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TC74 Demo Code.

 
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MikeValencia



Joined: 04 Aug 2004
Posts: 238
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TC74 Demo Code.
PostPosted: Thu Aug 18, 2005 4:14 pm     Reply with quote

this code works directly on a PICDEM-2 Plus with a TC74 temperature sensor. It is an endless loop that continuously prints out the temperature in Fahrenheit every several hundred milliseconds.

Code:

#include <16F876.h>
#device ADC=10
#fuses HS,NOWDT,NOPROTECT,NOLVP
#use delay(clock=4000000) /* one instruction=1us? */
#use rs232(baud=9600, xmit=PIN_C6, rcv=PIN_C7, ERRORS)
#use I2C(master, SCL=PIN_C3, SDA=PIN_C4)

void main(void)

{
            int data;
            int ack;
            long int fahr;

    printf ("\r\n\r\n\r\n");
    while (1)

    {     
        i2c_start();
        ack = i2c_write(0x9A);
        ack = i2c_write(0x00);

        /* send start again */
        i2c_start();
        ack = i2c_write(0x9b);
        data = i2c_read(0);
        i2c_stop();

        // Convert the A/D value to fahrenheit
        fahr = (9 * (long)data);
        fahr = fahr/5;
        fahr = fahr + 32;
        printf ("Temp: %ld\r\n", fahr);       
        delay_ms(200);
    }
}


Last edited by MikeValencia on Wed Aug 24, 2005 6:27 pm; edited 1 time in total
MikeValencia



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PostPosted: Tue Aug 23, 2005 6:50 am     Reply with quote

I have a mistake in the code. "i2c_stop()" should be "i2c_stop(0);"

Without the (0), the TC74 probably wouldn't relinquish the session. My original code works probably because, in my example, the TC74 is the only chip the PIC talks to.

Thanks to "PCM Programmer" for bringing this to my attention.
Mark



Joined: 07 Sep 2003
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PostPosted: Tue Aug 23, 2005 7:04 am     Reply with quote

I believe that you mean i2c_read(0). i2c_stop() doesn't take parameters.
PCM programmer



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PostPosted: Tue Aug 23, 2005 1:26 pm     Reply with quote

In my PM, I did say it should be i2c_read(0).
(I also suggested editing the original post)
hfelton



Joined: 07 Sep 2006
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link to newer-thread and code
PostPosted: Fri Oct 06, 2006 2:19 am     Reply with quote

howdee - i was just testing a PICDEM HPC demo board and stumbled here (on my TC74 search) in the forums. im going to include a link to another thread which makes the important distinction that the variables should be labelled 'signed' for ccs-c. the linked-code works perfectly on my demo board with the 'standard' addresses given. Smile

http://www.ccsinfo.com/forum/viewtopic.php?t=28089

good luck, h.
new2ccs



Joined: 29 Oct 2006
Posts: 10

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PostPosted: Thu Nov 16, 2006 1:06 pm     Reply with quote

why is he sending twice before he reads it ?. Also, on the picdem 2+ the eeprom(24lc256) is also connected to the SDA , SCL. with the code above, the pic just reads it from tc74 and doesn't do anything with eeprom. am i right?
PCM programmer



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PostPosted: Thu Nov 16, 2006 3:26 pm     Reply with quote

Quote:
why is he sending twice before he reads it

Download the TC74 data sheet and look at the "Read Byte" diagram
on page 7. His code matches the diagram.
http://ww1.microchip.com/downloads/en/DeviceDoc/21462c.pdf

Quote:

Also, on the picdem 2+ the eeprom(24lc256) is also connected to the
SDA , SCL. with the code above, the pic just reads it from tc74 and
doesn't do anything with eeprom. am i right?

The TC74 and the 24LC256 have different i2c addresses.
Therefore, they can be on the same bus without conflicting with each
other.
new2ccs



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PostPosted: Thu Nov 16, 2006 4:20 pm     Reply with quote

ok, now i kind of got it. I used one of the examples in the manual and didn't work for me and I also read the data sheet too, but still got confused. now it is some what clear.

another question PCM, so that only the communication between the pic and the TC74(sensor) right?. if my understanding is correct then, if i want to write to the eeprom(24LC256). i would do something like that but with the 24LC256' address right?

thanks PCM, you are the great help.
PCM programmer



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Posts: 20212

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PostPosted: Thu Nov 16, 2006 4:39 pm     Reply with quote

To use the 25LC256 eeprom, just #include the 24256.c driver in your
C program. The driver is located in this folder:

c:\Program Files\Picc\Drivers\24256.c

If you have questions about that driver, please post them in the main
forum. (not the Code library)
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