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The PBASIC version of Serout has a tremendously convenient feature; the ability to treat data for transmission as either bytes or numbers. The value 65, if sent as a byte, would appear as the letter "A" on the receiving end. If sent as a number, "65" shows up at the receiver. This routine, called BIN_ASC for binary-to-ASCII, converts a pair of bytes (interpreted as a 16-bit number) into text. For example, if the bytes both contain 0FFh, BIN_ASC creates a text string containing "65535" ready for transmission by Serout.
The routine suppresses leading zeros, just as the PBASIC version does. So the number 17 is output as "17" and not "00017".
BIN_ASC goes one step beyond the conversion built into the PBASIC's
Serout by allowing you to specify a fixed decimal point in positions 0
through 4 of the text string. Here are examples of the output:
Fixed Point at: Value = 1 Value = 65535 0 .00001 .65535 1 .0001 6.5535 2 .001 65.535 3 .01 655.35 4 .1 6553.5 5 1 65535By setting the fixed point to a value of 5 or greater, you can eliminate it entirely. BIN_ASC can also prepare data for other types of ASCII output devices, such as LCDs or parallel printers. Just write the driver to expect a Serout-style counted string, as described in the previous Serout entry.
The routine uses a short table called decade. Remember that tables and
subroutines must be located in the first 256 words of a 512-word program
memory page.
For a live demonstration, connect the circuit below to an erasable PIC or PIC emulator, such as the Parallax downloader. Assemble SEROUT_#.SRC from the accompanying disk and program the PIC or downloader with the assembled program. Make sure to use a 4-MHz clock on the PIC or downloader. Load a terminal program on the PC connected to the PIC and set it for 2400 baud, no parity, 8 data bits, 1 stop bit (N81). When you apply power to the PIC or reset the downloader, the string "655.35" will appear on the PC s creen.
; ; *************************************************************************** ; *** Bubble Software Parallax to PIC Source Converter. Copyright 1999. *** ; *** http://www.picnpoke.com email: sales@picnpoke.com *** ; *************************************************************************** ; ; BIN_ASC 16-bit value ; This routine converts a 16-bit number into a counted string of ; ASCII characters compatible with Serout. It suppresses ; leading zeros so that numbers like 17 are sent as "17" not "00017". P = pic16c55 #include <16c55.inc> ; processor assembler definitions _CONFIG _xt_osc & _wdt_off & _protect_off reset start buffer equ d'31' ; String buffer at end of memory. ASC_0 equ '0' ; ASCII numbers: 30h thru 39h. ASC_dp equ '.' ; ASCII char for decimal point (period). fix equ d'3' ; Position for fixed decimal point. org 8 dec_no Res d'1' ; Decade (1,10,100...) to work on. tempH Res d'1' ; 16-bit temporary variable used by tempL Res d'1' ; the BIN_ASC routine. hiB Res d'1' ; MSB of number to convert. lowB Res d'1' ; LSB of number to convert. flags Res 1 zs equ flags.0 ; Leading-zero suppression flag. org 0 decade ADDWF pcl RETLW d'39' RETLW d'16' RETLW d'3' RETLW d'232' RETLW d'0' RETLW d'100' RETLW d'0' RETLW d'10' RETLW d'0' RETLW d'1' start MOVLW 0x00FF ; To see routine's output, either MOVWF hiB MOVLW 0x00FF ; use the PSIM PIC simulator, or MOVWF lowB CALL BIN_ASC ; merge with Serout. GOTO $ ; Endless loop ; This routine accepts a 16-bit number in hiB, lowB and converts it into ; a counted ASCII text string located at the address "buffer." The buffer ; grows downward in memory. The first (0th) item in buffer is the number ; of characters in the string. BIN_ASC CLRF buffer ; Clear char count (item 0 in buf). CLRF flags ; Clear zs flag. CLRF dec_no ; Clear decade no. MOVLW buffer-1 ; Reserve 0th byte of buffer for count. MOVWF fsr BIN_ASC_loop MOVF dec_no,w ; Get 1st hex digit of decade no. CALL decade ; from the lookup table. MOVWF tempH INCF dec_no ; Get 2nd digit of decade no. MOVF dec_no,w ; from the table. CALL decade MOVWF tempL CALL d_point ; Insert decimal point. CALL sub_it ; Divide hiB,lowB by tempH,tempL MOVF indirect,w ; returning answer in indirect. BTFSC flags,d'0' ; If zs = 0 AND digit = 0 then GOTO BIN_ASC_no_zs BTFSC status,z ; digit is a leading zero to be GOTO BIN_ASC_no_zed BIN_ASC_no_zs MOVWF indirect ; ignored. Otherwise, it's either MOVLW ASC_0 ; an included zero (as in 7501) ADDWF indirect INCF buffer ; or a non-zero digit. DECF fsr ; Point to next memory location. BSF flags,d'0' ; First non-zero digit sets zs bit. BIN_ASC_no_zed INCF dec_no ; Next decade. MOVLW d'8' ; If dec_no = 8, we're down to ones. SUBWF dec_no,w BTFSS status,z GOTO BIN_ASC_loop ; Otherwise, do next decade. INCF dec_no ; Update dec_no CALL d_point ; and call d_point. MOVF lowB,w ; Whatever's left belongs in ones. MOVWF indirect MOVLW ASC_0 ; Add offset for conversion to ASCII. ADDWF indirect INCF buffer ; Add 1 to character count. RETLW 0h ; This routine performs division by iterated subtraction. It is efficient ; in this application because the dividend and divisor keep getting smaller ; as BIN_ASC runs, so the quotient is never larger than nine. A general- ; purpose division routine would be slower (and longer). sub_it CLRF indirect ; Clear to track no. of subtractions. sub_it_loop MOVF tempL,w ; Subtract LSB. SUBWF lowB BTFSC status,c ; If no borrow, continue w/MSB. GOTO sub_it_skip MOVLW d'1' ; Otherwise borrow from MSB. SUBWF hiB BTFSC status,c ; If borrow causes a carry, then GOTO sub_it_skip INCF hiB ; add numbers back and return. MOVF tempL,w ADDWF lowB RETLW 0h sub_it_skip MOVF tempH,w ; Subtract MSB. SUBWF hiB BTFSC status,c ; If no borrow, subtract again. GOTO sub_it_skip2 MOVF tempL,w ; Otherwise, undo the subtraction ADDWF lowB BTFSC status,c ; by adding entire 16-bit no. INCF hiB ; back together and return. MOVF tempH,w ADDWF hiB RETLW 0h sub_it_skip2 INCF indirect ; No borrow, so do it again. GOTO sub_it_loop ; This routine adds a decimal point in the location set by "fix" in the ; equates at the beginning of the program. The location of the decimal point ; is in front of the "fix"ed digit, numbered starting with 0. If you fix the ; point at 0, the first (0th) character in the string produced by BIN_ASC ; will be a decimal point. If you don't want a decimal point, either move ; it out of range (fix = 6), or delete this routine and the "call d_point" ; in the body of BIN_ASC above. d_point MOVLW fix*2+1 SUBWF dec_no,w BTFSS status,z RETLW 0h BSF flags,d'0' MOVLW ASC_dp MOVWF indirect INCF buffer DECF fsr RETLW 0h endSee also:
; BIN_ASC 16-bit value ; This routine converts a 16-bit number into a counted string of ; ASCII characters compatible with Serout. It suppresses ; leading zeros so that numbers like 17 are sent as "17" not "00017". buffer = 31 ; String buffer at end of memory. ASC_0 = '0' ; ASCII numbers: 30h thru 39h. ASC_dp = '.' ; ASCII char for decimal point (period). fix = 3 ; Position for fixed decimal point. org 8 dec_no ds 1 ; Decade (1,10,100...) to work on. tempH ds 1 ; 16-bit temporary variable used by tempL ds 1 ; the BIN_ASC routine. hiB ds 1 ; MSB of number to convert. lowB ds 1 ; LSB of number to convert. flags ds 1 zs = flags.0 ; Leading-zero suppression flag. device pic16c55,xt_osc,wdt_off,protect_off reset start org 0 decade jmp pc+w retw 39,16,3,232,0,100,0,10,0,1 start mov hiB, #0FFh ; To see routine's output, either mov lowB, #0FFh ; use the PSIM PIC simulator, or call BIN_ASC ; merge with Serout. jmp $ ; Endless loop ; This routine accepts a 16-bit number in hiB, lowB and converts it into ; a counted ASCII text string located at the address "buffer." The buffer ; grows downward in memory. The first (0th) item in buffer is the number ; of characters in the string. BIN_ASC clr buffer ; Clear char count (item 0 in buf). clr flags ; Clear zs flag. clr dec_no ; Clear decade no. mov fsr,#buffer-1 ; Reserve 0th byte of buffer for count. :loop mov w,dec_no ; Get 1st hex digit of decade no. call decade ; from the lookup table. mov tempH,w inc dec_no ; Get 2nd digit of decade no. mov w,dec_no ; from the table. call decade mov tempL,w call d_point ; Insert decimal point. call sub_it ; Divide hiB,lowB by tempH,tempL mov w,indirect ; returning answer in indirect. jb zs,:no_zs ; If zs = 0 AND digit = 0 then jz :no_zed ; digit is a leading zero to be :no_zs mov indirect,w ; ignored. Otherwise, it's either ADD indirect,#ASC_0 ; an included zero (as in 7501) inc buffer ; or a non-zero digit. dec fsr ; Point to next memory location. setb zs ; First non-zero digit sets zs bit. :no_zed inc dec_no ; Next decade. cse dec_no,#8 ; If dec_no = 8, we're down to ones. jmp :loop ; Otherwise, do next decade. inc dec_no ; Update dec_no call d_point ; and call d_point. mov indirect,lowB ; Whatever's left belongs in ones. ADD indirect,#ASC_0 ; Add offset for conversion to ASCII. inc buffer ; Add 1 to character count. ret ; This routine performs division by iterated subtraction. It is efficient ; in this application because the dividend and divisor keep getting smaller ; as BIN_ASC runs, so the quotient is never larger than nine. A general- ; purpose division routine would be slower (and longer). sub_it clr indirect ; Clear to track no. of subtractions. :loop sub lowB,tempL ; Subtract LSB. jc :skip ; If no borrow, continue w/MSB. sub hiB,#1 ; Otherwise borrow from MSB. jc :skip ; If borrow causes a carry, then inc hiB ; add numbers back and return. add lowB,tempL ret :skip sub hiB,tempH ; Subtract MSB. jc :skip2 ; If no borrow, subtract again. ADD lowB,tempL ; Otherwise, undo the subtraction snc ; by adding entire 16-bit no. inc hiB ; back together and return. ADD hiB,tempH ret :skip2 inc indirect ; No borrow, so do it again. jmp :loop ; This routine adds a decimal point in the location set by "fix" in the ; equates at the beginning of the program. The location of the decimal point ; is in front of the "fix"ed digit, numbered starting with 0. If you fix the ; point at 0, the first (0th) character in the string produced by BIN_ASC ; will be a decimal point. If you don't want a decimal point, either move ; it out of range (fix = 6), or delete this routine and the "call d_point" ; in the body of BIN_ASC above. d_point cse dec_no,#fix*2+1 ret setb zs mov indirect,#ASC_dp inc buffer dec fsr ret
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