Hello,
I am new to MSP430 series micro-controller and I am playing around the ADC of MSP430FR2433 development kit.
I have tried the msp430fr243x_adc10_01.c example for single channel ADC sampling and it works great.
However, when I modify the example to sample multiple channel ADC (P1.2 P1.3). The result seems very unstable.
Any suggestions and advice are appreciated.
1. connect both to GND pin
I expected the result should be both 0 but sometimes the suddenly jumps to 243.
Here is the log.
254 3 "▒ 0 0 "▒0 0 "▒254 4 "▒0 0 "▒0 0 "▒254 3 "▒0 0 "▒0 0 "▒254 3 "▒0 0 "▒0 0 "▒254 3 "▒0 0 "▒0 0 "▒254 4 "▒0 0 "▒0 0 "▒254 3 "▒0 0 "▒0 0 "▒254 3
2. connect both to VCC(3V3) pin
I expected the result should be both near 255 but sometimes the suddenly jumps to 4.
Here is the log.
255 255 207 207 253 4 255 255 206 206 252 3 254 255 207 203 253 3 255 254 207 207 251 3 254 254 204 207 253 4 254 255 207 207 253 3 255 255 204 207
#include <msp430.h>
#include <stdio.h>
unsigned char ADC_Result[2]; // 8-bit ADC conversion result array
int i;
void print_result_to_uart(void);
int main(void)
{
WDTCTL = WDTPW | WDTHOLD; // stop watchdog timer
P1DIR |= BIT0 | BIT1; // P1.0 & P1.1 as LED
P1OUT = 0x00;
P1REN = 0x00;
SYSCFG2 |= ADCPCTL2+ADCPCTL3; // Select P1.2 & P1.3 A2 as ADC
P1SEL1 &= ~(BIT4 | BIT5); // USCI_A0 UART operation
P1SEL0 |= BIT4 | BIT5;
UCA0CTLW0 |= UCSWRST; // Put USCI_A0 to software reset
UCA0CTLW0 |= UCSSEL__SMCLK; // Use SMCLK(1048576Hz) for baud rate calculation
UCA0BRW = 9; // N = f/BR = 1048576/115200 = 9
UCA0MCTLW = 0x0800;
UCA0CTLW0 &= ~UCSWRST; // Release USCI_A0 software reset
PM5CTL0 &= ~LOCKLPM5;
ADCCTL0 |= ADCSHT_2; // 16 ADCCLK cycles
ADCCTL0 |= ADCON; // ADC on
// ADCCTL0 |= ADCMSC; // ADC multiple sample-and-conversion
ADCCTL1 |= ADCSHP; // ADCCLK = MODOSC; sampling timer
ADCCTL1 |= ADCCONSEQ_1; // Repeat-sequence-of-channels
ADCCTL2 |= ADCRES_0; // Resolution 8-bit
ADCMCTL0 |= ADCINCH_2+ADCINCH_3; // A2 & A3 ADC input select; Vref=AVCC
ADCIE |= ADCIE0; // Enable ADC conv complete interrupt
__bis_SR_register(GIE); // LPM0, ADC_ISR will force exit
while(1)
{
i = 1;
ADCCTL0 |= ADCENC | ADCSC; // Sampling and conversion start
while (i >= 0);
print_result_to_uart();
if (ADC_Result[0] < 0x7F)
P1OUT &= ~BIT0; // Clear P1.0 LED off
else
P1OUT |= BIT0;
if (ADC_Result[1] < 0x7F) // P1.3 ADC3 result
P1OUT &= ~BIT1; // Clear P1.1 LED off
else
P1OUT |= BIT1;
__delay_cycles(1048576);
}
}
void print_result_to_uart(void)
{
char str[20];
sprintf(str, "%d %d\r\n", ADC_Result[0], ADC_Result[1]);
int j = 0;
for (j = 0; j < sizeof(str); j++){
UCA0TXBUF = str[j];
__delay_cycles(100);
}
}
#pragma vector=ADC_VECTOR
__interrupt void ADC_ISR(void)
{
switch(__even_in_range(ADCIV,ADCIV_ADCIFG))
{
case ADCIV_ADCIFG:
ADC_Result[i--] = ADCMEM0;
if (i >= 0)
ADCCTL0 |= ADCENC | ADCSC;
break;
default:
break;
}
}
