DS18B20.h File Reference

All code for the DS18B20 temperature sensor. More...

#include <stdint.h>

Go to the source code of this file.

Functions
int32_t	readTempDS18B20 (void)
	Get a temperature value from the DS18B20. More...

Detailed Description

All code for the DS18B20 temperature sensor.

Version

3.1

Author

Alec Vanderhaegen & Sarah Goossens
Modified by Brecht Van Eeckhoudt

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License

Copyright (C) 2019 - Brecht Van Eeckhoudt

This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

A copy of the GNU General Public License can be found in the LICENSE file along with this source code.

Some methods use code obtained from examples from Silicon Labs' GitHub. These sections are licensed under the Silabs License Agreement. See the file "Silabs_License_Agreement.txt" for details. Before using this software for any purpose, you must agree to the terms of that agreement.

Definition in file DS18B20.h.

Function Documentation

readTempDS18B20()

int32_t readTempDS18B20

(

void

)

Get a temperature value from the DS18B20.

USTimer gets initialized, the sensor gets powered, the data-transmission takes place, the timer gets de-initialized to disable the clocks and interrupts, the data and power pin get disabled and finally the read values are converted to an int32_t value.
Negative temperatures work fine.

Returns

The read temperature data.

Definition at line 113 of file DS18B20.c.

{
    /* Timeout counter */
    uint16_t counter = 0;

    /* Variable to indicate if a conversion has been completed */
    bool conversionCompleted = false;

    /* Variable to hold raw data bytes */
    uint8_t rawDataFromDS18B20Arr[9] = {0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0};

    /* Initialize timer
     * Initializing and disabling the timer again adds about 40 µs active time but should conserve sleep energy... */
    USTIMER_Init();

    /* Initialize and power VDD pin */
    powerDS18B20(true);

    /* Power-up delay of 5 ms */
    delay(5);

    /* Initialize communication and only continue if successful */
    if (init_DS18B20())
    {
        writeByteToDS18B20(0xCC); /* 0xCC = "Skip Rom" (address all devices on the bus simultaneously without sending out any ROM code information) */
        writeByteToDS18B20(0x44); /* 0x44 = "Convert T" */

        /* MASTER now generates "read time slots", the DS18B20 will write HIGH to the bus if the conversion is completed
         *   The datasheet gives the following directions for time slots, but reading bytes also seems to work...
         *     - Read time slots have a 60 µs duration and 1 µs recovery between slots
         *     - After the master pulls the line low for 1 µs, the data is valid for up to 15 µs */
        while ((counter < TIMEOUT_CONVERSION) && !conversionCompleted)
        {
            uint8_t testByte = readByteFromDS18B20();
            if (testByte > 0) conversionCompleted = true;

            counter++;
        }

        /* Exit the function if the maximum waiting time was reached */
        if (counter == TIMEOUT_CONVERSION)
        {

#if DEBUG_DBPRINT == 1 /* DEBUG_DBPRINT */
            dbcrit("Waiting time for DS18B20 conversion reached!");
#endif /* DEBUG_DBPRINT */

            /* Disable interrupts and turn off the clock to the underlying hardware timer. */
            USTIMER_DeInit();

            /* Disable data pin (otherwise we got a "sleep" current of about 330 µA due to the on-board 10k pull-up) */
            GPIO_PinModeSet(TEMP_DATA_PORT, TEMP_DATA_PIN, gpioModeDisabled, 0);

            /* Disable the VDD pin */
            powerDS18B20(false);

            error(29);

            /* Exit function */
            return (0);

        }
#if DBPRINT_TIMEOUT == 1 /* DBPRINT_TIMEOUT */
        else
        {

#if DEBUG_DBPRINT == 1 /* DEBUG_DBPRINT */
            dbwarnInt("DS18B20 conversion (", counter, ")");
#endif /* DEBUG_DBPRINT */

        }
#endif /* DBPRINT_TIMEOUT */

        init_DS18B20();           /* Initialize communication */
        writeByteToDS18B20(0xCC); /* 0xCC = "Skip Rom" */
        writeByteToDS18B20(0xBE); /* 0xCC = "Read Scratchpad" */

        /* Read the bytes */
        for (uint8_t i = 0; i < 9; i++) rawDataFromDS18B20Arr[i] = readByteFromDS18B20();

        /* Disable interrupts and turn off the clock to the underlying hardware timer. */
        USTIMER_DeInit();

        /* Disable data pin (otherwise we got a "sleep" current of about 330 µA due to the on-board 10k pull-up) */
        GPIO_PinModeSet(TEMP_DATA_PORT, TEMP_DATA_PIN, gpioModeDisabled, 0);

        /* Disable the VDD pin */
        powerDS18B20(false);

        /* Return the converted byte */
        return (convertTempData(rawDataFromDS18B20Arr[0], rawDataFromDS18B20Arr[1]));
    }
    else
    {
        /* Disable interrupts and turn off the clock to the underlying hardware timer. */
        USTIMER_DeInit();

        /* Disable data pin (otherwise we got a "sleep" current of about 330 µA due to the on-board 10k pull-up) */
        GPIO_PinModeSet(TEMP_DATA_PORT, TEMP_DATA_PIN, gpioModeDisabled, 0);

        /* Disable the VDD pin */
        powerDS18B20(false);

        /* Exit function */
        return (0);
    }
}