DS18B20.c File Reference

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

#include <stdint.h>
#include <stdbool.h>
#include "em_cmu.h"
#include "em_gpio.h"
#include "DS18B20.h"
#include "pin_mapping.h"
#include "debug_dbprint.h"
#include "delay.h"
#include "util.h"
#include "ustimer.h"

Go to the source code of this file.

Macros
#define	DBPRINT_TIMEOUT   0
#define	TIMEOUT_INIT   20
#define	TIMEOUT_CONVERSION   500 /* 12 bit resolution (reset default) = 750 ms max resolving time */

Functions
static void	powerDS18B20 (bool enabled)
	Enable or disable the power to the temperature sensor. More...
static bool	init_DS18B20 (void)
	Initialize communication to the DS18B20. More...
static void	writeByteToDS18B20 (uint8_t data)
	Write a byte (uint8_t) to the DS18B20. More...
static uint8_t	readByteFromDS18B20 (void)
	Read a byte (uint8_t) from the DS18B20. More...
static int32_t	convertTempData (uint8_t tempLS, uint8_t tempMS)
	Convert temperature data. More...
int32_t	readTempDS18B20 (void)
	Get a temperature value from the DS18B20. More...

Variables
bool	DS18B20_VDD_initialized = false

Detailed Description

All code for the DS18B20 temperature sensor.

Version

3.1

Author

Alec Vanderhaegen & Sarah Goossens
Modified by Brecht Van Eeckhoudt

---

Versions

• v1.0: Reformatted existing methods to use pin_mapping.h, changed unsigned char to uint8_t values, added comments and cleaned up includes.
• v1.1: Added documentation, removed unnecessary GPIO statements regarding DOUT values of VDD pin.
• v1.2: Removed some unnecessary GPIO lines and added comments about out (DOUT) argument.
• v1.3: Changed some methods to be static (~hidden).
• v1.4: Cleaned up includes.
• v1.5: Made more methods static.
• v1.6: Updated documentation.
• v1.7: Started using new delay functionality.
• v1.8: Added line to disable DATA pin after a measurement, this breaks the code but fixes the sleep current.
• v1.9: Enabled and disabled timer each time a measurement is taken.
• v2.0: Updated documentation.
• v2.1: Changed method to return uint32_t instead of float.
• v2.2: Changed error numbering, moved definition from header to source file and updated header file include.
• v2.3: Changed timeout variable and changed types to int32_t.
• v2.4: Fixed temperature measurement and refined timeout functionality.
• v2.5: Updated documentation.
• v2.6: Updated code to don't execute code further if the first initialization failed.
• v3.0: Disabled initialized functionality before entering an error function, added functionality to exit methods after error call and updated version number.
• v3.1: Removed static before the local variable (not necessary).

---

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 also 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.c.

Macro Definition Documentation

DBPRINT_TIMEOUT

#define DBPRINT_TIMEOUT   0

Enable (1) or disable (0) printing the timeout counter value using DBPRINT

Definition at line 80 of file DS18B20.c.

TIMEOUT_CONVERSION

#define TIMEOUT_CONVERSION   500 /* 12 bit resolution (reset default) = 750 ms max resolving time */

Definition at line 84 of file DS18B20.c.

TIMEOUT_INIT

#define TIMEOUT_INIT   20

Definition at line 83 of file DS18B20.c.

Function Documentation

convertTempData()

static int32_t convertTempData ( uint8_t  tempLS, uint8_t  tempMS  )

static

Convert temperature data.

Note

This is a static method because it's only internally used in this file and called by other methods if necessary.

Parameters

[in]	tempLS	Least significant byte.
[in]	tempMS	Most significant byte.

Returns

The converted temperature data.

Definition at line 423 of file DS18B20.c.

{
    uint16_t rawDataMerge;
    uint16_t reverseRawDataMerge;

    int32_t finalTemperature;

    /* Check if it is a negative temperature value
     * 0xF8 = 0b1111 1000 */
    if (tempMS & 0xF8)
    {
        rawDataMerge = tempMS;

        /* Left shift 8 times */
        rawDataMerge <<= 8;

        /* Add the second part */
        rawDataMerge += tempLS;

        /* Invert the value since we have a negative temperature */
        reverseRawDataMerge = ~rawDataMerge;

        /* Calculate the final temperature */
        finalTemperature = -(reverseRawDataMerge + 1) * 62.5;
    }
    /* We're dealing with a positive temperature */
    else
    {
        rawDataMerge = tempMS;

        /* Left shift 8 times */
        rawDataMerge <<= 8;

        /* Add the second part */
        rawDataMerge += tempLS;

        /* Calculate the final temperature */
        finalTemperature = rawDataMerge * 62.5;
    }

    return (finalTemperature);
}

init_DS18B20()

static bool init_DS18B20 ( void  )

static

Initialize communication to the DS18B20.

Note

This is a static method because it's only internally used in this file and called by other methods if necessary.

Returns

• true - Presence pulse detected in time.
• false - No presence pulse detected.

Definition at line 271 of file DS18B20.c.

{
    /* Timeout counter */
    uint32_t counter = 0;

    /* MASTER RESET: Pull data line LOW for at least 480 µs (Master TX) */
    GPIO_PinModeSet(TEMP_DATA_PORT, TEMP_DATA_PIN, gpioModePushPull, 0); /* gpioModePushPull: Last argument directly sets the pin state */
    USTIMER_DelayIntSafe(480);

    /* Change pin-mode to input - External pull-up resistor pulls data line back HIGH */
    GPIO_PinModeSet(TEMP_DATA_PORT, TEMP_DATA_PIN, gpioModeInput, 0);

    /* Check if the line becomes LOW (~ wait while it stays high) during the maximum waiting time
     *   The DS18B20 should detect the data line rising due to the pull-up resistor, waits 15 - 50 µs
     *    and then pulls the line back LOW (for 60 - 240 µs) to indicate it's PRESENCE */
    while ((counter < TIMEOUT_INIT) && (GPIO_PinInGet(TEMP_DATA_PORT, TEMP_DATA_PIN) == 1)) counter++;

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

#if DEBUG_DBPRINT == 1 /* DEBUG_DBPRINT */
        dbcrit("No DS18B20 presence pulse detected in time!");
#endif /* DEBUG_DBPRINT */

        error(28);

        return (false);
    }
#if DBPRINT_TIMEOUT == 1 /* DBPRINT_TIMEOUT */
    else
    {

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

    }
#endif /* DBPRINT_TIMEOUT */

    /* Master RX should be at least 480 µs */
    USTIMER_DelayIntSafe(480);

    return (true);
}

powerDS18B20()

static void powerDS18B20 ( bool  enabled )

static

Enable or disable the power to the temperature sensor.

This method also initializes the pin-mode if necessary.

Note

This is a static method because it's only internally used in this file and called by other methods if necessary.

Parameters

[in]

enabled

true - Enable the GPIO pin connected to the VDD pin of the temperature sensor. talse - Disable the GPIO pin connected to the VDD pin of the temperature sensor.

Definition at line 237 of file DS18B20.c.

{
    /* Enable necessary clocks (just in case) */
    CMU_ClockEnable(cmuClock_HFPER, true); /* GPIO is a High Frequency Peripheral */
    CMU_ClockEnable(cmuClock_GPIO, true);

    /* Initialize VDD pin if not already the case */
    if (!DS18B20_VDD_initialized)
    {
        /* In the case of gpioModePushPull", the last argument directly sets the pin state */
        GPIO_PinModeSet(TEMP_VDD_PORT, TEMP_VDD_PIN, gpioModePushPull, enabled);

        DS18B20_VDD_initialized = true;
    }
    else
    {
        if (enabled) GPIO_PinOutSet(TEMP_VDD_PORT, TEMP_VDD_PIN); /* Enable VDD pin */
        else GPIO_PinOutClear(TEMP_VDD_PORT, TEMP_VDD_PIN); /* Disable VDD pin */
    }
}

readByteFromDS18B20()

static uint8_t readByteFromDS18B20 ( void  )

static

Read a byte (uint8_t) from the DS18B20.

Note

This is a static method because it's only internally used in this file and called by other methods if necessary.

Returns

The byte read from the DS18B20.

Definition at line 378 of file DS18B20.c.

{
    /* Data to eventually return */
    uint8_t data = 0x0;

    /* Read the byte, bit by bit */
    for (uint8_t i = 0; i < 8; i++)
    {
        /* Change pin-mode to input */
        GPIO_PinModeSet(TEMP_DATA_PORT, TEMP_DATA_PIN, gpioModeInput, 0);

        /* Right shift bits once */
        data >>= 1;

        /* If the line is high, OR the first bit of the data:
         * 0x80 = 1000 0000 */
        if (GPIO_PinInGet(TEMP_DATA_PORT, TEMP_DATA_PIN)) data |= 0x80;

        /* In the case of gpioModePushPull", the last argument directly sets the pin state */
        GPIO_PinModeSet(TEMP_DATA_PORT, TEMP_DATA_PIN, gpioModePushPull, 1);

        /* Wait some time before going into next loop */
        USTIMER_DelayIntSafe(70);
    }
    return (data);
}

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);
    }
}

writeByteToDS18B20()

static void writeByteToDS18B20 ( uint8_t  data )

static

Write a byte (uint8_t) to the DS18B20.

Note

This is a static method because it's only internally used in this file and called by other methods if necessary.

Parameters

[in]

data

The data to write to the DS18B20.

Definition at line 329 of file DS18B20.c.

{
    /* In the case of gpioModePushPull", the last argument directly sets the pin state */
    GPIO_PinModeSet(TEMP_DATA_PORT, TEMP_DATA_PIN, gpioModePushPull, 0);

    /* Write the byte, bit by bit */
    for (uint8_t i = 0; i < 8; i++)
    {
        /* Check if we need to write a "1" */
        if (data & 0x01)
        {
            GPIO_PinOutClear(TEMP_DATA_PORT, TEMP_DATA_PIN);

            /* 5 µs delay should be called here but this loop works fine too... */
            for (uint8_t i=0; i<5; i++);

            GPIO_PinOutSet(TEMP_DATA_PORT, TEMP_DATA_PIN);
            USTIMER_DelayIntSafe(60);
        }
        /* If not, write a "0" */
        else
        {
            GPIO_PinOutClear(TEMP_DATA_PORT, TEMP_DATA_PIN);
            USTIMER_DelayIntSafe(60);
            GPIO_PinOutSet(TEMP_DATA_PORT, TEMP_DATA_PIN);

            /* 5 µs delay should be called here but this loop works fine too... */
            for (uint8_t i=0; i<5; i++);
        }
        /* Right shift bits once */
        data >>= 1;
    }

    /* Set data line high */
    GPIO_PinOutSet(TEMP_DATA_PORT, TEMP_DATA_PIN);
}

Variable Documentation

DS18B20_VDD_initialized

bool DS18B20_VDD_initialized = false

Definition at line 88 of file DS18B20.c.