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Problems with SPi 18F452 - >MAX6675

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Patrick Frank
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Problems with SPi 18F452 - >MAX6675

Posted: Fri Jul 09, 2004 3:10 am

Hi,
i want to read a 16bit value from a MAX6675.
I recieve data from the chip, but its allways the same data, it don`t send me the temperature i need.

Here is my code:

Code:

#include <18F452.h>
#use delay (clock= 4000000)
#fuses H4, PUT, NOPROTECT, BROWNOUT, NOWDT, NODEBUG, NOOSCSEN, NOLVP
#use fast_io ( A ) /* don't set TRIS on each I/O statement */
#use fast_io ( B ) /* don't set TRIS on each I/O statement */
#use fast_io ( C ) /* don't set TRIS on each I/O statement */
#use fast_io ( D ) /* don't set TRIS on each I/O statement */
#use fast_io ( E ) /* don't set TRIS on each I/O statement */

struct port_a_layout
{
short Opto_1_Out; //RA.0
short Opto_2_Out; //RA.1
short Relais_Out; //RA.2
short CS_Out; //RA.3
short Opto_1_In; //RA.4
short blank2; //RA.5
}porta;

struct port_b_layout
{
short Opto_2_In; //RB.0
short Opto_3_In; //RB.1
short Opto_4_In; //RB.2
short Led_Start; //RB.3
short Led_Stopp; //RB.4
short blank1; //RB.5
short blank2; //RB.6
short blank3; //RB.7
}portb;

struct port_c_layout
{
short Summer_Out; //RC.0
short Relais_1_Out;//RC.1
short Relais_2_Out;//RC.2
short SCK; //RC.3
short SDI; //RC.4
short blank1; //RC.5
short andere_tasten;//RC.6
short plus_minus_tasten; //RC.7
}portc;

struct port_d_layout
{
int data:8; //Anzeige 7-Seg, einlesen Tasten
}portd;

struct port_e_layout
{
int mux_dis:3; //Umschaltung Mux 7-Seg
}porte;

int mux=0,data1=0,data2=0;
int16 datakomp=0;
int plus_minus=0,menu=0,plus_minus_temp=0,menu_temp=0;
int Ziffer0,Ziffer1,Ziffer2,Ziffer3,Ziffer4,Ziffer5;
int16 datatemp=0;

void main(void)
{
set_tris_a ( 0x10 ); //00010000 1=IN 0=OUT
set_tris_b ( 0x07 ); //00000111
set_tris_c ( 0x10 ); //00010000
set_tris_d ( 0x00 ); //00000000
set_tris_e ( 0x00 ); //00000000
portc.plus_minus_tasten=1;
portc.andere_tasten=1;
portd.data=0;
porte.mux_dis=1;
portc.Summer_Out=0; //RC.0
setup_spi(SPI_MASTER | SPI_L_TO_H | SPI_CLK_DIV_16);
porta.CS_Out=1;
delay_ms(600);

while(1)
{
porta.CS_Out=0;
delay_cycles(1);
data2 = spi_read(0);
data1 = spi_read(0);
porta.CS_Out=1;
datakomp=make16(data2,data1);
datakomp=datakomp>>3;
datakomp=datakomp&&0x0FFF;
datatemp=datakomp;
delay_ms(600);
}
}

I have connected RC3/SCK to SCK. RC4 SDI to SO. RA3 to CS/.
The Datasheet from the MAX6675 means that i must put CS/ low to communicate and high to get a new value. But i recieve everytime the same value and this value is wrong.

Has anybody a idea? The MAX6675 sends a 16Bit value. Can i read this with my 2 spi_read(0) ?

Thanks and Greets

Patrick Frank

rwyoung

Joined: 12 Nov 2003
Posts: 563
Location: Lawrence, KS USA

Posted: Fri Jul 09, 2004 8:02 am

Code:

datakomp=datakomp&&0x0FFF;

Should probably be

Code:

datakomp=datakomp & 0x0FFF;

If your goal is to mask off the top 4 bits.
_________________
Rob Young
The Screw-Up Fairy may just visit you but he has crashed on my couch for the last month!

Patrick Frank
Guest

Posted: Fri Jul 09, 2004 12:12 pm

rwyoung wrote:

Code:

datakomp=datakomp&&0x0FFF;

Should probably be

Code:

datakomp=datakomp & 0x0FFF;

If your goal is to mask off the top 4 bits.

Hi,
I feel a bit sheepish about this. Embarassed

That was a mistake in writing.

But that is not my problem, the spi communication still don`t work.

Patrick

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