ChriX
Member
Good evening all. I wonder if anyone can see anything immediately wrong with my code excerpt below. I have spent a LONG time debugging this and I cannot get it to work as intended.
I put together a quick 64x16 LED matrix panel using shift registers, and am trying to drive it using a 16F870. I am driving it such that the rows are cycled top to bottom, and for each new row, the 64 bits are shifted in from right to left.
I have had no problem in putting together code to shift it, but the problem comes when I want to try and read a bitmap from a table.
SCREENLOOKUP is called with a value from 0 to 127 held in OFFSET. I have tested this by returning the value of OFFSET directly after SCREENLOOKUP is called, and I correctly get the binary values for 0 to 127 displayed via my LED matrix (see photo - it counts from L-R, T-B). This confirms that the offset value is normal, and that my SR routines are working correctly.
When I try to return the data from the table the chip seems to crash, and when using ICD will occasionally break at 0x00 when it hasn't been asked to, so I guess it's jumping somewhere it shouldn't. The OFFSET is generated as below, the code shows what is executed per row of the display.
Any help appreciated as I have now pretty much destroyed my code trying to work out what is wrong!
I put together a quick 64x16 LED matrix panel using shift registers, and am trying to drive it using a 16F870. I am driving it such that the rows are cycled top to bottom, and for each new row, the 64 bits are shifted in from right to left.
I have had no problem in putting together code to shift it, but the problem comes when I want to try and read a bitmap from a table.
Code:
org 0x200
SCREENLOOKUP
movlw high(SCREENDATA)
movwf PCLATH
movlw low(SCREENDATA)
addwf OFFSET,W
btfsc STATUS,C
incf PCLATH,F
movwf PCL
SCREENDATA
dt b'11111111', .... (128 bytes organised as 16 lines each with 8 bytes)SCREENLOOKUP is called with a value from 0 to 127 held in OFFSET. I have tested this by returning the value of OFFSET directly after SCREENLOOKUP is called, and I correctly get the binary values for 0 to 127 displayed via my LED matrix (see photo - it counts from L-R, T-B). This confirms that the offset value is normal, and that my SR routines are working correctly.
When I try to return the data from the table the chip seems to crash, and when using ICD will occasionally break at 0x00 when it hasn't been asked to, so I guess it's jumping somewhere it shouldn't. The OFFSET is generated as below, the code shows what is executed per row of the display.
Code:
movf CURRENT_ROWG,w
clrf CURRENT_ROWT
movwf CURRENT_ROWT
bcf STATUS,C
rlf CURRENT_ROWT,1
rlf CURRENT_ROWT,1
rlf CURRENT_ROWT,1
; shift the 64 cols of data
movlw b'00000000'
iorwf CURRENT_ROWT,W
movwf OFFSET
call SCREENLOOKUP
call SHIFTCOLS
movlw b'00000001'
iorwf CURRENT_ROWT,W
movwf OFFSET
call SCREENLOOKUP
call SHIFTCOLS
movlw b'00000010'
iorwf CURRENT_ROWT,W
movwf OFFSET
call SCREENLOOKUP
call SHIFTCOLS
movlw b'00000011'
iorwf CURRENT_ROWT,W
movwf OFFSET
call SCREENLOOKUP
call SHIFTCOLS
movlw b'00000100'
iorwf CURRENT_ROWT,W
movwf OFFSET
call SCREENLOOKUP
call SHIFTCOLS
movlw b'00000101'
iorwf CURRENT_ROWT,W
movwf OFFSET
call SCREENLOOKUP
call SHIFTCOLS
movlw b'00000110'
iorwf CURRENT_ROWT,W
call SCREENLOOKUP
call SHIFTCOLS
movlw b'00000111'
iorwf CURRENT_ROWT,W
movwf OFFSET
call SCREENLOOKUP
call SHIFTCOLS
bcf PIN_COL_TR
nop
bsf PIN_COL_TR
bcf PIN_ROW_EN
decf CURRENT_ROWG,f
bcf STATUS,C
rlf CURRENT_ROWL,f
btfsc STATUS,C
goto MOVEUPL
bcf STATUS,C
rlf CURRENT_ROWH,f
btfsc STATUS,C
goto MOVEDOWNL
goto ENDLOOP
MOVEUPL
movlw 1
movwf CURRENT_ROWH
movlw 0
movwf CURRENT_ROWL
goto ENDLOOP
MOVEDOWNL
movlw 1
movwf CURRENT_ROWL
movlw 0
movwf CURRENT_ROWH
; start from zero again on G
movlw b'00001111'
movwf CURRENT_ROWG
ENDLOOP
DELAY_MICRO 250
goto LOOP_BEGINAny help appreciated as I have now pretty much destroyed my code trying to work out what is wrong!