MCP3551

Hello,

I am making the interface between the MSP430FG4618 and MCP3551.

I am getting a value of 1048573 which is not consistent with the input state + VIN = VCC (+ 5V) and Vin = GND (0V).

When VIN + and -Vin = VCC (+ 5V) the value is 2097151 and when VIN + = GND and Vin (0V), the value is 2097151 also !. Would not it be 0?

I'm doing something wrong?

Already replaces the MCP3551 and is in the same state!

The following code:

#include "msp430xG46x.h"
#include "LCD16x2_Data_Logger.c"
#include <stdio.h>
#include <intrinsics.h>
#include <stdlib.h>
#include <string.h>

#define Time_80_ms 2622

unsigned int value;
long adcValue;
char strADC_Value[12];

void Delay_Timer(unsigned int Delay);
//************************************************************************************************************//
// Definições dos Pinos de Entrada e Saída do MSP430 do Data Logger //
//************************************************************************************************************//
void initPORTS(void)
{
P1IE = (BIT0+BIT1);
P1IES = !(BIT0+BIT1);
P2DIR |= BIT0+BIT1+BIT2; // P2.2 e P2.1 como saída
P2OUT |= BIT0; // Apaga LED1 e LED2
P2OUT &=~ BIT1+BIT2; // Apaga LED1 e LED2
P5DIR |= 0x002; // P5.1 output
P3SEL |= 0x0C; // P3.3,2 option select
P3DIR |= 0x01; // P3.0 output direction
P5DIR = 0x02; // Define P5.1 como Saída
P5OUT &=~ 0x02; // Apaga LED4
}
//************************************************************************************************************//
// Definições e Inicialização do BASIC TIMER para Temporizações do Data Logger //
//************************************************************************************************************//
void initBT(void)
{
BTCNT1 = BTCNT2 = 0;
BTCTL = BTDIV + BT_fCLK2_DIV128; // Configura o Basic Timer
}

void Delay_Timer (unsigned int Delay)
{
TACCTL0 &=~ CCIFG;
TACTL = TASSEL_1 + MC_1 + TACLR;
TACCR0 = Delay;
TACCTL0 = CCIE;
__bis_SR_register(LPM3_bits + GIE);
}
/*******************************************************************************
* Function MCP3551_Read
* ------------------------------------------------------------------------------
* Overview: Read over SPI ADC value in MCP3551 register
* Input: Nothing
* Output: ADC Value
*******************************************************************************/
long MCP3551_Read()
{
char ADC_Byte1, ADC_Byte2, ADC_Byte3 = 0;
long ADC_Value = 0;

P3OUT &=~ 0x01; // Enable MCP3551 CS_pin; Clear(port bit); put low
Delay_Timer(Time_80_ms);//__delay_cycles(1000000); // PowerUp Time (min.10us)

IFG2 &= ~UCB0RXIFG; // Clear int flag // I get the third byte
UCB0TXBUF = 0x00; // Dummy write to start SPI
while (!(IFG2 & UCB0RXIFG)); // RXBUF ready?
ADC_Byte3 = UCB0RXBUF; // Move value

IFG2 &= ~UCB0RXIFG; // Clear int flag // I get the third byte
UCB0TXBUF = 0x00; // Dummy write to start SPI
while (!(IFG2 & UCB0RXIFG)); // RXBUF ready?
ADC_Byte2 = UCB0RXBUF; // Move value

IFG2 &= ~UCB0RXIFG; // Clear int flag // I get the third byte
UCB0TXBUF = 0x00; // Dummy write to start SPI
while (!(IFG2 & UCB0RXIFG)); // RXBUF ready?
ADC_Byte1 = UCB0RXBUF; // Move value

// enter shutdown (typ.10us)
P3OUT |= 0x01; // Disable MCP3551 CS_pin; Set(port bit); put high
Delay_Timer(Time_80_ms);//__delay_cycles(100000); // PowerUp Time (min.10us)

// store 24 bits in ADC_Value
ADC_Value = ADC_Byte3;
ADC_Value = (ADC_Value << 8) | ADC_Byte2;
ADC_Value = (ADC_Value << 8) | ADC_Byte1;

// OVH (false) condition
if (ADC_Byte3 == 0x60 && ADC_Byte1 > 0)
ADC_Value = 3000000; // Vin+ >= Vref ; Vin- = GND

// OVL (false) condition
else if (ADC_Byte3 == 0x9F && ADC_Byte1 > 0){
ADC_Value = -3000000; // Vin- >= Vref ; Vin+ = GND
}

else {
if ((ADC_Byte3 & 0x20) >> 5) // Bit 21 = 1 ; value is negative
ADC_Value = ADC_Value - 4194304; // for 22 bit resolution
}

return ADC_Value;
}

void main(void)
{
volatile unsigned int i;

WDTCTL = WDTPW+WDTHOLD; // Stop watchdog timer
FLL_CTL0 |= XCAP14PF; // Configure load caps

// Wait for xtal to stabilize
do
{
IFG1 &= ~OFIFG; // Clear OSCFault flag
for (i = 0x47FF; i > 0; i--); // Time for flag to set
}
while ((IFG1 & OFIFG)); // OSCFault flag still set?

initPORTS();
initBT();

UCB0CTL1 |= UCSWRST;
UCB0CTL0 |= UCMST+UCSYNC+UCMSB; // 3-pin, 8-bit SPI mstr, MSb 1st
UCB0CTL1 |= UCSSEL_2; // SMCLK
UCB0BR0 = 0x02;
UCB0BR1 = 0;
UCB0CTL1 &=~ UCSWRST; // **Initialize USCI state machine**

P5OUT &=~ 0x02; // Liga o LCD16X2
InitLCD();
LCDClear();
LCDPrintString("Testando...");
__delay_cycles(1000000);
LCDSetPosition(1,0);
LCDPrintString("Display LCD16X2");
__delay_cycles(1000000);
LCDClear();
//P7OUT = 0;
//P5OUT |= 0x02; // Desliga o LCD16X2
LCDSetPosition(0,1);
LCDPrintString("ADC 2 Click Ex."); // Display message on the Lcd
LCDSetPosition(1,1);
LCDPrintString("Value: "); // Display message on the Lcd

do
{
adcValue = MCP3551_Read(); // Read ADC value from MCP3551
sprintf(strADC_Value,"%ld",adcValue);
LCDSetPosition(1,8);
LCDPrintString(" "); // Reading Error

if (adcValue == -4000000){
LCDSetPosition(1,8);
LCDPrintString("Erro"); // Reading Error
}
else if (adcValue == 3000000) {
LCDSetPosition(1,8);
LCDPrintString("OVH"); // Overflow High
}
else if (adcValue == -3000000) {
LCDSetPosition(1,8);
LCDPrintString("OVL"); // Overflow Low
}
else {
LCDSetPosition(1,8);
LCDPrintString(strADC_Value); // Display message on the Lcd
}
__delay_cycles(1000000);
//__bis_SR_register(LPM3_bits + GIE); // Entra em LPM3 (Modo de Baixo Consumo)
}while(1);
}
#pragma vector=TIMERA0_VECTOR
__interrupt void Timer_A(void) // When the value of the TimerA=TACCR0, we get out of the low power mode
{
__bic_SR_register_on_exit(LPM3_bits + GIE);
}