Well if you do not have command of the code and know what you are doing then
you should find out ;-)

-----Original Message-----
From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu]On Behalf
Of Roland
Sent: Friday, 21 January 2005 9:15 PM
To: Microcontroller discussion list - Public.
Subject: RE: [PIC] Looking for some simple A/D -> serial/usb code


Hi

I noticed the post ealier in the day, and wondered why these points were
not raised by the experts on your code, unless I've got the wrong end of
the stick;
- you refer to the F628, but I presume you mean F877
- you'r using interrupts, but org 04 is not defined or used
- you should write to the TRIS registers and others explicitly, instead of
alluding to them.
- when changing banks, you should define both RP1 and RP0, don't assume.
Also set IRP initially.
- there is overlap, but 4MHz is usually considered as XT, not HS
- you refer later to a 10MHz xtal freq in your A/D setting



At 06:06 PM 21/01/2005 +1000, you wrote:
>	LIST P=16F877A, R=DEC
>	#include "P16F877A.INC"
>	__config _HS_OSC & _LVP_OFF & _WDT_OFF & _PWRTE_ON & _BODEN_ON
>		ORG	0							; start code - this is where cpu starts on reset
>		goto	main					; goto main routine
>	   	cblock  0x20					; this is where the RAM starts in 16F628
>                temp                    ; Temoporary buffer
>				counta					; counter
>				countb					; counter
>				count1					; counter
>		endc							; we are done defining the RAM allocations
>main		bsf     STATUS,RP0              ; We need to switch to RAM bank 1
(set
>STATUS,RP0)
>        	movlw   b'00010000'             ; Set PORTA inputs and outputs
>        	movwf   PORTB					; This is really TRISA - it just maps as PORTA -
>with a bank swap
>        	movlw   b'00000111'             ; Set PORTB inputs and outputs
>        	movwf   PORTC					; This is really TRISB - it just maps as PORTB -
>with a bank swap
>	    	movlw	b'00000000'				; set port D as all outputs
>		movwf	PORTD					; This is really TRISD - it just maps as PORTB - with a
>bank swap
>		movlw   b'11010000'             ; INTF hi/lo, TMR0/2
>		movwf   TMR0					; This is really OPTION_REG - it just maps as TMR0 -
with
>a bank swap
>	    	movlw   b'00100010'             ; USART RX interrupt ON bit 5
76X43210
>        	movwf   PIR1                    ; This is really PIE1 - it just
>maps as PIR1 - with a bank swap
>	    	movlw	b'00000000'				; A/D right justified data bit [7], A/D clock
>rate bit [6]
>		movwf   ADCON0          		; commit A/D settings
>	      movlw   d'128'					; 4K8 data speed @ 10MHz xtal freq (9600 is
d'64')
>        	movwf   TXREG                   ; This is really SPBRG_REG - it
>just maps as TXREG - with a bank swap
>	    	bcf     STATUS,RP0              ; back to RAM page 0
>        	clrf    PIR1                    ; Reset PERIF interrupt bit
>        	movlw   b'01000000'             ; PIE1 and RB0 interrupt on
>		movwf	INTCON					; set the bits in the INTCON
>        	movlw   b'00000001'				; load 00000001
>        	movwf   T1CON                   ; TMR1 /1, on
>		movlw	b'00000000'				; load 00000000
>		movwf	T2CON					; TMR2 /1, off
>  		movlw   b'00000001'     		; A/D FOsc/2 bit [7-6], A/D Ch0 bits [5-3],
>A/D turn on bit [0]
>        	movwf   ADCON0					; commit A/D settings
>
>sample
>
>start 	bsf     ADCON0,GO       		; start A/D conversion
>wait		btfsc   ADCON0,GO       		; wait for conversion to complete
>        	goto    wait					; if A/D not ready just loop
>
>		movf	ADRESH,W				; high 8 bits of results
>		call	send
>		movf	ADRESL,W				; low 8 bits of results
>		call	send
>
>		goto	start
>
>send		movwf	TXREG					; send the data
>		bsf	STATUS,RP0				; swap to bank 1
>send2		btfss	RCSTA,TRMT				; test to see if char tx
>		goto 	send2					; loop until character away
>		bcf 	STATUS,RP0				; set the bank back again
>		return 					; return to where sub was called
>
>Delay255
>		movlw	0xff					;delay 255 ms (4 MHz clock)
>		goto	d0
>Delay100
>		movlw	d'100'					;delay 100ms (4 MHz clock)
>		goto	d0
>Delay50	movlw	d'50'					;delay 50ms (4 MHz clock)
>		goto	d0
>Delay20	movlw	d'20'					;delay 20ms (4 MHz clock)
>		goto	d0
>Delay1	movlw	d'1'
>		goto	d0
>Delay5	movlw	0x05					;delay 5.000 ms (4 MHz clock)
>d0		movwf	count1
>d1		movlw	0xC7					;delay 1ms (4 MHz clock)
>		movwf	counta
>		movlw	0x01
>		movwf	countb
>Delay_0	decfsz	counta, f
>		goto	$+2
>		decfsz	countb, f
>		goto	Delay_0
>		decfsz	count1	,f
>		goto	d1
>		return
>longdelay								; this is the long delay 1 second (4 MHz clock)
>		call	Delay255				; delay
>		call	Delay255				; delay
>		call	Delay255				; delay
>		call	Delay255				; delay
>		return							; return to where sub was called
>		end								; end of file
>
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>
Regards
Roland Jollivet

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