tmp102-sensor.c

/*
 * An interface to the TI TMP102 temperature sensor
 * 12 bit temperature reading, 0.5 deg. Celsius accuracy
 * -----------------------------------------------------------------
 *
 * Author  : Hedde Bosman (heddebosman@incas3.eu)
 */

#include "contiki.h"
#include "lib/sensors.h"
#include "dev/tmp102-sensor.h"

#ifndef bool
#define bool uint8_t
#endif

#ifndef false
#define false 0
#endif

#ifndef true
#define true 1
#endif


static void set_configuration(uint8_t rate, bool precision) {
        uint8_t tx_buf[] = {TMP102_REGISTER_CONFIGURATION, 
                                                0,
                                                (precision ? TMP102_CONF_EXTENDED_MODE : 0) | ((rate << 6) & TMP102_CONF_CONVERSION_RATE)
                                                };

        i2c_transmitinit(TMP102_ADDR, 3, tx_buf);
}

/*---------------------------------------------------------------------------*/
static int value(int type) {
        uint8_t reg = TMP102_REGISTER_TEMPERATURE;
        uint8_t temp[2];
        int16_t temperature = 0;
        
        /* transmit the register to start reading from */
        i2c_transmitinit(TMP102_ADDR, 1, &reg);
        while (!i2c_transferred()); // wait for data to arrive

        /* receive the data */
        i2c_receiveinit(TMP102_ADDR, 2, temp);
        while (!i2c_transferred()); // wait for data to arrive
        
        // 12 bit normal mode
        temperature = ((temp[0] <<8) | (temp[1])) >> 4; // lsb

        // 13 bit extended mode
        //temperature = ((temp[0] <<8) | (temp[1])) >> 3; // lsb

        temperature = (100*temperature)/16; // in 100th of degrees
        
        return temperature;
}
/*---------------------------------------------------------------------------*/
static int status(int type) {
        switch (type) {
                case SENSORS_ACTIVE:
                case SENSORS_READY:
                        return 1; // fix?
                        break;
        }
        return 0;
}
/*---------------------------------------------------------------------------*/
static int configure(int type, int c) {
        switch (type) {
                case SENSORS_ACTIVE:
                        if (c) {
                                // set active
                                set_configuration(1, false); // every 1 second, 12bit precision
                        } else {
                                // set inactive
                        }
                        return 1;
        }
        return 0;
}


/*---------------------------------------------------------------------------*/
SENSORS_SENSOR(tmp102_sensor, "Temperature", value, configure, status); // register the functions