; ; lcd_video7.asm: 09/12/08 Jeff Keyzer http://mightyohm.com ; ; Generates an RGB Video Signal (noninterlaced) using PIC16F628 @ 20MHz ; CSYNC->RA0, RED->RB0, GREEN->RB1, BLUE->RB2 ; External resistors needed to drop RGB voltages to 0.7Vpp ; horizontal sync is 4us for every 64us line ; vertical sync is 1 full line out of every 262 lines (once per field) ; CSYNC is composite sync, carries both sync signals (inverse TTL logic) ; ; ; v1 - display one row (12 pixels) broken implementation of image table ; v2 - image table fixed, code needs to be optimized ; v3 - added multiple rows of pixels ; v4 - added 2nd image and routine to alternate between them every FIELDSPERIMG fields ; v5 - added more images and routine to rotate between them ; v6 - changed image selection routine to alternate between two images every FIELDSPERIMG ; fields, and change images every IMGREPEAT cycles ; v7 - cleaned up code, added more comments and better variable names ; ; Note: PC clock is xtal/4 so for 20MHz clock that gives 5 instr/us (or 0.2us/instr) ; ; Includes LIST R=DEC ifdef __16F628 INCLUDE "p16f628.inc" endif ; Special Function Registers ifdef __16F628 __CONFIG _CP_OFF & _DATA_CP_OFF & _WDT_OFF & _HS_OSC & _PWRTE_ON & _LVP_OFF & _MCLRE_ON & _BODEN_ON endif ; Variables CBLOCK 0x070 ; start of general purpose registers (16 bytes) ; 0x070 is special because it can be accessed from any bank i, linecount, blankcnt, Dlay, pxline_cnt, imageoffset, tableindex:2, array_offset, fieldctr, imagecnt, alienstate, flag ENDC Image EQU 0x020 ; Here is where we store the currently displayed image ; 80 bytes of data memory in bank 0 ; Macros wait1us MACRO ; wait 1us (5 instructions at 20MHz) goto $+1 ; 0.4us (2 instr) goto $+1 ; 0.4us (2 instr) nop ; 0.2us (1 instr) ENDM dnop MACRO ; equivalent of two nop's goto $+1 ; only one instruction, does nothing, takes 2 instr cycles ENDM blankline MACRO ; Blank line, has HSYNC but no video data bcf PORTA, CSYNC ; Start of sync pulse dnop dnop ; delay=1us wait1us ; 2us wait1us ; 3us wait1us ; 4us bsf PORTA, CSYNC ; sync pulse end, now wait 60us (295 instr) movlw 0x3B ; load delay into w call Delay ; ENDM ; Definess #define CSYNC 0 ; PORTA bit 0 #define RED 0 ; PORTB bit 0 #define GREEN 1 ; PORTB bit 1 #define BLUE 2 ; PORTB bit 2 #define VISLINES 0xF3-3 ; Visible lines (243 - 3) throw away 3 lines so 240/8 is an integer #define BLANKLINES 0x11 ; Blanking interval (17 lines) #define PIXELS 0x0C ; Pixels per line (8) #define PXLINES 0x1E ; Lines per pixel (30) #define FIELDSPERIMG 0x1F ; Fields per image, controls speed of animation #define IMGREPEAT 0x09 ; Number of times to repeat an image before moving to the next one #define STATES 0x03 ; Number of states for the alien selection state machine ; Set program origin at base of program memory org 0x00 Init ; Set up hardware and initialize variables, etc. clrf PORTA ; Clear PORTA (set all outputs low) clrf PORTB ; Clear PORTB movlw 0x07 ; CM[2:0] = 111 (disabled) movwf CMCON ; Disable comparator so we can use RA0 as an output ; While in bank1, (REGISTER^0x80) gets rid of annoying warning message about banks in MPLAB bsf STATUS, RP0 ; Change to bank 1 bcf (OPTION_REG^0x80), 7 ; Enable PORTB pullups bcf (TRISA^0x80), CSYNC ; Set CSYNC to output movlw 0xF8 ; Set RB0-RB2 to output (RGB) movwf (TRISB^0x80) bcf STATUS, RP0 ; Back to bank 0 ; Initialize variables movlw VISLINES movwf linecount ; start linecounter at top of visible image movlw PIXELS/2 ; Pixels are read two at a time (one nibble per pixel) movwf i ; Counter for reading image table into memory movlw PXLINES ; # of lines each pixel lasts for movwf pxline_cnt ; counter to keep track of those lines clrf imageoffset ; imageoffset allows us to select which image to load into memory ; and is relative to the base address of the first image lookup table ; Only 8 bits - limits how far we can jump in the LUT movlw FIELDSPERIMG movwf fieldctr ; Set field counter, determines interval between images movlw IMGREPEAT movwf imagecnt ; Set image counter, how many frames should each alien be displayed clrf flag ; Flag to display frame 1 or 2 of each alien animation clrf alienstate ; Number of alien to display, 0-2 ; Begin main program loop ; Starting here, every instruction matters if we expect to maintain video timings across field vsync ; Vertical Sync - Hold CSYNC low for a full line (64us) bcf PORTA, CSYNC movlw 0x3D ; 62us delay + 2us at end for instructions = 64us call Delay ; Delay takes value in 'w' and delays 5*(w-1)-10 instructions ; Get ready to load image to display into memory movlw Image ; load address of image array movwf FSR ; set pointer to image array movf imageoffset, w ; Preload table offset for desired image movwf tableindex clrf tableindex + 1 ; At present imageoffset is only 1 byte wide clrf array_offset ; offset into image array in data memory movlw BLANKLINES ; initialize blanking interval counter movwf blankcnt dnop blankint ; Blanking interval (17 lines), has HSYNC but no video data bcf PORTA, CSYNC ; Start of sync pulse dnop dnop ; delay=1us wait1us ; 2us wait1us ; 3us wait1us ; 4us bsf PORTA, CSYNC ; end of HSYNC movlw 0x1B ; any unused instruction cycles get taken care of here call Delay dnop dnop nop tableread ; Reads a line from ImageTable, stores into memory starting at addr 'Image' movlw PIXELS/2 ; we read 2 pixels at a time from the table movwf i ; counter for table read tableloop call ImageTable ; table lookup routine movwf INDF ; store result in data memory so we can access it quickly later incf FSR, f ; move to next location in data memory incf tableindex, f ; move to next location in table btfsc STATUS, Z ; if tableindex=0 after incf we need to increment the high byte incf tableindex + 1, f xorlw 0xFF ; xor=0 only if table returned 0xFF (signals end of image) btfsc STATUS, Z goto table_exit ; we're done, stop (scroll way down to see the code for this) nop decfsz i, f ; when i=0 we have read a full line of pixels goto tableloop nop blanking_reentry ; if table read 0xFF we jump away to kill time and come back here decfsz blankcnt, f goto blankint ; write another blank line clrf PCLATH ; 1 spare instruction on loop exit hsync_loop bcf PORTA, CSYNC ; Start of sync pulse dnop dnop ; delay=1us wait1us ; 2us wait1us ; 3us wait1us ; 4us bsf PORTA, CSYNC ; sync pulse end, we have 8us to do stuff before visible part of line movlw 0x05 ; chew up any leftover instruction cycles here call Delay movlw PIXELS/2 ; each byte contains two pixels movwf i ; counter for pixel pairs on each line dnop dnop movlw Image ; starting address of image data addwf array_offset, w ; offset into array for desired line movwf FSR ; set pointer to image swapf INDF, w ; swap nibbles so we display high nibble first visible movwf PORTB ; BEGIN VISIBLE LINE movf INDF, w ; move unswapped byte to w so we can show other pixel incf FSR, f ; get ready for next pair of pixels dnop wait1us ; if we wanted higher resolution we'd get rid of these waits wait1us ; but then we'd run out of data memory pretty fast wait1us movwf PORTB ; display other pixel in the pair (low nibble) wait1us wait1us wait1us swapf INDF, w ; get ready for first pixel on next line decfsz i, f goto visible wait1us dnop ; The next 16 lines have to do with the fact that we need a pixel to last more than 1 line in the picture ; there is probably a better way to do this with fewer instructions. movlw PIXELS/2 ; preload array offset decfsz pxline_cnt, f ; if counter=0 it's time to increment array offset for next line goto $+2 addwf array_offset, f clrf PORTB ; END VISIBLE LINE ; We have 2us from here to beginning of scanline dnop movlw PXLINES ; if the pxline counter hits zero we need to reset it movf pxline_cnt, f ; wish I could find a way to do this in less instructions btfsc STATUS, Z movwf pxline_cnt ; if counter=0, reset it decfsz linecount, f ; check if we have more visible lines to display goto hsync_loop ; we're not done with the field, go back and do another line nop blankline ; 243/8 has remainder 3, so we need 3 blank lines here + final blank before VSYNC blankline blankline ; Blank line, has HSYNC but no video data, a little short to allow time for loop return bcf PORTA, CSYNC ; Start of sync pulse dnop dnop ; delay=1us wait1us ; 2us wait1us ; 3us wait1us ; 4us bsf PORTA, CSYNC ; HSYNC pulse end movlw 0x34 ; load delay into w call Delay movlw VISLINES movwf linecount nop decfsz fieldctr, f ; test is fieldctr=0, if so it's time to change images goto $+2 goto chooseimage wait1us ; We didn't choose a new image so we have a bunch of leftover instructions to kill wait1us wait1us wait1us wait1us dnop goto vsync ; END OF FIELD, time to vsync and start over again ; END OF MAIN PROGRAM ; Subroutines chooseimage ; State machine and some counters determine what should be displayed in a given field ; This code only gets executed every FIELDSPERIMG fields (slowly compared to the main program loop) decfsz imagecnt, f ; We change the displayed alien when imagecnt hits zero goto $+2 incf alienstate, f movlw STATES ; If present state is higher than number of valid states then reset it xorwf alienstate, w ; if this returns zero it's time for a reset btfsc STATUS, Z clrf alienstate movlw IMGREPEAT ; The image counter keeps track of how long a particular alien should be displayed movf imagecnt, f btfsc STATUS, Z ; if it's zero, reset it movwf imagecnt ; movlw FIELDSPERIMG ; movf fieldctr, f ; btfsc STATUS, Z ; movwf fieldctr ; if fieldctr=0, reset it movlw FIELDSPERIMG ; we got here, so it must be time to reset the field counter movwf fieldctr dnop nop movf alienstate, w ; alien selection state machine addwf PCL, f goto Alien1 goto Alien2 goto Alien3 Alien1 movlw Image1-Image1 ; compute table offset for 1st image movwf imageoffset ; preload imageoffset with first image movlw Image2-Image1 ; computer table offset for 2nd image btfsc flag, 0 ; if we showed image 1 last time movwf imageoffset ; load image 2 offset instead comf flag, f ; invert the flag so next time we show the opposite image goto vsync ; we're done with the field, start the next field with a new image Alien2 movlw Image3-Image1 ; see Alien1 for comments movwf imageoffset movlw Image4-Image1 btfsc flag, 0 movwf imageoffset comf flag, f goto vsync Alien3 movlw Image5-Image1 ; see Alien1 for comments movwf imageoffset movlw Image6-Image1 btfsc flag, 0 movwf imageoffset comf flag, f goto vsync table_exit ; exit routine for table if 0xFF was read (signals table end) decf FSR, f ; this keeps us from overwriting extra memory decf tableindex, f movlw 0x18 ; kill some cycles so each blank line always takes the same time call Delay goto blanking_reentry ; go back to finish blanking interval Delay ; Delays 5*(w-1)+10 cycles including prev inst, function call, and movlw in main loop movwf Dlay ; (1) nop Back decfsz Dlay, f ; (1 or 2) normal loop takes 5 clocks to get back here goto Bounce ; (2) return ; (2) END OF FUNCTION Bounce goto Back ; (2) we kill 4 clocks by jumping and returning ; IMAGE DATA ; Store image to display at base of 2nd block of program memory org 0x0400 ImageTable ;Image stored as two pixels per byte, in reverse order (low nibble of each byte comes first) movlw HIGH Image1 addwf tableindex + 1, w movwf PCLATH movlw Image1 & 0x0FF addwf tableindex, w btfsc STATUS, C incf PCLATH, f movwf PCL ; this modifies PCL so takes 2 instructions!! Image1 ; Begin Alien1 Closed Image retlw 0x00 retlw 0x00 retlw 0x11 retlw 0x11 retlw 0x00 retlw 0x00 retlw 0x01 retlw 0x11 retlw 0x11 retlw 0x11 retlw 0x11 retlw 0x10 retlw 0x11 retlw 0x11 retlw 0x11 retlw 0x11 retlw 0x11 retlw 0x11 retlw 0x11 retlw 0x10 retlw 0x01 retlw 0x10 retlw 0x01 retlw 0x11 retlw 0x11 retlw 0x11 retlw 0x11 retlw 0x11 retlw 0x11 retlw 0x11 retlw 0x00 retlw 0x11 retlw 0x10 retlw 0x01 retlw 0x11 retlw 0x00 retlw 0x01 retlw 0x10 retlw 0x01 retlw 0x10 retlw 0x01 retlw 0x10 retlw 0x00 retlw 0x11 retlw 0x00 retlw 0x00 retlw 0x11 retlw 0x00 retlw 0xFF ; end of image Image2 ; Begin Alien1 Open Image retlw 0x00 retlw 0x00 retlw 0x11 retlw 0x11 retlw 0x00 retlw 0x00 retlw 0x01 retlw 0x11 retlw 0x11 retlw 0x11 retlw 0x11 retlw 0x10 retlw 0x11 retlw 0x11 retlw 0x11 retlw 0x11 retlw 0x11 retlw 0x11 retlw 0x11 retlw 0x10 retlw 0x01 retlw 0x10 retlw 0x01 retlw 0x11 retlw 0x11 retlw 0x11 retlw 0x11 retlw 0x11 retlw 0x11 retlw 0x11 retlw 0x00 retlw 0x01 retlw 0x10 retlw 0x01 retlw 0x10 retlw 0x00 retlw 0x00 retlw 0x11 retlw 0x01 retlw 0x10 retlw 0x11 retlw 0x00 retlw 0x11 retlw 0x00 retlw 0x00 retlw 0x00 retlw 0x00 retlw 0x11 retlw 0xFF ; Signals end of image Image3 ; Begin Alien2 Closed Image retlw 0x00 retlw 0x20 retlw 0x00 retlw 0x00 retlw 0x20 retlw 0x00 retlw 0x00 retlw 0x02 retlw 0x00 retlw 0x02 retlw 0x00 retlw 0x00 retlw 0x00 retlw 0x22 retlw 0x22 retlw 0x22 retlw 0x20 retlw 0x00 retlw 0x02 retlw 0x20 retlw 0x22 retlw 0x20 retlw 0x22 retlw 0x00 retlw 0x22 retlw 0x22 retlw 0x22 retlw 0x22 retlw 0x22 retlw 0x20 retlw 0x20 retlw 0x22 retlw 0x22 retlw 0x22 retlw 0x20 retlw 0x20 retlw 0x20 retlw 0x20 retlw 0x00 retlw 0x00 retlw 0x20 retlw 0x20 retlw 0x00 retlw 0x02 retlw 0x20 retlw 0x22 retlw 0x00 retlw 0x00 retlw 0xFF ; Signals end of image Image4 ; Begin Alien2 Open Image retlw 0x00 retlw 0x20 retlw 0x00 retlw 0x00 retlw 0x20 retlw 0x00 retlw 0x20 retlw 0x02 retlw 0x00 retlw 0x02 retlw 0x00 retlw 0x20 retlw 0x20 retlw 0x22 retlw 0x22 retlw 0x22 retlw 0x20 retlw 0x20 retlw 0x22 retlw 0x20 retlw 0x22 retlw 0x20 retlw 0x22 retlw 0x20 retlw 0x22 retlw 0x22 retlw 0x22 retlw 0x22 retlw 0x22 retlw 0x20 retlw 0x02 retlw 0x22 retlw 0x22 retlw 0x22 retlw 0x20 retlw 0x00 retlw 0x00 retlw 0x20 retlw 0x00 retlw 0x00 retlw 0x20 retlw 0x00 retlw 0x02 retlw 0x00 retlw 0x00 retlw 0x00 retlw 0x02 retlw 0x00 retlw 0xFF ; Signals end of image Image5 ; Begin Alien3 Closed Image retlw 0x00 retlw 0x00 retlw 0x04 retlw 0x40 retlw 0x00 retlw 0x00 retlw 0x00 retlw 0x00 retlw 0x44 retlw 0x44 retlw 0x00 retlw 0x00 retlw 0x00 retlw 0x04 retlw 0x44 retlw 0x44 retlw 0x40 retlw 0x00 retlw 0x00 retlw 0x44 retlw 0x04 retlw 0x40 retlw 0x44 retlw 0x00 retlw 0x00 retlw 0x44 retlw 0x44 retlw 0x44 retlw 0x44 retlw 0x00 retlw 0x00 retlw 0x00 retlw 0x40 retlw 0x04 retlw 0x00 retlw 0x00 retlw 0x00 retlw 0x04 retlw 0x04 retlw 0x40 retlw 0x40 retlw 0x00 retlw 0x00 retlw 0x40 retlw 0x40 retlw 0x04 retlw 0x04 retlw 0x00 retlw 0xFF ; Signals end of image Image6 ; Begin Alien3 Open Image retlw 0x00 retlw 0x00 retlw 0x04 retlw 0x40 retlw 0x00 retlw 0x00 retlw 0x00 retlw 0x00 retlw 0x44 retlw 0x44 retlw 0x00 retlw 0x00 retlw 0x00 retlw 0x04 retlw 0x44 retlw 0x44 retlw 0x40 retlw 0x00 retlw 0x00 retlw 0x44 retlw 0x04 retlw 0x40 retlw 0x44 retlw 0x00 retlw 0x00 retlw 0x44 retlw 0x44 retlw 0x44 retlw 0x44 retlw 0x00 retlw 0x00 retlw 0x04 retlw 0x04 retlw 0x40 retlw 0x40 retlw 0x00 retlw 0x00 retlw 0x40 retlw 0x00 retlw 0x00 retlw 0x04 retlw 0x00 retlw 0x00 retlw 0x04 retlw 0x00 retlw 0x00 retlw 0x40 retlw 0x00 retlw 0xFF ; Signals end of image end