MCF51QE128 ADC problem

naldo3 — Wed, 27 Jan 2010 20:34:49 GMT

Hi everybody,

can anyone help me about my problem? I'm programming a MCF51QE128 Coldfire V1 and I want to get an adc value from a NTC resistor. The problem is that I receive from the ADCR a value that is not corresponding with the value read from a tester in the micro adc pin, in fact Vtester = 1.5 Vadcr.

The code is simply:

/*Includes*/
#include <hidef.h>                                     // For EnableInterrupts macro
#include "derivative.h"                                // Include peripheral declarations
#include <stdio.h>
#include <math.h>
#include <stdint.h>
#include <string.h>

/*Global Variables*/
unsigned char NTCHighValue = 0;
unsigned char NTCLowValue = 0;

/*Function Calls*/
void ICS_Configuration(void);
void MCU_Init(void);

/*Main Sequence*/
void main(void)
{

ICS_Configuration();
MCU_Init();                                         // Call Device Initialization

for(;
{
      NTCHighValue = ADCRH;
      NTCLowValue = ADCRL;
}
}

void MCU_Init(void)
{
/* Common initialization of the CPU registers */
SCGC1 = 0xFF;
PTASE &= (unsigned char)~0xDF;
PTADS = 0x00;
SCGC2 |= (unsigned char)0x7F;

/* ### Init_ADC init code */
APCTL2 = 0x00;
ADCCFG = 0x14;
ADCSC2 = 0x00;
ADCCV = 0x00;
ADCSC1 = 0x29;

/* ### */
asm {                                /* Set Interrupt level 0 */
    move.w SR,D0;
    andi.l #0xF8FF,D0;
    move.w D0,SR;
}
}

void ICS_Configuration(void)
{
/* ### MCF51QE128_80 "Cpu" init code ... */
/* PE initialization code after reset */
/* Common initialization of the write once registers */
SOPT1 = 0x52;
SPMSC1 = 0x1C;
SPMSC2 = 0x02;
SPMSC3 &= (unsigned char)~0x38;

/* Initialization of CPU registers */
asm {
    /* VBR: ADDRESS=0 */
    clr.l d0
    movec d0,VBR
    /* CPUCR: ARD=0,IRD=0,IAE=0,IME=0,BWD=0,FSD=0 */
    clr.l d0
    movec d0,CPUCR
}

/* System clock initialization */
ICSC1 = 0x04;                        /* Initialization of the ICS control register 1 */
ICSC2 = 0x40;                        /* Initialization of the ICS control register 2 */
while(!ICSSC_IREFST) {               /* Wait until the source of reference clock is internal clock */
}
ICSSC &= (unsigned char)~0xE0;       /* Initialization of the ICS status and control */
while((ICSSC & 0xC0) != 0x00) {      /* Wait until the FLL switches to Low range DCO mode */
}
INTC_WCR = 0x00;
}

Re: MCF51QE128 ADC problem

naldo3 — Thu, 28 Jan 2010 23:31:38 GMT

Ok, problem solved.

I made a mistake in the hardware design, I do not why but I put a 100nF capacitor in a ground pin between it and general ground...maybe I just looked quickly its pins & connections from the RM.

Next time, I will ask a smarter question.

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