ADC reading - Page 2 - Electronic Circuits Projects Diagrams Free

gramo · 25th March 2007, 08:09 AM

Considered a higher level programming language such as Proton?

Code:

Result = ADIN 0

Result = Result * 5 / 1023

Select Result

	   Case >= 3.000
	   		LED_1 = 1
	   Case 1.700 To 2.999
	   		LED_1 = 0
	   Case < 1.700
	   		LED_1 = 1
EndSelect

hjl4 · 1st April 2007, 01:08 PM

Can anyone go over this code, and tell me if I'm on right track. I tried the MPLAB simulator, but I am at a loss when it comes to (stimulus functions).

This code was partially copied from Pommie(thanks), and I hope it is well implemented.
All it does is read AN0 and AN1, and compare the results to < than or > than a certain value, and if out of range, LED goes on GP5. If in range LED stays off.

I hope code OK. May need some tweaking.

I know it's been a while since original post, but my family and work, are also a priority.

Here it is,

Code:

	list      p=12f675           ; list directive to define processor
	#include <p12f675.inc>        ; processor specific variable definitions

	errorlevel  -302              ; suppress message 302 from list file

	__CONFIG   _CP_OFF & _CPD_OFF & _BODEN_OFF & _MCLRE_OFF & _WDT_OFF & _PWRTE_ON & _INTRC_OSC_NOCLKOUT 

; '__CONFIG' directive is used to embed configuration word within .asm file.
; The lables following the directive are located in the respective .inc file.
; See data sheet for additional information on configuration word settings.




;***** VARIABLE DEFINITIONS

Word equ 0x30 





;**********************************************************************
		ORG     0x000             ; processor reset vector
		goto    main              ; go to beginning of program
	

		ORG     0x004             ; interrupt vector location
		

; isr code can go here or be located as a call subroutine elsewhere



; these first 4 instructions are not required if the internal oscillator is not used
main
		call    0x3FF             ; retrieve factory calibration value
		bsf     STATUS,RP0        ; set file register bank to 1 
		movwf   OSCCAL            ; update register with factory cal value 
		bcf     STATUS,RP0        ; set file register bank to 0


;*******************************************************************************************************
;**************************************  Begining of application code  *********************************
;*******************************************************************************************************


portsetup
                        ; ensure Bank "0" is previously selected
       clrf GPIO        ; clear GPIO 
                        ; the default chip configuration upon start up, or reset, is analogue input on GP0, GP1, GP2 and GP4
                        ; to alter this configuration, next 2 instructions are necessary, customize per your application.
       movlw 03h        ; move literal 03h working register
       movwf ANSEL      ; move working register to file ANSEL, setting GP2 as digital input and GP1 and GP0 as analogue input.                 
       movlw 07h        ; move literal to working register 
       movwf CMCON      ; turn comparators off as they are not used here
       bsf STATUS, RP0  ; switch to Bank "1" to set up ports
       movlw 0Bh        ; move literal to working register, 0Bh (001011b) (1 = input, 0 = output)
       movwf TRISIO     ; move working register value to TRISIO setting GP3, GP1 and GP0, as inputs, and GP2, GP4 and GP5, as digital outputs.
       bcf STATUS, RP0  ; return to Bank "0"
       
start  
       nop              ; small delay to settle micro
       nop
       nop
       nop
       nop
       btfss GPIO,3     ; check to see if PTO is engaged.(high) if set then skip next instruction
       goto start       ; if not set, loop back to start
       call Init_ADC0
       call Read_ADC1
       nop
       nop
       nop
       call result
       nop
       nop
       nop              ; small delay to settle micro
       btfss GPIO,3     ; check to see if PTO is engaged.(high) if set then skip next instruction
       goto start       ; if not set, loop back to start       
       call Init_ADC1
       nop
       nop
       nop
       call Read_ADC2
       nop
       nop
       nop
       call result
       goto start

Init_ADC0					;set for AN0
; Set ADCON0
    		movlw   b'10000001' 
    		movwf   ADCON0     ; bit 7 is set meaning results will be right justified, and bit 0 is also set, meaning A/D module is operating. no other bit are set so Channel 00 for AN0 will be read.
; Set ADCON1
    		BANKSEL ANSEL
    		movlw   b'10100001'
    		movwf   ANSEL      ; bit 7 is set, but is unimplemented. bit 0 is set, meaning GP0(AN0) is assigned as an analogue input.
    		BANKSEL ADCON0     ; switch to bank 0.
		    return

Init_ADC1					   ; set for AN1
; Set ADCON0
    		movlw   b'10000101'
    		movwf   ADCON0     ; bit 7 is set meaning results will be right justified, and bit 0 is also set, meaning A/D module is operating. bit 2 is set, meaning Channel 01 for AN1 is ready for reading.
; Set ADCON1
    		BANKSEL ANSEL
    		movlw   b'10100101'
    		movwf   ANSEL      ; bit 7 is set, but is unimplemented. bit 0 and 2 are  set, meaning GP0(AN0) and GP2(AN1), are assigned as an analogue input.
    		BANKSEL ADCON0
	    	return
         
Read_ADC1   ; read CHS0 ( channel 0)
    		bsf	ADCON0, GO_DONE		; initiate conversion
    		btfsc   ADCON0, GO_DONE
    		goto    $-1			    ; wait for ADC to finish

    		movf    ADRESH,W        ; move results from ADRESH file to W
    		movwf   Word            ; move value from W to file named Word
    		BANKSEL ADRESL          ; switch to bank 1
    		movf    ADRESL,W        ; move results from ADRESL file to W
    		movwf   Word+1          ; move value from W to file named Word and add 1
    		return
    		
    		
Read_ADC2   ; read CHS1 (channel 1)
    		bsf	ADCON0, GO_DONE		; initiate conversion
    		btfsc   ADCON0, GO_DONE
    		goto    $-1			    ; wait for ADC to finish

    		movf    ADRESH,W        ; move results from ADRESH file to W
    		movwf   Word            ; move value from W to file named Word
    		BANKSEL ADRESL          ; switch to bank 1
    		movf    ADRESL,W        ; move results from ADRESL file to W
    		movwf   Word+1          ; move value from W to file named Word and add 1
    		return
    		
    		
result
            movlw	low(0x015B)     ; load W with value of low 0x15
	        subwf	Word,W          ; subtract value in file Word, with value in W
        	movlw	high(0x015B)    ; load W with value of 0x15
          	btfss	STATUS,C        ; check to see if bit "C", in Status is set.
         	movlw	high(0x015B)+1  ; load W with value high 0x15 and add 1
        	subwf	Word+1,W        ; subtract value in file Word, with value in W
            btfss	STATUS,C        ; carry clear if word is less than 0x15B
	        call	LEDoff
         	movlw	low(0x0266)
        	subwf	Word,W
        	movlw	high(0x0266)
         	btfss	STATUS,C
         	movlw	high(0x0266)+1
	        subwf	Word+1,W
            
        	btfsc	STATUS,C        ; carry set if word is greater or equal to 0x266
	        call	LEDon
	        goto start

            ; turn LED off here 
	
	
	
		
LEDon
    
    bsf GPIO,5                      ; set bit 5 of GPIO register to 1 (high)
    return	
    
LEDoff
   
    bcf GPIO,5                      ; set bit 5 of GPIO register to 0 (low)
    return        		
; initialize eeprom locations	
   

		ORG	0x2100
		DE	0x00, 0x01, 0x02, 0x03


		END                       ; directive 'end of program'

Thanks to all.

eng1 · 1st April 2007, 01:48 PM

I would suggest to configure the ansel register at the beginnig only.

Code:

       movlw  b'00010011'
       movwf ANSEL

I would turn the ADC off before selecting channels and insert a short delay after turning it on again. Are you using low impedance sources?

hjl4 · 1st April 2007, 02:14 PM

Quote:

eng1

I would suggest to configure the ansel register at the beginnig only.
Code:

movlw b'00010011' movwf ANSEL

I would turn the ADC off before selecting channels and insert a short delay after turning it on again. Are you using low impedance sources?

Ok I'll try that, as for low impedance , yes.

eng1 · 1st April 2007, 02:19 PM

It seems that you can select a channel without turning the ADC off, but a minimum delay is reqiuired. I'm reading AN546.

hjl4 · 1st April 2007, 02:33 PM

Yes it is what I thought, as App notes state that after read and conversion done, GO_DONE bit is cleared. as for delay, 5micro secs should do it? Right?

P.S. thanks for the help, eng1.

hjl4 · 1st April 2007, 02:42 PM

Ok so I modified my code, so ANSEL at the beginning of portsetup, is only time ANSEL is setup.

Pommie · 1st April 2007, 02:44 PM

You need to change the comparison slightly. What it is doing at the moment is checking if the voltage is less than 1.7V and if it is then turn on LED. It then returns, because of the call, and checks if it's less than 3.0V which it will be as 1.7 is less than 3.0 so it turns it off again.

Try changing the code to,

Code:

result
            	movlw	low(0x015B)     ; load W with value of low 0x15
	        subwf	Word,W          ; subtract value in file Word, with value in W
        	movlw	high(0x015B)    ; load W with value of 0x15
          	btfss	STATUS,C        ; check to see if bit "C", in Status is set.
         	movlw	high(0x015B)+1  ; load W with value high 0x15 and add 1
        	subwf	Word+1,W        ; subtract value in file Word, with value in W
            	btfss	STATUS,C        ; carry clear if word is less than 0x15B
	        goto	LEDon ;    <-----changed
         	movlw	low(0x0266)
        	subwf	Word,W
        	movlw	high(0x0266)
         	btfss	STATUS,C
         	movlw	high(0x0266)+1
	        subwf	Word+1,W
            
        	btfsc	STATUS,C        ; carry set if word is greater or equal to 0x266
	        goto	LEDon  ;   <------changed
	 ;       goto start	   <------removed

            ; turn LED off here 

LEDoff		;		<-------moved
		bcf GPIO,5                      ; set bit 5 of GPIO register to 0 (low)
		goto	start ; <-------changed
		
LEDon    
		bsf GPIO,5                      ; set bit 5 of GPIO register to 1 (high)
		goto	start ; <-------changed

HTH

Mike.

hjl4 · 1st April 2007, 02:48 PM

Thanks Pommie, It needed some straightening out. I will try and see if it works.

Pommie · 1st April 2007, 02:50 PM

Also, I noticed you don't allow a delay for the ADC acquisition time. I posted some code in this thread that shows how to read the ADC.

Mike.

hjl4 · 1st April 2007, 03:14 PM

Here is code modified. Pommie, you will probably recognize a lot of your work.

Please go over this, as it compiles well for asm.

Code:

Init_ADC0					        ;set for AN0
                                    ; Set ADCON0
    		movlw   b'10000001' 
    		movwf   ADCON0          ; bit 7 is set meaning results will be right justified, and bit 0 is also set, meaning A/D module is operating. no other bit are set so Channel 00 for AN0 will be read.
            return                        
    		
    		
		    

Init_ADC1					        ; set for AN1
                                    ; Set ADCON0
    		movlw   b'10000101'
    		movwf   ADCON0          ; bit 7 is set meaning results will be right justified, and bit 0 is also set, meaning A/D module is operating. bit 2 is set, meaning Channel 01 for AN1 is ready for reading.
            return
         
Read_ADC1   
            call delay1             ; small delay for A/D aquisition time.
                                    ; read CHS0 ( channel 0)
    		bsf	ADCON0, GO_DONE		; initiate conversion
    		btfsc   ADCON0, GO_DONE
    		goto    $-1			    ; wait for ADC to finish
            movf    ADRESH,W        ; move results from ADRESH file to W
    		movwf   Word            ; move value from W to file named Word
    		BANKSEL ADRESL          ; switch to bank 1
    		movf    ADRESL,W        ; move results from ADRESL file to W
    		movwf   Word+1          ; move value from W to file named Word and add 1
    		nop
    		nop
    		nop
    		return
    		
    		
Read_ADC2   
            call delay1             ; small delay for A/D aquisition time.                        
                                    ; read CHS1 (channel 1)
    		bsf	ADCON0, GO_DONE		; initiate conversion
    		btfsc   ADCON0, GO_DONE
    		goto    $-1			    ; wait for ADC to finish
         	movf    ADRESH,W        ; move results from ADRESH file to W
    		movwf   Word            ; move value from W to file named Word
    		BANKSEL ADRESL          ; switch to bank 1
    		movf    ADRESL,W        ; move results from ADRESL file to W
    		movwf   Word+1          ; move value from W to file named Word and add 1
    		nop
    		nop
    		nop
    		return
    		
    		
result
            movlw	low(0x015B)     ; load W with value of low 0x15
	        subwf	Word,W          ; subtract value in file Word, with value in W
        	movlw	high(0x015B)    ; load W with value of 0x15
          	btfss	STATUS,C        ; check to see if bit "C", in Status is set.
         	movlw	high(0x015B)+1  ; load W with value high 0x15 and add 1
        	subwf	Word+1,W        ; subtract value in file Word, with value in W
            btfss	STATUS,C        ; carry clear if word is less than 0x15B
	        call	LEDon
         	movlw	low(0x0266)
        	subwf	Word,W
        	movlw	high(0x0266)
         	btfss	STATUS,C
         	movlw	high(0x0266)+1
	        subwf	Word+1,W
            
        	btfsc	STATUS,C        ; carry set if word is greater or equal to 0x266
	        goto	LEDon
	        

            ; turn LED off here 
	
	
	
LEDoff
   
            bcf GPIO,5                      ; set bit 5 of GPIO register to 0 (low)
            goto start      		
LEDon
    
            bsf GPIO,5                      ; set bit 5 of GPIO register to 1 (high)
            goto start
            
delay1                                      ; will delay W*8 cycles including the call/return
		    addlw	0xff                    ; add -1 to W			1
	    	btfsc	STATUS,Z                ; =zero?				1/2
	    	goto	DoneDelay               ; yes, better get out of here	2
		    nop                             ; delay a bit			1
	    	goto	$+1                     ; delay a bit more		2
	    	goto	delay1                  ; go around again			2
DoneDelay	return	                        ;						2

Thanks.

Pommie · 1st April 2007, 03:24 PM

One little problem, the delay routine requires a value in W so put a movlw 5 before the call. The 5 assumes you have a low impedance source, if you get incorrect readings then change the 5 to something bigger. Apart from that it looks fine. Does it work?

Mike.

hjl4 · 1st April 2007, 03:28 PM

I will keep you posted, and will add value to W for delay.

I should know by early afternoon if it works. Thanks for all the help.

hjl4 · 1st April 2007, 09:56 PM

Properly selecting Banks in portsetup would help. But it didn't help. I'm still wondering what is wrong, and maybe 2V on AN0 or 1.5V on AN1 isn't enough.

I will try opamp LM358 or similar.

LED does not light up.

OH well, it's Sunday after all.

hjl4 · 12th April 2007, 01:49 PM

It's been a week, and I think I finally got it. Here is code, and again if it looks like you can improve on it, let me know.

Code:

;***** VARIABLE DEFINITIONS

Word equ 0x30 





;**********************************************************************
		ORG     0x000             ; processor reset vector
		goto    main              ; go to beginning of program
	

		ORG     0x004             ; interrupt vector location
		

; isr code can go here or be located as a call subroutine elsewhere



; these first 4 instructions are not required if the internal oscillator is not used
main    
        
		call    0x3FF             ; retrieve factory calibration value
		bsf     STATUS,RP0        ; set file register bank to 1 
		movwf   OSCCAL            ; update register with factory cal value 
		bcf     STATUS,RP0        ; set file register bank to 0


;*******************************************************************************************************
;**************************************  Begining of application code  *********************************
;*******************************************************************************************************


portsetup
       bcf STATUS, RP0  ; ensure Bank "0" is previously selected 
                        ; The default chip configuration upon start up, or reset of 12f675, is analogue input on GP0, GP1, GP2 and GP4
                        ; to alter this configuration, next 2 instructions are necessary, customize per your application.
       movlw 07h        ; move literal to working register 
       movwf CMCON      ; turn comparators off as they are not used here
       bsf STATUS, RP0  ; switch to Bank "1" to set up analogue ports                 
       movlw 03h        ; move literal 03h working register
       movwf ANSEL      ; move working register to file ANSEL, setting GP1 and GP0 as analogue input.                 
       movlw 0Bh        ; move literal to working register, 0Bh (001011b) (1 = input, 0 = output)
       movwf TRISIO     ; move working register value to TRISIO setting GP3, GP1 and GP0, as inputs, and GP2, GP4 and GP5, as digital outputs.
       bcf STATUS, RP0  ; return to Bank "0"
       
start  
       nop              ; small delay to settle micro
       nop
       nop
       nop
       nop
       btfss GPIO,3     ; check to see if PTO is engaged.(high) if set then skip next instruction
       goto start       ; if not set, loop back to start
       call Init_ADC0
       call Read_ADC0
       nop
       nop
       BANKSEL GPIO     ; this is necessary only if control of pins,(such as outputs) on GPIO5 is needed after reading A/D.
       call result
       nop
       nop
       nop              ; small delay to settle micro
       btfss GPIO,3     ; check to see if PTO is engaged.(high) if set then skip next instruction
       goto start       ; if not set, loop back to start       
       call Init_ADC1
       call Read_ADC1
       nop
       nop
       BANKSEL GPIO     ; this is necessary only if control of pins,(such as outputs) on GPIO5 is needed after reading A/D.
       call result
       goto start

Init_ADC0					        
       movlw   b'10000001' 
       movwf   ADCON0   ; bit 7 is set meaning results will be right justified, and bit 0 is also set, meaning A/D module is operating. no other bits are set so Channel 00 for AN0 will be set for read.
       return                        
    		
    		
		    

Init_ADC1					        
    	movlw   b'10000101'
    	movwf   ADCON0  ; bit 7 is set meaning results will be right justified, and bit 0 is also set, meaning A/D module is operating. bit 2 is set, meaning Channel 01 for AN1 is set for reading.
        return	
         
Read_ADC0   
        call delay1             ; small delay for A/D aquisition time.
                                    ; read CHS0 ( channel 0)
        bsf	ADCON0, GO_DONE		; initiate conversion
    	btfsc   ADCON0, GO_DONE
    	goto    $-1			    ; wait for ADC to finish, after which GO/DONE bit is cleared automaticaly after conversion.
        movf    ADRESH,W        ; move results from ADRESH file to W
    	movwf   Word            ; move value from W to file named Word
    	BANKSEL ADRESL          ; switch to bank 1
    	movf    ADRESL,W        ; move results from ADRESL file to W
    	movwf   Word+1          ; move value from W to file named Word and add 1
    	nop
    	nop
    	nop
    	return
    		
    		
Read_ADC1   
        call delay1             ; small delay for A/D aquisition time.                        
                                    ; read CHS1 (channel 1)
    	bsf	ADCON0, GO_DONE		; initiate conversion
    	btfsc   ADCON0, GO_DONE
    	goto    $-1			    ; wait for ADC to finish, after which GO/DONE bit is cleared automaticaly after conversion
        movf    ADRESH,W        ; move results from ADRESH file to W
    	movwf   Word            ; move value from W to file named Word
    	BANKSEL ADRESL          ; switch to bank 1
    	movf    ADRESL,W        ; move results from ADRESL file to W
    	movwf   Word+1          ; move value from W to file named Word and add 1
    	nop
    	nop
    	nop
    	return
    		
    		
result
        movlw	low(0x015B)     ; load W with value of low 0x15
	    subwf	Word,W          ; subtract value in file Word, with value in W
        movlw	high(0x015B)    ; load W with value of 0x15
        btfss	STATUS,C        ; check to see if bit "C", in Status is set.
        movlw	high(0x015B)+1  ; load W with value high 0x15 and add 1
        subwf	Word+1,W        ; subtract value in file Word, with value in W
        btfss	STATUS,C        ; carry clear if word is less than 0x15B
	    call	LEDon
        movlw	low(0x0266)
        subwf	Word,W
        movlw	high(0x0266)
        btfss	STATUS,C
        movlw	high(0x0266)+1
	    subwf	Word+1,W
            
        btfsc	STATUS,C        ; carry set if word is greater or equal to 0x266
	    goto	LEDon
	        
LEDoff
   
        bcf GPIO,5              ; set bit 5 of GPIO register to 0 (low)
        goto start      		
LEDon
    
        bsf GPIO,5              ; set bit 5 of GPIO register to 1 (high)
        goto start
            
delay1      
        movlw 05h               ; will delay W*8 cycles including the call/return
		addlw	0xff            ; add -1 to W			1
	    btfsc	STATUS,Z        ; =zero?				1/2
	    goto	DoneDelay       ; yes, better get out of here	2
		nop                     ; delay a bit			1
	    goto	$+1             ; delay a bit more		2
	    goto	delay1          ; go around again			2
DoneDelay
    	return	                 



        
		END                       ; directive 'end of program'

Does anybody know what the minimum readable voltage on A/D module is???
Can it read 1 volt,to a maximum of 5v??
Is it necessary to amplify above 1 v as this is too low???

Thanks to all who have helped me.

P.S. what stumped me for so long, was the fact that, to control an output pin,after reading A/D, you have to switch back to bank "0", after manipulating value in ADRESL.
Otherwise nothing happens.

Also,the datasheet is wrong .

Code:

movlw 07h
movwf CMCON

This is example given to setup analogue pins on (ANSEL) register.
It does not setup ANSEL register or modify analogue inputs, but makes sure that Comparators are turned off.
[code]

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25th March 2007, 08:09 AM	(permalink)
gramo	Considered a higher level programming language such as Proton? Code: Result = ADIN 0 Result = Result * 5 / 1023 Select Result Case >= 3.000 LED_1 = 1 Case 1.700 To 2.999 LED_1 = 0 Case < 1.700 LED_1 = 1 EndSelect __________________ Spency. PIC Micro's - Your mind is the limit PIC's and interfacing with other devices - a PIC Basic Guide @ digital-diy.net

1st April 2007, 01:48 PM	(permalink)
eng1	I would suggest to configure the ansel register at the beginnig only. Code: movlw b'00010011' movwf ANSEL I would turn the ADC off before selecting channels and insert a short delay after turning it on again. Are you using low impedance sources?

1st April 2007, 02:19 PM	(permalink)
eng1	It seems that you can select a channel without turning the ADC off, but a minimum delay is reqiuired. I'm reading AN546.

1st April 2007, 02:33 PM	(permalink)
hjl4	Yes it is what I thought, as App notes state that after read and conversion done, GO_DONE bit is cleared. as for delay, 5micro secs should do it? Right? P.S. thanks for the help, eng1.

1st April 2007, 02:42 PM	(permalink)
hjl4	Ok so I modified my code, so ANSEL at the beginning of portsetup, is only time ANSEL is setup.

1st April 2007, 02:48 PM	(permalink)
hjl4	Thanks Pommie, It needed some straightening out. I will try and see if it works.

1st April 2007, 02:50 PM	(permalink)
Pommie	Also, I noticed you don't allow a delay for the ADC acquisition time. I posted some code in this thread that shows how to read the ADC. Mike.

1st April 2007, 03:24 PM	(permalink)
Pommie	One little problem, the delay routine requires a value in W so put a movlw 5 before the call. The 5 assumes you have a low impedance source, if you get incorrect readings then change the 5 to something bigger. Apart from that it looks fine. Does it work? Mike.

1st April 2007, 03:28 PM	(permalink)
hjl4	I will keep you posted, and will add value to W for delay. I should know by early afternoon if it works. Thanks for all the help.

1st April 2007, 09:56 PM	(permalink)
hjl4	Properly selecting Banks in portsetup would help. But it didn't help. I'm still wondering what is wrong, and maybe 2V on AN0 or 1.5V on AN1 isn't enough. I will try opamp LM358 or similar. LED does not light up. OH well, it's Sunday after all.