Hi everyone. I'm connecting a potentiometer to my MSP430 RF2500 development
board. The potentiometer center and right output which creates the potential
differential that I need to measure to know the position of the
potentiometer are connected to P2.0 and P2.2 and the OA is set as general
purpose (which I guessed that it makes the difference of the potencial
between P2.0 and P2.2).

The range of the potentiometer goes from 100 mV to 2100 mV approx. That's
why I decided to set a gain of 1 (0+1) and set the upper reference voltage
to 2.5V (and the lower reference voltage to 0).

Well, after that, I set the ADC10. And the result? It doesn't work. The
ADC10MEM register always is 1023 (as if the result is over the range).

This is the code (sorry for the comments in spanish as i'm spanish)

#include "msp430x22x4.h"
void TXString( char* string, int length );

void main(void){
WDTCTL = WDTPW + WDTHOLD; // Stop WDT
long volt=0, posmin=0, posmax=0, dr=0, res=0, vmin=0, vmax=0;
long nmax=0, nmin=0, degC;
long posicion;



BCSCTL1 = CALBC1_1MHZ; // Set DCO
DCOCTL = CALDCO_1MHZ;
P3SEL = 0x30; // P3.4,5 = USCI_A0 TXD/RXD
P2DIR |= 0x00;


UCA0CTL1 |= UCSSEL_2; // SMCLK
UCA0BR0 = 104; // 1MHz 9600
UCA0BR1 = 0; // 1MHz 9600
UCA0MCTL = UCBRS0; // Modulation UCBRSx = 1
UCA0CTL1 &= ~UCSWRST; // **Initialize USCI state
machine**
IE2 |= UCA0RXIE; // Enable USCI_A0 RX interrupt
while(1){
//__bis_SR_register(LPM0_bits + GIE); /00/ Enter LPM0, interrupts
enabled
//Función 1: Recepción de datos del sensor
//Se realiza la función 1 directamente con la función 2

//Función 2: Amplificación de la señal recibida

// __bis_SR_register(LPM3_bits+GIE); // LPM3 con interrupcions
habilitadas
OA0CTL0 = OAPM_1+ OAN_1 + OAP_0 + OAADC1 ; // Señal + del sensor
conectada a OA0IO (Pin 3)
// Salida conectada en el A1
OA0CTL1 = OAFBR_0 + OAFC_7; // Modo Amplificador Operacional General, G=1




//Función 3: Conversión A/D

ADC10AE0 |= 0x02; //Entrada por el puerto A1
ADC10CTL1 = INCH_1 + ADC10DIV_4; // Entrada A1
ADC10CTL0 = SREF_1 + ADC10SHT_3 + ADC10ON + ADC10IE + ADC10SR + REFON +
REF2_5V;
// Tensión máxima 2.5 V, mínima 0 V
for( degC = 240; degC > 0; degC-- );//Retraso para que se fije la
configuración
ADC10CTL0 |= ENC + ADC10SC; // Comienzo de la conversión
// __bis_SR_register(CPUOFF + GIE); // LPM0 con interrupciones
habilitadas
volt=ADC10MEM; //guardamos en la variable VOLT el dato de la
conversión

ADC10CTL0 &= ~ENC;
ADC10CTL0 &= ~(REFON + ADC10ON); // se desactiva el A/D para ahorrar
energia
}
--


Start a New Thread

hi,
> P2DIR |= 0x00;
What's that supposed to do? It doesn't do anything

I don't see you selecting P2.0 and P2.2 in peripheral mode. I'm not sure it's necessary, but I think you should do so.

What MSP chip does your development board have?

I didn't understand how you're connecting the potentiometer.

Michael K.

--- In m..., gbadvancero wrote:
>
>
> Hi everyone. I'm connecting a potentiometer to my MSP430 RF2500 development
> board. The potentiometer center and right output which creates the potential
> differential that I need to measure to know the position of the
> potentiometer are connected to P2.0 and P2.2 and the OA is set as general
> purpose (which I guessed that it makes the difference of the potencial
> between P2.0 and P2.2).
>
> The range of the potentiometer goes from 100 mV to 2100 mV approx. That's
> why I decided to set a gain of 1 (0+1) and set the upper reference voltage
> to 2.5V (and the lower reference voltage to 0).
>
> Well, after that, I set the ADC10. And the result? It doesn't work. The
> ADC10MEM register always is 1023 (as if the result is over the range).
>
> This is the code (sorry for the comments in spanish as i'm spanish)
>
>
>
>
> #include "msp430x22x4.h"
>
>
> void TXString( char* string, int length );
>
> void main(void){
> WDTCTL = WDTPW + WDTHOLD; // Stop WDT
> long volt=0, posmin=0, posmax=0, dr=0, res=0, vmin=0, vmax=0;
> long nmax=0, nmin=0, degC;
> long posicion;
>
>
>
> BCSCTL1 = CALBC1_1MHZ; // Set DCO
> DCOCTL = CALDCO_1MHZ;
> P3SEL = 0x30; // P3.4,5 = USCI_A0 TXD/RXD
> P2DIR |= 0x00;
>
>
> UCA0CTL1 |= UCSSEL_2; // SMCLK
> UCA0BR0 = 104; // 1MHz 9600
> UCA0BR1 = 0; // 1MHz 9600
> UCA0MCTL = UCBRS0; // Modulation UCBRSx = 1
> UCA0CTL1 &= ~UCSWRST; // **Initialize USCI state
> machine**
> IE2 |= UCA0RXIE; // Enable USCI_A0 RX interrupt
> while(1){
> //__bis_SR_register(LPM0_bits + GIE); /00/ Enter LPM0, interrupts
> enabled
> //Función 1: Recepción de datos del sensor
> //Se realiza la función 1 directamente con la función 2
>
> //Función 2: Amplificación de la señal recibida
>
> // __bis_SR_register(LPM3_bits+GIE); // LPM3 con interrupcions
> habilitadas
> OA0CTL0 = OAPM_1+ OAN_1 + OAP_0 + OAADC1 ; // Señal + del sensor
> conectada a OA0IO (Pin 3)
> // Salida conectada en el A1
> OA0CTL1 = OAFBR_0 + OAFC_7; // Modo Amplificador Operacional General, G=1
>
>
>
>
> //Función 3: Conversión A/D
>
> ADC10AE0 |= 0x02; //Entrada por el puerto A1
> ADC10CTL1 = INCH_1 + ADC10DIV_4; // Entrada A1
> ADC10CTL0 = SREF_1 + ADC10SHT_3 + ADC10ON + ADC10IE + ADC10SR + REFON +
> REF2_5V;
> // Tensión máxima 2.5 V, mínima 0 V
> for( degC = 240; degC > 0; degC-- );//Retraso para que se fije la
> configuración
> ADC10CTL0 |= ENC + ADC10SC; // Comienzo de la conversión
> // __bis_SR_register(CPUOFF + GIE); // LPM0 con interrupciones
> habilitadas
> volt=ADC10MEM; //guardamos en la variable VOLT el dato de la
> conversión
>
> ADC10CTL0 &= ~ENC;
> ADC10CTL0 &= ~(REFON + ADC10ON); // se desactiva el A/D para ahorrar
> energia
> }
> --
>
>

Start a New Thread