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Max31820

Category: Software
Hi Team,
   I want to interface Max31280 temperature sensor with TMS320 microcontroller. I wrote the code for communication. My reset function perform well. I got the presence signal back from the device. But when I send the read rom command the received value is 255. Here is my code
#include "DSP28x_Project.h"     // Device Headerfile and Examples Include File
void Gpio_init();
void Gpio_write_bit(int data);
int Gpio_read_bit();
int system_reset();
int Gpio_read_byte();
void Gpio_write_byte(int data);
enum DELAY { A = 5, B = 70, C = 70, D = 5, E = 10, F = 53, G = 0, H = 480, I = 70, J = 410 };
enum COMMANDS { READ_ROM = 0x33, CONVERT = 0x44, READ_SCRATCHPAD = 0xBE,
                SKIP_ROM = 0xCC, WRITE_SCRATCHPAD = 0x4E, COPY_SCRATCHPAD = 0x48, MATCH_ROM = 0x55
              };
void main()
{
 int reset=0,i;
 int ROM_Code[64]={0};
InitSysCtrl();
//InitScibGpio();
DINT;
    IER = 0x0000;
    IFR = 0x0000;
    InitPieVectTable();
    // Enable CPU and PIE interrupts
    // This example function is found in the DSP2833x_PieCtrl.c file.
     //   EnableInterrupts();
Gpio_init();
reset=system_reset();
//data_value= Gpio_read_bit();
if(reset==0){while(1);}
else{Gpio_write_byte(READ_ROM );
        for ( i = 0; i < 64; ++i) {
            ROM_Code[i] = Gpio_read_byte();
        }
}
while(1);
}
int system_reset()
{
    int data=0;
    int flag=0;
    GpioDataRegs.GPACLEAR.bit.GPIO18=1;GpioDataRegs.GPASET.bit.GPIO18=0;
    //DELAY_US(480);
    DELAY_US(H);
    GpioDataRegs.GPACLEAR.bit.GPIO18=0;GpioDataRegs.GPASET.bit.GPIO18=1;
    //DELAY_US(70);
    DELAY_US(I);
    data= GpioDataRegs.GPADAT.bit.GPIO19;
    DELAY_US(J);
    if(data==0){flag=1;}
    else{flag=0;}
    //DELAY_US(1000);
return flag;
}
void Gpio_init()
{
    EALLOW;
    GpioCtrlRegs.GPAPUD.bit.GPIO18 = 0;   // Enable pullup on GPIO18
    GpioCtrlRegs.GPAPUD.bit.GPIO19 = 0;   // Enable pullup on GPIO18
    GpioCtrlRegs.GPAMUX2.bit.GPIO18 = 0;// select GPIO from mux
    GpioCtrlRegs.GPAMUX2.bit.GPIO19 = 0;// select GPIO from mux
    GpioCtrlRegs.GPADIR.bit.GPIO18 = 1;// select direction as out
    GpioCtrlRegs.GPADIR.bit.GPIO19 = 0;// select direction as in
   EDIS;
}
void Gpio_write_bit(int data)
{
    if(data==0){
        GpioDataRegs.GPACLEAR.bit.GPIO18=1;GpioDataRegs.GPASET.bit.GPIO18=0;
        DELAY_US(15);
        DELAY_US(45);
       // DELAY_US(C);
       // DELAY_US(D);
    }
    else {
    GpioDataRegs.GPASET.bit.GPIO18=0;GpioDataRegs.GPACLEAR.bit.GPIO18=1;
    DELAY_US(10);
    //DELAY_US(A);
    GpioDataRegs.GPASET.bit.GPIO18=1;GpioDataRegs.GPACLEAR.bit.GPIO18=0;
    DELAY_US(5);
    DELAY_US(45);
    //DELAY_US(B);
    }
    //DELAY_US(60);
   // DELAY_US(1);
    return;
}
int Gpio_read_bit()
{
    int temp_data;
   GpioDataRegs.GPASET.bit.GPIO18=0;GpioDataRegs.GPACLEAR.bit.GPIO18=1;
   DELAY_US(1);
   // DELAY_US(A);
  GpioDataRegs.GPASET.bit.GPIO18=1;GpioDataRegs.GPACLEAR.bit.GPIO18=0;
    //DELAY_US(E);
    DELAY_US(10);
    temp_data=GpioDataRegs.GPADAT.bit.GPIO19;
   // DELAY_US(F);
    DELAY_US(4);
    DELAY_US(45);
   //DELAY_US(1);
    return temp_data;
}
void Gpio_write_byte(int data)
{
   int i,buff;
for(i=0;i<8;i++)
{
    buff=data&0x01;
    Gpio_write_bit(buff);
    data=data>>1;
}
}
int Gpio_read_byte()
{
   int i,buff,temp_value=0;
for(i=0;i<8;i++)
{
    buff=Gpio_read_bit();
    temp_value|=(buff<<i);
}
return temp_value;
}
During read function, if I don't give 1 after give a 0 signal the read function will give all zeros. Kindly review my code and let me know the updates.
In hardware I have connected GPIO18 and GPIO19 of microcontroller  to one wire of Temperature sensor and 4.7 Kohm pull up to Vcc.
Thanks
Anu
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