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PIC18F2580 I2C interfacing with Si7005 sensor

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DarqueChaton

New Member
Hello all! Please forgive me if this is in the wrong category, I am new here !

So I have a Si7005 sensor from Silicon Labs which is a humidity and temperature sensor that communicates with an I2C interface. I've been trying to at the very least retrieve the device ID from the register specified in the datasheet with little to no result.

When I attempt to retrieve the device ID, I get 255 value, which is not what is specified in the datasheet at all (I should be getting 80)

Here is a sample of the C code I wrote for it , I am attempting to get the value and printing it out on an NHD LCD I have setup . I am us CCS C Compiler and MPLAB X :

#include "projet.h"
#include "ecran.h"



void main (void)
{
int8_t devid=24;

Initialiser_Ecran(); // LCD initialisation
Effacer_Ecran(); // Erase LCD

while(1)
{

i2c_start();
i2c_write(0x40); // Slave adress
i2c_write(0x11); // Device ID Register
i2c_start();
i2c_write(0x41); // R/W bit set to READ
devid = i2c_read(1); // No ACK
i2c_stop();


Positionner_Curseur(1,1); // Place cursor
fprintf(Ecran, "Device ID = %U",devid); // Print


}

Here is a link to the datasheet of my sensor : http://www.ccontrols.ch/cms/upload/downloads/active-components/Siliconlabs-Si7005.pdf

Any help I can get is appreciated =) Thank you!
 

Pommie

Well-Known Member
Most Helpful Member
Although the datasheet states that the slave address is 0x40 it is in fact shifted left one place to allow for the read\write bit. Try using ox80 to write and 0x81 to read.

HTH,

Mike.
 

DarqueChaton

New Member
Although the datasheet states that the slave address is 0x40 it is in fact shifted left one place to allow for the read\write bit. Try using ox80 to write and 0x81 to read.

HTH,

Mike.
I tried , and it worked! I got the proper address returned! At first it didn't work but it is in fact a 0 for no ACK as Master and not a 1 . Thank you!
 
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