Other Parts Discussed in Thread: TMP235
Tool/software: Code Composer Studio
Hi,
I'm trying to do a single channel conversion with my MSP430 and send the values to my PC and plot it with MatLab. I use a potmeter connected to 3v+, P1.1(A1), GND to test my code.
My problem is that the ADC result is stuck at a fixed value (216) and but sometimes it starts to actually read something that resembles the change of the potmeter. I guess I set the A1 incorrectly and I'm reading wrong the wrong pin but I couldn't find anything in the datasheet or in the code that could be wrong.
#include <msp430.h>
unsigned int ADC_Result;
void Init_GPIO();
void Software_Trim(); // Software Trim to get the best DCOFTRIM value
#define MCLK_FREQ_MHZ 8 // MCLK = 8MHz
int main(void)
{
WDTCTL = WDTPW | WDTHOLD; // Stop watchdog timer
// Configure GPIO
Init_GPIO();
// Configure GPIO
TA0CCTL0 |= CCIE; // TACCR0 interrupt enabled
TA0CCR0 = 50000;
TA0CTL |= TASSEL__SMCLK | MC__CONTINUOUS; // SMCLK, continuous mode
PM5CTL0 &= ~LOCKLPM5; // Disable the GPIO power-on default high-impedance mode
// to activate 1previously configured port settings
__bis_SR_register(SCG0); // disable FLL
CSCTL3 |= SELREF__REFOCLK; // Set REFO as FLL reference source
CSCTL1 = DCOFTRIMEN_1 | DCOFTRIM0 | DCOFTRIM1 | DCORSEL_3;// DCOFTRIM=3, DCO Range = 8MHz
CSCTL2 = FLLD_0 + 243; // DCODIV = 8MHz
__delay_cycles(3);
__bic_SR_register(SCG0); // enable FLL
Software_Trim(); // Software Trim to get the best DCOFTRIM value
CSCTL4 = SELMS__DCOCLKDIV | SELA__REFOCLK; // set default REFO(~32768Hz) as ACLK source, ACLK = 32768Hz
// default DCODIV as MCLK and SMCLK source
// Configure UART pins
P1SEL0 |= BIT4 | BIT5; // set 2-UART pin as second function
// Configure ADC A1 pin
P1SEL0 |= BIT1;
P1SEL1 |= BIT1;
// Configure UART
UCA0CTLW0 |= UCSWRST;
UCA0CTLW0 |= UCSSEL__SMCLK;
// Baud Rate calculation
// 8000000/(16*9600) = 52.083
// Fractional portion = 0.083
// User's Guide Table 17-4: UCBRSx = 0x49
// UCBRFx = int ( (52.083-52)*16) = 1
UCA0BR0 = 52; // 8000000/16/9600
UCA0BR1 = 0x00;
UCA0MCTLW = 0x4900 | UCOS16 | UCBRF_1;
UCA0CTLW0 &= ~UCSWRST; // Initialize eUSCI
UCA0IE |= UCRXIE; // Enable USCI_A0 RX interrupt
// Configure ADC12
ADCCTL0 |= ADCSHT_2 | ADCON; // ADCON, S&H=16 ADC clks
ADCCTL1 |= ADCSHP; // ADCCLK = MODOSC; sampling timer
ADCCTL2 &= ~ADCRES; // clear ADCRES in ADCCTL
ADCCTL2 |= ADCRES_2; // 12-bit conversion results
ADCMCTL0 |= ADCINCH_1; // A1 ADC input select; Vref=DVCC
ADCIE |= ADCIE0; // Enable ADC conv complete interrupt
while(1)
{
ADCCTL0 |= ADCENC | ADCSC; // Sampling and conversion start
__bis_SR_register(LPM0_bits | GIE); // LPM0, ADC_ISR will force exit
__no_operation(); // For debug only
if (ADC_Result < 0x7FF)
P1OUT &= ~BIT0; // Clear P1.0 LED off
else
P1OUT |= BIT0; // Set P1.0 LED on
__delay_cycles(5000);
}
}
// Timer A0 interrupt service routine
#if defined(__TI_COMPILER_VERSION__) || defined(__IAR_SYSTEMS_ICC__)
#pragma vector = TIMER0_A0_VECTOR
__interrupt void Timer_A (void)
#elif defined(__GNUC__)
void __attribute__ ((interrupt(TIMER0_A0_VECTOR))) Timer_A (void)
#else
#error Compiler not supported!
#endif
{
UCA0TXBUF=ADC_Result;
__delay_cycles(5000);
UCA0TXBUF=ADC_Result<<8;
TA0CCR0 = 50000; // Add Offset to TACCR0
}
void Software_Trim()
{
unsigned int oldDcoTap = 0xffff;
unsigned int newDcoTap = 0xffff;
unsigned int newDcoDelta = 0xffff;
unsigned int bestDcoDelta = 0xffff;
unsigned int csCtl0Copy = 0;
unsigned int csCtl1Copy = 0;
unsigned int csCtl0Read = 0;
unsigned int csCtl1Read = 0;
unsigned int dcoFreqTrim = 3;
unsigned char endLoop = 0;
do
{
CSCTL0 = 0x100; // DCO Tap = 256
do
{
CSCTL7 &= ~DCOFFG; // Clear DCO fault flag
}while (CSCTL7 & DCOFFG); // Test DCO fault flag
__delay_cycles((unsigned int)3000 * MCLK_FREQ_MHZ);// Wait FLL lock status (FLLUNLOCK) to be stable
// Suggest to wait 24 cycles of divided FLL reference clock
while((CSCTL7 & (FLLUNLOCK0 | FLLUNLOCK1)) && ((CSCTL7 & DCOFFG) == 0));
csCtl0Read = CSCTL0; // Read CSCTL0
csCtl1Read = CSCTL1; // Read CSCTL1
oldDcoTap = newDcoTap; // Record DCOTAP value of last time
newDcoTap = csCtl0Read & 0x01ff; // Get DCOTAP value of this time
dcoFreqTrim = (csCtl1Read & 0x0070)>>4;// Get DCOFTRIM value
if(newDcoTap < 256) // DCOTAP < 256
{
newDcoDelta = 256 - newDcoTap; // Delta value between DCPTAP and 256
if((oldDcoTap != 0xffff) && (oldDcoTap >= 256)) // DCOTAP cross 256
endLoop = 1; // Stop while loop
else
{
dcoFreqTrim--;
CSCTL1 = (csCtl1Read & (~DCOFTRIM)) | (dcoFreqTrim<<4);
}
}
else // DCOTAP >= 256
{
newDcoDelta = newDcoTap - 256; // Delta value between DCPTAP and 256
if(oldDcoTap < 256) // DCOTAP cross 256
endLoop = 1; // Stop while loop
else
{
dcoFreqTrim++;
CSCTL1 = (csCtl1Read & (~DCOFTRIM)) | (dcoFreqTrim<<4);
}
}
if(newDcoDelta < bestDcoDelta) // Record DCOTAP closest to 256
{
csCtl0Copy = csCtl0Read;
csCtl1Copy = csCtl1Read;
bestDcoDelta = newDcoDelta;
}
}while(endLoop == 0); // Poll until endLoop == 1
CSCTL0 = csCtl0Copy; // Reload locked DCOTAP
CSCTL1 = csCtl1Copy; // Reload locked DCOFTRIM
while(CSCTL7 & (FLLUNLOCK0 | FLLUNLOCK1)); // Poll until FLL is locked
}
void Init_GPIO()
{
P1DIR = 0xFF; P2DIR = 0xFF;
P1REN = 0xFF; P2REN = 0xFF;
P1OUT = 0x00; P2OUT = 0x00;
}
// ADC interrupt service routine
#if defined(__TI_COMPILER_VERSION__) || defined(__IAR_SYSTEMS_ICC__)
#pragma vector=ADC_VECTOR
__interrupt void ADC_ISR(void)
#elif defined(__GNUC__)
void __attribute__ ((interrupt(ADC_VECTOR))) ADC_ISR (void)
#else
#error Compiler not supported!
#endif
{
switch(__even_in_range(ADCIV,ADCIV_ADCIFG))
{
case ADCIV_NONE:
break;
case ADCIV_ADCOVIFG:
break;
case ADCIV_ADCTOVIFG:
break;
case ADCIV_ADCHIIFG:
break;
case ADCIV_ADCLOIFG:
break;
case ADCIV_ADCINIFG:
break;
case ADCIV_ADCIFG:
ADC_Result = ADCMEM0;
__bic_SR_register_on_exit(LPM0_bits); // Clear CPUOFF bit from LPM0
break;
default:
break;
}
}
MatLab code:
clear all
clc;
if ~isempty(instrfind)
fclose(instrfind);
delete(instrfind);
end
s = serial('COM5','BaudRate',9600,'TimeOut',10,'Terminator','LF');
fopen(s);
n=1:1000;
y=1:1000;
shg
for i=1:1000
received=fread(s,2)
y(i)=received(1)+received(2)*256;
ylim([0 1200])
plot(y(:),'g'); drawnow
ylim([0 1000])
end
fclose(s);
shg
