Internal ADC reference at the output pin

Development Boards MicroMod
1

Hi, everybody. I am solving very easy task, but I am not able to achive the results…

It is simple. All I need is get the internal ADC reference of MSP430F2132 at the output pins Vref+ and Vref- (P2.4 resp. P2.3). I have tried almost everything including I/O pin function selection, ADC10AE0 analog (input) register, but nothing works. I believe there is nothing difficult about it, but I can not see it…

Relevant code part: (assume nothing else was done considering this issue)

mov.w #1011000000000000B, &ADC10CTL1
	
                ; input (Vcc-Vss)/2 (1011), sample clock inter. (00),
                ; straight binary output (0), not invert sample (0),
                ; clock divider /1 (000), ADC clock internal (00),
                ; single channel, single conversion (00),
                ; ADC busy 0 (0)
		     
mov.w #0010001001110000B, &ADC10CTL0	    
						
                ; VR+ = Vref, VR- = Vss (001), sample = 4 (00),	
                ; sampl. rate 50ksps (0), reference output (1), 
                ; ref. buffer all the time (0), not needed (0),
                ; Vref = 2,5V (1), ref. generator on (1),
                ; ADC10 on (1), interrupt enable (0),
                ; flag cleared (0), enable conversion (0),
                ; start sample and conversion (0)
 
jmp	$

Can anyone suggest, how can I get that internal reference to the output pins?

Thank you very much…

2

Did you hold the watchdog?

3

Yes, the watchdog is stopped.

Do I need to do anything with pins directions using PxDIR, or pin functions using PxSEL and PxSEL2, or anything else?

4

According to page 63 of the [MSP430F12x2 Mixed Signal Controller, the CAPD.x bit needs to be reset (0) along with the ADC10AE0.x bit being set (1).

HTH,

gm](http://focus.ti.com/lit/ds/symlink/msp430f2132.pdf)

5

Your suggestion does not work, I´ve tried it. Here is the code of the whole simplified programme, which should put the internal reference voltage of ADC10 at the pins 2.3 and 2.4. But when I connect voltmeter at these pins, I can see nothing…

    .cdecls C,LIST, "msp430x21x2.h"
     	          	             
;------------------------------------------------------------------------------
    .text                           ; Progam Start
;------------------------------------------------------------------------------
main		
         mov.w   #0x3FE, SP              ; Initialize stackpointer
         mov.w   #WDTPW+WDTHOLD, &WDTCTL ; Stop WDT
         mov.b	&CALBC1_16MHZ, &BCSCTL1 ; BCSCTL1 Calibration Data for 16MHz
			mov.b	&CALDCO_16MHZ, &DCOCTL  ; DCOCTL Calibration Data for 16MHz
			or.b    #0x80, &BCSCTL1;		  ; XT2 off, XTS = 0 low freq mode, ACLK divider 0
			or.b    #0x00, &BCSCTL2;		  ; mclk -> Dco, divider 1, smclk -> DCO, divider 1, internal Rco
			mov.b	#0x0C, &BCSCTL3;		  ; LFXT1 = extern watch krystal, 12,5 pF capacity
      
;********************************************************************
			bic.b	#00011000B, &CAPD2 	  ; P2.3 and P2.4 CAPD = 0 
			bis.b	#00011000B, &ADC10AE0	; P2.3 and P2.4 analog input enable
 
			mov.w #1011000000000000B, &ADC10CTL1
										; input (Vcc-Vss)/2 (1011), sample clock inter. (00),
										; straight binary output (0), not invert sample (0),
										; clock divider /1 (000), ADC clock internal (00),
										; single channel, single conversion (00),
										; ADC busy 0 (0)
		     
			mov.w #0010001001110000B, &ADC10CTL0	    
										; VR+ = Vref, VR- = Vss (001), sample = 4 (00),			 
										; sampl. rate 50ksps (0), REFERENCE OUTPUT (1), 
										; ref. buffer all the time (0), not needed (0),
										; Vref = 2,5V (1), REF. GENERATOR ON (1),
										; ADC10 on (1), interrupt enable (0),
										; flag cleared (0), enable conversion (0),
										; start sample and conversion (0)
  
			 
			
			jmp	$

		
;************************* INTERRUPT VECTORS **********************************
            .sect   ".reset"                ; MSP430 RESET Vector
            .short  main                    ;   
            .end

Thank you for any suggestions and tips.

6

Solved. The voltage has to be measured between P2.4 and GND and not between P2.4 and P2.3 as I thought.