LM75 Addressing Problem

[jleblanc]

Hello,

I'm trying to develop some code that will allow me to talk to multiple LM75 temperature sensors on an I2C bus. The problem I'm having though is my code will only communicate with an LM75 at it's base address (A0-A2 pins on the LM75 all grounded). When I try to communicate with a chip on base address+1 (A0 high, A1-A2 ground) my code doesn't work. I've posted my code below, any ideas?

When I'm conducting my tests I only have the one LM75 on the I2C bus.

Thanks!

[PCM programmer]

Please edit your post, and fix the garbled lines of code, and
then submit the post with the checkbox for "Disable HTML in this post"
selected. If you use Less Than or Greater Than symbols with HTML
enabled, your code will get scrambled. The checkbox is directly
below the posting composition window.

[PCM programmer]

OK, that's better.

I see one immediate problem. The last i2c_read() needs to do a "NAK".
In CCS, this is done by giving the function a 0 parameter. Change
your code so it does this. See the line shown in bold below.

[jleblanc]

That change didn't fix my problem.

Here are my constants:

[PCM programmer]

I think you need to show a small test program that shows how
you are calling the LM75 function with different addresses.

There's another bug in your program. This line right here
is not doing what you think it's doing.

[jleblanc]

[jleblanc]

Here's a sample program:

[PCM programmer]

The "%f" format specifier doesn't really work by itself, in many versions
of the compiler. You need to give it a width and a precision value.
Use something like "%3.2f" instead.

Also, you need a while(1); statement right before the closing brace of
main(). If you don't have it, the PIC will execute a hidden SLEEP
instruction and cut off the last two characters that are sent to the
hardware UART.

Also, the setup_vref() statement is wrong. There is no "-2" parameter.
The PCWH wizard has a bug. I would just delete that whole statement.
The Vref generator is disabled upon reset, anyway.

[jleblanc]

Made those changes; same results.

Thanks a lot for the help/pointers by the way. It is much appreciated.

[rnielsen]

From looking at the spec. sheet it seems as though the base address(lowest) would be 0x90. You have assigned the variable, LM75_BASE_ADDRESS to a value of 72 which is HEX 0x48. The possible addresses are 0x90(A0,A1,A2=low), 0x92, 0x94, 0x96 and so on up to 0x9E. I have no idea what address you are sending to the routine as pADDRESS but make sure it ends up to be one of 0x90 to 0x9E.

Also, when declaring a double does that make it signed or unsigned. If you want to be returning a negative number you will want to make sure that it is signed.

Ronald

[jleblanc]

[PCM programmer]

1. Remove the first LM75 chip from the bus, physically, so that only
the 2nd chip is present.

2. Hardcode your program to talk to the 2nd LM75 only.
Hardcode the addresses.

See if that works.

[jleblanc]

[claude]

How much distance can i get bi using a lm75 , i mean how far from the pic can i put it. I'm pplanning of making a 24 lm75 sensor logging pic program, that will outpus the temperatures over 232, and add the them into nice draw....is it possible to put them as far as 5 meters ? i have made this program , and it work, i managed to get the data on a lcd whit 1*16 characters.
My question is what must i change to be able to use more lm 75's by them adresses ? A0A1A2

#include <16F870.h>
#use delay(clock=4000000)
#fuses XT,NOWDT,PUT,NOPROTECT,BROWNOUT,NOLVP,NOCPD,NOWRT,NODEBUG
#define SDA_PIN PIN_C2 // i2c serial data in/out
#define SCL_PIN PIN_C3 // i2c serial clock
// Variabile pentru citire LM75
int8 dataH,dataL,current_temp, max_temp, min_temp;
int1 flgSign;
char txt;
#define p1 PIN_A3 //push button for temperature reset
#define p4 PIN_A0
#define buz PIN_A4 //buzzer
#define fan PIN_A5
#use i2c(master,sda=SDA_PIN, scl=SCL_PIN)
void i2c_init(void)
{
output_high( SCL_PIN );
output_high( SDA_PIN );
}

void lm75_start(void)
{
i2c_start();
i2c_write(0x90);
i2c_write(0x01); // Pointer Byte
i2c_write(0x00); // Configuration Byte (operating)
i2c_stop();
}

void lm75_setandread(void)
{
i2c_start();
i2c_write(0x90);
i2c_write(0x00); // Pointer Byte
i2c_start();
i2c_write(0x91);
dataH = i2c_read(); // with ACK
dataL = i2c_read(0); // with NOACK
// dataL &= 0x80; // // D6-D0 sunt undefined
i2c_stop();
}
#include <lcdme.c>

void sounds() {
output_low(buz);delay_ms(20);
output_high(buz);delay_ms(20);
output_low(buz);delay_ms(30);
output_high(buz);delay_ms(30);
output_low(buz);delay_ms(40);
output_high(buz);delay_ms(40);
output_low(buz);delay_ms(50);
output_high(buz);delay_ms(50);
output_low(fan);
}
void reset_temp() {

current_temp = dataH;
min_temp=current_temp;
max_temp=current_temp;
}

main() {

i2c_init();
delay_ms( 10 );
lcd_init();
reset_temp();
txt=223;
while(1)

{

lm75_start();
delay_ms( 30 );
// lm75_read();
lm75_setandread();
// lm75_shutdown();
delay_ms( 100 );

// Stabileste valoarea/semnul temperaturii (in 0,5 grade Celsius)
flgSign = 0;
if( bit_test( dataH, 7 ) ){ // semn negativ (bit-ul 7 setat)
flgSign = 1;
dataH = ( 0xFF - dataH + 1 );
}
dataH = ( dataH <<1>max_temp) max_temp=current_temp;
else if(current_temp<min_temp>=27) sounds();
else {output_high(buz);output_high(fan);}
lcd_gotoxy(1,1);
printf(lcd_putc,"%u %cC" ,min_temp,txt);
lcd_gotoxy(6,1);
printf(lcd_putc,">%u" ,dataH);
lcd_gotoxy(1,2);
printf(lcd_putc,"< %u %cC" ,max_temp,txt);

if (!input(p4)) {lcd_gotoxy(1,1);printf(lcd_putc, "Claudiu ");
lcd_gotoxy(1,2);printf(lcd_putc, "Godinel ");
output_high(buz);}

delay_ms(250);
}}

[godinel claudiu]

#include <16F870.h>
#use delay(clock=4000000)
#fuses XT,NOWDT,PUT,NOPROTECT,BROWNOUT,NOLVP,NOCPD,NOWRT,NODEBUG
#define SDA_PIN PIN_C2 // i2c serial data in/out
#define SCL_PIN PIN_C3 // i2c serial clock
#define p1 PIN_A3
#define LM75_WRITE1 0x90 // 1001 0000
#define LM75_READ1 0x91 // 1001 0001
#define LM75_WRITE2 0x9e // 1001 1110
#define LM75_READ2 0x9f // 1001 1111

#use i2c(master,sda=SDA_PIN, scl=SCL_PIN)
int8 dataH,dataL,temp,senz,x;
int1 flgSign;
char grad;

void i2c_init(void)
{
output_high( SCL_PIN );
output_high( SDA_PIN );
}


void lm75_start(int8 x)
{
i2c_start();
if (x==1) i2c_write(LM75_WRITE1);
else i2c_write(LM75_WRITE2);
i2c_write(0x01); // Pointer Byte
i2c_write(0x00); // Configuration Byte (operating)
i2c_stop();
}

void lm75_setandread(int8 x)
{
i2c_start();
if (x==1) i2c_write(LM75_WRITE1);
else i2c_write(LM75_WRITE2);
i2c_write(0x00); // Pointer Byte
i2c_start();
if (x==1) i2c_write(LM75_READ1);
else i2c_write(LM75_READ2);
dataH = i2c_read(); // with ACK
dataL = i2c_read(0); // with NOACK
i2c_stop();
}

#include <lcdme.c>

main() {

i2c_init();
delay_ms( 10 );
lcd_init();
senz=1;
grad=223;

while(1)
{

lcd_gotoxy(1,1);
printf(lcd_putc,"Senz");
lcd_gotoxy(6,1);
printf(lcd_putc,"%u =",senz);

lm75_start(senz);
delay_ms( 30 );
lm75_setandread(senz);
//lm75_shutdown();
delay_ms( 100 );

// Stabileste valoarea/semnul temperaturii (in 0,5 grade Celsius)
flgSign = 0;
if( bit_test( dataH, 7 ) ){ // semn negativ (bit-ul 7 setat)
flgSign = 1;
dataH = ( 0xFF - dataH + 1 );
}
dataH = ( dataH << 1 );
if( bit_test( dataL, 7 ) ) // 0,5 grade (bit-ul 7 setat)
dataH |= 0x01;
//facut de Godinel claudiu
// Ajusteaza valoarea temperaturii (cu +2 grade) (4 unitati de 0,5 grade)
if (senz==1) dataH -= 25 ;
if (senz==2) dataH -= 33 ;
dataL += 128 ;
temp=dataH;

lcd_gotoxy(1,2);
printf(lcd_putc,"Tmp");
lcd_gotoxy(5,2);
printf(lcd_putc,"%u" ,dataH);
lcd_gotoxy(7,2);
printf(lcd_putc,"%cC",grad);
if (!input(p1)) {senz=senz+1; if(senz==3) senz=1;}
delay_ms(100);

//if (!input(p4)) {lcd_gotoxy(1,1);printf(lcd_putc, "Claudiu ");
//lcd_gotoxy(1,2);printf(lcd_putc, "Godinel ");
//output_high(buz);}
}}