 
Main:
for value = 0 to 65535
arraywrite buff ,[HEX4 value,0]

pause 100
next value
value = 0
GOTO Main

;---[TMR1 - interrupt handler]--------------------------------------------------
DISP:

asm
    MOVE?CT 0, T1CON, TMR1ON ; 1 stop timer
    MOVLW LOW(_timer1_reload) ; 1 Add TimerReload to the 
    ADDWF TMR1L,F ; 1 value in Timer1
    BTFSC STATUS,C ; 1/2
    INCF TMR1H,F ; 1
    MOVLW HIGH(_timer1_reload) ; 1
    ADDWF TMR1H,F ; 1
    MOVE?CT 1, T1CON, TMR1ON ; 1 start timer
    MOVE?CB  high _buff, FSR0H         ;load highbyte 
    MOVE?CB  low  _buff, FSR0L         ;load low byte
    MOVE?BA  _d_index  
    ADDWF  FSR0L,F
    MOVF   INDF0,W
    L?CALL seg_val
    MOVE?AB _segment
    MOVE?BB  _d_index ,_tmp
    BANKSEL   _tmp
    MOVLW 1
    ADDWF  _tmp,F
    BANKSEL   _d_pointer
    CLRF _d_pointer
    BSF STATUS ,C
N_BIT 
    BANKSEL   _d_pointer
    RLF    _d_pointer,F
    BCF STATUS ,C
    BANKSEL   _tmp
    DECFSZ  _tmp,F
    GOTO N_BIT 
    MOVLW 1
    BANKSEL  _d_index
    ADDWF  _d_index,F
    MOVLW 3 
    ANDWF  _d_index,F
    BANKSEL  LPORT
    BCF LPORT ,_LPIN
    BANKSEL PIR1
    BCF     PIR1,3 
    BANKSEL  _segment
    MOVF    _segment,W 
    ;COMF    _segment,W  ;COMMENT USED TO INVERT DATA FOR COMMON ANODE DISPLAY
    BANKSEL SSP1BUF
    movwf   SSP1BUF
    BANKSEL PIR1
    BTFSs   PIR1,3
    GOTO    $-1
    BANKSEL  _d_pointer
    COMF    _d_pointer,W 
    ;MOVF    _d_pointer,W  ;COMMENT USED FOR COMMON ANODE DISPLAY
    BANKSEL PIR1
    BCF     PIR1,3 
    BANKSEL SSP1BUF
    movwf   SSP1BUF
    BANKSEL PIR1
    BTFSs   PIR1,3
    GOTO    $-1
    BANKSEL  LPORT
    BSF LPORT ,_LPIN
    BANKSEL 0
    INT_RETURN
endasm

[louislouis]

here is a 12f1822 version
with full hex [upper and lower case] space and - sign also
note comments for common anode/cathode

Thanks Richard, that code works, but that is a way more difficult understand to me because ASM and so on.
A few things I've noticed when I tried the code:
- your code is a way shorter in MCU memory like mine, which is good
- multiplex is a bit slower I see some flickers
- if I put in to the "value" variable mumber "1234" the display shows "4321"
of course I changed this line
arraywrite buff ,[HEX4 value,0]
to
arraywrite buff ,[DEC4 value,0]

Anyway, it is a good example how the skilled programmer thinks, and how a beginner thinks.

[richard]

multiplex is a bit slower I see some flickers

the refresh rate is 8mS to speed it up to 4mS change timer1_reload to 33543

if I put in to the "value" variable mumber "1234" the display shows "4321"

sic

the digit scan direction can be reversed easily and would result in even smaller code

the difference with this method is that the mcu can now do other tasks and not spend all its time being just a display controller

[louislouis]

the difference with this method is that the mcu can now do other tasks and not spend all its time being just a display controller

Yes that's great, now the MCU has a way more time to do other tasks which I write using my poor skills in picbasic.
Probably this piece of your code will be used in my future projects with that type of 7 segment displays.
Thanks.

[richard]

digit order reversed,scan 4mS
and I moved the lookup out of the isr into the foreground (reduce isr overhead)

'****************************************************************
'*  Name    : 4 bit 7 segment display                           *
'*  Author  : RICHARD                                           *
'*  Notice  :                                                   *
'*          :                                                   *
'*  Date    : 18. 2. 2018                                       *
'*  Version : 1.0                                               *
'*  Notes   :                                                   *
'*  MCU     : PIC 12F1822 @32MHZ                                *
'****************************************************************
#CONFIG
  __config _CONFIG1, _FOSC_INTOSC & _WDTE_OFF & _PWRTE_ON & _MCLRE_OFF & _CP_OFF & _CPD_OFF & _BOREN_ON & _CLKOUTEN_OFF & _IESO_ON & _FCMEN_ON
  __config _CONFIG2, _WRT_OFF & _PLLEN_ON & _STVREN_ON & _BORV_19 & _LVP_OFF
#ENDCONFIG

 goto overasm
ASM
   
seg_val 
    CHK?RP  _TM_TMP
    MOVWF   _TM_TMP
    SUBLW   0x21
    btfsc   STATUS, C
    retlw   0   ;" "
    MOVF    _TM_TMP,W
    SUBLW   0x2f
    btfsc   STATUS, C
    retlw   64   ;"-"
    MOVF    _TM_TMP,W
    MOVLW   0X40
    SUBWF   _TM_TMP,W
    btfsC   STATUS, C
    GOTO    TM_ALPHA
    MOVF    _TM_TMP,W
    ANDLW   0X0F
    GOTO    TM_LU
TM_ALPHA 
    ANDLW   0xdf    ;ucase
    SUBLW   6
    btfsS   STATUS, C
    retlw   0       ;ERROR
    MOVLW   0X37
    SUBWF   _TM_TMP,W
    ANDLW   0xdf    ;ucase
TM_LU     
    BRW                                         
    retlw 	0X3F    ;0   
    retlw 	6            	
    retlw 	0X5B   
    retlw 	0X4F 
    retlw 	0X66
    retlw 	0X6D                        
    retlw 	0X7D  
    retlw 	7   
    retlw 	0X7F          
    retlw 	0X67    ;9
    retlw 	0X77    ;A
    retlw 	0X7C    ;b
    retlw 	0X39    ;C
    retlw 	0X5E    ;d
    retlw 	0X79    ;E
    retlw 	0X71    ;F 
endasm 



 overasm:

DEFINE OSC 32            ; Use internal clock 
ANSELA=0
SSP1CON1=$22  
SSP1STAT=$40
OSCCON=$70

INCLUDE "DT_INTS-14.bas" ; Base Interrupt System

TRISA = %11111000
@LPORT=LATA 
LPIN CON 2     ;var LATa.2         ; Latch
DPIN var porta.0         ; Data  SDO
CPIN var porta.1         ; Clock SCK

segment var byte
value var word
d_index var byte
buff var byte[5]
seg_buff   var byte[4]
seg_cnt    var byte
seg_dat    var byte 
tmp var byte 
TM_TMP    var byte         
d_pointer      var byte  

timer1_reload con    33543  ;4mS
                       
ASM
INT_LIST macro ; IntSource, Label, Type, ResetFlag?
    INT_Handler TMR1_INT, _DISP, ASM, yes
  endm
  INT_CREATE ; Creates the interrupt processor
ENDASM

@ INT_ENABLE TMR1_INT ; enable Timer 1 interrupts
T1CON = $1
d_index=0
;---[simple counter 0 - to ffff]------------------------------------------------ 
Main:
    for value = 0 to 65535
        arraywrite buff ,[HEX4 value,0]
        gosub load_seg
        pause 100
    next value
    value = 0
GOTO Main

load_seg :
    for seg_cnt=0 to 3
        seg_dat= buff[seg_cnt]
        asm
            MOVE?BA  _seg_dat 
            L?CALL seg_val
            MOVE?AB _seg_dat
        endasm
        seg_buff[seg_cnt]= seg_dat
    next
return




;---[TMR1 - interrupt handler]--------------------------------------------------
DISP:

asm
    MOVE?CT 0, T1CON, TMR1ON ; 1 stop timer
    MOVLW LOW(_timer1_reload) ; 1 Add TimerReload to the 
    ADDWF TMR1L,F ; 1 value in Timer1
    BTFSC STATUS,C ; 1/2
    INCF TMR1H,F ; 1
    MOVLW HIGH(_timer1_reload) ; 1
    ADDWF TMR1H,F ; 1
    MOVE?CT 1, T1CON, TMR1ON ; 1 start timer
    MOVE?CB  high _seg_buff, FSR0H         ;load highbyte 
    MOVE?CB  low  _seg_buff, FSR0L         ;load low byte
    MOVE?BA  _d_index  
    ADDWF  FSR0L,F
    MOVF   INDF0,W
    ;L?CALL seg_val
    MOVE?AB _segment
    MOVE?BB  _d_index ,_tmp
    BANKSEL   _tmp
    MOVLW 1
    ADDWF  _tmp,F
    MOVLW 16
    BANKSEL   _d_pointer
    movwf _d_pointer
    BcF STATUS ,C
N_BIT 
    BANKSEL   _d_pointer
    RRF    _d_pointer,F
    BANKSEL   _tmp
    DECFSZ  _tmp,F
    GOTO N_BIT 
    MOVLW 1
    BANKSEL  _d_index
    ADDWF  _d_index,F
    MOVLW 3 
    ANDWF  _d_index,F
    BANKSEL  LPORT
    BCF LPORT ,_LPIN
    BANKSEL PIR1
    BCF     PIR1,3 
    BANKSEL  _segment
    MOVF    _segment,W   ;COMMENT USED TO INVERT DATA FOR COMMON cathode DISPLAY
    ;COMF    _segment,W  ;COMMENT USED TO INVERT DATA FOR COMMON ANODE DISPLAY
    BANKSEL SSP1BUF
    movwf   SSP1BUF
    BANKSEL PIR1
    BTFSs   PIR1,3
    GOTO    $-1
    BANKSEL  _d_pointer
    COMF    _d_pointer,W   ;COMMENT USED FOR COMMON cathode DISPLAY
    ;MOVF    _d_pointer,W  ;COMMENT USED FOR COMMON ANODE DISPLAY
    BANKSEL PIR1
    BCF     PIR1,3 
    BANKSEL SSP1BUF
    movwf   SSP1BUF
    BANKSEL PIR1
    BTFSs   PIR1,3
    GOTO    $-1
    BANKSEL  LPORT
    BSF LPORT ,_LPIN
    BANKSEL 0
    INT_RETURN
endasm