=A0
Hello All
    I am trying to interface a 16F877 to MCP3202(12 bit ADC with SPI interf=
ace).
    I am not able to get data from the MCP3202(ALL I GET IS ZERO.
I am using the standard SPI module of 16F877A, connected to the SPI pins of=
 MCP3202 as required.
    I tried pulling up as well as pulling down the CS,Clk,SDI,SDO pins with=
out any results.
    I used a DSO and saw that the wave forms of the CS,CLK,SDO of the 16F87=
7A are as required.
    CS goes low. then the data transmission on clk fro 16F877 are just as r=
equired.
    Still i do not get the ADC values. what could be wrong.where could i ha=
ve gone wrong.
    Is there anything else i have to consider.

Please find the code i used below for hi-tech c compiler


////start of code for MCP3202<-->16F877A
#include<pic1687x.h>
#define ADCS 0x04 /* I/O bit position for CS line */
#define BUSY 0x01 /* Bit0 of SSPSTAT, indicated when SPI xmission complete =
*/
#define BUTTON 0x10 /* I/0 bit position for RA4 line */
void Wait_for_Press()
{
while(PORTA & BUTTON)
{
/* wait for button press */
}
while(!(PORTA & BUTTON))
{
/* wait for button release */
}
}
unsigned char	datah,datal;
int	del;
void main(void)
{
PORTA=3D0;
PORTB=3D0;
PORTC=3D0;
PORTD=3D0;
PORTE=3D0;
	=

TRISA =3D	0x00;	=

TRISD =3D 0x00;
TRISE =3D 0x00;
TRISB =3D 0x00;
PORTB =3D 0x00; /* reset PortB outputs */
SSPCON =3D 0x32; /* set up SSP to clock data out on falling edge */
TRISC =3D 0x90; /* clock data in on rising edge, clock idle high */
PORTC |=3D ADCS; /* de-select A/D device */
////////////UART///////////////////////////
    TXSTA=3D0x84;
    RCSTA=3D0x90;	=

    =

    TXEN=3D1;	=

    TMR1IE=3D0;	=

//OPTION=3D0X97;	=

    SPBRG=3D0X19;	=

    T0IF=3D0;
    T0IE=3D0;
    PEIE=3D1;
    RCIE=3D0;
    CREN=3D1;
    SPEN=3D1;
    SYNC=3D0;
TXEN=3D1;
datal=3D0xAA;
datah=3D0xBB;
while(TRMT!=3D1);
TXREG=3D66;
///////////////////////////////////////////
while(1)
{
PORTC &=3D ~ADCS; /* select A/D device */
//RC2=3D1;
SSPBUF =3D 0x00; /* output start bit */
while(!(SSPSTAT & BUSY))
{
/* wait for transfer complete */
}

SSPBUF =3D 0x01; /* output start bit */
while(!(SSPSTAT & BUSY))
{
/* wait for transfer complete */
}
datah =3D SSPBUF; /* mask and output conversion MSb=92s */
SSPBUF =3D 0xa0; /* output 3 command, 5 dummy bits */
while(!(SSPSTAT & BUSY))
{
/* wait for transfer complete */
}
datah =3D SSPBUF;// & 0x0F; /* mask and output conversion MSb=92s */
SSPBUF =3D 0x00; /* output dummy word */
while(!(SSPSTAT & BUSY))
{
/* wait for transfer complete */
}
datal=3DSSPBUF;

PORTC |=3D ADCS; /* de-select A/D device */
//RC2=3D0;
TXEN=3D1;
while(TRMT!=3D1);
TXREG=3Ddatah;

while(TRMT!=3D1);
TXREG=3Ddatal;

for(del=3D32000;del>0;del--)
{
# asm
	nop
	nop
	nop
	nop
	nop
	nop
# endasm
}

}
}

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